TECHNOLOGICAL AND ECONOMIC EVALUATION OF DISTRICT COOLING ...

TECHNOLOGICAL AND ECONOMIC

EVALUATION OF DISTRICT COOLING

WITH ABSORPTION COOLING SYSTEMS

IN GÄVLE (SWEDEN)

Elixabet Sarasketa Zabala

June 2009

Master’s Thesis in Energy Systems

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DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT

Master Programme in Energy Systems

Examiner: Ulf Larsson

Supervisor: Åke Björnwall

Preface

This investigation, as final Thesis Project of Master in Energy Systems

(University of Gävle), was started to carry out in February, in collaboration with

the company Gävle Energi AB. Many people have been involved answering my

questions, providing me with information and so forth; some of those are

mentioned below.

First of all, I would like to thank Åke Björnwall, my supervisor at Gävle

Energi AB, very much for his attention, help and support. His knowledge,

comments, guidance and advices have been essential for the development of my

work. Needless to say that I have learnt a lot from him.

Secondly, I would like to thank the rest of workers at Gävle Energi AB,

who have done everything they can to help me, in addition to make pleasant my

stay in the company.

I would also like to thank Ulf Larsson at the University of Gävle for his

help. Furthermore, I am very grateful for all information I have received from

other companies.

Finally, I do not forget the invaluable support of my mother, Rosa, during

all my studies.

No one mentioned, no one forgotten.

Gävle, June 2009

Elixabet Sarasketa Zabala

Abstract

Gävle Energi AB is a company which produces electricity as well as heat

that is delivered through a district heating network in the municipality of Gävle.

Apart from that, as cooling demand is large when seen from a global perspective,

at present it is building a district cooling network based on refrigerant compressor

technology with the idea of replacing less efficient individual HVAC systems in

the city center.

High electricity prices lead to reduce its use as far as possible, so it is also

needed to consider absorption systems as cooling technology. This way, the main

aim of this thesis is to analyze possible benefits with the use of heat driven

absorption chillers compared with conventional vapour compressor chillers.

For carrying out this investigation, first of all background and literature

study have been essential. As a result, information about cooling technologies,

district energy and cogeneration plants is gathered in this work.

The research is focused on three areas of the victinity of Gävle: city center,

Kungsbäck and Johannesbergsvägen.

In the first area, Gävle Energi AB might take the opportunity of using a

new ORC plant in biomass based cogeneration system that Bionär is planning to

build at LEAF, turning it into a trigeneration plant. So how bigger the installation

should be (according to the expected cooling demand that has been calculated in

the earliest steps) and the profits related to extra electricity production are

estimated in this study, in addition to examine the absorption chillers to be

introduced and their operational conditions.

On the other hand, Mackmyra whisky factory, which is in Valbo

nowadays, is going to build a new plant in Kungsbäck. Likewise, it is considering

that extra steam might be produced to fire absorption chillers and fulfil the

cooling demand of the hospital (Gävle Sjukhus), technological park

(Teknikparken) and university (Högskolan i Gävle), which are located in this area.

Like this, the same methodology as for LEAF has been followed for making

decisions.

Finally, there is Johannesbergsvägen area, where Johannes CHP plant is (a

description of the plant is included in the Appendix) and which is runned by

Gävle Energi AB. This plant is shut down in summer, as the demand for district

heating is low, and hence, electricity production, from which the company makes

a profit, is cut and restricted. A good solution to increase electricity output in

warm periods is to introduce absorption cooling technology, as it is run on steam

or hot water. Thus, Johannes could be the third trigeneration plant in Gävle that

would supply Hemlingby shopping centers (which are located less than two

kilometers far away from the production site) with cooling. Thus, the task has

been also to decide on installations and gauge the profits.

Next Table 0. gathers together costs, amount of heat that would be

demanded to produce and accordingly generated electricity in each of the three

production sites. It has been decided that double-effect chillers sets in the first two

cases and single-effect hot-water fired absorption cooling machines in the last one

might be introduced.

Table 0. Costs of absorption cooling installations, extra heat to be produced for the

absorption chillers and extra electricity output in the three studied sites

PRODUCTION

SITE &TOTAL

COOLING

LOAD

INVESTMENT

COST [SEK]

OPERATIONAL

COSTS

[SEK/year]

HEATING

DEMAND

[MWh/year]

ELECTRICITY

PRODUCTION

[MWh/year]

LEAF

21 385 MWh/year 22 627 000 4 753 485 17 977 4 135

MACKMYRA

9 298 MWh/year 17 700 000 2 504 835 7 819 1 173

JOHANNES

8 496 MWh/year 8 800 000 3 561 396 10 460 3 033

Furthermore, explanations and calculations regarding distribution systems

are presented, as these are also a component of district cooling systems.

Nevertheless, they are not taken into consideration for final decisions, since

necessary pumps and piping system would be the same in case of using vapour

compressor chillers for cooling production.

Lastly, it has been come to the conclusion that a sustainable energy system

for Gävle for fulfilling the cooling demand can be the erection of district cooling

networks with trigeneration plants by producing cooling in heat driven absorption

cooling machines. Despite larger investment cost of absorption systems compared

to compression ones, total costs after roughly five years are lower. Moreover,

electric coefficient of performance is about 23% higher for the absorption cooling

technology and there is a great electricity output too, which makes possible to

reduce electrical loads, to use the biofuel in an effective way and, last but not

least, to decrease global carbon dioxide emissions.

I

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION ..................................................................... 1

1.1. BACKGROUND ....................................................................................... 2

1.1.1. COOLING AND ITS PRODUCTION .................................................................... 2

1.1.2. GÄVLE ENERGI AB AND ITS PLANS FOR THE FUTURE................................ 3

1.2. PURPOSE .................................................................................................. 4

1.3. SCOPE....................................................................................................... 4

1.4. LIMITATIONS .......................................................................................... 5

1.5. METHOD .................................................................................................. 5

1.6. OUTLINE OF THE THESIS...................................................................... 6

CHAPTER 2. COOLING SYSTEM TECHNOLOGIES ................................ 8

2.1. REFRIGERANT COMPRESSOR INSTALLATIONS ................................ 10

2.1.1. COMPRESSOR AND SYSTEM EFFICIENCY ..................................................... 12

2.2. ABSORPTION COOLING INSTALLATIONS .......................................... 13

2.2.1. CONSIDERATIONS FOR DIMENSIONING ABSORPTION CIRCUITS............. 17

2.2.2. WORKING FLUID ............................................................................................... 18

2.2.2.1. WATER/ LITHIUM BROMIDE (H2O/ LiBr) .......................................... 19

2.2.2.2. AMMONIA/WATER (NH3/ H2O) ........................................................... 20

2.2.2.3. COMPARISON BETWEEN WATER/ LITHIUM BROMIDE AND

AMMONIA/WATER SOLUTIONS.......................................................... 21

2.2.3. PRIMARY ENERGY ............................................................................................ 25

2.2.4. TYPES OF ABSORPTION CHILLERS ................................................................ 26

2.2.4.1. SINGLE-EFFECT ABSORPTION CHILLERS ....................................... 27

2.2.4.2. DOUBLE-EFFECT ABSORPTION CHILLERS ..................................... 28

2.3. REFRIGERANT COMPRESSOR TECHNOLOGY VERSUS

ABSORPTION COOLING TECHNOLOGY ............................................ 30

CHAPTER 3. DISTRICT COOLING SYSTEM ............................................ 35

3.1. PRODUCTION ........................................................................................... 37

3.1.1. COGENERATION. BENEFITS WITH ABSORPTION COOLING ...................... 37

TABLE OF CONTENTS

II

3.2. COOLING DISTRIBUTION SYSTEM....................................................... 39

3.2.1. PIPING NETWORK ............................................................................................. 39

3.2.2. MATERIALS FOR THE PIPES ............................................................................ 40

CHAPTER 4. PROCESS ................................................................................. 41

4.1. GATHERING OF INFORMATION ABOUT EXISTING

INSTALLATIONS AND PRESENT SITUATION ..................................... 42

4.1.1. STEAM BOILERS AT LEAF AND KAPPA ........................................................ 42

4.1.2. BIOFUELED JOHANNES CHP PLANT .............................................................. 44

4.1.3. MACKMYRA ...................................................................................................... 46

4.1.4. REFRIGERATION COMPRESSOR COOLING PROJECT .................................. 47

4.2. GATHERING OF DATA: CUSTOMERS. LOAD REQUIRED AND

DISTANCES ............................................................................................... 48

4.3. ANALYSIS OF ABSORPTION COOLING PLANTS ................................ 51

4.3.1. ABSORPTION CHILLERS .................................................................................. 51

4.3.3.1. STUDY OF THE OPERATIONAL CONDITIONS ................................. 52

4.3.2. REST OF THE EQUIPMENTS ............................................................................ 52

CHAPTER 5. RESULTS ................................................................................. 56

5.1. PRODUCTION PLANTS ............................................................................ 57

5.1.1. LEAF .................................................................................................................... 57

5.1.1.1. OPERATIONAL CONDITIONS ............................................................. 57

5.1.1.2. COSTS .................................................................................................... 58

5.1.1.2.1. INVESTMENT COSTS .......................................................... 58

5.1.1.2.2. OPERATIONAL COSTS ........................................................ 59

5.1.1.2.3. TOTAL COSTS ...................................................................... 59

5.1.2. MACKMYRA ....................................................................................................... 61


5.1.2.2. COSTS .................................................................................................... 62



5.1.2.2.3. TOTAL COSTS ...................................................................... 63

5.1.3. JOHANNES .......................................................................................................... 64


5.1.3.2. COSTS .................................................................................................... 64



5.1.3.2.3. TOTAL COSTS ...................................................................... 65

5.1.4. SENSITIVITY ANALYSIS ................................................................................... 67

5.1.4.1. LEAF ...................................................................................................... 67

5.1.3.2. MACKMYRA ......................................................................................... 69

TABLE OF CONTENTS

III

5.1.3.2. JOHANNES ............................................................................................ 71

5.2. COMPRESSION TECHNOLOGY VERSUS ABSORPTION

TECHNOLOGY. COMPARISON FOR LEAF PRODUCTION SITE......... 72

5.3. DISTRIBUTION SYSTEM ......................................................................... 75

5.3.1. INSTALLATION .................................................................................................. 75

5.3.3. COST OF THE MAIN PIPING NETWORKS ....................................................... 75

CHAPTER 6. DISCUSSIONS ......................................................................... 76

6.1. PRODUCTION PLANTS ............................................................................ 77

6.2. MOST PROFITABLE TECHNIQUE FROM ECONOMIC POINT OF

VIEW. SUSTAINABILITY ........................................................................ 80

6.3. COOLING DEMAND VERSUS COSTS AND BENEFITS OF

ABSORPTION COOLING TECHNOLOGY .............................................. 83

6.3.1. ELECTRICITY PRODUCTION AND CONSUMPTION ...................................... 83

6.3.2. COSTS AND PROFITS. THE BEST OPTIONS .................................................... 84

CHAPTER 7. CONCLUSIONS ....................................................................... 86

REFERENCES ................................................................................................. 88

APPENDICES .................................................................................................. 92

Appendix 1. PLANNED REFRIGERANT COMPRESSION

INSTALLATION ................................................................ 93

A1.1. INSTALLATION ................................................... 93

A1.2. COOLING LOAD ................................................. 99

A1.3. INPUT LOAD AND COSTS ................................ 100

A1.4. TOTAL COSTS ................................................... 102

A1.5. PAY-BACK TIME FOR THE INVESTMENTS... 103

Appendix 2. EXPECTED COOLING DEMAND ................................ 104

TABLE OF CONTENTS

IV

Appendix 3. SPECIFICATIONS AND CALCULATIONS

REGARDING ABSORPTION COOLING

INSTALLATIONS ........................................................... 108

A3.1. ABSORPTION CHILLERS.................................. 108

A3.1.1. MODELS AND THEIR CHARACTERISTICS ........ 108

A3.1.2. INVESTMENT COSTS ........................................... 118

A3.1.3. OPERATIONAL CONDITIONS ............................. 119

A3.2. THE REST OF EQUIPMENTS ............................ 131

Appendix 4. MAPS OF CUSTOMERS AND DISTANCES FROM

THE PRODUCTION SITES ............................................ 133

Appendix 5. CALCULATIONS ABOUT DIMENSIONS OF PIPES,

DISTRIBUTION PUMPS AND THEIR COSTS ............ 140

A5.1. DIMENSIONING ................................................. 140

A5.2. COSTS ................................................................. 146

Appendix 6. FALUN COOLING PROJECT: A REFERENCE ......... 150

A6.1. INSTALLATION ................................................. 150

A6.2. TOTAL COSTS.................................................... 152

Appendix 7. EXTRA INFORMATION ABOUT JOHANNES

POWER PLANT............................................................... 153

V

LIST OF FIGURES

Figure 1. Refrigerant compression cycle ........................................................... 10

Figure 2. Temperature-Entropy (T-s) diagram for a Vapour-Compression

Refrigeration Cycle ........................................................................... 11

Figure 3. Scheme of basic absorption cycle ....................................................... 14

Figure 4. Schematic of the fundamental absorption refrigeration system ........... 17

Figure 5. Ammonia/Water absorption cycle ...................................................... 20

Figure 6. Crystallization temperatures of water/lithium bromide solution

against the mass concentration of lithium bromide ............................. 21

Figure 7. Maximum system pressures against the condenser temperature .......... 22

Figure 8. Minimum system pressures against the evaporator temperature ......... 23

Figure 9. COP of the absorption systems against the condenser temperature

(heat exchanger efficiency 0,6) .......................................................... 24

Figure 10. COP of the absorption systems against the generator temperature

(heat exchanger efficiency 0,6) ........................................................ 24

Figure 11. COP of the absorption systems against the evaporator temperature

(heat exchanger efficiency 0,6) ........................................................ 25

Figure 12. Cooling cycle schematic .................................................................. 27

Figure 13. Double-Effect Water/Lithium Bromide Absorption Chiller

Schematic ....................................................................................... 28

Figure 14. Sketch for a double effect absorption heat pump in a log pressure-

temperature diagram ........................................................................ 29

Figure 15. Comparison between compression and absorption technologies

using ammonia as refrigerant and cooling water with a temperature

of 25 ºC ........................................................................................... 31

Figure 16. Components of district cooling systems ........................................... 36

Figure 17. District cooling system (or district heating system) .......................... 36

Figure 18. An schematic of cogeneration process that shows the consumed

and produced power in the whole system ........................................ 37

Figure 19. Illustration of a CHP plant connected to a district heating network ... 38

Figure 20. Energy efficiency of ORC units in cogeneration applications ............ 43

Figure 21. ORC plant in biomass based cogeneration system ............................. 43

Figure 22. Johannes CHP plant before 2003 ...................................................... 44

Figure 23. Production of heat (for District Heating) and electricity at

Johannes .......................................................................................... 45

Figure 24. Existing electric boiler in Mackmyra ................................................ 46

Figure 25. Existing and planned boilers at Mackmyra ........................................ 47

Figure 26. Three cooling production and customer sites and main pipes ............ 49

Figure 27. Cooling power to be produced in different sites during the year ........ 53

Figure 28. Typical piping diagram of an absorption system ............................... 56

Figure 29. Graph that shows the breakdown of total costs for 10 years at

LEAF ............................................................................................... 60

LIST OF FIGURES

VI

Figure 30. Graph that shows the breakdown of total costs for 10 years in

Mackmyra production site ................................................................ 63

Figure 31. Graph that shows the breakdown of total costs for 10 years in

Johannes production site .................................................................. 66

Figure 32. Comparison of cooling installations with absorption and

compression machines at LEAF ....................................................... 74

Figure 33. Increased heat load for the three absorption plants and the possible

extra electricity that would be produced ........................................... 79

Figure 34. Increased heat and electricity load in the probable Johannes

trigeneration plant ............................................................................ 79

Figure 35. Required operational conditions of the boiler for the cooling plant at

Johannes .......................................................................................... 80

Figure 36. Comparison of total costs for ten years for the different cooling

production technologies at LEAF ..................................................... 81

Figure 37. Electricity production and consumption according to the cooling

demand in three different scenarios .................................................. 84

Figure 38. Costs and profits (due to electricity production) according to the

cooling demand in three different scenarios ...................................... 84

Figure A1. 1. Draft of the whole compression installation.................................. 90

Figure A1. 2. Draft of the devices of the compression installation...................... 90

Figure A1. 3. Maintenance costs in the course of time ....................................... 99

Figure A3. 1. Water streams (steam and DH) at Johannes CHP plant ............... 111

Figure A3. 2. Cooling demand load curve (2008) divided in periods

according to the power needed to be produced ........................... 116

Figure A4. 1. Map of the city center with the main pipe that leaves LEAF

production site and its length ..................................................... 130

Figure A4. 2. Map with the customers, pipes and distances for Mackmyra

production site ........................................................................... 132

Figure A4. 3. Map with the customers for Johannes production site, pipe and

its length .................................................................................... 134

Figure A4. 4. Map of the shopping centers under construction in Hemlingby ... 135

Figure A4. 5. Map of the future residential area close to Johannes plant .......... 136

Figure A5. 1. SBI monogram showing the parameters of the different pipes .... 140

Figure A5. 2. Differential pressures in a direct return distribution system with

one terminal unit ........................................................................ 141

Figure A5. 3. Piping excavation section ........................................................... 143

Figure A5. 4. Distribution system cost split up in its components and their

contribution to the total cost....................................................... 145

Figure A6. 1. Draft of the whole cooling installation in Falun .......................... 147

Figure A7. 1. Scheme of Johannes CHP plant .................................................. 150

Figure A7. 2. Fuel storage and conveyor belt carrying biofuel to the boiler at

Johannes .................................................................................... 151

Figure A7. 3. Bubble Fluidized Bed (BFB) boiler of Johannes CHP plant ....... 152

LIST OF FIGURES

VII

Figure A7. 4. Illustrative drawing of Olga turbine and components .................. 153

Figure A7. 5. Olga turbine on the left side and heat exchangers on the right

Side. Johannes CHP plant .......................................................... 153

Figure A7. 6. Schematic of the FGC at Johannes ............................................. 154

Figure A7. 7. Detailed scheme of the condensate treatment plant at Johannes .. 154

VIII

LIST OF TABLES

Table 1. Production sites and customers ............................................................ 4

Table 2. Absorption working fluids´ properties ................................................ 23

Table 3. Comparison of parallel and series flow for double-effect water/lithium

bromide cycles .................................................................................... 29

Table 4. Energy saving with cogeneration for α = 0,54 ..................................... 33

Table 5. Summary of characteristics for cooling options .................................. 34

Table 6. Comparison between two 1000kW chillers ......................................... 34

Table 7. Different types of plants using a steam boiler and their

characteristics ..................................................................................... 38

Table 8. Cooling load demand at each site ....................................................... 50

Table 9. Possibilities to fulfill the cooling demand in the city center by using

steam-fired absorption chillers ............................................................ 51

Table 10. Possibilities to fulfill the cooling demand in Kungsbäck by using

steam-fired absorption chillers ........................................................... 52

Table 11. Possibilities to fulfill the cooling demand corresponding to Johannes

plant ................................................................................................. 54

Table 12. Cooling that should be produced for different sites during the year .... 55

Table 13. Power and steam demand of different chillers sets for the required

cooling load at LEAF during the year ................................................ 57

Table 14. Biofuel (for producing steam), electricity and water consumption.

LEAF ................................................................................................ 58

Table 15. Investment costs [SEK] for LEAF ..................................................... 58

Table 16. Operational costs at LEAF ................................................................ 59

Table 17. Total costs of LEAF absorption cooling plants for 10 years ............... 59

Table 18. Power and steam demand of different chillers sets for the required

cooling load in Mackmyra production during the year ....................... 61


Mackmyra ......................................................................................... 61

Table 20. Investment costs [SEK] for Mackmyra .............................................. 62

Table 21. Operational costs in Mackmyra production site ................................. 62

Table 22. Total costs of Mackmyra absorption cooling plants for 10 years ........ 63

Table 23. Power and hot water demand of chillers set for the required cooling

load at Johannes during the year ........................................................ 64


Johannes ............................................................................................ 64

Table 25. Investment costs [SEK] for Johannes................................................. 65

Table 26. Operational costs in Johannes production site .................................... 65

Table 27. Total costs of Johannes absorption cooling plant for 10 years ............ 65

Table 28. Operational conditions of different chillers sets at LEAF during

the year when the cooling demand is 10% higher than the estimated

one .................................................................................................... 67

LIST OF TABLES

IX

Table 29. Total costs of LEAF absorption cooling plants for 10 years when the

cooling demand is 10% higher than the estimated one ....................... 67

Table 30. Operational conditions of different chillers sets at LEAF during the

year when the cooling demand is 10% lower than the estimated one .. 68

Table 31. Total costs of LEAF absorption cooling plants for 10 years when the

cooling demand is 10% lower than the estimated one ........................ 68

Table 32. Operational conditions of different chillers sets in Mackmyra

production site during the year when the cooling demand is 10%

higher than the estimated one ............................................................ 69

Table 33. Total costs of Mackmyra absorption cooling plants for 10 years

when the cooling demand is 10% higher than the estimated one ........ 69

Table 34. Operational conditions of different chillers sets in Mackmyra


lower than the estimated one.............................................................. 70


when the cooling demand is 10% lower than the estimated one ......... 70

Table 36. Operational conditions of different chillers sets in Johannes


higher than the estimated one ............................................................ 71

Table 37. Total costs of Johannes absorption cooling plants for 10 years when

the cooling demand is 10% higher than the estimated one .................. 71

Table 38. Operational conditions of different chillers sets in Johannes


lower than the estimated one.............................................................. 71

Table 39. Total costs of Johannes absorption cooling plants for 10 years when

the cooling demand is 10% lower than the estimated one ................... 71

Table 40. Operational conditions of the existing cooling project but with

absorption machines .......................................................................... 73

Table 41. Power and steam demand of chillers set for the required cooling load

in the existing cooling project but with absorption machines ............. 73

Table 42. Operational costs in the existing cooling project but with absorption

machines ........................................................................................... 73

Table 43. Total costs of the existing cooling project but with absorption

machines for 10 years ........................................................................ 73

Table 44. Data about the distribution systems ................................................... 75

Table 45. Cost of the distribution systems ......................................................... 75

Table 46. Operational conditions and costs of distribution pumps ..................... 75

Table 47. Most adequate chillers and costs & profits for the three production

sites ..................................................................................................... 78

Table 48. Annual benefits of absorption cooling technology at LEAF after 10

years .................................................................................................... 81

LIST OF TABLES

X

Table R. 1. Information about personal contacts ............................................... 88

Table A1. 1. Pump specifications of compression cooling installation I ............ 92

Table A1. 2. Pump specifications of compression cooling installation II ........... 93

Table A1. 3. Pump specifications of compression cooling installation III .......... 93

Table A1. 4. Pump specifications of compression cooling installation IV .......... 93

Table A1. 5. Pump specifications of compression cooling installation V ........... 93

Table A1. 6. Pump specifications of compression cooling installation VI .......... 94

Table A1. 7. Pump specifications of compression cooling installation VII ........ 94

Table A1. 8. Pump specifications of compression cooling installation VIII ....... 94

Table A1. 9. Vapour Compressor chillers specifications I ................................. 94

Table A1. 10. Vapour Compressor chillers specifications II .............................. 95

Table A1. 11. Vapour Compressor chillers specifications III ............................. 95

Table A1. 12. Heat exchanger specifications of compression cooling

installation .................................................................................. 95

Table A1. 13. Operational conditions of VKA1 and VKA2 compressors

(YRWCWCT3550C) in time steps .............................................. 96


(YKKKKLH95CQF) in time steps .............................................. 96

Table A1. 15. Operating time for cooling delivering during the year ................. 96

Table A1. 16. Power needed in the compression cooling installation during the

year ............................................................................................ 97

Table A1. 17. Input load VKA1 and VKA2 compressors (YRWCWCT3550C)

in time steps................................................................................ 98

Table A1. 18. Input load VKA4 and VKA5 compressors (YKKKKLH95CQF)

in time steps................................................................................ 98

Table A1. 19. Total input load and operating costs in the compression cooling

installation .................................................................................. 99

Table A1. 20. Costs of the compressor refrigerant system ................................. 99

Table A1. 21. Pay-back times for the compression installation ......................... 100

Table A1. 22. Total costs for the refrigeration compression system for the first

10 years ..................................................................................... 100

Table A2. 1. Cooling demand of possible future customers in the city center

and additional data ....................................................................... 101

Table A2. 2. Customers and their cooling demand in Kungsbäck ..................... 103

Table A2. 3. Cooling demand for Johannes production site .............................. 104

Table A3. 1. Production data and pressure of the first steam stream extracted

from the turbine ........................................................................... 112

Table A3. 2. Price comparison of single- and double-effect units ..................... 115

Table A3. 3. Investment costs for different absorption chiller units .................. 116

Table A3. 4. Average city center´s cooling demand in time steps for 2008 ....... 117

Table A3. 5. Cooling load to be produced and working power of different

chillers (double- and single- effect) at LEAF during the year ....... 118

Table A3. 6. Cooling power to be supplied to the chillers at LEAF during the

year .............................................................................................. 118

LIST OF TABLES

XI


chillers (double- and single- effect) at LEAF during the year when

the cooling demand is 10% higher than the estimated one ............ 119


year when the cooling demand is 10% higher than the estimated

one ............................................................................................... 119


chillers (double- and single- effect) at LEAF during the year when

the cooling demand is 10% lower than the estimated one ............. 120


year when the cooling demand is 10% lower than the estimated

one ............................................................................................ 120


chillers (double- and single- effect) in Mackmyra production

site during the year .................................................................... 121

Table A3. 12. Cooling power to be supplied to the chillers during the year and

necessary cooling towers in Mackmyra production site .............. 121


chillers (double- and single- effect) in Mackmyra production site

during the year when the cooling demand is 10% higher than the

estimated one ............................................................................. 122


necessary cooling towers in Mackmyra production site when the

cooling demand is 10% higher than the estimated one................ 122


chillers (double- and single- effect) in Mackmyra production site

during the year when the cooling demand is 10% lower than the

estimated one ............................................................................. 123


necessary cooling towers in Mackmyra production site when the

cooling demand is 10% lower than the estimated one ................. 123


chillers in Johannes production site during the year.................... 124


necessary cooling towers in Johannes production site ................ 125


chillers in Johannes production site when the cooling demand is

10% higher than the estimated one ............................................. 125

Table A3. 20. Cooling power to be supplied to the chillers in Johannes


higher than the estimated one ..................................................... 126


chillers in Johannes production site when the cooling demand is

10% lower than the estimated one .............................................. 126

LIST OF TABLES

XII

Table A3. 22. Cooling power to be supplied to the chillers in Johannes


lower than the estimated one ...................................................... 127

Table A3. 23. Required cooling towers and heat exchangers´ technical data..... 128

Table A5. 1. Dimensioning of pipes and pressure drop (part I) ......................... 137

Table A5. 2. Dimensioning of pipes and pressure drop (part II) ....................... 138

Table A5. 3. PE Pressure Pipes for water supply: EN 12201, ISO 4427 ........... 142

Table A5. 4. Data of the pipes needed .............................................................. 143

Table A5. 5. Values of parameters C and B for the required dn ....................... 144

Table A5. 6. Total cost of the pipes .................................................................. 144

Table A5. 7. Calculation of the pipes´ costs ..................................................... 145

Table A5. 8. Needed distribution pumps and their cost .................................... 146

Table A6. 1. Reference specifications about absorption chiller in Falun .......... 148

Table A6. 2. Investment costs for different installations in Falun ..................... 149

Table A6. 3. Input electric power in Falun installations .................................... 149

Table A7. 1. Characteristics of the obtained outputs at Johannes ...................... 153

CHAPTER 1

2

Introduction

This chapter is a definition of the thesis, which describes the issues to be

studied and the reasons for their investigation, as well as the main purpose, scope,

limitations and so forth.

In general terms, the task can be summed up as the evaluation of

technological and economic possibilities regarding district cooling with

absorption cooling technology at three specific sites in the victinity of Gävle.

1.1. BACKGROUND

1.1.1. COOLING AND ITS PRODUCTION

It is a fact that cooling demand is as high as or even higher than heating

demand, since it is needed for both thermal comfort and many industrial processes

and, in addition, it is required more energy for producing cooling than heating.

Hence, production of cold could be very profitable for energy companies when it

is a part of the existing energy system.

District cooling system (DCS) offers massive and collective cooling

energy production, which is higher in efficiency than the conventional plants at

individual premises, and allows users to utilise building space more effectively

[1]. Generally, the chilled water for pipeline distribution is produced by

refrigerant compressor technique; nonetheless, it is needed to face up to a large

electricity consumption, which involves a large expense due to the deregulation of

the european electricity market.

In 2004 Sweden became part of a common european electricity market and

swedish plant will therefore meet higher european prices, which will lead to a

Chapter 1. INTRODUCTION

3

precarious scenario because of its intensive utilization of electricity [2].

Consequently, the use of electricity has to be decreased, for instance by changing

energy carrier when it is used for non-electricity specific purposes. To reach this

target, the choice of absorption facilities as cooling technology is clear.

Absorption cooling sytem uses heat as fuel, which make it possible to

combine with cogeneration plants and make the most of surplus heat. Moreover, it

is especially benefitial in summer periods when there is a large amount of waste

heat and electricity generation needs to be therefore reduced or stopped.

1.1.2. GÄVLE ENERGI AB AND ITS PLANS FOR THE

FUTURE

Gävle Energi AB is an energy company that belongs to Gävle community

and it develops, produces and sells products and services in energy and

communication with great view of the environment and nature. The company

owns and runs most of the electricity as well as district heating network in the

municipality of Gävle.

Gävle Energi AB not only ensures short-term goals but it has always long-

term objectives to contribute actively to the Gävle region's development. Thus, as

cooling demand is large when seen from a global perspective, it is building a

district cooling network which will be finished in a near future. In a first step, the

planned production of cold is based on refrigerant compressor technology and at

present, it is thinking of future possibilities of using absorption cooling systems

because of its low operational costs.

This way, the company wants to study the construction of district cooling

systems by absorption cooling facilities for three small islands as large customers:

city center, Hemlingby shopping centers and, finally, Kungsbäck area (university,

hospital and technological park as a whole). Power for producing cold for these


4

sites could be supplied by steams boilers at LEAF, Johannes and future

Mackmyra whisky factory respectively.

Table 1. Production sites and customers

SITE NEARBY LARGE

CUSTOMER

1) Planned biofueled ORC plant at LEAF

production site in Gävle Planned network in the central

of Gävle.

2) Planned production site of Mackmyra

whiskys in Kungsbäck HiG, Gävle general hospital and

technological park

3) Biofueled steam boiler at Johannes CHP

plant Hemlingby shopping centers

It needs to be underlined that customers and areas have been chosen

according to the possible disposal production sites. If other adequate steam boilers

were, perhaps Gävle Energi AB might think about other customer islands in the

victinity of Gävle.

1.2. PURPOSE

The aim of this thesis is to study economic and technological aspects of

absorption cooling in the three cases already presented (see Table 1.). Therefore,

it is required to decide needed size of installations in order to analyze costs and

profits.

1.3. SCOPE

A district cooling system consists of three primary components: central

plant (production), distribution system and customer system (market). The first

two will be studied, starting from technological aspects and going through

economic ones after.


5

It should be investigated the following with regards to each of the three

sites in Gävle:

- Operational conditions (maximum/minimum power, hours of operation per

year and so forth).

- Operational and investment cost of absorption system installations.

- Cost of distribution systems by only concentrating on costs of main pipes

(from production plant to customer substations).

- Most economical size of installations.

1.4. LIMITATIONS

Even though more aspects ought to be taken into account, the matters

mentioned in the scope are at focus and neither investment costs of steam boilers

nor costs regarding customer substations should be considered. On the one hand,

boilers either already exist or will be built anyway (this way, operational costs of

producing steam for absorption chillers are also not pondered because boilers are

working anyway and extra costs are negligible). On the other hand, it is very

difficult to estimate the cost of customer facilities and furthermore, they will be

the same whichever way the cold is produced (the main aim is to compare cooling

production systems).

Moreover, it has to be underlined that the research is only centred on those

three areas of the municipality.

1.5. METHOD

First of all, the issues of the thesis and reasons why they are interesting to

investigate have been analyzed. In this way, the project has been specified and

tasks for carrying it out have been defined in depth. Afterwards, a literature study


6

has been done to get enough knowledge about subjects: cooling technologies,

district cooling systems and CHP plants using biofueled steam boilers.

Secondly, in the project´s early stages, it has been got in touch with

consultants of Gävle Energi AB and experts at absorption cooling (Ramboll) and

refrigerant compressor (SWECO) technologies for gathering together information

about real installations and equipments in the market, as well as for examining

them from different points of view.

Once different parts have been understood, it has been gone ahead with the

thesis by concentrating on the real cases the investigation had to be focused on.

Like this, it has been asked for data about customers´ cooling demand (load

required), distribution distances and so on to make a first estimation of needed

size of the installations and thus, the operational conditions.

The next step has been to decide on production plant size, for later weigh

costs up. This has let profits of the new technology be known as regards extra

electricity production and use of steam for cooling production. And, to finish with

the production part, the compression installation has been compared with

absorption one and, in addition, a sensitivity analysis, which ranges over size of

equipments, costs and profits, has been done.

Last but not least, decisions regarding distribution systems have been

made and costs has been also assessed.

1.6. OUTLINE OF THE THESIS

Chapter 2 explains the existing two main cooling production systems,

refrigerant compressor and absorption technologies, but it is mainly concentrated

on absorption installations. Then, it is finished with a comparison between them

and advantages as well as disadvantages are discussed.


7

In Chapter 3 district cooling systems are presented. Section 3.1. describes

production plants shortly, that is, what cogeneration or a CHP plant is and profits

of working with them. Section 3.2. is about cooling distribution systems, which

covers both characteristics of the piping networks (Section 3.2.1.) and type of

pipes which are going to be used (Section 3.2.2.).

Chapter 4 studies thoroughly the real cases. This way, firstly it is presented

the current situation and future plans (Section 4.1.). Thereafter, it is explained

how decisions about production sites and customer areas have been made, in

addition to sum up collected data about cooling demands and estimations about

distances (Section 4.2.). Finally, data researchs and analysis regarding absorption

cooling plants are included (Section 4.3.).

In Chapter 5 the obtained results are shown. Firstly, operational conditions

and total costs of all production sites are gathered together (Section 5.1.).

Moreover, Section 5.2. presents compression and absorption cooling systems´

comparison based on the existing project at LEAF. Lastly, Section 5.3. decribes

the distribution systems and the costs they involve.

To finalize, there is the most important part: discussions and conclusions

(Chapter 6), where types of absorption chillers to be used are decided, economical

and technological aspects of the two cooling production technologies are

compared and it is reasoned out which the best solution is.

CHAPTER 2

9

Cooling system technologies

Production of cold is like considering extraction of heat. There are several

procedures that allow it, which are based on the fact that the heat can be

transferred from one to another body with a difference in temperature by

conduction and radiation. In this way, there are several procedures: chemicals,

physicals and systems that are based on phase transformation of substances.

Likewise, refrigerating machines can be classified into: adsorption, absorption,

compression and ejector machines. [3]

In industry, refrigerant compressor and absorption cooling systems are

mostly used. Refrigerant cycles for vapour compression and absorption are similar

in that both evaporate and condensate a refrigerant at different pressures to

produce chilled water. Nevertheless, a vapour compressor chiller uses a

mechanical means to compress and carry refrigerant vapour to condenser, whereas

absorption chiller establishes differential pressure depending on a thermodynamic

process that involves refrigerant and water. In addition, the energy source is

electricity for compression chillers, while it is heat for absorption ones. It bears

mentioning that there are also other heat-driven cooling alternatives, which are

ejector, desiccant and hybrid heat-driven cooling technologies.

Next stage is to study both technologies.

Chapter 2. COOLING SYSTEM TECHNOLOGIES

10

2.1. REFRIGERANT COMPRESSOR INSTALLATION

The most common cooling system used is refrigerant compressor

technology, vapour compression heat pump to be precise. It is widely used for

residential and commercial cooling, food refrigeration and automobile air

conditioning. [4]

Vapour-compression system is a work-driven cycle that is illustrated in

Figure 1. Main parts of the system are: condenser, evaporator, compressor and

expansion valve. Depending on the system, it is possible to find more accessories,

such as units to purge and valves for controlling the flow of refrigerant.

Figure 1. Refrigerant compression cycle [5]

The evaporator is a heat exchanger where refrigerant is evaporated at the

expense of cooling space. It can be either an air coil, if air is directly cooled, or a

chiller (shell heat exchanger) if it cools a liquid.

The compressor increases the pressure of refrigerant vapour, which is

coming from the evaporator, in order to rise its temperature. The cooling capacity

is regulated by varying the output of the compressor in most of the systems.


11

The condenser is a heat exchanger where high-pressure refrigerant vapour,

which is coming from the compressor, is cooled down until it is transformed into

liquid. The cooling media can be air or water; larger systems use water since it

allows reducing the condensing temperature, whereas small systems and those

with limitation of water release directly heat to the air.

Some systems can have an accumulator, which depends on evaporator and

condenser sizes and capacities, and pipes. It is actually a storage tank for liquid

refrigerant.

In this way, how a vapour-compression cycle operates can be summed up

(Figure 2.). First, input work in the compressor rises the pressure and temperature

of the refrigerant (State 2). Then, refrigerant vapour with high pressure and

temperature passes through the condenser, where it is converted into liquid by

rejecting heat to ambient air (State 3). After that, refrigerant passes through an

expansion valve where its temperature and pressure is reduced (State 4). Finally,

low-pressure liquid refrigerant is transformed into low pressure vapour in the

evaporator by absorbing heat from ambient environment (State 1). The cycle is

completed when low pressure refrigerant enters the compressor. [5]

Figure 2. Temperature-Entropy (T-s) diagram for a Vapour-Compression Refrigeration

Cycle (Source: http://www.qrg.northwestern.edu/thermo/design-library/refrig/refrig.html)

http://www/


12

It is common a temperature lift of up to 50°C between evaporator and

condenser and if water cooled chillers are used, a coefficient of performance

(COP)1 of 4,5 can be reached.

Nowadays, the most usual refrigerants are ammonia (NH3) and R134A

(CHF2CHF2).

2.1.1. COMPRESSOR AND SYSTEM EFFICIENCY

The system efficiency analysis requires compressor design and

compression process characteristics study [4]:

a. Selection of refrigerant

The potential system efficiency depends on refrigerant used.

Regarding compressors, centrifuging compressors work well at low

pressures and high specific volumes whereas alternative compressors work better

at high pressures and small specific volumes.

Likewise, refrigerant’s temperature in the condenser and evaporator

depends on cold and warm areas, which also define pressure regions. According

to the previous description, high pressure is needed in the evaporator and low in

the condenser.

1 The coefficient of performance for compression refrigerant systems is:

COPcooling = ∆Qcold /∆W

where ∆Qcold is the heat moved from the cold reservoir (to the hot reservoir) and ∆W is the work

consumed by the system.


13

Thus, refrigerant has to be selected taking into account required saturation

pressure and temperature for each particular application. Moreover, it is necessary

to consider chemical stability, toxicity, how corrosive it is and cost.

b. Flow in the compressor

The kinetic energy of the flow is influenced by its turbulence, which

entails its conversion in waste heat energy. But leakages are the main problem of

the compressor.

c. Primary energy: compressor driver

All energy input in a compression system goes into the compressor driver,

which can be an electric motor (mostly), a reciprocating engine, a gas turbine or

another machine.

2.2. ABSORPTION COOLING INSTALLATIONS

Absorption cooling cycle is similar to compression cycle, which uses a

volatile refrigerant. Refrigerant vaporizes alternately under low pressure in the

evaporator, by absorbing cooling latent heat from materia to be cooled, and

condenses at high pressure, delivering latent heat into condensing means.

The main difference between absorption and compression cycles is, as

shortly mentioned before, the motivating force that makes refrigerant to flow

through the system and provides the differential pressure required between

evaporating and condensing processes. In the absorption cycles, the compressor is

replaced by an absorber and a generator (as it is shown schematically in Figure 3.,

components to the left of the dashed Z-Z line are the same as the ones used in

compression cycles). Moreover, while energy required in compression cycles is


14

provided by compressor’s mechanical work, energy input in absorption cycles is

in the form of heat supplied directly to the generator, which is typically steam or

hot water.

Figure 3. Scheme of basic absorption cycle [5]

The system consists of four basic components: evaporator and absorber,

which are located on the low pressure side of the system, and generator and

condenser, which are located on the high pressure side. Two fluids are used,

refrigerant and absorbent. The flow of refrigerant follows the cycle condenser-

evaporator-absorber-generator-condenser, while absorbent goes from the absorber

to the generator and returns to the absorber.

The sequence of operation is as follows: high pressure liquid refrigerant

leaving the condenser passes through an expansion or restrictor device which

reduces the pressure of refrigerant before it goes into the low pressure evaporator.

Refrigerant vaporizes in the evaporator by means of absorbing latent heat of the

material being cooled and low pressure refrigerant vapour is absorbed through a

not restricted conduit to the absorber, where it is mixed in a solution together with

the absorbernt.

Refrigerant flows from the evaporator to the absorber because vapour

pressure of solution absorbent-refrigerant is lower in the absorber than vapour


15

pressure of refrigerant in the evaporator. Vapour pressure of solution absorbent-

refrigerant in the absorber determines the pressure in low-pressure side of the

system and accordingly, refrigerant´s evaporating temperature. In turn, vapour

pressure of solution absorbent-refrigerant depends on absorber’s nature,

temperature and concentration. The lower the temperature of absorbent is and, in

addition, the higher its concentration is, the pressure in the solution will be lower.

As refrigerant vapour from the evaporator is dissolved in absorbing

solution, volume of refrigerant decreases (compression) and heat is released. To

keep the temperature and vapour pressure at the required level in absorbent

solution, heat released in the absorber (which sums up latent heat of condensation

of refrigerant vapour and heat from the absorption) should be given off to

surroundings. Since the efficiency of absorber increases as the temperature of

absorbent solution decreases, it is clear that the efficiency of the absorber depends

on the temperature of refrigerant available.

When refrigerant vapour is dissolving in absorbing solution, resistance

(percentage of refrigeration) and vapour pressure of the solution is increasing.

Therefore, it is necessary to make continuously more concentrate the solution in

order to keep the vapour pressure of it low enough, just as it is required in the

evaporator. This is got by eliminating constantly the ―strong‖ absorbing solution

from the absorber and flowing again through the generator, where it is evaporated

by means of a heat source. In this way, the ―weak‖ absorbing solution is returned

to the absorber, where it absorbs more refrigerant vapour from the evaporator.

According to all this, since the absorber is in the low pressure side of the

system and the generator in the high pressure one, the ―strong‖ solution must be

pumped from the absorber to the generator and the ―weak‖ solution must be

returned through a pressure reducing valve or restrictor to the absorber.

Refrigerant is not compressed in the process of increasing its pressure, since it has

to take place in the absorber. Consequently, power required by the pump is

relatively small.


16

In the generator, solution is heated up and refrigerant is evaporated; like

that, it is separated from absorbent. Afterward, obtained high pressure refrigerant

vapour passes to the condenser, where its latent heat goes outside and it is

condensed. Finally, it is ready for starting again the cycle.

With regard to the ―weak‖ solution that remains in the generator, as before

described, it is returned to the absorber through the return pipe. Relative resistance

on the ―weak‖ solution is controlled by the amount of heat supplied to generator.

[4], [6], [7]

Once how the system works is known, it has to be underlined that

maximum efficiency in the system is attained when pressure difference between

low and high pressure sides in the system is as small as possible (by maintaining

pressure in its low side as high as possible and as low as possible in the high

pressure side). It should be remembered that the pressure in the low pressure side

is mainly determined by absorbing solution’s vapour pressure, which in turn

depends on the temperature and concentration of the solution. Since control of

temperature in the solution is limited by available temperature of refrigerant,

control in the low pressure side (evaporator) is usually obtained by means of

varying concentration of absorbing solution.

The next stage is to study whether efficiency can be improved even more.

This can be achieved by introducing a heat exchanger between the ―strong‖

solution that goes to the generator and the ―weak‖ solution (with high

temperature) that returns from the generator to the absorber. As temperature of the

solution that goes to the generator is increased, whereas it is decreased in that

which goes to the absorber, it is needed to supply the generator with less heat as

well as to cool down less in the absorber. [7]

From Figure 4. in the next page it can be seen an illustration of the

described absorption system, where streams 11-12 represent heat source (steam or

hot water), streams 15-16 cooling water, streams 17-18 district cooling water,

streams 13-14 cooling water and so forth.


17

Figure 4. Schematic of the fundamental absorption refrigeration system [8]

Furthermore, as well as in compression cycles, some gas is created in

liquid refrigerant when it goes from the condenser to the evaporator, as a result of

a pressure drop while it is passing through an expansion devise (valve).

Consequently, effect of the refrigerant is reduced. Therefore, cooling effect and

efficiency of the system would be improved if refrigerant that goes from the

condenser to the evaporator was subcooled by means of introducing a heat

exchanger between the evaporator and absorber.

2.2.1. CONSIDERATIONS FOR DIMENSIONING

ABSORPTION CIRCUITS

It is more difficult to dimension absorption systems than compression

ones. That is due to the fact that they work according to the thermodynamic

balance, which changes depending on environmental conditions. For this reason,

to determine whether instantaneous performance of certain equipments is correct,


18

it is necessary to measure periodically purity of water and saline solutions. With

this purpose, there are used instruments, such as decanting pumps, and chemical

additives are added.

Moreover, the efficiency depends on the quantity and quality of energy

consumed in the generator. Hence, for those reasons, it is very important to obtain

thermodynamic equilibrium (Qin = Qout → QE + QG = QC + QA).

2.2.2. WORKING FLUID

All absorption chillers just work as the presented basic cycle (Figure 3.),

but their design and performance are based on the used working fluids (refrigerant

and absorber). Likewise, their efficiency depends widely on (in addition to what

has been explained before) properties of the working fluid.

Desirable properties are [9]:

Large affinity between absorbent and refrigerant.

Low heat of mixing.

An absorbent with very low volatility (refrigerant vapour that goes to the

generator should contain few or nothing of absorbent).

Low pressures, close to the atmospheric pressure, to minimize leakages.

High latent heat of refrigerant, for minimizing flow rate.

The most conventional medias (refrigerant/absorbent) are water/lithium

bromide and ammonia/water. Absorption chillers working with the first ones use

water as refrigerant and lithium bromide as absorbent, whereas ammonia is the

refrigerant and water the absorbent in the second combination.


19

2.2.2.1. WATER/ LITHIUM BROMIDE (H2O/LiBr)

Lithium bromide as absorbent has the advantage of not being volatile (it is

an hygroscopic salt), so it is not needed to purify desorbed water vapour.

Nevertheless, it can crystallize easily.

The use of water as refrigerant is restricted by its freezing point. Hence, it

must be used above 0 ºC but it may be achieved up to 5ºC.

Water/lithium bromide systems are typically used for production of chilled

water for air conditioning systems in large buildings. Available sizes of these

machines range from 10 to 1500 tons and their COP2 is between 0,7 and 1,2 [5].

2.2.2.2. AMMONIA/WATER (NH3/H2O)

High volatility of water makes to be necessary the introduction of a

rectifier (reflux condenser) after the generator so that water steam that refrigerant

contains is eliminated before it goes into the condenser. Otherwise, temperature in

the evaporator is increased and consequently, cooling capacity decreases.

Moreover, it may form ice in the evaporator and expansion device.

2 The coefficient of performance for absorption cooling systems is defined as:

COPcooling = ∆Qcold /Qh where ∆Qcold is the heat moved from the cold reservoir (to the hot

reservoir), that is, the refrigeration capacity, and Qh the heating energy.


20

Figure 5. Ammonia/Water absorption cycle [5]

The mixture ammonia/water requires higher pressure and larger

temperature differences: the driving temperature is usually 140 ºC.

With regards to the temperature of refrigerant, it is allowed to use much

lower temperatures, around -60 ºC (the freezing temperature of ammonia is

-77,7 ºC).

Concentration of ammonia has to be controlled as the mixture could

become explosive if there is 15,5-27% of ammonia by volume (although

ammonia/air mixtures are barely inflammable). [10]

Ammonia/water systems are more common for small tonnages, from 3 to

25 tons, and have generally COPs of around 0,5. This way, they are usually used

in air conditioning systems. [5]

The use of ammonia as refrigerant has a large disadvantage. Toxicity of

ammonia3 makes its use not possible in no well-ventilated areas. There might not

3 Ammnois is caustic, has a pungent smell and is toxic.


21

be problems in an industry (since emissions from ammonia/water chillers could be

solved in water and, as a result, a caustic solution would be formed), but they can

be harmful to occupants in commercial and residential buildings. [11]

2.2.2.3. COMPARISON BETWEEN WATER/LITHIUM BROMIDE AND

AMMONIA/WATER SOLUTIONS

Water/lithium bromide solution has two problems mainly: it exists the

possibility of solid formation and the absorbent (LiBr) crystallizes at moderate

concentrations. Then, this mixture can be normally used only when the absorber is

water cooled, which temperature is kept by means of reconcentrating and

controlling the absorbent solution. [12]

Figure 6. Crystallization temperatures of water/lithium bromide solution against the mass

concentration of lithium bromide [12]

Thereby, temperature difference between evaporator and absorber cannot

be higher than 40°C in order to avoid risk for crystallization. If higher temperature

lifts are required, it is needed either to change chiller configuration or to use

another working pair with higher hygroscopic temperature lift. [13]

Other disadvantages regarding water/lithium bromide pair are the low

pressure (see Figure 7. and Figure 8.) that is required (improperly operated or


22

maintained units can lead to leak of atmospheric air into them) and the high

viscosity of the solution. On the contrary, it is very safe and has high volatility

ratio, affinity and stability, in addition to high latent heat. [12]

Figure 7. Maximum system pressures against the condenser temperature [12]

Figure 8. Minimum system pressures against the evaporator temperature [12]

As it can be observed from previous Figure 7. and Figure 8., operation

pressures of the ammonia/water system are higher than water/lithium bromide

ones.


23

An evaporator temperature of around 3-4°C is normal for water/lithium

bromide systems if the lowest temperature in the cooling net is 6°C [13]. A

temperature of 30°C in the absorber and condenser would be reasonable for

applications with low temperature cooling water (temperature in the condenser

will set pressure in the generator) [13].

Ammonia/water systems are more complex than the water/lithium bromide

ones (rectifier and so) and their performance depend on design parameters (it is

required higher pressure and larger temperature differences). For this reason,

construction of plants using ammonia is more expensive. Moreover, better heat

recovery means is required [12].

Next Table 2. sums up properties of both solutions.

Table 2. Absorption working fluids´ properties [14]

PROPERTY AMMONIA/WATER WATER/LITHIUM

BROMIDE

RE

FR

IGE

RA

NT

High latent

heat Good Excellent

Modearate

vapor pressure Too high Too low

Low freezing

temperature Excellent Limited application

Low viscosity Good Good

AB

SO

RB

EN

T Low

vapour

pressure

Poor Excellent

Low

viscosity Good Good

MIX

TU

RE

No solid fase Excellent Limited application

Low toxicity Poor Good

High affinity

between

refrigerant and

absorbent

Good Good


24

In this way, let´s say that water/lithium bromide systems have much less

problems and are simple to operate, although concentration of the mixture has to

be controlled to prevent crystallization. Likewise, its COP (also limited by

crystalization) is higher.

Figure 9. COP of the absorption systems against the condenser temperature (heat exchanger

efficiency 0,6) [12]

Figure 10. COP of the absorption systems against the generator temperature (heat

exchanger efficiency 0,6) [12]


25

Figure 11. COP of the absorption systems against the evaporator temperature (heat

exchanger efficiency 0,6) [12]

Even though absorption cycles are mostly based on water/lithium bromide

solutions (ammonia/water systems are unusual in the market), there are a lot of

applications where ammonia/water can be used and especially where lower

temperatures are needed. Main industrial applications for refrigeration are in the

temperature range below 0ºC, which is the field for the binary system

ammonia/water [11]. Hence, absorption systems using water as refrigerant are

commonly used for air conditioning, whereas ammonia is used in large-tonnage

industrial applications (such as food industry and slaughter houses) [12].

Consecuently, calculations of this thesis are based on water/lithium bromide

systems.

2.2.3. PRIMARY ENERGY

There are two parts that need energy supply in absorption cycles: the

generator and pump, which need heat and electricity respectively.

The required electricity represents 1-2% of the total cooling effect. With

regards to the heat, depending on how absorption chillers are fired, the system can

be:


26

Direct-fired system. Gas or another type of fuel is burned in the system.

This system is used in residential applications to produce chilled water

at 6ºC. In addition, it can supply hot water if an auxiliary heat exchanger is

introduced.

Indirect-fired system. Fuel is steam or high temperature water that comes from

a separate source such as CHP plants, geothermal, solar or waste heat. This

thesis studies these ones.

Finally, it cannot be left behind that the absorber as well as condenser are

cooled down by a refrigeration tower, which energy consumption has to be

considered. Natural water, such as water from the river, can be used instead of

cooling towers for optimizing overall efficiency of the system.

2.2.4. TYPES OF ABSORPTION CHILLERS

Although simple or single-effect absorption cycles (see Figure 5.) have

just been studied, there are more types of absorption equipments in the market.

The most common are single-effect (water/lithium bromide or ammonia/water)

and double-effect (water/lithium bromide) chillers. Nevertheless, there are

advanced H2O/LiBr cycles, such as low-temperature or half-effect chillers and

triple-effect absorption chillers (the latest ones are in development), as well as two

stage ammonia/water systems. Moreover, energy storage is possible in

water/lithium bromide systems in the form of chemical potential difference [14].

The main difference between single- and double-effect absorption chillers

is that the last ones uses two stages of lithium bromide solution reconcentration,

which increases efficiency and reduces therefore energy consumption.


27

2.2.4.1. SINGLE-EFFECT ABSORPTION CHILLERS

Single-effect absorption chillers use low-presure steam or hot water as

energy source. The typical temperature range is from 93 to 132 °C. [5]

The COP for these chillers is, depending on the model, around 0,7 [13]

(for instance, Carrier 16TJ-41 and 16TJ-42 have a COP of 0,73 and 0,72

respectively).

Figure 12. Cooling cycle schematic

(Source: Carrier-Sanyo)


28

2.2.4.2. DOUBLE-EFFECT ABSORPTION CHILLERS

Because of the relative low COP associated with single-effect machines, it

is difficult for them to compete economically with conventional vapour

compression systems except for low waste heat applications where the input

energy is free [14]. Double-effect technology, which purpose is to increase COP

of the cycle, is much more competitive.

Double-effect absorption chillers, which are also known as super

absorbers, use a second generator, condenser and heat exchanger that operate at

higher temperature. Likewise, they require higher driving heat temperature and

use steam.

Figure 13. Double-Effect Water/Lithium Bromide Absorption Chiller Schematic [5]

Schematic of double-effect machine provided as Figure 13. shows that the

cycle includes two solution heat exchangers, which represents that internal heat

exchange is achieved in practice by means of incorporating these two components

into a single transfer device [14]. Low pressure condenser and generator operate


29

at approximately the same conditions as the ones of a single-effect mahine [14].

Operating temperature and pressure of high pressure devices can be inferred from

Figure 14., which represents pressure-temperature chart schematic of double-

effect water/lithium bromide chiller.

Figure 14. Sketch for a double effect absorption heat pump in a log pressure-temperature

diagram [13]

The COP of two stages cycles is in the range of 1,0 to 1,2 [14] (for

instance, Carrier 16NK-53 has a COP of 1,42).

Design for a double-effect absorption chiller is more complex compared to

a single-effect chiller. How to connect solution circuits is one of the major design

choices: parallel or series flow are the basic options [14]. A summary of

performance of different types of double-effect technology configurations is

presented in Table 3. (results are based on the same heat exchanger sizes and

external fluid loop conditions).

Table 3. Comparison of parallel and series flow for double-effect water/lithium bromide

cycles [14]

CONFIGURATION COP CAPACITY [KW]

Parallel 1,325 354,4

Serie, high-pressure generator first 1,244 371,1

Serie, low-pressure generator first 1,238 370,2


30

As it can be seen from Table 3. in the previous page, parallel flow

configuration is the best option according to the COP. Nevertheless, capacity

favors series flow configurations.

Even though a double-effect system needs more devices than a single-

effect one, if a cooling tower is needed as a heat sink, less cooling tower capacity

is needed per unit cooling effect due to the higher COP in a double-effect chiller

[13]. Taking this into account, total system cost may be comparable to a single-

effect chiller [13].

2.3. REFRIGERANT COMPRESSOR TECHNOLOGY

VERSUS ABSORPTION COOLING

TECHNOLOGY

As it has already been said, absorption cycles have some common

characteristics with vapour compression cycles, but they differ in two important

aspects:

1. Constitution of the compression process. In absorption cooling system

vapour is not compressed between the evaporator and condenser, but

refrigerant is absorbed by a secondary substance (absorbent) in order to

form a liquid solution that is compressed to high pressure.

As the average specific volume of liquid solution is much lower

than the average specific volume of refrigerant vapour, less work is

needed. So absorption cooling systems have the advantage of, compared to

vapour compression systems, requiring less power for compression.

2. In absorption systems a means should be introduced to recover the coolant

steam from liquid solution before refrigerant enters the condenser, where it


31

is transferred heat from a source at a relatively high temperature. This

makes economic residual heat and steam that otherwise would be thrown

away untapped in environment.

Therefore, application of absorption equipments is a really interesting

alternative for decreasing electricity consumption. Furthermore, companies which

use steam in their processes have an additional advantage, since they would be

using waste or residual steam.

Heat demand in absorption systems is higher than in compression ones.

Actually, it can be, depending on evaporation temperature, more than three times

higher; nevertheless, it has to bear in mind that waste heat is often used as driving

heat. With regards to energy demand, following diagrams (Figure 15.), which

show ratios between driving energy and produced refrigeration capacity, can be

studied for making a comparison.

Figure 15. Comparison between compression and absorption technologies using ammonia as

refrigerant and cooling water with a temperature of 25 ºC [10]


32

As it can be observed from the diagrams (Figure 15.), COP for absorption

technology is much less affected by a drop in evaporating temperature. This is a

significant advantage in overall economy. [11]

Initial costs for an absorption system are higher than for a compressor one

of the same cooling capacity as:

Absorption system needs more metallic materials in heat exchangers.

Lower pressures are requiered in absorption technologies, which implies

higher diameter of tubes in order to reduce pressure losses.

Size of condenser water pump is generally a function of flow rate per unit

cooling capacity. Cooling technologies with lower COP typically require a

significantly higher condenser water flow rate and, consequently, a larger

pump too, than those technologies with higher COP. Similarly, absorption

chillers require larger cooling tower capacity than electric chillers because of

larger volume of water.

It is needed more space for absorption systems since the equipments are

bigger.

In addition, cost and volume of absorption machines increase when temperature of

the generator is low.

A compression cooling machine needs roughly 0,5 kWh of electricity for

providing 1 kWh cooling, whereas in an absorption process 1-1,2 kWh of heat is

needed for that [15]. Regarding energy costs, it works out cheaper and more

efficient to supply energy directly in form of heat than when it must go through

several stages of transformation. Undoubtedly, economical advantages of

absorption systems depend on how the driving heat is produced: it is generally not

economic when a boiler has to be installed to generate cooling, but it is an

interesting technology when waste heat or renewable energies with low price are

used, as well as when capacity of the boiler is available all the time.

If investment and running costs are taken into consideration, absorption

systems can compete against compression systems when the price of electricity is


33

from 8 to 9 times higher than the cost of heat. In CHP plants, high investment cost

of absorption machines are thwart by the more efficient use of fuel (see Table 4.).

Table 4. Energy saving with cogeneration for α 4 = 0,54

CHP

SEPARATE

ELECTRICITY

production

(condensing plants)

SEPARATE

HEAT

production

(steam boiler)

TOTAL FUEL

CONSUMPTION

FUEL

CONSUMPTION 100 73,3 63,6 136,9

EFFICIENCY 0,88 0,42 0,9

ELECTRICITY

PRODUCTIOIN 30,8 30,8 ―

HEAT

PRODUCTION 57,2 ― 57,2

During warm periods, heat in excess in CHP plants decreases electricity

production, since those plants are dimensioned for the heating demand in winter

and hot water is only needed in summer. On the contrary, cooling demand

increases in summer, so it takes the advantage of using the excess of heat for

cooling systems.

Finally, operation and maintenance can be mentioned. The most important

part in compression systems is compressor´s work, whereas it is the equilibrium

obtained by thermodynamic effects in absorption systems. For this reason,

operating with absorption technologies is more complicated (see Section 2.2.1.).

In this way, to sum up, absorption refrigeration systems´ operating

characteristics can be listed [10]:

- It is driven by ―economic‖ heat (waste or ―free‖ heat) and it has low

consumption of electricity.

- Simple design and maintenance (no moving machinery).

- Long service life.

- It is reliabiled, then it is more available.

- Environmentaly ―friendly‖ working media (in addition, it is easy to

clean effluent gases) and oil-free refrigerant. It is very clean and heat

4 Electric-thermal ratio: α = Wel/Qheat = ηel/ηt where Wel is the electrical power output, Qheat is the

useful thermal power output, ηel is the electrical efficiency and ηt is the thermal efficiency.


34

transfer resistances due to contamination are not produced. In addition,

carbon dioxide emissions are reduced at the same time.

- Low noise level and there is no vibrations.

The earliest three characteristics are the most important criteria when comparing

absorption systems with vapour compression systems.

To finish with cooling technologies, Table 5. summarizes their

characteristics and Table 6. makes a short comparison between them.

Table 5. Summary of characteristics for cooling options [13]

TECHNOLOGY COP

(cooling) COPel

5

DRIVING HEAT

TEMPERATURE

[°C]

SCALE

[kWcooling]

Conventional (Single-effect)

H2O/LiBr absorption chiller 0,7 20-50 120 >250

Double-effect

H2O/LiBr absorption chiller 1,2 15-40 150-170 >350

NH3/H2O absorption chiller 0,5 10-25 >100 ―

Vapour compression chiller ― 1-5 ― ―

Table 6. Comparison between two 1000kW chillers [10]

5 It only includes the chiller electricity consumption for absorption systems

CHAPTER 3

36

District Cooling System

Distrist cooling system or technology delivers coolant, commonly chilled

water, from a central refrigeration plant to multiple buildings through a

distribution network. At each connection point of the distribution mains, energy is

delivered to the terminal devices at the user premises to meet their space/process

cooling requirements [1].

District cooling system is mainly made up of three components: cooling

production plant, distribution network and building substations.

Figure 16. Components of district cooling systems

Figure 17. District cooling system (or district heating system

6) [15]

6 The same concept applies when it comes to district heating systems.

Chapter 3. DISTRICT COOLING SYSTEM

37

District energy systems enable to use energy in a more efficient way and

reduce greenhouse gas emissions because, on the one hand, it is used a central

refrigeration plant instead of many small machines which are less efficient and, on

the other hand, it is produced electricity for the central grid that can replace other

electricity sources such as coal-fired plants.

3.1. PRODUCTION

3.1.1. COGENERATION. BENEFITS WITH INTEGRATION

OF COOLING TECHNOLOGY

Cogeneration (combined heat and power, CHP) is the use of a power

station for simultaneous generation of both electricity and useful heat

(conventional power plants produce but not use a large amount of heat). That is, it

is an energy conversion technology where two separate systems are integrated

together by a cascade of thermal energy [14]. Thus, it can be led to increase the

system performance7 by designing systems that can use the heat: the efficiency of

energy production can be increased from current levels that range from 35% to

55%, to over 80% [16]. In addition, some of the obligatory heat rejection is at a

high enough temperature to supply energy for comfort heating and cooling.

Figure 18. An schematic of cogeneration process that shows the consumed and produced

power in the whole system [15]

7 Overall efficiency: ηtot = ηel + ηt = We/Qfuel + Qheat /Qfuel = (Wel + Qheat)/Qfuel

It is also called energy utilization factor, EUF.

http://en.wikipedia.org/wiki/Power_station



http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Heat


38

Figure 19. Illustration of a CHP plant connected to a district heating network

(Source: Gävle Energi AB)

This way, shopping malls and blocks of business, university and collages,

hospitals, industries and so forth take the advantage of the economic benefits

provided by a central plant, through the use of boilers that produce hot water or

steam for heating and vapour compression or steam-driven absorption

refrigeration machines that produce chilled water for cooling.

Table 7. Different types of plants using a steam boiler and their characteristics

HEATING CONDENSING

BOILER

Flexible, low operating and investment costs

No full use of all heat in the fuel

CHP plant

(BIOFUELED STEAM BOILER)

Heat and electricity production

Full use of heat in the fuel

TRIGENERATION plant

(BIOFUELED STEAM BOILER)

Heat, electricity and cooling production

Energy Export → CO2-negative

"Free" energy

There is only one requirement for the integration of two technologies:

temperature of available heat from one system must be adequate to fulfil

requirements of the mating system. The source of energy for district energy

systems is usually a steam boiler, which is fired, in the cases to be considering in

this thesis, by biofuel.


39

3.2. COOLING DISTRIBUTION SYSTEM

3.2.1. PIPING NETWORK

Flow in cooling (as well as in heating) distribution systems varies with the

load, so the flow through each substation is regulated by two-way control valves.

The reasons for this are mainly to lower pumping costs and to increase the

difference between supply and return temperatures, which affects the efficiency of

the whole system [15]: a higher supply and return temperature differential is able

to lower the distribution pump power consumption, but will increase the heat loss

at pipe surfaces [17]. Consequently, a high return temperature is preferable in

district cooling system. This way, forward temperature is roughly 6 °C and return

temperature is alternatively between 12 and 16 °C.

Anyway, distribution losses can be almost always neglected in district

cooling systems since temperature difference between outdoor and forward water

is very low and the resistances are therefore despised. For this reason, there is not

needed, unlike in district heating, to insulate the pipes. This makes cooling

distribution systems cheaper than heating ones.

Control valves must regulate the flow, but the pressure too. The available

differential pressure becomes lower at substations which are furthest away in the

system (because of greater pressure drops caused by the increased flow in the

distribution system) and it might not be enough for the required flow. Hence,

either another pump has to be used or the speed of the existing one has to be

increased to maintain the differential pressure. [15]


40

3.2.2. MATERIALS FOR THE PIPES

There are different types of pipes depending on the application (pressure,

gravity, drainage and so on). In this case, pressure pipe systems are studied.

There are polyethylene (PE), polypropylene (PP), PVC and PEX pipes, in

addition to steel and cooper ones. For water applications, PE pipes are widely

used because their quality is high and they are economic at the same time. This

way, polyethylene pressure pipes offer the following benefits:

- Cost saving with faster installation

- Long life time and maintenance free

- Suitability for renovation

- Corrosion resistance

- Flexibility (it allows ground movement)

- Joint thightness

Plastic pipes are much cheaper than, for instance, steel ones. As the last

ones are widely used in district heating systems, let´s say that the material for

cooling pipes is less costly. Likewise, construction of networks works out cheaper

than as appropiate for district heating pipes.

CHAPTER 4

42

Process

4.1. GATHERING OF INFORMATION ABOUT

EXISTING INSTALLATIONS AND PRESENT

SITUATION

4.1.1. STEAM BOILERS AT LEAF AND KAPPA

There is an oil steam boiler at LEAF

8 nowadays, which has a maximum

capacity of 5 MW and produces satured vapour at 8 bar. The average power it

operates is 2 MW all over the year except for 48 h at Easter.

In addition, there is Kappa paper mill close to that boiler, which has

another oil boiler of 2 MW and produces steam at 12 bar for 80 hours per week9.

In this way, Bionär10

is thinking about building a new biofueled steam

boiler which would replace those two11

. It is wanted to make the most of that and

it is therefore planning to produce electricity too. Ramboll consultancy has

considered building a biomass fired CHP plant based on Organic Rankine Cycle

(ORC), as a low capacity boiler to produce needed steam at roughly 70 bar (which

requires a sophisticate water purification system) and a turbine are much more

expensive.

8 It is a factory which is located in Gävle and produces confectionery, candy and pastilles. 9 It is working 5 days/week, not at weekends, and 16h/day, not during night. 10 It is a subsidiary of Gävle Energy AB, which owns the 45%. One of the customers of Bionär is

LEAF. 11 Although the operating times of the boilers are different, the new boiler can work at 2 MW

during the day and increase its capacity during the night, when it can be produced the steam

which is needed in the paper mill during the day (storage in accumulator vessels).

4. PROCESS

43

Figure 20. ORC plant in biomass based cogeneration system

(Source: http://www.turboden.it/en/products.asp)

ORC units have high overall energy efficiency: 20% of the thermal power

is transformed into electric power, while 78% remains as steam. Nowadays, it is

planning to build a TURBODEN 14 CHP plant that costs 5 300 000 SEK and

which performance is 1,26 MW of net active electric power and 5,35 MW of

steam (α = 0,23), with a biomass consumption of 7,63 MW.

.

Figure 21. Energy efficiency of ORC units in cogeneration applications

(Source: http://www.turboden.it/en/products.asp)

Gävle Energi AB, as knows of this project, might take the opportunity to

use this installation turning it into a trigeneration plant by means of introducing an

absorption cooling system that would use the steam produced in it. Hence, it is

needed an even bigger ORC unit and to make a decision about it is one of the

tasks of this project.

4. PROCESS

44

4.1.2. BIOFUELED JOHANNES CHP PLANT

Johannes CHP plant (Figure 22.), which is owned by Gävle

Kraftvärme AB12

, is located in the south of Gävle, exactly in Johannesbergsvägen.

Figure 22. Johannes CHP plant before 2003 (Source: Gävle Energi AB)13

The steam boiler was built in 1999, which aim is to produce heat to deliver

in the district heating network of the municipality. It is a Bubble Fluidized Bed

(BFB) boiler and has a maximum capacity of 77 MW, whereas the minimum

power output is 20 MW.

Johannes is not able to fulfil the heating demand of Gävle in winter, so

waste heat is bought from Korsnäs pulp and paper mill in Gävle for distributing it

in the system. In summer time, when the demand decreases noticeably (as it is

only needed for hot water), the steam coming from Korsnäs is enough to meet

customer requirements and therefore, the boiler at Johannes is shut down (in other

periods, its power output is reduced). Last year (2008) the plant was operating

6500 hours continiously (24 h/day), which means that it was stopped roughly

95 days during summer.

In 2003 a backpressure turbine of 22 MW was introduced, turning this way

the installation into a cogeneration plant. This enables to increase profits to great

extends; actually, the company makes money from electricity, although its

12 It owns all production facilities in Gävle Energi AB but it is owned 100% by Gävle Energi AB. 13 The turbine is missing since it was introduced in 2003.

4. PROCESS

45

production has to be managed according to the heating demand of the

municipality.

Taking into consideration average values, 320 GWh of steam are

produced, which entails 406,4 GWh of biofuel consumption. With regards to

electricity, the production is around 97 GWh (as α value is 0,29), which means a

large profit.

Figure 23. Production of heat (for District Heating) and electricity at Johannes

The next challenge could be to introduce an absorption cooling plant and

Johannes would have to do with a trigeneration, which would be able to fulfil the

cooling demand in the shopping centers (Hemlingby) close to that by means of a

distribution system. Furthermore, electrically driven refrigeration devices that are

mainly used for the turbine could be replaced. And last but not least, the boiler

could be kept running almost the whole year with a large income because of the

electricity produced (there are possibilities to increase electricity output by

increased heat load from heat-driven chillers, especially in June-August. See

Figure 23.)

For more information about Johannes CHP plant, see Appendix 7.

4. PROCESS

46

4.1.3. MACKMYRA

Nowadays, Mackmyra Svensk Whisky is located in Valbo, at the outskirts

of Gävle. There is an electric boiler with a capacity of 850 kW that operates

continuously all over the year14

, which is owned by Bionär.

Figure 24. Existing electric boiler in Mackmyra (Source: Gävle Energi AB)

According to an already approved project, a new plant, Mackmyra

Whiskyby, will be probably built with a bigger production capacity. It is planned

to be in Western Kungsbäck, just at the west of the central Gävle and few

kilometers from the existing distillery, and it will be built in several stages,

starting in the second half of this year (2009).

A bigger distillery entails, among other things, the necessity of a bigger

boiler. Thus, it has been proposed to replace the electric boiler by a biofueled

boiler with capacity doubled so that it could be turned into a cogeneration plant by

introducing a turbine. This means that, in addition to produce steam needed in the

factory, profits would be increased because of electricity output.

It could be even thought about a bigger boiler and a third step could take

place. As well as for LEAF, Gävle Energi AB might turn it into a trigeneration

plant where cold would be produced by firing absorption cooling machines with

steam. It is estimated that it would be needed a ten times bigger boiler;

14 ≈ 8760 h/year. It is only switched off because of breakdowns and maintenance.

4. PROCESS

47

nonetheless, it will be calculated according to the cooling demand in that site of

the victinity.

Figure 25. Existing and planned boilers at Mackmyra (different stages)

4.1.4. REFRIGERATION COMPRESSOR COOLING

PROJECT

The refrigerant compressor cooling project, which plans to fulfil the

cooling demand in the city center by producing chilled water at LEAF and

delivering it by district system, is being built now and it is thought the first stage

will be finished for next summer (2009). Nowadays, there is only one customer,

which has a cooling demand of roughly 250 kW.

The drafts of installations and equipments needed are in Appendix 1.

According to the calculations, that can be also seen in Appendix 1., the investment

cost for the installation is 22 629 000 SEK, which has a pay-back time of

approximately 10 years. There are needed roughly 4 240 675 kWh of electricity

per year for running the whole installation, which means 4 240 675 SEK per year,

and there are produced 7 142 836 kWh of cooling per year by means of

compression technology. With regards to the maintenance costs, those are time

dependant and 170 000 SEK for the first year (see Section A1.4. in Appendix 1.).

This way, the total cost of the system for ten years is 66 204 500 SEK.

4. PROCESS

48

4.2. GATHERING OF DATA: CUSTOMERS. LOAD

REQUIRED AND DISTANCES

Once different existing possibilities of building absorption cooling systems

have been studied, two small islands with future large district cooling customers

have been defined: Hemlingby shopping centers in Johannesbergsvägen and

Kungsbäck area, which would comprise the university (Högskolan i Gävle),

hospital (Gävle Sjukhus) and technological park (Teknikparken). This way, the

production sites would be Johannes and planned new Mackmyra whisky factory.

Moreover, the city center is also subject of investigation, so that it is the

third island, which cooling demand could be supplied by introducing absorption

chillers at LEAF. Then, it will have to be studied if it is economic to replace the

compression refrigeration plant.

4. PROCESS

49

Figure 26. Three cooling production and customer sites and main pipes

4. PROCESS

50

Next Table 8. shows different cooling demands for the planned three

production sites (see Appendix 2.).

Table 8. Cooling load demand at each site

PRODUCTION

SITE/AREA

CUSTOMER

COOLING

DEMAND

[MW]

LEAF/CITY CENTER

LEAF 2,5

CITY CENTER 9,0

11,5 TOTAL

MACKMYRA/

KUNGSBÄCK

MACKMYRA ± 0

HOSPITAL 1,7

UNIVERSITY 1,8

TECHNOLOGIC PARK 1,0

5,0 TOTAL

JOHANNES/

JOHANNESBERGSVÄGEN

JOHANNES 1,4

HEMLINGBY SHOPPING

CENTERS 2,0

3,4 TOTAL

Regarding distribution systems, as it can be seen in Appendix 4., the main

pipe in the city center is 1370 meters long. Far away from the city center,

Johannesbergsvägen area is and, according to the estimations (see Appendix 4.),

there are 1775 m between the plant and the buildings that need cooling. The third

and last area is Kungsbäck, where it would be needed a pipe from Mackmyra to

the hospital, 2390 m, and to the university too, 810 m; nonetheless, it could be

used the same pipe for both of them in the first 500 meters (see Appendix 4.).

4. PROCESS

51

4.3. ANALYSIS OF ABSORPTION COOLING PLANTS

4.3.1. ABSORPTION CHILLERS

Next task is to study the absorption cooling machines to be used. There are

mainly two options, starting with a premise that they have to be steam-fired:

single- and double-effect steam-fired absorption chillers. The difference between

them is that the double-effect has two generators, thus a better COP and higher

cost, roughly from 2 to 2,5 times the price of the single-effect.

Single-effect absorption chillers are designed for using available low

sature pressure waste steam (100-150 kPa), so they are a recovery solution. With

regards to double-effect chillers, they use satured steam at around 500-800 kPa. In

this context, as mentioned before (Section 2.2.2.3.), water/lithium bromide units

are only considered

Following Table 9. and Table 10. gather information about different

possible installations (calculations and specifications are in Appendix 3.). Even

though chillers with highest cooling capacity have been considered, they cannot

cover the cooling demand and therefore, it is necessary to add several units in

parallel.

Table 9. Possibilities to fulfill the cooling demand in the city center by using steam-fired

absorption chillers

PRODUCTION

SITE

DOUBLE-EFFECT STEAM-

FIRED ABSORPTION

CHILLER: TSA-16NK- 81

SINGLE-EFFECT STEAM-

FIRED ABSORPTION

CHILLER: TSA-16TJ- 53

NUMBER OF CHILLERS NUMBER OF CHILLERS

LEAF 3 5

4. PROCESS

52

Table 10. Possibilities to fulfill the cooling demand in Kungsbäck by using steam-fired

absorption chillers

PRODUCTION

SITE

DOUBLE-EFFECT STEAM-

FIRED ABSORPTION

CHILLER: TSA-16NK- 81

SINGLE-EFFECT STEAM-

FIRED ABSORPTION

CHILLER: TSA-16TJ-53

NUMBER OF CHILLERS NUMBER OF CHILLERS

MACKMYRA 2 2

At first, it was focused on steam-fired machines for being more efficient.

Nonetheless, it has been deduced it is not possible their use at Johannes plant from

the analysis of steam streams. During summer, when the boiler is at its minimum

capacity nowadays, the pressure of the steam leaving the turbine is lower than

1 bar (see Table A3. 1.), which is the minimum pressure required for satured

steam needed in single-effect steam-fired absorption chillers. It would be possible

to use high-pressure super-heated steam that enters the turbine (see Figure A3. 1.);

however, it is not an interesting alternative as electricity production would be

therefore reduced (it would mean going down in profits). As a result,

water/lithium bromide single-effect hot water-fired absorption chillers have been

studied (Table 11.).

Table 11. Possibilities to fulfill the cooling demand corresponding to Johannes plant

PRODUCTION

SITE

SINGLE-EFFECT HOT WATER-FIRED

ABSORPTION CHILLER: TSA-16LJ- 53

NUMBER OF CHILLERS

JOHANNES

2

4.3.1.1. STUDY OF OPERATIONAL CONDITIONS

Cooling demand changes during the year mainly because of climatic

conditions (time period). Despite total or maximum cooling demand is only

known, an estimation can be made for the whole year (see Section A3.3.,

Appendix 3.):

4. PROCESS

53

Table 12. Cooling that should be produced for different sites during the year

TIME PERIOD

COOLING

POWER PRODUCTION [kW]

LEAF MACKMYRA JOHANNES

Winter time: 15 November-15 March 895 389 1556

15 March-1 April & 1-15 November 3512 1527 2011

April & 15 October-1 November 4683 2036 2214

1-15 May & 15 September-15 October 6749 2934 2574

15 May-15 June & 15 August-15 September 9779 4252 3101

Summer time: 15 June-15 August 11500 5000 3400

Figure 27. Cooling power to be produced in different sites during the year

In winter the cooling demand is very low. Hence, there is no need for

producing cooling at LEAF (899 kW) and Mackmyra (389 kW) due to the fact

that free cooling is allowed in this time of the year15

. With regards to Johannes

(1556 kW), there is no river around the plant, so it is necessary to fulfil the

demand in another way. As heat demand is the highest in winter, produced hot

water cannot be used for firing absorption chillers (all heat ought to be delivered

in the district heating network) and consequently, the best solution would be to

use the already existing cooling and HVAC systems in Hemlingby and Johannes

during winter.

15 The river is far away from Mackmyra production site but the customers (university and

hospital) are quite close to it. Therefore, it is possible to introduce heat exchangers there for

free cooling in this area.

4. PROCESS

54

4.3.2. THE REST OF EQUIPMENTS

Figure 28. Typical piping diagram of an absorption system (Source: Carrier-Sanyo)

The operation of chillers needs additional devices and equipments:

- Cooling towers.

- Chilled water pumps and cooling water pumps for each chiller.

- Strainier, pressure gauge and drain trap, which should be near the steam inlet,

for each chiller.

- Air vent valve in each of the chilled and cooling water lines.

- Shut-off valve to prevent the steam flow into the chiller during shut-down.

- Etc.

Necessary pumps, valves, pipes, etc. inside production installations cannot

have been calculated because of limited provided information. Thus, same

investment and operational costs (power input) as for absorption cooling project

which has just been built in Falun (see Appendix 6.) have been considered.

Regarding cooling towers, they produce cold water for cooling down

absorbers and condensers inside the chillers and their size is decided according to

the required cooling power. This equipment can be replaced by a heat exchanger

at LEAF, as water from the river is cold enough.

4. PROCESS

55

Lastly, there are two more heat exchangers which are planning to be used

for free cooling at LEAF and Mackmyra in winter time.

Specifications about cooling equipments (cooling towers and heat

exchangers) are gathered together in Table A3. 8. (Appendix 3.).

CHAPTER 5

57

_ Results

5.1. PRODUCTION PLANTS

5.1.1. LEAF

5.1.1.1. OPERATIONAL CONDITIONS

Table 13. Power and steam demand of different chillers sets for the required cooling load at LEAF during the year

16 Operation hours data are taken from Anders Kedbrant estimations, Table A1. 15. (Appendix 1.), for all calculations because of lack of information.

TIME PERIOD

NUMBER OF

CHILLERS

WORKING

COOLING LOAD16

[MWh]

POWER SUPPLY

TO CHILLERS

[MWh]

STEAM SUPPLY

TO CHILLERS

[MWh]

16NK-81 16TJ-53 FREE

COOLING

ABSORPTION

COOLING 16NK-81 16TJ-53 16NK-81 16TJ-53

15 November-15 March — — 862,78 — — — — —

15 March-1 April & 1-15 November 1 2 — 856,93 2,62 1,72 750,96 1412,95

April & 15 October-1 November 1 2 — 1704,61 3,90 2,56 1483,92 2811,27

1-15 May & 15 September-15 October 2 3 — 2902,07 9,22 4,54 2543,56 4785,81

15 May-15 June & 15 August-15 September 3 4 — 6571,49 21,61 9,46 5759,41 10836,57

15 June-15 August 3 5 — 8487 23,73 12,99 7438,75 13993,87

TOTAL [MWh/year] 862,78 20 522,10 61,08 31,27 17 976,60 33 840,46

5. RESULTS

58

Table 14. Biofuel (for producing steam), electricity and water consumption. LEAF

16NK-81 16TJ-53 TOTAL BIOFUEL CONSUMPTION

17 [GWh/year] 25,71 48,39

ELECTRIC POWER

SUPPLY [MWh/year]

CHILLERS 61,08 31,27

REST OF THE PLANT18

450,82 TOTAL 511,91 482,10

5.1.1.2. COSTS

5.1.1.2.1. INVESTMENT COSTS Table 15. Investment costs [SEK] for LEAF

3 ABSORPTION CHILLERS

TSA-16NK- 81 (CARRIER-SANYO) 3 * 6 200 000

5 ABSORPTION CHILLERS TSA-16TJ- 53

(CARRIER-SANYO) 5 * 2 700 000

BACK-UP COMPRESSOR CHILLER 19

YRTBTBT0550C (YORK) 600 000

BACK-UP COMPRESSOR CHILLER


3 HEAT EXCHANGERS

S121-IS10-502-TMTL47-LIQUIDE (Sondex)

+

FILTERS BSG350/1,0P (Bernoulli)

3 * 619 000 5 HEAT EXCHANGERS (+ FILTER)

MX25-MFMS (Alfa Laval) 5 * 550 000

HEAT EXCHANGER (+FILTER)

TL10-BFG 120 000

HEAT EXCHANGER (+FILTER)

TL10-BFG 120 000

REST OF THE INSTALLATION20 1 450 000 REST OF THE INSTALLATION 1 450 000

TOTAL [SEK] 22 627 000 TOTAL [SEK] 18 420 000

NOTE: all specifications are in Appendix 3.

17 Biofuel consumption in the ORC CHP plant (TURBODEN 14) = 1,43 MW biofuel/MW steam 18 Reference: Falun Cooling Project (see Appendix 6.).

Considered operation hours = chiller´s operation hours. It is known that submersible pumps for the whole installation are working the whole year

but data about them is missing.

It has been assumed the same for both Mackmyra and Johannes production plants. 19 The considered back-up chiller is the one planned for compression refrigeration project (VKA3). It is only considered its investment cost as it is not

usually running (it is just started up because of breakdowns and when the cooling demand is higher than the expected one). Calculations for

Mackmyra and Johannes production sites are also based on the same compressor. 20 Reference: Falun Cooling Project (see Appendix 6.).

It has been assumed the same for both Mackmyra and Johannes production plants.

5. RESULTS

59

5.1.1.2.2. OPERATIONAL COSTS

Table 16. Operational costs at LEAF

21

16NK-81 16TJ-53 BIOFUEL [SEK/year]

-165 SEK/MWh-22 4 241 579,13 7 984 657,3

ELECTRICITY [SEK/year] - 1 SEK/kWh-

511 906,24 482 095,36

TOTAL [SEK/year] 4 753 485,4 8 466 752,7

5.1.1.2.3. TOTAL COSTS

PAY-BACK time of the equipments (chillers, pumps, etc.) is roughly 10

years (the investment is recovered approximately after ten years). Thus, costs are

calculated for this period of time:

Table 17. Total costs of LEAF absorption cooling plants for 10 years

16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 22 627 000 70 164 854

18 420 000 103 087 527

OPERATING 47 534 854 84 667 527

PROFITS: ELECTRICITY

PRODUCTION [SEK]

- 770 SEK/MWh-23

- 31 836 561 - 59 931 460

TOTAL [SEK] 38 328 293 43 156 067

Maintenance costs are very low because there are few components that

demand maintenace and there is just cleaning work mainly. As a result, these

costs can be neglected.

21 Operational costs of producing steam are not considered as explained in Chapter 1

(Limitations). 22 Biofuel price was 150 SEK/MWh in 2008. As it is rising all the time, it has been considered

10% more expensive for the future. 23 Electricity selling price to the grid was 700 SEK/MWh in 2008. As it is rising all the time, it has

been estimated that profits are 10% larger in the future.

Electricity selling price is made up of two major parts: actual electricity (MWh) delivered

into the electrical grid (400 SEK/MWh) + green certificates, GCs (1 MWh = 1 certificate;

300 SEK/MWh).

5. RESULTS

60

Next graph, Figure 29., compares all costs for different chillers sets at

LEAF.

Figure 29. Graph that shows the breakdown of total costs for 10 years at LEAF

After ten years, there are only operational costs, which are lower for

16NK-81 chillers set. If profits due to electricity production are taken into

account, costs for fulfilling customer’s demand in the city center will be

1 569 829 SEK/year and 2 473 607 SEK/year for 16NK-81 and 16TJ-53 chillers

set installations respectively.

5. RESULTS

61

5.1.2. MACKMYRA


Table 18. Power and steam demand of different chillers sets for the required cooling load in Mackmyra production during the year

Table 19. Biofuel (for producing steam), electricity and water consumption. Mackmyra

16NK-81 16TJ-53 TOTAL BIOFUEL CONSUMPTION

24 [GWh/year] 11,18 20,90

ELECTRIC POWER

SUPPLY [MWh/year]

CHILLERS 34,15 15,09

COOLING TOWERS (fans) 26,32 43,49

REST OF THE PLANT 450,82 TOTAL 511,30 509,40

TOTAL WATER FOR COOLING TOWERS [m3/year] 37 147,6 34 148,2

24 It has been assumed that the biofuel consumption in the future boiler at Mackmyra is the same as in the one at LEAF, as the boiler might be small

and its efficiency is not therefore very high.

TIME PERIOD

NUMBER OF

CHILLERS

WORKING

COOLING LOAD [MWh]

POWER SUPPLY

TO CHILLERS

[MWh]

STEAM SUPPLY

TO CHILLERS

[MWh]

16NK-81 16TJ-53 FREE

COOLING

ABSORPTION

COOLING 16NK-81 16TJ-53 16NK-81 16TJ-53

15 November-15 March — — 375 — — — — —

15 March-1 April & 1-15 November 1 1 — 372,59 2,62 0,86 326,51 614,35

April & 15 October-1 November 1 1 — 741,10 3,90 1,28 649,46 1221,98

1-15 May & 15 September-15 October 1 2 — 1261,62 4,61 3,03 1105,60 2080,23

15 May-15 June & 15 August-15 September 1 2 — 2857,34 7,20 4,73 2503,99 4711,36

15 June-15 August 2 2 — 3690 15,82 5,20 3233,68 5989,37

TOTAL [MWh/year] 375 8922,66 34,15 15,09 7819,23 14 617,29

5. RESULTS

62

5.1.2.2. COSTS

5.1.2.2.1. INVESTMENT COSTS

Table 20. Investment costs [SEK] for Mackmyra


TSA-16NK- 81 (CARRIER-SANYO) 2 * 6 200 000

2 ABSORPTION CHILLERS TSA-16TJ- 53

(CARRIER-SANYO) 2 * 2 700 000





2 COOLING TOWERS

OCT09HB05-5-90 (Vestas Aircoil) 2 * 1 595 000

2 COOLING TOWERS

OCT09HB03-3-120 (Vestas Aircoil) 2 * 998 000

HEAT EXCHANGER (+ FILTER)

TL6-BFG 60 000

HEAT EXCHANGER (+ FILTER)

TL6-BFG 60 000

REST OF THE INSTALLATION 1 450 000 REST OF THE INSTALLATION 1 450 000

TOTAL [SEK] 17 700 000 TOTAL [SEK] 9 506 000


Table 21. Operational costs in Mackmyra production site

16NK-81 16TJ-53 BIOFUEL [SEK/year]

-165 SEK/MWh- 1 844 948,48 3 448 948,8

ELECTRICITY [SEK/year]

- 1 SEK/kWh- 511 296,31 509 404,38

WATER [SEK/year]

- 4 SEK/m3- 148 590,4 136 592,8

TOTAL [SEK/year] 2 504 835,19 4 094 945,98

5. RESULTS

63



16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 17 700 000 42 748 352

9 506 000 50 455 460

OPERATING 25 048 352 40 949 460


PRODUCTION [SEK]

- 770 SEK/MWh-25

- 9 031 216 - 16 882 966

TOTAL [SEK] 33 717 136 33 572 494

Next graph, Figure 30., compares all costs for different chillers sets in

Mackmyra production site.

Figure 30. Graph that shows the breakdown of total costs for 10 years

in Mackmyra production site

After ten years, if profits due to electricity production are taken into

account, costs for fulfilling customer’s demand in Kungsbäck area will be

25 Assumption: α = 0,15. It has to be quite smaller than for Johannes (α = 0,29) since the boiler is

smaller and works at lower pressure. The smaller the boiler is, the lower the efficiency is.

Moreover, the lower pressure in the boiler is, the lower electricity production is (α value

depends mainly on the pressure of the boiler).

5. RESULTS

64

1 601 714 SEK/year and 2 406 649 SEK/year for 16NK-81 and 16TJ-53 chillers

set installations respectively.

5.1.3. JOHANNES


Table 23. Power and hot water demand of chillers set for the required cooling load at

Johannes during the year

5.1.3.2. COSTS

Table 24. Biofuel (for producing steam), electricity and water consumption. Johannes

26 Biofuel consumption in Johannes = 1,27 GWh biofuel/GWh steam 27 HVAC systems´cooling factor: COP =cooling/(electricity to compressor) = 2-3. As the systems

are not new and operational conditions are unknown, COP = 2 has been considered.

TIME PERIOD

NUMBER OF

16LJ-53

CHILLERS

WORKING

ABSORPTION

COOLING

LOAD [MWh]

POWER

SUPPLY TO

CHILLERS

[MWh]

HOT

WATER

SUPPLY TO

CHILLERS

[MWh]

15 November-15 March — — — —

15 March-1 April

1-15 November 2 490,68 1,72 733,84

April

15 October-1 November 2 805,90 2,56 1204,65

1-15 May

15 September-15 October 2 1106,82 3,03 1654,47

15 May-15 June

15 August-15 September 2 2083,87 4,73 3115,98

15 June-15 August 2 2509,2 5,20 3750,75

TOTAL [MWh/year] 6996,47 17,23 10459,69

16LJ-53 TOTAL BIOFUEL CONSUMPTION

26 [GWh/year] 13,28

ELECTRIC POWER

SUPPLY [MWh/year]

CHILLERS 17,23

HVAC systems (winter time)27

749,99

COOLING TOWERS (fans) 36,50

REST OF THE PLANT 450,82 TOTAL 1254,55

TOTAL WATER FOR COOLING TOWERS [m3/year] 28 753,8

5. RESULTS

65

5.1.3.2.1. INVESTMENT COSTS

Table 25. Investment costs [SEK] for Johannes


TSA-16LJ- 53 (CARRIER-SANYO) 2 * 2 700 000



2 COOLING TOWERS OCT09HB02-2-120 (Vestas Aircoil)

2 * 675 000

REST OF THE INSTALLATION 1 450 000

TOTAL [SEK] 8 800 000


Table 26. Operational costs in Johannes production site

16LJ-53 BIOFUEL [SEK/year]

-165 SEK/MWh- 2 191 828,57

ELECTRICITY [SEK/year] - 1 SEK/kWh-

1 254 551,77

WATER [SEK/year]

- 4 SEK/m3- 115 015,2

TOTAL [SEK/year] 3 561 395,54


Table 27. Total costs of Johannes absorption cooling plant for 10 years

16NK-81

TOTAL

COSTS [SEK]

INVESTMENT 8 800 000 44 413 955

OPERATING 35 613 955


PRODUCTION [SEK]

- 770 SEK/MWh-

- 23 356 493

TOTAL [SEK] 21 057 462

Next graph, Figure 31., shows all costs for 10 years in Johannes

production site.

5. RESULTS

66

Figure 31. Graph that shows the breakdown of total costs for 10 years

in Johannes production site

After ten years, if profits due to electricity production are taken into

account, costs for fulfilling customer’s demand in Johannesbergsvägen area will

be 1 225 746 SEK/year.

5. RESULTS

67

5.1.4. SENSITIVITY ANALYSIS

Apart from studying different production sites according to possible

customers´ demand, a sensitivity analysis28

, which ranges over size of absorption

units and other equipments, costs and profits, has been carried out for when the

cooling demand is both ten percent higher and lower than the estimated one.

5.1.4.1. LEAF

When cooling demand is 10% higher, one more 16 TJ-53 single-effect

absorption chiller is needed at LEAF. Hence, one more MX25-MFMS (Alfa Laval)

heat exchanger for cooling down single-effect chillers set (with six chillers in

parallel) has to be introduced too. Furthermore, it cannot be left behind that

cooling load is also higher in winter time (1012,7 kW).

Next Table 28. and Table 29. gather together new operational conditions

and total costs respectively.

Table 28. Operational conditions of different chillers sets at LEAF during the year when the

cooling demand is 10% higher than the estimated one

Table 29. Total costs of LEAF absorption cooling plants for 10 years when the cooling

demand is 10% higher than the estimated one

16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 22 627 000 75 758 141

21 670 000 124 300 077

OPERATING 53 131 141 102 630 077


PRODUCTION [SEK] - 36 007 749 - 73 355 610

TOTAL [SEK] 39 750 391 50 944 467

28 Calculations in this Section 5.1.4. are based on the same assumptions and estimations as for the

three cases studied before.

TOTAL

COOLING LOAD

[MWh/year]

TOTAL STEAM

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

FREE

COOL.

ABSORP.

COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53

976,24 23 198,59 20 331,87 41 420,45 515,81 489,85 29 074,58 59 231,24

5. RESULTS

68

When cooling demand is 10% lower, chiller configurations do not change;

either three 16NK-81 units or five 16TJ-53 units in parallel are still needed. In this

case, 779 kW of free cooling are necessary.

Following Table 30. and Table 31. show, on the one hand, new total

cooling load and operational conditions; on the other hand, the total costs (take

note that investment costs are the same).

Table 30. Operational conditions of different chillers sets at LEAF during the year when the

cooling demand is 10% lower than the estimated one

Table 31. Total costs of LEAF absorption cooling plants for 10 years when the cooling

demand is 10% lower than the estimated one

16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 22 627 000 64 577 824

18 420 000 92 672 852

OPERATING 41 950 824 74 252 852


PRODUCTION [SEK] - 27 699 356 - 52 114 385

TOTAL [SEK] 36 878 468 40 558 467

TOTAL

COOLING LOAD

[MWh/year]

TOTAL STEAM

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

FREE

COOL.

ABSORP.

COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53

750,96 17 845,07 15 640,52 29 426,53 504,70 482,10 22 365,94 42 079,94

5. RESULTS

69

5.1.4.2. MACKMYRA

When cooling demand is 10% higher, one more 16 TJ-53 single-effect absorption chiller is also required in Mackmyra production

site. This way, one more OCT09HB03-3-120 (Vestas Aircoil) cooling tower is needed too. Likewise, roughly 39 kW cooling/year more

ought to be produced by means of free cooling in winter.

New total cooling load and operational conditions as well as total costs are shown in Table 32. and Table 33.

Table 32. Operational conditions of different chillers sets in Mackmyra production site during the year

when the cooling demand is 10% higher than the estimated one



16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 17 700 000 44 893 151

13 204 000 58 100 671

OPERATING 27 193 151 44 896 671


PRODUCTION [SEK] - 9 934 004 - 18 689 819

TOTAL [SEK] 34 959 146 39 410 852

TOTAL COOLING

LOAD [MWh/year]

TOTAL STEAM

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

TOTAL WATER

CONSUMPTION

[m3/year]

FREE

COOL.

ABSORP.

COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53

413,03 9 814,79 8 600,87 16 181,66 512,05 510,02 12 299,24 23 139,78 44 472,4 40 396,1

5. RESULTS

70

When cooling demand is 10% lower, it is only necessary one 16NK-81 double-effect absorption chiller (one less) and, therefore,

only one OCT09HB05-5-90 (Vestas Aircoil) cooling tower too. Regarding demanded cooling in winter, 351 kW are just required.

Following Table 34. and Table 35. gather together new total cooling load as well as operational conditions and total costs,

respectively.

Table 34. Operational conditions of different chillers sets in Mackmyra production site during the year

when the cooling demand is 10% lower than the estimated one



16NK-81 16TJ-53

TOTAL

COSTS [SEK]

INVESTMENT 9 905 000 32 734 801

9 506 000 47 097 672

OPERATING 22 829 801 37 591 672


PRODUCTION [SEK] - 8 127 503 - 15 293 040

TOTAL [SEK] 24 607 298 31 804 632

TOTAL COOLING

LOAD [MWh/year]

TOTAL STEAM

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

TOTAL WATER

CONSUMPTION

[m3/year]

FREE

COOL.

ABSORP.

COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53

337,93 8 030,28 7 036,80 13 240,73 511,07 498,42 10 062,62 18 934,24 27 893,3 34 148,2

5. RESULTS

71

5.1.4.3. JOHANNES

The installations remain the same in Johannes production site when

cooling demand is 10 % higher or lower. Cooling load and hence, operational

conditions are only changed.

Next Table 36. and Table 38. show the new operational conditions and

Table 37. and Table 39. the consistent new total costs.

Table 36. Operational conditions of different chillers sets in Johannes production site during

the year when the cooling demand is 10% higher than the estimated one

Table 37. Total costs of Johannes absorption cooling plants for 10 years


16LJ-53

TOTAL

COSTS [SEK]

INVESTMENT 8 800 000 45 664 168



PRODUCTION [SEK] - 24 543 860

TOTAL [SEK] 21 120 308

Table 38. Operational conditions of different chillers sets in Johannes production site during

the year when the cooling demand is 10% lower than the estimated one

Table 39. Total costs of Johannes absorption cooling plants for 10 years


16LJ-53

TOTAL

COSTS [SEK]

INVESTMENT 8 800 000 43 140 656



PRODUCTION [SEK] - 22 158 526

TOTAL [SEK] 20 982 130

TOTAL

ABSORPTION

COOLING

LOAD

[MWh/year]

TOTAL HOT

WATER

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

TOTAL WATER

CONSUMPTION

[m3/year]

7 353,12 10 991,43 1 268,15 13 959,11 28 753,8

TOTAL

ABSORPTION

COOLING

LOAD

[MWh/year]

TOTAL HOT

WATER

SUPPLY

[MWh/year]

TOTAL

ELECTRICITY

SUPPLY

[MWh/year]

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

TOTAL WATER

CONSUMPTION

[m3/year]

6 639,31 9 923,21 1 241,36 2 079 408,443 28 324,8

5. RESULTS

72

5.2. COMPRESSION TECHNOLOGY VERSUS

ABSORPTION TECHNOLOGY. COMPARISON

FOR LEAF PRODUCTION SITE

Technological possibilities and aspects of absorption cooling systems at

three specific sites in the victinity of Gävle, as well as the costs and profits

(economic aspects), have been evaluated. Nevertheless, the main aim of this thesis

is to analyze possible benefits with the use of heat driven absorption chillers

instead of conventional vapour compressor chillers. Thus, compression cooling

machines at LEAF have been replaced by equivalent absorption ones in order to

make a comparison.

Compression cooling installation (see Appendix 1.) will be made up of

five chillers: VKA1 (1254 kW), VKA2 (1254 kW), VKA3 (717 kW), VKA4

(3226 kW) and VKA5 (3226 kW), which are going to be replaced except for

VKA3, as it is a back-up chiller that would be also used in the absorption cooling

plant. The rest of the installation (building, pumps and so on)29

as well as

operational conditions30

remain the same.

This way, four double-effect steam fired absorption chillers are going to be

introduced: two 16NK-41 (1371 kW) and other two 16NK-71 (3446 kW), which

has been choosen taking into account different sizes and models of chillers that

exist in the market. Both VKA1 and VKA2 could be replaced with just a single

bigger absorption machine (16NK-62); nevertheless, five machines ought to be in

total so that absorption cooling installation would have been also built in two

stages31

. Likewise, an installation with single-effect absorption chillers is not

29 KM1 pumps are not taken into consideration as electricity consumption of absorption chillers,

which belongs with pumps, is calculated. Regarding distribution pumps, those are taken into

account in this case as they are also included in the costs of the refrigeration compression

installation. 30 Compression cooling plant is using free cooling not only in winter but all around the year

except for May-August (altogether 1936 h/year). Even though it is not right (it should be used only in winter time: ≈ 15 November-15 March), the same operational conditions have been

considered so that new calculations are comparable with the existing compression project. 31 There are only VKA1 and VKA2 cooling machines in the first stage of the compressor

refrigerant cooling project and one of them is a back-up chiller. For that reason, there are two

small compressor chillers when the installation is totally built (in addition to VKA4 and

VKA5) instead of a bigger one.

5. RESULTS

73

studied since more than four absorption chillers would be needed (their maximum

capacity is 2461 kW).

Next, all calculations are shown.

Table 40. Operational conditions of the existing cooling

project but with absorption machines

OPERATING TIME

[h/year]

CAPACITY [kW]

VKA1 →16NK-41,1

VKA2 →16NK-41,2

VKA4 →16NK-71,1

VKA5 →16NK-71,2

44,28 1254 3226

487,08 940,5 2419,5

605,16 627 1613

339,48 315,5 806,5

Table 41. Power and steam demand of chillers set for the required cooling load in the

existing cooling project but with absorption machines

VKA1 →16NK-41,1

VKA2 →16NK-41,2

VKA4 →16NK-71,1

VKA5 →16NK-71,2

TOTAL

[MWh/year]

STEAM SUPPLY

TO THE CHILLERS

[MWh/year]

2 * 876,51 2 * 2249,84 6252,67

TOTAL POWER SUPPLY

TO THE CHILLERS

[MWh/year]

2 * 9,78 2 * 15,99 51,53

TOTAL BIOFUEL

CONSUMPTION

[MWh/year]

2 * 1253,42 2 * 3217,30 8941,37

Table 42. Operational costs in the existing cooling project but with absorption machines

ELECTRICITY [SEK/year]

- 1 SEK/kWh-

CHILLERS 51 530,11

REST OF THE EQUIPMENTS 3 192 656

BIOFUEL [SEK/year] - 165 SEK/MWh- 1 475 326,19

TOTAL [SEK/year] 4 719 512,30

Table 43. Total costs of the existing cooling project but with

absorption machines for 10 years

INVESTMENT COSTS

[SEK]

COOLING

EQUIPMENTS

VK3 600 000

16NK-41 2 * 3 000 000

16NK-71 2 * 5 300 000

BUILDING 4 000 000

PIPES INSIDE THE BUILDING 4 500 000

PUMPS AND FILTERS INSIDE THE BUILDING

3 000 000

TOTAL 28 700 000

COSTS OF OPERATION [SEK] 47 195 123


PRODUCTION [SEK]

- 770 SEK/MWh-

- 11 073 544

TOTAL [SEK] 64 821 579

5. RESULTS

74

Next Figure 32. gathers together all information about both cooling installations at LEAF.

Figure 32. Comparison of cooling installations with absorption and compression machines at LEAF

ORC

α = 0,23

ABSORPTION COOLING INSTALLATION COMPRESSION COOLING INSTALLATION

28 700 000 SEK 22 629 000 SEK

6253 MWh

steam

3245 MWh

electricity

0,001 SEK/MWh

8941 MWh

biofuel

165 SEK/MWh

4241 MWh

electricity

0,001 SEK/MWh 7143 MWh 7143 MWh

COOLING COOLING

1438 MWh electricity

to the grid

770 SEK/MWh

MAINTENANCE

COSTS

[SEK]

= 170 000 x when x = 1 x: years

= 340 000 – 10 200 x when 1 < x ≤ 5

= 289 000 + 89 250 (x – 5) when x ≥ 6

TOTAL COSTS FOR 10 YEARS:

64 821 579 SEK

(profits due to electricity production are

taken into account)

TOTAL COSTS FOR 10 YEARS:

66 204 500 SEK

5. RESULTS

75

5.3. DISTRIBUTION SYSTEM

5.3.1. INSTALLATION

The most important information about the main networks is gathered in the

following Table 44. Calculations and estimations, as well as all explanations, are

presented in Appendix 5.

Table 44. Data about the distribution systems

PRODUCTION

SITE

PIPE

KWH PE

(PN10)

DISTANCE

[m]

INTERNAL

DIAMETER

OF THE

PIPE

[mm]

EXTERNAL

DIAMETER

OF THE

PIPE,

dn [mm]

CHILLED

WATER

FLOW

[m3/h]

ΔP

[kPa]

(in the

distribution

system)

LEAF LEAF 1370 175 200 771 328

MACKMYRA

Mackmyra I 500 262 315

317 250

Mackmyra II 310 166 200

Mackmyra III 1890 203 250

JOHANNES Johannes 1775 370 450 171 718

5.3.3. COST OF THE MAIN PIPING NETWORKS

Total costs of the distribution systems for each of the three studied sites

can be seen in the next Table 45. They are made up of cost for distribution pumps

and pipes; the later one includes, apart from the material (pipe itself), digging,

construction and calculation plus quality control costs. Moreover, Table 46.

gathers together power consumption of the distribution pumps as well as

operational costs. For further information, see Section A5.2. in Appendix 5.

Table 45. Cost of the distribution systems

PRODUCTION

SITE

PUMP COST

[SEK]

PIPES COST

[SEK]

TOTAL COSTS

[SEK]

LEAF 110 000 6 850 000 6 960 000

MACKMYRA 62 000 16 621 100 16 683 100

JOHANNES 69 000 9 577 900 9 646 900

Table 46. Operational conditions and costs of distribution pumps

PRODUCTION SITE

ELECTRIC POWER SUPPLY

TO DISTRIBUTION PUMPS

[MWh/year]

OPERATIONAL

COSTS [SEK/year]

- 1 SEK/kWh-

LEAF 336,04 336 040

MACKMYRA 119,39 119 390

JOHANNES 193,20 193 200

CHAPTER 6

77

Discussions

Amount of provided information was limited and to collect accurate

information was difficult. Therefore, results are only approximations, as they are

based on quiet a lot assumptions. As a result, definitive conclusions cannot be

come up with.

6.1. PRODUCTION PLANTS

To finish with this research, one of the tasks is to make a decision about

more adequate types of absorption chillers to be used. In the case of Johannes

cooling production plant, hot-water absorption cooling machines ought to be

introduced as there are no more options from the technical point of view.

Regarding the other two sites, investment costs are higher for double-effect steam

fired chillers than for single-effect ones, whereas operational costs are much

more, about 50%, lower. Both scenarios, LEAF and Mackmyra, can be examined

in depth.

On the one hand, investment costs for double-effect installation are

4 207 000 SEK higher at LEAF. Nevertheless, operational costs are

3 713 268 SEK lower per year, which means that the initial extra costs would be

paid back in less than 2 years. If profits due to electricity output are taken into

consideration, the difference in annual costs would not be so large, but still

903 778 SEK/year (in this case, higher investment costs would be paid back in

5 years).

On the other hand, despite double-effect facilities cost 8 194 000 SEK

more than single-effect ones at Mackmyra, operational costs are

6. DISCUSSIONS

78

1 590 110 SEK lower per year. As a result, the extra investment costs are paid

back in 5 years. This time rises up to 10 years if produced electricity is taken into

account.

Therefore, needless to say that it is more profitable to introduce double-

effect chillers in both sites, since the pay-back times for extra investments are

short and the earnings would be considerable. This way, costs and profits for the

possible future three absorption cooling plants in Gävle would be those that are

gathered together in the following Table 47.

Table 47. Most adequate chillers and costs & profits for the three production sites

PRODUCTION

SITE

ABSORPTION

CHILLERS SETS

INVESTMENT

COST [SEK]

OPERATIONAL

COSTS

[SEK/year]

PROFITS

FROM

ELECTRICITY

PRODUCTION

[SEK/year]

LEAF

3 double-effect

chillers (4652 kW)

in parallel

22 627 000 4 753 785 3 183 656

MACKMYRA

2 double-effect

chillers (4652 kW)

in parallel

17 700 000 2 504 835 903 122

JOHANNES

2 single-effect hot

water chillers

(1846 kW) in

parallel

8 800 000 3 561 396 2 335 649

Next graph in Figure 33. shows total heat that might be produced in

different biofuel boilers for the three absorption plants and accordingly obtained

extra electricity output.

6. DISCUSSIONS

79

Figure 33. Increased heat load for the three absorption plants and the possible extra

electricity that would be produced

In Figure 23. was shown that when the load in the district heating network

is low there is almost none electricity production in Johannes CHP plant. In

addition, it is shut down during summer, June-August. If heat driven absorption

chillers were introduced, heat load and therefore, electricity output, would be

increased as it is shown in the next graph in Figure 34.

Figure 34. Increased heat and electricity load in the probable Johannes trigeneration plant

6. DISCUSSIONS

80

Nevertheless, this heat load would not be even enough to keep the boiler

running during summer because of efficiency problems, that is, the minimum

working capacity. The graph in Figure 35. shows that the boiler would have to

work at around 5 MW, whereas it is shut down when the loading is lower than

25% of its maximum capacity (20 MW).

Figure 35. Required operational conditions of the boiler for the cooling plant at Johannes

Consequently, cooling production at Johannes is a contribution but at

present it is not possible to keep the plant running during summer because of the

minimum load problem. It might be feasible if either heat or cooling market grew

in the future.

6.2. MOST PROFITABLE TECHNIQUE FROM

ECONOMIC POINT OF VIEW. SUSTAINABILITY

Next graph in Figure 36. depicts all costs for the two different cooling

systems with absorption and vapour compressor technologies at LEAF. It has to

be underlined that the comparison is limited since water from the river is used for

cooling down the chillers and one of the main differences between these machines

is the required size of cooling towers.

6. DISCUSSIONS

81

Figure 36. Comparison of total costs for ten years for the different cooling production

technologies at LEAF

The larger investment costs of the absorption cooling compared to

compression cooling, 6 071 000 SEK, are paid back after five years (4,39 years)

because of lower electricity consumption and larger fuel utilization32

, in addition

to increased electricity production.

Next Table 48. gathers together annual benefits after the first 10 years

when using absorption chillers instead of compression cooling machines:

Table 48. Annual benefits of absorption cooling technology at LEAF after 10 years

CASE

ELECTRICITY

CONSUMPTION

[MWh/year]

ELECTRICITY

PRODUCTION

[MWh/year]

PROFITS

FROM

ELECTRICITY

[SEK/year]

LEAF 8905 kW - 996 1438 1 107 354

32 It bears reminding from Section 2.3. that absorption systems can compete against compression

ones when price of electricity is around 8 times higher than cost of heat.

6. DISCUSSIONS

82

An efficiency comparison between system including absorption or vapour

compressor chillers can be made too. If overall system is taken into account, total

efficiency for compressor cooling system is 58% higher33

. Nevertheless, if

internal electricity consumption is analyzed, the coefficient of performance

(COPel) is 23% greater for the absorption machines’ installation34

, as absorption

chillers only use electricity for pumping the absorbent solution whereas

compression ones are driven by electric power.

Deregulation and real-time pricing for electricity give an incentive to

manage electrical loads. A compression chiller is a very big target when looking

for ways to reduce electrical loading and to control costs. Thus, absorption units

allow it without sacrificing either performance or reliability.

Moreover, as mentioned before, an absorption cooling system contributes

to an increased electricity production. Hence, it gives good opportunities of

utilizig the biofuel in an effective way.

This way, it is come to the conclusion that a sustainable energy system for

Gävle for meeting the cooling demand can be the erection of district cooling

networks with trigeneration plants by producing cooling in heat driven absorption

cooling machines. Increasing of the energy system with a third output (cooling)

would optimize the system even more. Furthermore, it is also very good from

environmental point of view, since extra electricity produced could be sold as

green in the Swedish market and it could replace, this way, margin produced

electricity.

It bears mentioning that the system border of electricity production and

consumption has to be taken into consideration when studying environmental

aspects and, like this, carbon dioxide emissions. From global point of view,

electricity production in Gävle would affect European energy system and total

33 ηTOT, compression system = Wcooling/Welectricity = 1,684

ηTOT, absorption system = (Wcooling + Welectricity)/(Qfuel + Welectricity) = 0,705

34 COPel, compression chillers set = Wcooling/Welectricity = 1,684

COPel, absorption chillers set = Wcooling/Welectricity = 2,201

6. DISCUSSIONS

83

CO2 emissions would be therefore negative. However, the local emissions would

be negatively affected because of increased use of fuel; anyway, biofuel, that is,

clean fuel, would be used.

6.3. COOLING DEMAND VERSUS COSTS AND

BENEFITS OF ABSORPTION COOLING

TECHNOLOGY

There are three scenarios that it does not even compare at all to each other

as the installations are quiet different. Even though double-effect steam fired

chillers might be at both LEAF and Mackmyra production sites, water from the

river could be used for cooling down the chillers at LEAF whereas cooling towers

are required at Mackmyra, which entails electricity consumption and higher

investment costs for the latest case. Regarding Johannes production site, although

it also needs cooling towers, steam is not used, but hot water.

As a result, each case is going to be studied separately.

6.3.1. ELECTRICITY PRODUCTION AND CONSUMPTION

The environmental and economical effects with absorption systems

compared with vapour compression ones are consistently positive and become

more and more evident with higher cooling demands and higher electricity prices

(note Figure 37. in the next page).

6. DISCUSSIONS

84

Figure 37. Electricity production and consumption according to the

cooling demand in three different scenarios

6.3.2. COSTS AND PROFITS. THE BEST OPTIONS

Figure 38. Costs and profits (due to electricity production) according

to the cooling demand in three different scenarios

Johannes absorption cooling plant with hot-water chillers is the smallest

one. The previous graph in Figure 38. shows how investment costs are kept

JOHANNES

6. DISCUSSIONS

85

constant with variations of ±10% in cooling demand. This means the same

machines can be used to produce up to 10% more than required cooling nowadays

with higher profits, as electricity output together with income from customers

increase while variation in costs of operation is little.

On the other hand, steam-fired chillers are under study. The trend at LEAF

is the same as at Johannes. However, there is a big difference at Mackmyra when

demand decreases by 10%: investment costs are 44% lower. Therefore, the best

option would be to build smaller installations and meet the cooling demand in

Kungsbäck area by other means. This could be accomplished in two different

ways: by storing energy or by making the network smaller and using another.

The university, which cooling demand is 1,8 MW, could be connected to

the network in the city center, as it is not far away from Konserthuset (where the

main pipe might reach). In addition, as mentioned earlier, there would be no

problem to produce required extra cooling with the same facility at LEAF.

Research on advantages and disadvantages of this option could make possible the

execution of a new thesis project.

Regarding energy storage, accumulator tanks for chilled water should be

considered for many reasons: problems to fulfil the cooling demand, dynamic

demand during the year, security in the system and so forth. Consecuently, further

research into those systems could be done.

CHAPTER 7

87

Conclusions

This research seeks to compare compression and absorption cooling

technologies and to make a decision about which one is the best solution, in

addition to deal with the analysis of three trigeneration plants with absorption

cooling systems in Gävle. In connection with this, next all interesting made

conclusions are summed up and gathered together.

- Development of district cooling systems with trigeneration plants that

produce chilled water in absorption machines is the best solution to

meet the cooling demands.

Benefits with absorption systems compared with vapour

compression ones become more and more evident with higher cooling

demands and higher electricity prices.

- It is more profitable to introduce double-effect steam-fired absorption

chillers than single-effect ones.

- Even though steam-fired chillers are more efficient, single-effect hot

water chillers might be introduced at Johannes, as the pressure of the

steam leaving the turbine is lower than the required one for steam fired

cooling machines.

- The cooling plant at Johannes might be a contribution, but at present

it is not feasible because of boiler´s minimum load problem.

- It would be more profitable to increase the production of cooling in

10% over the demand at LEAF and Johannes. Nevertheless, regarding

Mackmyra production site, the best option would be to build smaller

installations and meet the demand by other means.

REFERENCES

REFERENCES

89

[1] T.T. Chow, K.F. Fong, A.L.S. Chan, R.Yau, W.H. Au, V. Cheng, Energy

modelling of district cooling system for new urban development, Energy and

Building 36 (2004) 1153-1162.

[2] L. Trygg, B. G. Karlsson, Industrial DSM in a deregulated European

electricity market-a case study of 11 plants in Sweden, Department of

Mechanical Engineering, Division of Energy Systems, Linköping Institude of

Technology, Linköping S-581 83, Sweden.

[3] A. Rojey, Cold producing process, 4,037,426 United States Patent.

[4] M. J. Moran, H. N. Shapiro, ―Fundamentos de termodinámica técnica”

(Fundamentals of Engineering Thermodynamics), Reverté (2004). ISBN 84-

291-4313-0.

[5] United States Departament of Energy (DOE), Mississippi Cooling, Heating,

and Power (micro-CHP) and Bio-fuel Center, micro- Cooling, Heating, and

Power (m-CHP) Instructional Module, Mississippi State, MS 39762

(December 2005 First Printing).

[6] R. Gianfrancesco, Method and apparatus for the absorption-cooling of a fluid,

5,177,979 United States Patent.

[7] R. Darío Ochoa V., ‖Absorción como una alternativa de ahorro de energía”

(Absorption as alternative for saving energy), Tecnología Empresarial S.A.

(2003). [8] A. Şencan, K. A. Yakut, S. A. Kalogirou, Exergy analysis of lithium

bromide/water absorption systems, Renewable Energy 30 (2005) 645-657.

[9] G. Cohen, A. Rojey, Absorbers used in absorption heat pumps and

refrigerators, 4,299,093 United States Patent.

[10] Y. Hassan, Cold from Waste Energy. The Absorrption System, Mechanical

Department, Sudan University.

[11] D W Hudson, Gordon Brothers Industries Pty Ltd, Ammonia absoption

refrigeration plant, The official journal of AIRAH (August 2002).

[12] I. Horuz, A comparison between ammonia-water and water-lithium bromide

solutions in vapor absorption refrigeration systems, PII S0735-

1933(98)00058-X.

[13]M. Rydstrand, Heat driven cooling in district energy systems, KTH Chemical

Engineering and Technology, Stockholm (2004). ISBN 91-7283-794-2.

[14] K.E. Herold, R.Radermacher, S. A. Klein, Absorptioni Chillers and Heat

Pumps, CRC Press (1996). ISBN 0-8493-9429-9.

REFERENCES

90

[15] P. E. Nilsson, Achieving the Desired Indoor Climate. Elergy Efficiency

Aspects od Systen Design, Studentlitteratur, Lund (2003). ISBN 91-44-03235-

8.

[16] M.A. Rosen, M. N. Le, I. Dincer, Efficiency analysis of a cogeneration and

district energy system, Applied Thermal Engineering 25 (2005) 147-159.

[17] F. Lin, J. Yi, Y. Weixing, Q. Xuzhong, Influence of supply and return water

temperatures on the energy consumption of a district cooling system, Applied

Thermal Engineering 21 (2001) 511-521.

INTERNET SOURCES:

1. http://www.air-conditioning-and-refrigeration-guide.com/refrigeration-

cycle.html

2. http://www.qrg.northwestern.edu/thermo/design-library/refrig/refrig.html,

Design of Vapour-Compression Refrigeration Cycles

3. http://www.commercial.carrier.com, Absorption Chillers

4. http://www.nationmaster.com/encyclopedia/Gas-absorption-refrigerator

5. http://www.grappa.co.yu/b/index.php?page=shop.getfile&file_id=36&product_

id=48&option=com_virtuemart&Itemid=30, Carrier-Sanyo Super Absorption

16LJ 11-53

6. http://www.kwhpipe.com

7. http://www.carrier.com

8. http://www.turboden.it/en/products.asp

BROCHURES:

1. 16TJ Single-Effect Steam-fired chillers (Carrier-Sanyo).

2. 16NK Double-Effect Steam-Fired Absorption Chillers (Carrier-Sanyo).

3. 16LJ Single-Effect Hot water-fired chillers (Carrier-Sanyo).

4. The Complete Pipework Solution (KWH Pipe).

5. PE Pressure Pipe Systems (KWH Pipe).

6. OCR technology, biomass application (TURBODEN).

http://www.air-conditioning-and-refrigeration-guide.com/refrigeration-cycle.html

http://www.air-conditioning-and-refrigeration-guide.com/refrigeration-cycle.html

http://www.qrg.northwestern.edu/thermo/design-library/refrig/refrig.html

http://www.commercial.carrier.com/

http://www.nationmaster.com/encyclopedia/Gas-absorption-refrigerator

http://www.grappa.co.yu/b/index.php?page=shop.getfile&file_id=36&product_id=48&option=com_virtuemart&Itemid=30

http://www.grappa.co.yu/b/index.php?page=shop.getfile&file_id=36&product_id=48&option=com_virtuemart&Itemid=30

http://www.kwhpipe.com/

http://www.carrier.com/

http://www.turboden.it/en/products.asp

REFERENCES

91

PERSONAL CONTACTS:

Table R. 1. Information about personal contacts

NAME COMPANY/ CAPACITY INFORMATION AREA OF EXPERTISE

Åke Björnwall Gävle Energi AB: Project & Development

Supervisor

Tel direct 026 – 17 86 15

[email protected]

- General

- Gävle Energi

Håkan Rannestig Gävle Energi AB: Manager P&U 026-17 26 60

Cooling project

Ulf Hedman Ramböll Sverige AB (www.ramboll.se)

Consultant

Tel direct 026-149507

[email protected]

- Boiler-projects

- Absorption cooling

Anders Kedbrant SWECO Systems AB (www.sweco.se)

Consultant

Tel direct 026-66 20 02

Mobil 0706-623262

[email protected]

- Existing project

- Compression

Refrigeration

Per-Arne Vahlund Gävle Energi AB: Marketing 026-17 86 80 Customer data

Inger Wiklund Gävle Energi AB: Documentation 026-17 86 59 GIS

Greger Berglund Gävle Energi AB: Project Manager 026-17 85 25

Distribution system

Lucas Enström Gävle Energi AB: Operation Manager 026-17 26 65

[email protected]

Johannes CHP plant

Daniel Widman Falu Energi & Vatten AB : Project Manager

Tel direct 023-77049052

[email protected]

District Cooling project in

Falun

- Sale assistants: Tomas Lundgren and Tyko Sandell from Carrier, Thomas Nyström from Z&I Pumps, Anna Schlegel

from Grudfos, Robert Lindberg from Baltimore Air Coil (BAC), etc.

mailto:[email protected]

http://www.ramboll.se/


http://www.sweco.se/




APPENDICES

93

Appendix 1. PLANNED REFRIGERANT COMPRESSION INSTALLATION

A1.1. INSTALLATION

Figure A1. 1. Draft of the whole compression installation (Source: Anders Kedbrant, SWECO)

Appendix 1. Planned refrigeration compression installation

94

Figure A1. 2. Draft of the devices of the compression installation (Source: Anders Kedbrant, SWECO)

1st

stage

1st

stage

2nd

stage

2nd

stage


95

INSTALLATION ON ITS FIRST STAGE

- Submersible pumps for the whole installation: KM1-P6A and KM1-P6B

- Main pumps for the distribution pipes: KB1-P6A and KB1-P6B

► Cooling water in the distribution system:

FORWARD PIPE: 5,5 °C

RETURN PIPE: 13,2 °C

- 2 cooling machines (compressor, evaporator, condenser): VKA1 and

VKA2

o 2 dry single pumps: KB1-P1 and KB1-P2

o 2 dry single pumps: KM1-P1 and KM1-P2 (they keep set flow in the

condenser).

- Heat exchanger unit: KB1-VVX1

MACHINES AND DEVICES TO BE INTRODUCED IN THE

SECOND STAGE

- 3 cooling machines (compressor, evaporator, condenser): VKA3, VKA4

and VKA5

o 3 dry single pumps: KB1-P3, KB1-P4 and KB1-P5

o 3 dry single pumps: KM1-P3, KM1-P4 and KM1-P5

PUMPS:

Table A1. 1. Pump specifications of compression cooling installation I

TYPE KM1-P6A / P6B

(SUBMERSIBLE, BRUNN1, BRUNN2)

PROCEDURE

DRY SINGLE PUMP

Wilo / FA 25.93D WITH ENGINE FK34.1-

6/50

MEDIA WATER 20°C

FLOW 265 l/s

MAXIMUM PRESSURE 150 kPa

POWER 75 kW

RATED CURRENT 151 A

MINIMUM EFFICIENCY 88 %


96

Table A1. 2. Pump specifications of compression cooling installation II

TYPE KB1-P6A / P6B

PROCEDURE Grundfos / : TP300/590/4 A-F-A DBUE or

equivalent

MEDIA WATER 5,5°C

FLOW 320 l/s


POWER 200 kW

RATED CURRENT 340/196 A

MINIMUM EFFICIENCY ---

Table A1. 3. Pump specifications of compression cooling installation III

TYPE KB1-P1, KB1-P2

PROCEDURE DRY SINGLE PUMP

Wilo / : IL 150/190-5,5/4 or equivalent

MEDIA WATER 5,5°C

FLOW 45 l/s


POWER 5,5 kW

RATED CURRENT 11,4 A


Table A1. 4. Pump specifications of compression cooling installation IV

TYPE KB1-P3


Wilo / IL 80/170-2,2/4

MEDIA WATER 5°C

FLOW 25 l/s


POWER 2,2 kW

RATED CURRENT 4,7 A


Table A1. 5. Pump specifications of compression cooling installation V

TYPE KB1-P4, KB1-P5


Wilo / IL 200/240-15/4

MEDIA WATER 5°C

FLOW 110 l/s


POWER 15 kW

RATED CURRENT 28,5 A



97

Table A1. 6. Pump specifications of compression cooling installation VI

TYPE KM1-P1, KM1-P2


Wilo / IL 100/170-3/4

MEDIA WATER 20°C

FLOW 40 l/s


POWER 3 kW

RATED CURRENT 6,4 A


Table A1. 7. Pump specifications of compression cooling installation VII

TYPE KM1-P3


Wilo / IL 100/160-2,2/4

MEDIA WATER 5°C

FLOW 30 l/s


POWER 2,2 kW

RATED CURRENT 4,7 A


Table A1. 8. Pump specifications of compression cooling installation VIII

TYPE KM1-P4, KM1-P5


Wilo / IL 200/240-7,5/6

MEDIA WATER 5°C

FLOW 80 l/s


POWER 7,5 kW

RATED CURRENT 16 A


CHILLERS:

Table A1. 9. Vapour Compressor chillers specifications I

TYPE VKA1, VKA2

MODEL: YRWCWCT3550C

REFRIGERANT R134 A

MAXIMUM CAPACITY 1254 kW

INPUT POWER 187 kW

VOLTAGE 400/ 50 Hz


98

Table A1. 10. Vapour Compressor chillers specifications II

TYPE VKA3

MODEL: YRTBTBT0550C

REFRIGERANT R134 A


INPUT POWER 110 kW

VOLTAGE 400/ 50 Hz

Table A1. 11. Vapour Compressor chillers specifications III

TYPE VKA4, VKA5

MODEL: YKKKKLH95CQF

REFRIGERANT R134 A


INPUT POWER 451 kW

VOLTAGE 400/ 50 Hz

FREE COOLING HEAT EXCHANGER UNIT:

Table A1. 12. Heat exchanger specifications of compression cooling installation

TYPE/MANUFACTURER KB1-VVX1 AlfaLaval

CAPACITY 500 kW

STREAMS TEMPERATURE 4,5/15 ºC (primary)

5,5/165 ºC (secondary)

FLOW 11,3 l/s (primary & secondary)

PRESSURE DROP 96,9 kPa (primary)

98,8 kPa (secondary)

VKA2 is a back-up chiller in the first stage. When the second stage is

built, both VKA1 and VKA2 will be working together with VKA4 and VKA5 and

VKA3 will be the back-up chiller (it is not considered for calculations).

All calculations, which are shown next, are for the whole installation.


99

A1.2. COOLING LOAD


(YRWCWCT3550C) in time steps

% LOAD

CAPACITY

[kW] COP

% OPERATING

(during year)

OPERATING

TIME

[h/year]

COOLING

LOAD

[kWh/year]

100 1254 6,712 3 44,28 55 527,12

75 940,5 7,524 33 487,08 458 098,74

50 627,0 7,377 41 605,16 379 435,32

25 315,5 4,679 23 339,48 107 105,94

TOTAL

1476

(see Table A1. 15.) 1 000 167,12


(YKKKKLH95CQF) in time steps

% LOAD

CAPACITY

[kW]

COP

% OPERATING

(during year)

OPERATING

TIME

[h/year]

COOLING

LOAD

[kWh/year]

100 3226,0 7,148 3 44,28 142 847,28

75 2419,5 7,830 33 487,08 1 178 490,06

50 1613,0 7,868 41 605,16 976 123,08

25 806,5 6,350 23 339,48 273 790,62

TOTAL 1476 2 571 251,04

NOTE: the following Table A1. 15. shows the operation hours.

Table A1. 15. Operating time for cooling delivering during the year

Month Days hours/day hours/month

January 31 8 248

February 28 8 224

March 31 8 248

April 30 8 240

May 31 12 372

June 30 12 360

July 31 12 372

August 31 12 372

September 30 8 240

October 31 8 248

November 30 8 240

December 31 8 248

Free cooling (1936 h/year)

Compression refrigeration (1476 h/year)


100

Thus, as there are two YRWCWCT3550C compressors and other two

YKKKKLH95CQF,

TOTAL COOLING LOAD PRODUCED BY COMPRESSION

REFRIGERATION TECHNOLOGY: 7 142 836,32 kWh/year

A1.3. INPUT LOAD AND COSTS

Table A1. 16. Power needed in the compression cooling installation during the year

INPUT POWER

[kW]

OPERATING TIME

[h/year] INPUT

LOAD

[kWh/year]

Winter

time

Winter

time

Shut down

compressors

FIR

ST

ST

AG

E

KM1-P6A 75 22,5 1476 1936 6260 295 110

KM1-P6B 75 22,5 1476 1936 6260 295 110

KB1-P6A 200 60 1476 1936 6260 786 960

KB1-P6B 200 60 1476 1936 6260 786 960

VKA1/VKA2

see

Table

A1. 17. ― 1476 ― ― 149 046,48

KB1-P1 5,5 ― 1476 ― ― 8118

KB1-P2 5,5 ― 1476 ― ― 8118

KM1-P1 3 ― 1476 ― ― 4428

KM1-P2 3 ― 1476 ― ― 4428

KB1-VVX1 ― 500 ― 1936 968 000

SE

CO

ND

ST

AG

E

VKA2 see

Table

A1. 17. ― 1476 ― ― 149 046,48

VKA3 110 ― ― ― ― ―

VKA4

see

Table

A1. 18. ― 1476 ― ― 359 465,04

VKA5

see

Table

A1. 18. ― 1476 ― ― 359 465,04

KB1-P3 2,2 ― ― ― ― ―

KB1-P4 15 ― 1476 ― ― 22 140

KB1-P5 15 ― 1476 ― ― 22 140

KM1-P3 2,2 ― ― ― ― ―

KM1-P4 7,5 ― 1476 ― ― 11 070

KM1-P5 7,5 ― 1476 ― ― 11 070

TOTAL 4 240 675,04


101

Working the whole year (when the compressors are shut down too)

30% of the total power is just used in winter time and when

the compressors are not working

It is ony used in winter time, when free cooling is allowed

NOTES:

- Following Table A1. 17. and Table A1. 18. show input load for different

compressors in time steps.

Table A1. 17. Input load VKA1 and VKA2 compressors

(YRWCWCT3550C) in time steps

%

LOAD

INPUT

POWER

[kW]

OPERATING

TIME

[h/year]

INPUT

LOAD

[kWh/year]

100 187 44,28 8 280,36

75 140,25 487,08 68 312,97

50 93,5 605,16 56 582,46

25 46,75 339,48 15 870,69

TOTAL 1476 149 046,48

Table A1. 18. Input load VKA4 and VKA5 compressors

(YKKKKLH95CQF) in time steps

%

LOAD

INPUT

POWER

[kW]

OPERATING

TIME

[h/year]

INPUT

LOAD

[kWh/year]

100 451 44,28 19 970,28

75 338,25 487,08 164 754,81

50 225,5 605,16 136 463,58

25 112,75 339,48 38 276,37

TOTAL 1476 359 465,04

- Input loads for pumps should be calculated in the same way, as they

depend on the cooling load (system curve). Nevertheless, their design

curves are unkown and therefore, it has been considered they are working

at their maximum capacity except for winter time (and when compressors

are shut down too), when they work at 30% of the maximum capacity

(minimum capacity).


102

Finally, Table A1. 19. gathers together total needed load in the system and

operational costs.

Table A1. 19. Total input load and operating costs in the compression cooling installation

TOTAL INPUT LOAD [kWh/year] 4 240 675

OPERATING COSTS [SEK/year] -1SEK/kWh- 4 240 675

A1.4. TOTAL COSTS

Table A1. 20. Costs of the compressor refrigerant system

Evolution of maintenance costs (it includes parts and working time,

412 h/year, of 2 people) is shown in Figure A1. 3. below:

Figure A1. 3. Maintenance costs in the course of time

INVESTMENT

COSTS

[SEK]

COOLING EQUIPMENTS 11 129 000

BUILDING 4 000 000

PIPES INSIDE THE BUILDING 4 500 000

PUMPS AND FILTERS

INSIDE THE BUILDING 3 000 000

TOTAL: 22 629 000

COSTS OF

OPERATION

[SEK/year]

4 240 675

MAINTENANCE

COSTS

[SEK]

1st year

2nd

year

3th

year …

5th

year

6th

year …

10th

year

159 800 149 600 139 400 … 119 000 89 250 89 250 89 250


103

A1.5. PAY-BACK TIME FOR THE INVESTMENTS

Table A1. 21. Pay-back times for the compression installation

INVESTMENTS PAY-BACK TIME [years]

COOLING EQUIPMENT (compression machine) 10

PIPES 20-30

PUMPS AND FILTERS 10

As the depreciation of equipments is in roughly 10 years (the investment is

recovered), costs can be calculated for this period of time:

Table A1. 22. Total costs for the refrigeration compression

system for the first 10 years

INVESTMENT COSTS [SEK] 22 629 000

COSTS OF OPERATION [SEK] 42 406 750

MAINTENANCE COSTS 35

[SEK] 1 168 750

TOTAL [SEK] 66 204 500

Thus, TOTAL COSTS FOR 10 YEARS are: 66 204 500 SEK

6 620 450 (SEK/year)

Later on, after the first 10 years, there will be only operational and

maintenance costs.

35 Total maintenance costs are equal to the area under the curve in Figure A1. 3. This way, they

will be: (51000*5/2) + (119000-89250)*5 + (89250*10) = 1168750 SEK for ten years.

104

Appendix 2. EXPECTED COOLING DEMAND

A. CITY CENTER (LEAF)

Table A2. 1. Cooling demand of possible future customers in the city center and additional data

OWNER

NAME

OF

ESTATE

ADDRESS

N°

COOLING

INSTALLED

COOLING

DEMAND

[KW]

NOTES

Yes No

Norrporten

Kv Hövdingen, N skepparg 2 1 X 150

Kv Notanus, N Strandgatan 1 2 X 70

Kv Syndicus Kyrkogatan 4 3 X 200

Länsstyrelsen, Borgmästarplan 2 4 X Not interested

Polishuset S Centralg 1-3 5 X 350 New cooling system installed 2007

Kv Vulkanus S Sjötullsgatan 6 X 100 ‖Byggforskningen‖

Kv Vasen Lantmäterigatan 7 X 700

Kv Kapellbacken Skomakargatan 1 8 X 400 ‖Skattehuset‖

Kv. Klockstapeln Vågskrivargatan 5 9 X 200

Kv Gevalia Nygatan 25-27 10 X 250 Cooling machine installed 2004

Norrvidden Kv Skampålen 11 X 400 Present cooling system contain R22.

Kv Lektorn 12 X 200 Cooling machine installed 1998

Diös Fastigheter

Norr 23:5

(‖Skandihuset‖)

13 X 200 Old cooling machine which

need to be replaced

Postterminalen 14 X 100

Kv Nattväktaren 15 X 700 Cooling machine installed 2000

Sankt George:1 16 X 40

Kv Hoppet 17 X 40

Kv Pechlin ―Folksamhuset‖ 18 X 100 New cooling machine installed 2005

Appendix 2. Expected cooling demand

105

Table A2.1 (continuation). Cooling demand of possible future customers in the city center and additional data

OWNER

NAME

OF

ESTATE

ADDRESS

N°

COOLING

INSTALLED

COOLING

DEMAND

[KW]

NOTES

Yes No

Gavlegårdarna Alderholmen

servicehus

19 X 30

Building not erected yet.

Gavlefastigheter Kv Trähästen Förvaltningshuset 20 X 400 ―Sure‖ customer

Biblioteket ―The library‖ 21 X 700

Kv Tomväkaren

―Kommunhuset‖ 22 X 300

Teatern ―The theatre‖ 24 X 300 Need cooling solution

Konserthuset 25 350 Problem with present solution

Boultbee 26 Have two machines built 2004

Kv Kärrlandet ―Nian‖ 27 X 700 Cooling machines installed 2004.

Boetten Gamla domstolarna 28 X 45 Existing customer

Drottningatan 48 29 X 20

Kraft Foods Kv Alderholmen 30 X 500 100 kW sure, 400 kW potential

Handelsbanken Kv Skolstuvan 31 X 200

Länsmuséet Kv Plantagen ―The museum‖ 32 X 250

Jernhusen station AB Centralstationen ―Railway station‖ 33 X 60 New cooling machines installed 2005.

Banverket Kv Storön 34 X 100 Need to expand present capacity

Allokton Kv Gesällen 35 X 350

F2 Hyresbostäder Kv Borgen 36 X 40

Folkets Hus 37 X 120 Not interested at present

Kv islandsskolan 38 X 40

Norr 23:3 39 X 100 Contact by SWECO


106

Total cooling demand in the city center is 8905 kW (data for

Konserthuset was missing but it has been considered slightly bigger than for the

theatre because it is quite bigger building but activities going on there are similar).

Nevertheless, taking into account that it is unkown cooling demand of some

places (such as nº 26) and there could be more customers in the future, it is

considered a cooling demand of 9000 kW. In addition, LEAF itself needs

2500 kW of cooling. Like this,

TOTAL COOLING DEMAND FOR LEAF PRODUCTION SITE:

11 500 kW

B. KUNGSBÄCK AREA (MACKMYRA)

Table A2. 2. Customers and their cooling demand in Kungsbäck

CUSTOMER COOLING DEMAND [kW]

HOSPITAL 1700

UNIVERSITY 1800

TECHNOLOGIC PARK 1000

4500 kW has to be delivered through the main pipe of district cooling

distribution system that leaves the cooling production plant. However, it is needed

to increase production output power since the whisky factory might use cold as

well. Anyway, this cooling demand would not be much, as there is not any

cooling system in the current factory and storage rooms that are planning to build

would be underground, where temperature would be adequate (under 17 ºC). This

way,

TOTAL COOLING DEMAND FOR MACKMYRA PRODUCTION SITE:

≈ 5000 kW


107

C. JOHANNESBERGSVÄGEN AREA (JOHANNES)

Table A2. 3. Cooling demand for Johannes production site

CUSTOMER COOLING DEMAND [kW]

HEMLINGBY SHOPPING CENTERS 2000

Cooling demand of possible customers in Johannesbergsvägen area is

2000 kW. Moreover, cooling is also used at Johannes CHP plant, mainly for

the refrigeration of the turbine, which is produced by electrically driven

devices. Thus, this cooling system could be also replaced and it is like this

planning to produce the cooling needed too, which is roughly 1,3-1,4 MW, in

the absorption plant. So,

TOTAL COOLING DEMAND FOR JOHANNES PRODUCTION SITE:

3400 kW

108

Appendix 3. SPECIFICATIONS AND CALCULATIONS

REGARDING ABSORPTION COOLING

INSTALLATIONS

A3.1. ABSORPTION CHILLERS

A.3.1.1. MODELS AND THEIR CHARACTERISTICS

A. LEAF AND MACKMYRA

- SINGLE-EFFECT STEAM-FIRED ABSORPTION CHILLERS:

Carrier-Sanyo 16TJ

Appendix 3. Specifications and calculations regarding absorption cooling installations

109



110

According to the brochure, 16TJ-53 absorption chiller consumes 5460 kg/h

satured steam at 100 kPa. It is known that the enthalpy of satured vapour at 1 bar

is 2675,5 kJ/kg [4] (Pressure Table of Properties of Satured Water), so:

Thus,

4,1 MW satured steam

at 1 bar 2,5 MW cooling

On the other hand, electric and cooling power to be supplied are:

P = 400V * 11,0 A * 0,8 (power factor that most generators use) = 3520 W

Pelectricity supply = 3,52 kW

P = 159 kg/s * 4,2 kJ/(kg.K) * (38,4 – 29,4) K= 6010,2 kW

Pcooling supply = 6,01 MW

Take note that the relation between capacity of the chiller used and cooling

water power as well as steam needed can be considered linear (part-load curve is

almost linear). However, the cooling water flow is usually constant. That is, i.e. an

16TJ-53 absorption chiller working at 50% of its maximum capacity (1230,5 kW)

needs 2028,92 kW of satured steam and 3005,1 kW of cooling (the water flow is

159 l/s). With regards to the electric power supply (for pumps), it is constant.

5460 kg

* 1 h

* 2675,5 kJ

= 4057,84 kW satured steam h 3600 s kg

16TJ-53

ABSORPTION

CHILLER


111

- DOUBLE-EFFECT STEAM-FIRED ABSORPTION CHILLERS:

Carrier-Sanyo 16NK


112



113

According to the brochure, 16NK-81 absorption chiller consumes

5300 kg/h satured steam at 784 kPa. It is known that the enthalpy of satured

vapour at 8 bar is 2769,1 kJ/kg [4] (Pressure Table of Properties of Satured

Water), so:

Thus,

4,1 MW satured steam

at 8 bar 4,7 MW cooling


P = 400V * 33,5 A * 0,8 = 10 720 W


P = 333,9 kg/s * 4,2 kJ/(kg.K) * (35,4 – 29,4) K= 8414,28 kW


5300 kg

* 1 h

* 2769,1 kJ

= 4076,71 kW satured steam h 3600 s kg

16NK-81

ABSORPTION

CHILLER


114

B. JOHANNES

Figure A3. 1. Water streams (steam and DH) at Johannes CHP plant (Source: Gävle Energi AB)


115

Next Table A3. 1. shows pressures of the first steam stream extracted from

the turbine related to electricity and district heating production capacities during

the year. The values in blue point out the steam cannot be used in absorption

chillers. The last four values belong to summer period, when the boiler is running

at its minimum capacity (20 MW).

Table A3. 1. Production data and pressure of the first steam stream extracted from the

turbine (Source: Gävle Energi AB)

ELECTRICITY

[MW]

DISTRICT HEATING

[MW]

P

[kPa]

23,704 56,168 1

24,367 59,375 1,044

20,531 55,589 2,25

19,848 52,422 2,23

21,738 50,532 0,8835

11,137 34,355 2,13

10,679 32,022 2,12

12,687 30,004 0,5511

3,602 18,624 2,05

3,683 18,555 2,05

4,244 15,991 0,7415

4,449 15,723 0,7409

4,677 15,558 0,4139

4,877 15,28 0,4136

As the pressure of steam is not suitable during peak periods of cooling

demand (summer)36

, a steam-fired absorption machine cannot be introduced.

36 It is not considered the last steam stream leaving the turbine since its pressure is even lower.


116

- SINGLE-EFFECT HOT WATER-FIRED ABSORPTION

CHILLERS: Carrier-Sanyo 16LJ


117



118

According to the brochure, 16LJ-53 absorption chiller consumes 73 l/s hot

water (95,0 °C → 86,0 °C) at its maximum cooling capacity. This is a heat supply

of:

P = m * Cp * ∆T

P [kW] = 73 [kg/s] * 4,2 [kJ/kg K] * 9 [K] = 2759,4 kW

Pheat supply = 2759 kW


P = 400V * 11,0 A * 0,8 = 3520 W


P = 119,2 kg/s * 4,2 kJ/(kg.K) * (38,4 – 29,4) K= 4505,76 kW


A3.1.2. INVESTMENT COSTS

Next Table A3. 2. shows price and capacity comparison of different

chillers (LJ and TJ units compared to NK units).

Table A3. 2. Price comparison of single- and double-effect units



119

Investment costs for different needed models are the followings

(Table A3. 3.):

Table A3. 3. Investment costs for different absorption chiller units

(Source: Ulf Hedman, Ramboll)

ABSORPTION CHILLER PRICE [SEK]

16TJ-53 2 700 000

16LJ-53 2 700 000

16NK-81 6 200 000

16NK-71 5 300 000

16NK-41 3 000 000

A3.1.3. OPERATIONAL CONDITIONS

According to the estimations Anders Kedbrant did for refrigerant

compression cooling project, the cooling demand load curve in the city center for

2008 is as shown in Figure A3. 2., which has been divided in different cooling

power production periods.

Figure A3. 2. Cooling demand load curve (2008) divided in periods according to

the power needed to be produced

8900

7568

5223

3624

2718

693


120

Information from the previous graph (Figure A3. 2.) is gathered in

Table A3. 4.

Table A3. 4. Average city center´s cooling demand in time steps for 2008

TIME PERIOD

COOLING

DEMAND

[kW]

% of max.

power 37

PRODUCTION

HOURS

(reference:

compression

refrigeration project)

Winter time:

15 November-15 March 693 7,79 964

15 March-1 April

1-15 November 2718 30,54 244

April

15 October-1 November 3624 40,72 364

1-15 May

15 September-15 October 5223 58,69 430

15 May-15 June

15 August-15 September 7568 85,03 672

Summer time:

10 June-15 August 8900 100 738

NOTE: There is no production of cooling in winter time, since free

cooling is allowed (it is needed to introduce a heat

exchanger).

Taking into account calculated percentages, cooling load during the year can

be estimated for the three production sites that are subject of studying:

37 Information from first column can be translated into percentages taking the maximum power as

reference.


121

A. LEAF

Table A3. 5. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF during the year

TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]

NUMBER OF CHILLERS WORKING

& CAPACITY [kW]

TSA-16NK-81 TSA-16TJ-53

15 November-15 March 7,79 895,45 — —

15 March-1 April & 1-15 November 30,54 3512,02 3512 1756 1756

April & 15 October-1 November 40,72 4682,70 4652 (max.) 2342 2342

1-15 May & 15 September-15 October 58,69 6748,82 3375 3375 2250 2250 2250

15 May-15 June & 15 August-15 September 85,03 9778,88 3260 3260 3260 2445 2445 2445 2445

15 June-15 August 100 11500 3834 3834 3834 2300 2300 2300 2300 2300

NOTE: minimum working power of absorption chillers is 20% of their maximum capacity

Table A3. 6. Cooling power to be supplied to the chillers at LEAF during the year

TIME PERIOD COOLING OF CHILLERS –free cooling- [kW]


15 November-15 March — —

15 March-1 April & 1-15 November 6352,31 4288,46 4288,46

April & 15 October-1 November 8414,28 5719,58 5719,58

1-15 May & 15 September-15 October 6104,51 6104,51 5494,9 5494,9 5494,9

15 May-15 June & 15 August-15 September 5896,51 5896,51 5896,51 5482,69 5482,69 5482,69 5482,69

15 June-15 August 6934,73 6934,73 6934,73 5617,01 5617,01 5617,01 5617,01 5617,01

NOTE: Heat exchangers are going to be calculated for cooling down the chillers when they are working at their maximum capacity

(security margin, just in case). Although cooling water flow is better to be constant, in this case it needs to be changed as

conditions of free cooling (temperature of water from the river), that is, the cooling power, cannot be controlled. Therefore,

necessary water flow can be set by a valve just before it goes into the chillers.


122

Table A3. 7. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF during the year


TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]


& CAPACITY [kW]


15 November-15 March 7,79 1012,7 — —

15 March-1 April & 1-15 November 30,54 3970,2 3970 1985 1985

April & 15 October-1 November 40,72 5293,6 2647 2647 1766 1766 1766

1-15 May & 15 September-15 October 58,69 7529,7 3815 3815 1908 1908 1908 1908

15 May-15 June & 15 August-15 September 85,03 11053,9 3685 3685 3685 2211 2211 2211 2211 2211

15 June-15 August 100 13000 4334 4334 4334 2600 2600 2600 2600 2600 2600







April & 15 October-1 November 4787,75 4787,75 4312,89 4312,89 4312,89

1-15 May & 15 September-15 October 6900,36 6900,36 4659,68 4659,68 4659,68 4659,68

15 May-15 June & 15 August-15 September 6665,22 6665,22 6665,22 5399,66 5399,66 5399,66 5399,66 5399,66

15 June-15 August 7839,10 7839,10 7839,10 6349,66 6349,66 6349,66 6349,66 6349,66 6349,66


123

Table A3. 9. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF

during the year when the cooling demand is 10% lower than the estimated one

TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]


& CAPACITY [kW]


15 November-15 March 7,79 779 — —

15 March-1 April & 1-15 November 30,54 3054 3054 1527 1527

April & 15 October-1 November 40,72 4072 4072 2036 2036

1-15 May & 15 September-15 October 58,69 5869 2935 2935 1957 1957 1957

15 May-15 June & 15 August-15 September 85,03 8503 4252 4252 2126 2126 2126 2126

15 June-15 August 100 10000 3334 3334 3334 2000 2000 2000 2000 2000







April & 15 October-1 November 7365,21 4972,27 4972,27

1-15 May & 15 September-15 October 5308,57 5308,57 4779,34 4779,34 4779,34

15 May-15 June & 15 August-15 September 7690,78 7690,78 5192,07 5192,07 5192,07 5192,07

15 June-15 August 6030,35 6030,35 6030,35 4884,36 4884,36 4884,36 4884,36 4884,36


124

B. MACKMYRA

Table A3. 11. Cooling load to be produced and working power of different chillers

(double- and single- effect) in Mackmyra production site during the year

TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]


& CAPACITY [kW]


15 November-15 March 7,79 389,33 — —

15 March-1 April & 1-15 November 30,54 1526,97 1527 1527

April & 15 October-1 November 40,72 2035,96 2036 2036

1-15 May & 15 September-15 October 58,69 2934,27 2934 1467 1467

15 May-15 June & 15 August-15 September 85,03 4251,69 4252 2126 2126

15 June-15 August * 100 5000 2500 2500 2461 (max.) 2461

* TSA-16TJ- 53. Back-up chiller can be used to produce extra cooling (78 kW) which is needed

Table A3. 12. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra production site

TIME PERIOD

COOLING OF CHILLERS [kW] COOLING TOWERS NEEDED

TSA-16NK-81 TSA-16TJ-53 TSA-16NK-81 TSA-16TJ-53

15 November-15 March — — Capacity: 7691 kW

Flow: 1202,04 m3/h

ΔTmax. = 5,76 K

Capacity: 6010 kW

Flow: 572,4 m3/h

ΔTmax. = 9 K

15 March-1 April & 1-15 November 2762,12 3729,21

April & 15 October-1 November 3682,60 4972,27

1-15 May & 15 September-15 October 5306,86 3582,68 3582,68 Capacity: 4523 kW

Flow: 1202,04 m3/h

ΔTmax. = 3,39 K

Capacity: 6010 kW

Flow: 572,4 m3/h

ΔTmax. = 9 K

15 May-15 June & 15 August-15 September 7690,78 5192,07 5192,07

15 June-15 August 4522,14 4522,14 6010,2 6010,2


125

Table A3. 13. Cooling load to be produced and working power of different chillers (double- and single- effect) in Mackmyra

production site during the year when the cooling demand is 10% higher than the estimated one

TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]


& CAPACITY [kW]


15 November-15 March 7,79 428,45 — —




15 May-15 June & 15 August-15 September 85,03 4676,65 2338 2338 2338 2338

15 June-15 August 100 5500 2750 2750 1833 1833 1833

Table A3. 14. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra

production site when the cooling demand is 10% higher than the estimated one

TIME PERIOD




Capacity: 5839 kW

Flow: 1202,04 m3/h

ΔTmax. = 4,37 K

Capacity: 5710 kW

Flow: 572,4 m3/h

ΔTmax. = 8,98 K 15 March-1 April & 1-15 November 3038,69 4102,86

April & 15 October-1 November 4051,59 5470,48 Capacity: 5710 kW

Flow: 572,4 m3/h

ΔTmax. = 8,98 K 1-15 May & 15 September-15 October 5838,63 3941,68 3941,68

Capacity: 4975 kW

Flow: 1202,04 m3/h

ΔTmax. = 3,72 K 15 May-15 June & 15 August-15 September 4228,84 4228,84 5709,81 5709,81 Capacity: 4477 kW

Flow: 572,4 m3/h

ΔTmax. = 7,04 K 15 June-15 August 4974,05 4974,05 4476,51 4476,51 4476,51


126

Table A3. 15. Cooling load to be produced and working power of different chillers (double- and single- effect)

in Mackmyra production site during the year when the cooling demand is 10% lower than the estimated one

TIME PERIOD

% of

max.

power

COOLING

POWER

PRODUCTION

[kW]


& CAPACITY [kW]


15 November-15 March 7,79 350,55 — —




15 May-15 June & 15 August-15 September 85,03 2826,35 3826 1913 1913

15 June-15 August 100 4500 4500 2250 2250

Table A3. 16. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra

production site when the cooling demand is 10% lower than the estimated one

TIME PERIOD




Capacity: 8140 kW

Flow: 1202,04 m3/h

ΔTmax. = 6,09 K

Capacity: 5495 kW Flow: 572,4 m3/h

ΔTmax. = 8,64 K



1-15 May & 15 September-15 October 4776,89 3226,12 3226,12 Capacity: 5495 kW

Flow: 572,4 m3/h

ΔTmax. = 8,64 K

15 May-15 June & 15 August-15 September 6920,26 4671,87 4671,87

15 June-15 August 8139,35 5494,90 5494,90


127

C. JOHANNES

Table A3. 17. Cooling load to be produced and working power of different chillers in Johannes production site during the year

TIME PERIOD

% of max.

power for

Hemlingby

COOLING

POWER

PRODUCTION

FOR

HEMLINGBY

[kW]

TOTAL

COOLING

POWER

PRODUCTION

[kW]

NUMBER OF TSA-16LJ-53

CHILLERS WORKING

& CAPACITY [kW]

15 November-15 March 7,79 155,8 1555,8 —

15 March-1 April & 1-15 November 30,54 610,8 2010,8 1006 1006

April & 15 October-1 November 40,72 814,4 2214,4 1107 1107

1-15 May & 15 September-15 October 58,69 1173,8 2573,8 1287 1287

15 May-15 June & 15 August-15 September 85,03 1700,6 3100,6 1551 1551

15 June-15 August 100 2000 3400 1700 1700

NOTE: Cooling demand in Johannes represents the cooling needed for the turbine itself (to cool it

down because of friction energy generated by turbine´s axis and generator). Therefore, it is the

same all over the year, that is, it does not depend on the time period (outdoor temperature). This

way, cooling demand during the year has been estimated for Hemlingby shopping centers and

then, 1,4 MW for Johannes have been added up to each of them.


128

Table A3. 18. Cooling power to be supplied to the chillers during the year

and necessary cooling towers in Johannes production site

TIME PERIOD COOLING OF

CHILLERS [kW]

COOLING TOWERS

NEEDED

15 November-15 March — Capacity: 4150 kW

Flow: 858,24 m3/h

ΔTmax. = 8,70 K



1-15 May & 15 September-15 October 3141,34 3141,34 Capacity: 4150 kW

Flow: 858,24 m3/h ΔTmax. = 8,70 K

15 May-15 June & 15 August-15 September 3785,72 3785,72

15 June-15 August 4149,40 4149,40

Table A3. 19. Cooling load to be produced and working power of different chillers in Johannes production site


TIME PERIOD

% of max.

power for

Hemlingby

COOLING

POWER

PRODUCTION

FOR

HEMLINGBY

[kW]

TOTAL

COOLING

POWER

PRODUCTION

[kW]


CHILLERS WORKING

& CAPACITY [kW]

15 November-15 March 7,79 171,38 1571,38 —





15 June-15 August 100 2200 3600 1800 1800


129

Table A3. 20. Cooling power to be supplied to the chillers in Johannes production site during the year



CHILLERS [kW]

COOLING TOWERS

NEEDED

15 November-15 March — Capacity: 4394 kW

Flow: 858,24 m3/h

ΔTmax. = 9,22 K




Flow: 858,24 m3/h ΔTmax. = 9,22 K

15 May-15 June & 15 August-15 September 3990,75 3990,75

15 June-15 August 4393,48 4393,48

Table A3. 21. Cooling load to be produced and working power of different chillers in Johannes production site


TIME PERIOD

% of max.

power for

Hemlingby

COOLING

POWER

PRODUCTION

FOR

HEMLINGBY

[kW]

TOTAL

COOLING

POWER

PRODUCTION

[kW]


CHILLERS WORKING

& CAPACITY [kW]

15 November-15 March 7,79 140,22 1540,22 —





15 June-15 August 100 1800 3200 1600 1600


130

Table A3. 22. Cooling power to be supplied to the chillers in Johannes production site during

the year when the cooling demand is 10% lower than the estimated one


CHILLERS [kW]

COOLING TOWERS

NEEDED

15 November-15 March — Capacity: 3906 kW Flow: 858,24 m3/h

ΔTmax. = 8,19 K




Flow: 858,24 m3/h

ΔTmax. = 8,19 K

15 May-15 June & 15 August-15

September 3575,81 3575,81

15 June-15 August 3905,32 3905,32


131

A3.2. THE REST OF EQUIPMENTS

Table A3. 23. Required cooling towers and heat exchangers´ technical data

PRODUCTION SITE COOLING TOWERS HEAT EXCHANGERS (+FILTER)

-chillers´cooling down-

HEAT EXCHANGERS

(+FILTER)

-free cooling-

LEAF

16NK-81

chillers —

S121-IS10-502-TMTL47-LIQUIDE (Sondex)

Flow: 339 kg/s

Capacity: 8505 kW

FILTER: BSG350/1,0P (Bernoulli)

TL10-BFG (Alfa Laval)

Flow: 38,7 l/s

Capacity: 895,0 kW 16TJ-53

chillers —

MX25-MFMS (Alfa Laval)

Flow: 241,4 l/s

Capacity: 6010 kW

MACKMYRA

16NK-81

chillers

OCT09HB05-5-90 (Vestas Aircoil)

Flow: 1221 m3/h. Evaporation: 10,9 m3/h

Capacity: 5988 kW

Number of fans: 5

Air flow/fan: 30,41 m3/s. Rotation speed: 439 rpm

Electric power supply/fan: 6,1 kW

—

TL10-BFG (Alfa Laval)

Flow: 16,8 l/s

Tin = 12,2ºC. Tout = 6,7 ºC

16TJ-53

chillers



Capacity: 8499 kW

Number of fans: 3



—

JOHANNES 16LJ-53

chillers



Capacity: 4483 kW

Number of fans: 2



— —


132

NOTE 1: Power of cooling towers is determined by fan´s air flow (cooling

water flow is constant), of which relation can be considered to be

linear. For calculating power of fans (electricity supply), following

equations are used:

q1/q2 =n1/n2

P1/P2 = (n1/n2)3

where:

- q: fan´s air flow

- n: fan´s rotation speed (rpm)

- P: power

NOTE 2: Size of equipments

- LEAF. Same heat exchangers have been considered for the three cases

since differences between the needed capacities are not so large and, in

addition, those equipments can work at 10% higher capacity than the

specified one.

- MACKMYRA. The highest capacity between required cooling

equipments have been approximately taking into consideration to make

the decision about the cooling towers to be introduced. They are valid for

all cases as the flow is constant, so they will work according to the needed

cooling capacity (they are too big in some cases but data about more

adequate towers could not be obtained).

- JOHANNES. Cooling tower has been choosen so that it can cover the

cooling demand in the three cases, as the differences are not so large.

133

Appendix 4. MAPS OF CUSTOMERS AND DISTANCES FROM THE PRODUCTION SITES

A. CITY CENTER (LEAF)

Figure A4. 1. Map of the city center with the main pipe that leaves LEAF production site and its length

Appendix 4. Plans of customers and distances from the production sites

134

It has been followed the same way for the main pipe as in the refrigerant

compression cooling project, since the production site and customers are the same

and, in addition, as necessary remarks for this decision have been already taken

into account.


135

B. KUNGSBÄCK AREA (MACKMYRA)

Figure A4. 2. Map with the customers, pipes and distances for Mackmyra production site


136

The pipe which arrives at hospital from Mackmyra would need to go

through the technologic park, since it is also a customer. This way, it has been

decided to follow the direction of roads and the existing district heating

installation.


137

C. JOHANNESBERGSVÄGEN AREA (JOHANNES)

Figure A4. 3. Map with the customers for Johannes production site, pipe and its length

HEMLINGBY SHOPPING CENTERS

Johannes


138

The absorption plant at Johannes would be used to fulfil the cooling

demand of the existing Hemlingby shopping center and buildings which are under

construction now, with a total cooling floor area of 35 000 m2

(see Figure A4. 4.).

The extension is expected to be finished by this summer (2009).

Figure A4. 4. Map of the shopping centers under construction in Hemlingby

For this reason, the main distribution pipe is planning to be between all

these buildings. Once the pipe would leave the constructed area, it would go

through the forest, since its digging is cheaper than road´s, and cross E4 highway

taking the advantage that it already exists a tunnel there. Thereafter, it would

reach the production plant as drawn because of the possibility of future customers

over there. Next Figure A4. 5. shows the future plan of the municipality of

building a new area close to Johannes CHP plant.


139

Figure A4. 5. Map of the future residential area close to Johannes plant

140

Appendix 5. CALCULATIONS ABOUT DIMENSIONS OF PIPES, DISTRIBUTION PUMPS

AND THEIR COSTS

A5.1. DIMENSIONING

Table A5. 1. Dimensioning of pipes and pressure drop (part I)

PRODUCTION

SITE PIPES CUSTOMER

COOLING

DEMAND

[kW]

DISTANCE

[m]

MASS FLOW

[kg/s]

VOLUMETRIC

FLOW

[m3/h]

LEAF LEAF CITY CENTER 9000 1370 214,29 771,43

MACKMYRA

Mackmyra I

HOSPITAL 1700

UNIVERSITY 1800

TECHNOLOGIC

PARK 1000

TOTAL 4500 500 107,14 385,71

Mackmyra II UNIVERSITY 1800 310 42,86 154,29

Mackmyra III

HOSPITAL 1700

TECHNOLOGIC

PARK 1000

TOTAL 2700 1890 64,29 231,43

JOHANNES Johannes

HEMLINGBY

SHOPPING

CENTERS 2000 1775 47,62 171,43

NOTE: Mass flow: P [kW] = m [kg/s] * Cp [kJ/kg K] * ∆T [K] → m = P/Cp/∆T

Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs

141

Table A5. 2. Dimensioning of pipes and pressure drop (part II)

PRODUCTION

SITE PIPES CUSTOMER

CROSS

SECTION OF

THE PIPE [m2]

INTERNAL

DIAMETER

OF THE PIPE

[mm]

RESISTANCE

[Pa/m]

PRESSURE

LOSS for

each pipe [Pa]

PRESSURE FOR

DISTRIBUTION

PUMP [Pa] 38

LEAF LEAF CITY CENTER 0,11 369,44 65 89050 328100

MACKMYRA

Mackmyra I

HOSPITAL

UNIVERSITY

TECHNOLOGIC

PARK

TOTAL 0,05 261,24 100 50000 25000

Mackmyra II UNIVERSITY 0,02 165,22 175 54250 258500

Mackmyra III

HOSPITAL

TECHNOLOGIC

PARK

TOTAL 0,032 202,35 130 245700 641400

JOHANNES Johannes

HEMLINGBY

SHOPPING

CENTERS

0,02 174,16 160 284000 718000

NOTES (in the next page):

38 As the flow passes through pipes and other components in the system, the pressure decreases. Thus, it is needed a pressure difference in the system which is

generated in the pump and which is progressively dissipated by pressure losses in the distribution system with increasing distance from the pump. This is

shown in schematic Figure A5. 2.


142

NOTES:

- Diameter of pipes: ø = 2 √(A/π)

- The cross section of pipes has been calculated for a velocity of water flow of 2 m/s

(it is usually between 1 and 3 m/s for large pipes), for considering it the most

suitable (Greger Berglund).

- The resistances have been calculated by using a SBI nomogram that can be seen in

the following page (Figure A5. 1.).

- Pressure increase that is needed (distribution pump) has been calculated considering

that there is a pressure drop of 150 kPa in the customer site (Greger Berglund),

although it is usually enough with 30-50 kPa –safety margin-.


143

Figure A5. 1. SBI monogram showing the parameters of the different pipes


144

Figure A5. 2. Differential pressures in a direct return distribution

system with one terminal unit

Distribution losses could be calculated as following:

(Source: lecture of Energy Systems, HIG, by Heimo Zeinko)

Nevertheless, they are not taken into consideration because of being very small.

There is only a temperature difference of 4ºC between the water that goes through

pipes and outside, so the resistances are therefore almost zero.


145

Going back to the diameter of pipes, outer diameters have been obtained

by using the following Table A5. 3. once internal diameters (see Table A5. 2.)

have been calculated.

Table A5. 3. PE Pressure Pipes for water supply: EN 12201, ISO 4427

(Source: PE Pressure Pipe Systems brochure)


146

Finally, Table A5. 4. shows the dimension of pipes needed.

Table A5. 4. Data of the pipes needed

PIPES MATERIAL dn 39

[mm]

LEAF KWH PE, PN10 40 450

Mackmyra I KWH PE, PN10 315

Mackmyra II KWH PE, PN10 200

Mackmyra III KWH PE, PN10 250

Johannes KWH PE, PN10 200

A5.2. COSTS

A. DIGGING FOR PIPES AND TOTAL COSTS

The distribution system in ground looks like it is shown in Figure A5. 3..

Ground is dug and two pipes, forward and return ones, are introduced keeping the

distances (Greger Berglund) that can be observed in the figure. The hole is filled

with sand.

Figure A5. 3. Piping excavation section

39 dn: nominal outer diameter 40 PN: nominal pressure. Maximum pressure for plastic pipes is 10 bar (PN10).


147

The values of parameters B and C from Figure A5. 3. depend on the outer

diameter, dn. Those are gathered in Table A5. 5.

Table A5. 5. Values of parameters C and B for the required dn

(Source: Greger Berglund, Gävle Energi AB)

dn [mm] C [mm] B [mm]

200 400 1000

250 450 1100

315 525 1250

NOTE: data for dn = 315 mm was missing, so the values have been interpolated

from the values of the original data and rounded off.

When pipes are going through water (as appropiate for LEAF), the

installation is totally different. Pipes are placed in the bottom of the river (or sea,

in other cases), keeping a distance of described C value between them. It would be

750 mm for LEAF pipes (dn = 450).

Next, costs of the main distribution system are shown, Table A5. 6.,

without taking into account the pumps.

Table A5. 6. Total cost of the pipes

(Source: Greger Berglund, Gävle Energi AB, and Anders Kedbrant, SWECO)

PIPE COST SINGLE

PIPE [SEK/m]

COUNTRY SIDE

MACKMYRA I 3408

MACKMYRA II 2698

MACKMYRA III 3053

JOHANNES 2698

WATER –river- LEAF 2500

Cost for pipes in countryside can be splitted up in its different

components. This way, the following graph in Figure A5. 4. shows it in

percentages.


148

Figure A5. 4. Distribution system cost split up in its components and their contribution to

the total cost

Finally, total costs of the distribution system except for the pumps can be

calculated:

Table A5. 7. Calculation of the pipes´ costs

PRODUCTION

SITE PIPE

DISTANCE

[m]

COST

[SEK/m]

COST

PER PIPE

[SEK]

TOTAL

COST

[SEK]

LEAF LEAF 1 370 2500 3 425 000 6 850 000

MACKMYRA

Mackmyra I 500 3 408 1 704 000 3 408 000

Mackmyra II 310 2 698 836 380 1 672 760

Mackmyra III 1 890 3 053 5 770 170 11 540 340

TOTAL 16 621 100

JOHANNES Johannes 1 775 2 698 4 788 950 9 577 900


149

B. PUMPS

Table A5. 8. Needed distribution pumps and their cost (Source: Zander & Ingeström AB)

PRODUCTION

SITE

Q 41

[m3/h]

P

[kPa] PUMP TYPE

MAX.

POWER

CONS.

[kW]

PRICE

[SEK]

LEAF 771,43 328,1 KENFLO centrifugal

pump, KPS 30-250 77,4 110 000

MACKMYRA 317,14 250 KENFLO centrifugal

pump, ISO 200x150-315 27,5 62 000

JOHANNES 171,43 718 KENFLO centrifugal

pump, ISO 100x65-250 44,5 69 000

NOTE: Electric power consumption cannot be calculated in accordance

with pumps´ working power during the year as their design curves

are unkown. Thus, it has been assumed that they work the same

way as pumps from compression refrigerant cooling project and

therefore considered that they are working at their maximum

capacity all over the year except for winter time and for when

chillers are shut down, when they work at 30% of the maximum

capacity.

41 Q: volumetric flow

150

Appendix 6. FALUN COOLING PROJECT: A REFERENCE

A6.1. INSTALLATION

Figure A6. 1. Draft of the whole cooling installation in Falun (Source: Daniel Widman, Falu Energi & Vatten AB)

Appendix 6. Falun cooling project: a reference

151

Table A6. 1. Reference specifications about absorption chiller in Falun


There are additional remarkable devices in the installation, such as:

- A compression chiller of 1290 kW. It has two functions: to keep cooling in

reserve and to fulfil the demand in periods of higher loads.

- Two BAC (Baltimore Air Coil) VXT 470 cooling towers.

- Grundfos pumps. Distribution pumps: FK-P01 (50 kW).

Appendix 6. Falun cooling project: a reference

152

A6.2. TOTAL COSTS

Table A6. 2. Investment costs for different installations in Falun

COST OF THE WHOLE INSTALLATION [SEK] 10 000 000

COST OF THE COMPRESSION COOLING MACHINE [SEK] 1 500 000

COST OF THE ABSORPTION CHILLER [SEK] 2 700 000

COST OF THE COOLING TOWERS [SEK] 2 * 675 000

COST OF THE DISTRIBUTION PUMPS [SEK] 100 000

Like this, the COST of the INSTALLATION without distribution pumps,

chillers and cooling towers is 1 450 000 SEK.

Maintenance costs are very low, so they are therefore not taken into

account. With regards to operational costs, they are calculated as sum of electric

power needed and water for cooling towers (it is assumed that steam is free). This

way, it is needed to assess costs for 250 kW plus 50 kW per each distribution

pump of electricity (≈1 SEK/kWh) and 10 m3/h of water (≈4 SEK/ m

3).

Total electric consumption of the whole installation is made up of:

Table A6. 3. Input electric power in Falun installations

TOTAL 250 kW

POWER SUPPLY TO THE ABSORPTION CHILLER 5,84 kW 42

POWER SUPPLY TO THE COOLING TOWERS

(there are 2 fans in each cooling tower) 2 * 30,0 kW

POWER NEEDED IN THE REST OF THE INSTALLATION 184,16 kW

NOTE: Compressor chiller´s input power at its maximum capacity is

300 kW. Nevertheless, it is not included as it is seldom

working.

42 P = 7,3 kVA * 0,8 (power factor that most generators use) = 5,84 kW

153

Johannes plant has a biofueled steam boiler, where there are mainly burnt

bark, forest residues and waste wood43

. Nonetheless, it is needed oil to start up the

plant (which takes between 12 and 18 hours) and unfortunately, this fuel has to be

also sometimes used because of technical problems.

Next, basic scheme of the plant is shown in Figure A7. 1. for explaining

how it operates thereafter.

Figure A7. 1. Scheme of Johannes CHP plant (Source: Gävle Energi AB)

The different types of biofuel, which are stored according to their

composition in different piles outside (see Figure A7. 2.), are mixed and carried

43 The blending changes frecuently, which depends on the availability of different fuels, costs and

so forth.

Appendix 7. EXTRA INFORMATION ABOUT

JOHANNES POWER PLANT

1

4

5

7

8

9

10

1. FUEL INTAKE

2. SIEVING (fuel mixer)

3. FUEL STORAGE

4. CONVEYOR BELT FOR BIOFUEL UP TO THE BOILER

5. STEAM BOILER

6. DIRECT CONDENSER

7. TURBINE

8. VESSEL ACCUMULATORS

9. ELECTROSTATIC PRECIPITATOR

10. FLUE GAS CONDENSER (FGC)

11. CHIMNEY STACK

12. CONTROL ROOM

13. OIL TANK

14. AMMONIA TANK

11

2

3

6

12

13 14

Appendix 7. Extra information about Johannes power plant

154

into a silo (sieving). Afterwards, the fuel mixture is put on a fuel storage building.

This place has a fuel capacity of a weekend production, since there is nobody

working on fulfilling it during this period.

Figure A7. 2. Fuel storage

44 and conveyor belt carrying biofuel to the boiler at Johannes

The biofuel mixture is transported to the boiler using a conveyor belt

(which gets in a fuel container) as means of transport (see Figure A7. 2.), where it

is then burned. The steam boiler, which scheme is shown in Figure A7. 3., is a

Bubble Fluidized Bed (BFB) with a maximum capacity of 77 MW.

Biofuel enters the boiler through two intakes together with some air (it is

injected in order to avoid flames go into fuel silo). Primary air goes in the bottom,

where a sand bed is. There, solid fuel is suspended on upward-blowing jets of air

and a turbulent mixing is achieved. As a result, more effective combustion and

heat transfer take place.

The combustion heats water, which is coverted into superheated steam at

high and constant pressure. The steam leaving the boiler goes thereafter to the

turbine.

44 This picture was taken the 24th of March of 2009, when it was still winter. Despite the snow

and cold weather, biofuel keeps well since it is warm inside due to reactions (aerobic

decomposition of organic matter) that take place in there.

http://en.wikipedia.org/wiki/Aerobic_decomposition



http://en.wikipedia.org/wiki/Organic_matter


155

Figure A7. 3. Bubble Fluidized Bed (BFB) boiler of Johannes CHP plant


The turbine called Olga was installed in 2005, which means that there

was previously a direct condenser instead that was used to cool down the steam by

means of district heating return water (it is still in there in case of a breakdown or

higher heating demands). It is a backpressure turbine, model Siemens SST-600,

which works in two steps and has a power output capacity of 22 MW (see

Figure A7. 4. and left side of Figure A7. 5.), where electricity is produced by

expanding and cooling the steam.

The exhaust steam leaving the turbine is then condensed in two heat

exchangers (see right side of Figure A7. 5.) and the water that extracts heat from

the steam goes to the supply pipe of the district heating network. When heat

supply is higher than the demand, hot water is stored, what there are two heat

accumulators for, and this way, it is delivered when the demand is higher

(compensation of load variations).

Characteristics of obtained electricity and water for district heating are

gathered in Table A7. 1.

29 kg/s

94 bar


156

Figure A7. 4. Illustrative drawing of Olga turbine and components


Figure A7. 5. Olga turbine on the left side and heat exchangers on the right side. Johannes

CHP plant

Table A7. 1. Characteristics of the obtained outputs at Johannes

ELECTRICITY

Power 23MW

Generator voltage 11 kV

DISTRICT HEATING

Power 50 MW

Forward temperature 96 ºC

Return temperature 67 ºC

Exhaust gases leaving the boiler go through an electrostatic precipitator in

order to eliminate particulate matter and after that heat is extracted in a flue-gas

Turbine

Generator

Heat exchangers


157

condensation system (see Figure A7. 6. and for more specified information,

Figure A7. 7.). This waste heat is also used in the district heating network and

sand-ashes, together with the sand extracted from the bottom of the boiler and

cleaned in a rotational sieve, are recycled for reutilizing them in the boiler.

Figure A7. 6. Schematic of the FGC at Johannes (Source: Gävle Energi AB)

Figure A7. 7. Detailed scheme of the condensate treatment plant at Johannes


Moreover, there is a water purification system where ultrapure water

(conductivity < 20 μS/m) is obtained as it is required for the boiler. The

technology is called EDI (electrodeionisation), which combines ion exchange and

membrane filtering.

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