MAXIMIZATION OF ENERGY GENERATION FROM

SMALL HYDROPOWER PLANT IN SRI LANKA

A dissertation submitted to the Department of Energy Technology, Royal Institute of Technology,

Sweden for the partial fulfillment of the requirement for the Degree of Master of Science in Engineering

By

Pathiranage Guminda Sanjeewa Priyadarshana

2014

Department of Energy Technology

Royal Institute of Technology

Stockholm, Sweden

2

MAXIMIZATION OF ENERGY GENERATION FROM

SMALL HYDROPOWER PLANTIN SRI LANKA

By

Pathiranage Guminda Sanjeewa Priyadarshana

Supervised by

OUSL Supervisors:

Dr. N.S. Senanayake& Mr. Ruchira Abeyweera

KTH Supervisors:

Prof. Mark Howells& Mr. Francesco Fuso Nerini

3

Declaration

The work submitted in this thesis is the result of my own investigation, except where otherwise stated.

It has not already been accepted for any other degree and is also not being concurrently submitted for any other degree.

Pathiranage Guminda Sanjeewa Priyadarshana

Date

We/I endorse declaration by the candidate.

Dr. N.S. Senanayaka Prof. Mark Howells& Mr. Ruchira Abeyweera & Mr. Francesco Fuso Nerini

(OUSL Supervisors) (KTH Supervisors)

4

Abstract

Sri Lanka has a number of small waterfalls and channels. Related to this there is a significant

potential to develop small hydropower plants, thus to generate much needed electricity for

country’s development efforts. Small hydro power plants cause less environmental effects

compared to large scale hydro power generation and power generation using fossil fuel.

Therefore, it is a timely requirement to explore the possibilities of utilizing small water streams to

generate electricity as much as possible as well as to optimize the energy generation with the

available water in those water streams. The importance of small hydro power is highlighted in

the Sri Lanka’s energy generation plan, and the Ceylon Electricity Board (CEB) annual report

states that in year 2011 total installed capacity of small hydro plant was around 200MW and it is

expected to expand energy generation to around 800GWh.

This study focuses on finding out optimum operating parameters to maximize the energy

generation of existing small hydro power plant in the country. By selecting a few small hydro

power plants, preliminary studies were performed to identify optimum values of water flow rate

to maximize the efficiency of the power generation. The study revealed that the selected plants

had not operated at the maximum efficiency; hence they did not optimally utilize the available

water.

5

Acknowledgments

I would like to express my sincere gratitude to Professor Torsten H. Fransson Head, Department

of energy technology for expanding the DSEE Programme to Sri Lanka and pave the way for us

to explore the world of sustainable energy engineering. I am really grateful to Professor Mark

Howells and Mr. Francesco Fuso Nerini for their unwavering guidance, support towards

successful research activity.

I specially thank my local supervisors, Dr. N.S. Senanayaka and Mr. Ruchira Abeyweera for their

unwavering guidance, support and advice for carrying out this research work successfully. I am

also very appreciative for their extensive help in fulfillment of some publications related to this

research work, in some prestigious international forums.

I am indebted to my parents, wife and son for constant support and encouragement for

successfully carrying out this work. My gratitude also due to all academic staff of Open

University Sri Lanka, all academic staff of KTH Sweden and Sri Lanka Sustainable Energy

Authority for the support given with my studies.

I have been assisted extensively by Mr. Asela, Mr. Manjula Wickramathilaka in obtaining required

measurements and data for the research activity which I should greatly appreciate. Finally, my

thanks go to various other personnel without whose help this work wouldn’t be a success.

Understandably, their individual names cannot be mentioned here due to being large in number.

6

Table of contents

Declaration ....................................................................................................................................................3

Abstract ………………………………………………………………………………………...4

Acknowledgement………………………………………………………………………...…….5

Abbreviation..................................................................................................................................................7

List of figures…………………………………………………………………...........................…8

List of tables………………………………………………………………………………….…9

1 Introduction……………………………………………………………………..………..10

1.1 Litterature survey .......................................................................................................................10

1.2 Hydropower sector in Sri Lanka..............................................................................................15

2 Problem formulation and objectives...............................................................................................22

3 Method ................................................................................................................................................23

4 Analysis of Data………………………………………………………………………......25

4.1 Data collected from Ella Pita Ella Small hydro plant ……………………………...………..25

4.2 Data collected from Kebilladowa Small hydro plant……………………………...…………...25

4.3 Data collected from Watawala Small hydro plant ………………………...………………....26

4.4 Electrical power – flow rate curves………………………………………………………... 26

4.5 Turbine efficiency – flow rate curves…………………………………………………….... 27

4.6 Maximum energy from the available water……………………………………………….... 30

4.6.1 Kebilladowa Plant……………………………………………………….... 30

4.6.2 Watawala Plant…………………………………………………….…….. 33

5 Conclusions and future work ...........................................................................................................35

References ...................................................................................................................................................37

Annexure A: Rain fall data of Nuwara Eliya (1981-2011)……………………………………...38

Annexure B: Rain fall data of Watawala (1993-2012)…………………………………………..39

Annexure C: US 300PM Protable Ultrasonic Flow Meter Catalogue…………………………..40

AnnexureD: US 300PM Protable Ultrasonic Flow Meter – Photogrphs of Flow Measurements

at Ella Pita Ella Small Hydro Power Plant……………………………...………………………50

7

Abbreviation

g

Q

H

a

P

T

CEB

MHPP

SHPP

SLSEA

DMSL

Overall efficiency

Gravitational Constant

Water flow Rate

Water head

Constant

Generator electric power output

Time period of operation at optimum condition

Ceylon Electricity Board

Mini hydro power plant

Small hydro power plant

Sri Lanka Sustainable Energy Authority

Department of Meteorology Sri Lanka

Subscripts

n nthelement

8

List of figures

Figure 1.1.1 Original and Degrade Performance curves of turbine……..…………………....…12

Figure 1.1.2 Efficiency curves of typical hydro turbine……………………….…...……….…...13

Figure 1.2.1 CO2 emission data analysis in 2013…………………………...……...……………15

Figure 1.2.2 The electricity generation in CEB…………………………………...……….….…16

Figure 1.2.3 Typical layout of hydro power plant…………………………….……...……..…...17

Figure 4.4 Electrical Power Vs. Average Flow Rate…………………………….……....……....27

Figure 4.5.1 Turbine Efficiency vs. Flow Rate curve for Ella Pita Ella SHPP……………...…28

Figure 4.5.2 Turbine Efficiency vs. Flow Rate curve for Kebilladowa SHPP…………...………….…29

Figure 4.5.3 Turbine Efficiency vs. Flow Rate curve for Watawala SHPP……………..…………......29

Figure 4.6.1.1 Comparison of actual flow rate and optimum flow rate on monthly basis for

Kebilladowa SHPP……………………...………………………………………………….......31

Figure 4.6.1.2 Actual generation of energy and the optimum generation on monthly basis for

Kebilladowa SHPP…………………………………...……………………………………..….32

Figure 4.6.1.3 Loss of generation due to non-operation of the plant at optimum efficiency for

Kebilladowa SHPP………………...……………………………………………………...……32

Figure 4.6.2.1 Comparison of actual flow rate and optimum flow rate on monthly basis for

Watawala SHPP……………………...………………………...……………………………….33

Figure 4.6.2.2 Actual generation of energy and the optimum generation on monthly basis for

Watawala SHPP…………………………………………...……………………...…………….34

Figure 4.6.2.3 Loss of generation due to non-operation of the plant at optimum efficiency for

Watawala SHPP……………………...……………...………………………………………….34

9

List of tables

Table 1.2.1Hydro Power Plant Category ……..………..……………………….………….…15

Table 1.2.2 Total Energy generation Laxapana Complex……..………..…………………….…18

Table 1.2.3 Total Energy generation Mahaweli Complex….……………………………….…...18

Table 1.2.4 Total Energy generation Other Hydro Complex……….………………………..…19

Table 1.2.5 Age analysis of hydropower stations in Sri Lanka…………………………….….…21

Table 4.1 Summary of data from Ella Pita Ella Small Hydro Plant……………...……………....25

Table 4.2 Summary of data from Kebilladowa Small Hydro Plant……………………...……..….25

Table 4.3 Summary of data from Watawala Small Hydro Plant………………...………….……26

Table 4.4 Electrical Power and Average Flow Rate data……………………………………..…26

Table 4.5.1 Summary of overall efficiency calculation for Ella Pita Ella Power Plant…………27

Table 4.5.2 Summary of overall efficiency calculation for Kebilladowa Power Plant……...……27

Table 4.5.3 Summary of overall efficiency calculation for Watawala Power Plant……………..28

Table 4.6.1.1 Details calculation results of Kebilladowa SHPP……...……………………….…31

Table 4.6.2.1 Detail calculation results of Watawala SHPP…………...……………………...…33

10

1 Introduction

The government owned Ceylon Electricity Board (CEB) is the main producer and the provider

of electricity in Sri Lanka. CEB generation divisions consist of sixteen large hydro power plants

totaling to an installed capacity of 1205 MW. As per the annual report of CEB most of them

exceeded their 25 years of operation. The rest of the small hydro power plant is mainly owned by

private power producers. At the same time there are large numbers of rural hydro power projects

which are available most frequently in the area of still not covered by national grid. Hydro power

unit cost is around 1.50 Sri Lanka rupees whereas thermal power generation takes it more than

20.00 Sri Lanka rupees. Therefore effectiveness and improvement of hydro power generation

more effective to national economy of Sri Lanka.

In the backdrop of end of conflict situation that existed for over 30 years, Sri Lanka has is geared

to fast development and the expansion of economic activity. This situation inevitably call for

higher energy demands that the country could not meet unless it focus on new sources as well as

maximizing efficiency of power generation together with sustainable utilization. In this scenario,

hydro power generation has a major role to play, and furthermore with the reach of limit in

exploitation of large hydro power sources, small water streams can make a major impact in

satisfying the demand at affordable costs. Therefore, it is very timely requirement to study the

problems of the present small hydro power plant and research on ways and means to optimize

the energy generation from these resources. In view of searching solutions to this uncertain

situation in the energy sector, this study was undertaken to find out possible means of

maximizing the water potentials in small hydro power generation.

1.1 Literature survey

Hydropower is energy that comes from the force of moving water. The fall and movement of

water is part of a continuous natural cycle called the water cycle. Energy from the sun evaporates

water in the Earth’s oceans and rivers and draws it upward as water vapour. When the water

vapour reaches the cooler air in the atmosphere, it condenses and forms clouds. The moisture

eventually falls to the Earth as rain or snow, replenishing the water in the oceans and rivers.

Gravity drives the water, moving it from high ground to low ground. The force of moving water

can be extremely powerful. Hydropower is called a renewable energy source because the water on

11

Earth is continuously replenished by precipitation. As long as the water cycle continues, we won’t

run out of this energy source [1].

Hydropower has been used for centuries. The Greeks used water wheels to grind wheat into

flour more than 2,000 years ago. In the early 1800s, American and European factories used the

water wheel to power machines. The water wheel is a simple machine. The water wheel is located

below a source of flowing water. It captures the water in buckets attached to the wheel and the

weight of the water causes the wheel to turn. Water wheels convert the potential energy

(gravitational energy) of the water into motion. That energy can then be used to grind grain; drive

sawmills, or pumps water. In the late 19th century, the force of falling water was used to generate

electricity. The first hydroelectric power plant was built on the Fox River in Appleton, WI in

1882. In the following decades, many more hydroelectric plants were built. At its height in the

early 1940s, hydropower provided 33 percent of this country’s electricity. By the late 1940s, the

best sites for big dams had been developed. Inexpensive fossil fuel plants also entered the

picture. At that time, plants burning coal or oil could make electricity more cheaply than hydro

plants. Soon they began to underprice the smaller hydroelectric plants. It wasn’t until the oil

shocks of the 1970s that people showed a renewed interest in hydropower [1].

Devapura Jayasena Wimalasurendra (1874-1953) was a Sri Lankan engineer who played a

prominent role in the establishment of hydropower in Sri Lanka and is known as the "Father of

Hydropower”. Having had his initial proposals on hydro power he constructed the first Ceylon's

small hydro power station in at Blackpool, between Nanu Oya and Nuwara Eliya, to supply

electricity to the Nuwara Eliya town. In 1918 he submitted a paper to the Engineering

Association of Ceylon titled "Economics of Hydro Power Utilization in Ceylon", in it he

proposed the possibility of hydro power from Maskelioya and Kehelgamuoya capable of lighting

100,000 lamps (114.5 MW) and the concept of developing a national grid [2]. With his initiation

Sri Lankan hydro power generation sector was groomed to present condition and Sri Lanka

energy sector has enriched with hydro power generation, approximately it could be higher than

45% of total generation as per the data shown in CEB annual report 2010. Hydro power

contributes around 45% of the national electricity generation in year 2010, whereas wind

contributes less than 1% of total generation [3]. As a renewable energy source it has become

more important economical resource compared to other renewable sources. Hydro power

produces no direct waste and contribution to CO2, green house gasescompared to fossil fuel

plants.At present, all most all hydro potentials available in the country have been utilized for

electricity generation and few remaining are under construction.therefore it is very important to

improve the efficiency of the existing power plants.

12

The performance levels for the turbine design could be identified as three levels such as Installed

Performance Level (IPL), Current Performance Level (CPL) as well as Determination of

Potential Performance Level (PPL). The Installed Performance Level (IPL) is described by the

unit performance characteristics at the time of commissioning. These may be determined from

reports and records of efficiency and/or model testing conducted prior to and during unit

commissioning. The Current Performance Level (CPL) is described by an accurate set of unit

performance characteristics determined by unit efficiency testing, which requires the

simultaneous measurement of flow, head, and power under a range of operating conditions, as

specified in the standards referenced in this document. Determination of the Potential

Performance Level (PPL) typically requires reference to new turbine design information from

manufacturer to establish the achievable unit performance characteristics of replacement turbine.

Turbines installed performance level (IPL) degrade after operating it long time period and ended

up with lower efficiency than design values. As can be seen in figure 1.4 the turbine efficiency

reduce after operating it long time period [7]. According to previous research activity (Figure 1.4)

the Overall efficiency of the turbine was reduced from 90% to 86% approximately during the

period of operation from 1950 to 1985.

Figure 1.1.1 Original and Degrade Performance curves of turbine(Source: HAP best practices catalogue – Francis turbine)

With the change of turbine size and type efficiency characteristic curves will be differ from one to

another. It could be observed each and every type of turbine has coherent peak efficiency range

at particular flow rate range, It could be seen in figure 1.5 [8].

13

Figure 1.1.2 Efficiency curves of typical hydro turbine(Source: HAP best practices catalogue – Francis turbine)

As can be seen in above figures (Figure 1.1.1 and Figure 1.1.2) turbine performance curve will

change with time period of operation as well as turbine type and sizes. Other important matter is

at a particular water flow rate every given turbine gives its peak efficiency. Therefore it is very

important to consider above characteristic for the purpose of enhancing maximum energy output

from a given particular water resource.

The selection of type of turbine is one of the problems in design of hydro plant. The

characteristics, parameters, and classification involved facilitate the choice of turbine. There are

two methods of selection. The first method is graphical selection. It is the various types of

turbine, graphs relating discharges, head work, model test result, and test report. Turbine is

selected according to the head and discharge values. The Analytical Selection will be the second

method. According to the head and discharge values, the turbine parameters are calculated using

the formula and conclude turbine type [9]. As a thumb rule pelton wheel type turbine is suitable

where high water head and low specific speed applications. If the water head and specific speeds

are medium it could be suitable Francis type turbine. Whereas low water head and high specific

speed applications are goes for Kaplan and Propeller type turbine selection. Where Specific speed

(Ns) is a dimensional parameter used to characterize turbo machinery speed.

In order to enhance small hydro power plant efficiency it is very important to conduct both

absolute and relative efficiency tests of hydro turbines. It is invariably in the best interest of a

power plant to have the efficiency of its hydraulic turbines to measure at the start of operation

14

and subsequently at regular intervals [10]. Normally large type turbines performance is

determined initially in model test and consequently absolute installation and testing. During the

efficiency testing of the turbine it’s normally tested whether the manufacturer recommended

performance have been met, and checking for the adjustments of blades and gate mechanism as

well as the hydraulic governor. In the same time it could obtain information that could be used to

evaluate machine wear and cavitations. Prototype turbine installations always have some

differences from their models which alter their performance characteristics.

The model must be subjected to conditions that would be detrimental to a prototype such as

severe and maximum runway speed [10]. However turbine model test is very important to

identify full performance of the system in actual situation.

There are two basic types of turbine efficiency testing the absolute and the relative. These terms

denotes whether the discharge is measured absolutely or in relation to some other known

parameter. The absolute methods are invariably more complex, expensive and difficult; and are

generally done only once to ensure the contract guarantees have been meat. The discharge water

flow rate measurement will be vital to analyse the current performance of the turbine and the

following techniques methods could be used to measure the water flow rate [10].

1. Gibson Method: The changing the momentum of the fluid column resulting from a load

change is measured to determine the flow rate.

2. Allen Salt Velocity Method: The time for the passage of an injected saline solution two

electrode station is measured to determine the flow rate.

3. Weir Method: A calibrated weir, usually downstream is used to measure discharge.

4. Piezometer Traverse Method: Piezometers are used to determine the velocity profile

which is integrated over the cross-sectional area to determine flow rate.

5. Current Meter Method: Same as the piezometer traverse expect for the use of current

meter instead of piezometers.

6. Sonic Method: Acoustic transducers are used to measure the Doppler or phase shift

between two stations the average flow rate separating the two.

7. Thermodynamic Method: Minute changes in the temperature of the discharge water

compared with the incoming are used to evaluate efficiency.

The relative efficiency testing is comparatively easier than absolute method. For the flow is only

measured relative to or is indexed against some parameter which is a direct function of flow rate.

Almost any parameter will do, such as venturi suction in the penstock or the friction head loss in

a penstock or the centrifugal force of the flow around a bend and so on [10].

15

1.2 Hydro power sector in Sri Lanka

With the increasing electricity demand, Sri Lanka has to think about efficiency improving of the

existing hydro power plants or implementing new thermal power plants with comparatively

higher cost and higher environment effects. Presently Sri Lanka has implemented 300 MW of

coal power plant in Puttalam area, and idea is to extend coal power Generation Island wide. As

can be seen in figure 1.1, coal power plants and other thermal generation create more

environmental adverse effects compare with small & lager hydropower plants. On the other hand

power generation cost per is very high in thermal power generation compared with hydro power

generation. As per the Ceylon Electricity Board (CEB) data in year 2010, power generation cost

per one unit of energy (kWh) for hydro Rs. 1.17 whereas thermal generation it’s goes up to Rs.

15.77.

Figure 1.2.1 CO2 emission data analysis in 2013(Source: http://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11, statistics 2013)

Renewable energy technologies are getting cheaper and environment friendly [11]. As amongst

renewable technologies Hydro Power in Sri Lanka is already a consolidated technology and with

relevant potentials, Sri Lanka energy sector has to think about improvement and efficient usage

of the available water resources island wide. Hydro power plant could be categorized from Pico

hydro plant to small & large hydro plant and this research work focuses on small hydro plants.

Table 1.2.1: Hydro Power Plant Category (Source: http://en.wikipedia.org/wiki/Hydroelectricity)

Hydro Power Plant CapacityPico Hydro Power Plant Less than 5 kWMicro Hydro Power Plant 5 kW to 100 kWSmall Hydro Power Plant 100 kW to 10 MWLarge Hydro Power Plant More than 10 MW

16

Most of the large scale power plants are owned and operated by CEB whereas Pico, Micro and

small hydro plants are most probably owned and operated by private companies. As can be seen

in figure 1.2, reasonably higher contribution of energy generation is come from hydro power

plant in Sri Lanka.

Figure 1.2.2 The electricity generation in CEB(Source: CEB annual report 2010)

Micro or small hydro, wind, biomass and solar are the main renewable sources capable of

offering a sustainable contribution to the Sri Lanka’s electricity generation apart from large scale

hydro power generation. Penetration of renewable energy to the electricity generation sector has

been extremely limited by the various constraints such as lack of investment, attitudes,

technology and management of resources. However, during the recent past some interest has

been shown in the construction of small-hydro plants due to its relatively low capital investment

and greater opportunities for grid connection [4].

In general small hydro power plant electrical power output range from 100kW to 10 MW. Since

the most suitable source of energy generation to Sri Lanka would be hydro power this research

activity mainly focus to enhance hydro power generation. Therefore, it is essential to obtain the

maximum capacity from the existing plants by improving the efficiency as much as possible. As

17

can be seen in figure 1.3 the major components of hydro power plant could be identified as water

diversion & screens, pipe line (penstock line), turbine and generator set, tailrace as transmission

line. Therefore hydro power plant efficiency will be depended on friction effects of pipelines,

internal blocking of flow path as well as turbine generator set efficiency.

Figure 1.2.3 Typical layout of hydro power plant(Source: An introduction to hydro power concepts and planning, a publication of canyon hydro)

Mahaweli Hydro complex, Laxapana Hydro Complex and Other Hydro Complexes contributes

40% of the total requirement to the national energy supply while the rest is coming from thermal

Power, mainly diesel and coal. Laxapana Power Complex, having a total installed capacity of

335MW, comprises of five main generating stations at four locations. These include the first

major hydro power station in Sri Lanka, i.e. Old Laxapana Generating Station, which was built

on a pioneering proposal of the visionary engineer, late Mr. D.J. Wimalasurendra. These Power

Stations are situated in cascade in two contributory streams of Kelani River; Wimalasurendra and

Old Laxapana plants fed by KehelgamuOya, and Canyon and New Laxapana Plants fed by

MaskeliyaOya, while Samanala PowerStation at Polpitiya is finally supplied with water from both

these streams. The total Power Generation of the Laxapana Complex was 1,779.5 GWh during

the year 2010, which accounts for 17.8% of the total generation of the network.

18

Table 1.2.2: Total Energy generation Laxapana Complex

(Source: Ceylon Electricity Board, Generation data 2010)

Mahaweli Complex will be the next hydro power scheme which comprises of Kotmale, Victoria,

Randenigala, Rantambe, Ukuwela, Bowatanna and Nillambe Power Stations. The total installed

capacity of the Complex is 666 MW. Mahaweli Complex had generated 2,445 GWh during the

year 2010, which accounts for 22.8% of the total generation of the network. In addition to the

planned maintenance activities of power stations, replacement of the defective excitation system

with Brushless Excitation of two generators at Kotmale Power Station, and the Procontic

Control System at Randenigala Power Station were in progress during the year.

Table 1.2.3: Total Energy generation Mahaweli Complex(Source: Ceylon Electricity Board, Generation data 2010)

Other than the main complexes few hydro power plants are taking in to consider as other hydro

complex which is comprises of Samanalawewa, Kukule, Inginiyagala, and Udawalawe hydro

power stations and Hambantota Wind Power Station. The installed capacity of the Complex is

213 MW. Other Hydro Complex generated 767 GWh during the year 2010, which accounts for

7.2% of the total generation of the network. It is to note that the operating patterns of

Inginiyagala and Udawalawe are solely dependent on the irrigation water releases, and hence the

low plant factors attributed to these stations.

19

Table 1.2.4: Total Energy generation Other Hydro Complex(Source: Ceylon Electricity Board, Generation data 2010)

Ukuwella power station, Old Laxapana and New Laxapana hydro power plants are already exceed

their life span more than 25 year and CEB has plan to rehabilitate them in order to enhance

efficiency of the system. CEB entered into a contract with consortium of Mitsubishi Corporation,

Japan and Indo East Engineering and Construction (Lanka) Pte Ltd for rehabilitation works of

Ukuwela Power Station, initially commissioned in 1976. Under this rehabilitation project,

Turbines, Generators and their associated equipment will be replaced and/or rehabilitated in

order to achieve better efficiency and reliability of the plant at a total cost of Rs. 1,800.0 million.

About 85% of this cost is funded by the JBIC on export credit basis and the Loan Agreement

between Ministry of Finance and JBIC was signed in February 2008. In terms of the Agreement,

the Contract is in force from April 2008, and the works will be completed by the end April 2011

and presently work has completed. Under Laxapana Power plant rehabilitation project, 2 x 50

MW New Laxapana and 2 x 25 MW Wimalasurendra Power Plants will be refurbished and

modernized. Under this contract, the Generator, Turbine Control and Auxiliaries will be

rehabilitated or replaced at a cost of Rs. 6,500 million.

Alstom Hydro France is the contractor for project and 85% of the contract value is provided by

Credit Agricole CIB, France on Export Credit terms and balance 15% is funded by Hatton

National Bank. The Project works started in February 2008 and completed during year 2013.

34Most of hydro power plants in Sri Lanka where constructed and put into operation more than 20

years ago and now they are having long period of operation time. Since the long period of

operation, turbine performance may change with their original condition. Therefore the research

activity mainly focuses on overall efficiency of turbine generator set. Electricity generation sector

of Sri Lanka has higher potential of sustainable energy development and improvement. As far

concern about sustainable energy sources, small hydro, wind and biomass would play vital role.

20

Small hydro power is one of the most efficient and well elaborated kinds of renewable sources of

energy [5].

According to CEB annual report data during the year 2010, four wind power projects of total

capacity 30 MW have been connected to the grid. The total generation was 50 GWh. By the end

of the year, CEB has entered in to 8 Standardized Power Purchase Agreements (SPPA) for an

aggregate capacity of 119MW. SPPA's have been signed for 8 plants of total capacity 92MW. The

construction of some of the above wind plants are in progress. Biomass will be the next

alternative renewable energy source in Sri Lanka. Biomass Power plants consist of three main

categories such as Dendro, Municipal Waste and Agricultural and Industrial Waste. With regard

to Biomass Power Projects, there are two Agricultural and Industrial waste power plants of total

capacity of 11MW have been connected to the grid. The total generation was 32GWh and the

same for the year 2009 was 23GWh. By the end of the year, CEB has entered in to 08

Standardized Power Purchase Agreements (SPPA) for an aggregate capacity of 37MW.

During the year 2010, three small hydro power projects of total capacity 3.7 MW were connected

to the grid. The total grid-connected installed capacity of 84 small hydro power plants reached

170 MW by the end of the year. The total energy generated by these was 642 GWh and for the

year 2009 the corresponding amount was 524 GWh. By the end of 2010, CEB has entered in to

61 Standardized Power Purchase Agreements for an aggregate capacity of 119MW [3].

According to above literatures Sri Lanka energy sector mainly enrich with hydro power and it

contribute more than 45% of total requirement. Electricity generated in three major hydropower

complexes such as Mahaweli Hydro complex, Laxapana Hydro Complex and Other Hydro

Complexes contributes 40% to the national energy supply while the rest is coming from thermal

power, mainly diesel and coal. Hence, obtaining the maximum possible share from hydropower

has the potential of giving overall benefits to the national economy. In order to enhance hydro

power generation CEB has initiated few rehabilitation projects as well as new construction

project such as rehabilitation project of Ukuwela power station, rehabilitation project of new &

old Laxapana power station, construction projects of Upper Kotmale and Broadland power

station etc.

21

Table 1.2.5: Age analysis of hydropower stations in Sri Lanka(Source: Ceylon Electricity Board, Generation data 2010)

Name of the Station Installed Capacity (MW)

Commissioned year Age (years)

InginiyagalaNorton UdawalaweOld LaxapanaPolpitiyaUkuwelaBowatennaNew LaxapanaCanyonKotmaleVictoriaSamanalawelaRandenigalaNilambeRantambeKukule

11.2550650754040100602012101201223.25070

1950195019551955196019761981198419841985198519851986198819902002

65656060503429262625252524222008

As per the data collected from CEB, around 95% of existing hydro power plants in Sri Lanka

have passed the 25 year limit of their life span and previous research activities proves efficiency

deviation with the operating time periods [6]. With the existing energy demand Sri Lanka is not in

a situation to replace old-hydro power plants, within a short period and also its energy

production is mainly depends on hydropower. Age analysis of the hydropower plants in Sri

Lanka is shown in Table 1.

Therefore, it is essential to obtain the maximum capacity from the existing plants by improving

the efficiency as much as possible. As can be seen in figure 1.3 the major components of hydro

power plant could be identified as water diversion & screens, pipe line (penstock line), turbine

and generator set, tailrace as transmission line. Therefore hydro power plant efficiency will be

depended on friction effects of pipelines, internal blocking of flow path as well as turbine

generator set efficiency.

22

2 Problem formulation and objectives

This research activity mainly focuses on overall efficiency of turbine generator set. Since the most

of hydro power plants in Sri Lanka have passed 25 years limit of their life span, field performance

testing of hydraulic turbine is required to find head, power, flow rate relationship which identify

the turbine’s peak operating point [6].

As per the literature review it was identified that turbines performance level goes down with the

time periods of operation. Most of the hydro power plants of Sri Lanka had installed more than

25 years ago. Therefore turbines efficiency and performance could be change from its original

value and optimum level of operation may not be come in to play in present operation condition.

Therefore this research activity is aiming to find out optimum level of operation and possible

extra energy harness from existing water resources.

The objective of this research activity can be listed down as follows:

To identify operation difficulties of small hydro power plants that result in reduction

of total energy generation in Sri Lanka.

Establish operating conditions or operating pattern of small hydro power plant that

will give maximum energy output.

23

3 Method

Three small hydro plants were selected as a sample for the study. These were namely Ella Pita

Ella, Kebilladowa and Watawala. The flow rates were measured at different power outputs for

each plant. The efficiency was computed at different flow rates to obtain the efficiency variation

with the flow rate. The Ella Pita Ella small hydro power plant was analyzed only for the

observation of efficiency & flow rate characteristic curve. Then it could extend for other small

hydro plant which has little bit higher installed capacities.

The flow velocity was measured with the simple float method using plastic ball without rope.

When the measurements were taken the power generation of the plant was adjusted by

controlling the flow rate. Also channel width and flow height were measured to determine the

volume flow rate.

The turbine efficiency was calculated using the following formula for different measured values

of the electrical power output.

Where

Turbine efficiency values were plotted against the flow rate to obtain the efficiency-flow

characteristic curve for each plant.

The actual monthly average flow rates available from past records were used to determine the

volume of water consumed in each month.

24

In the computation, it was assumed that the plant is in operation 24h day and all days in a month.

Then, the number of hours (T) for utilizing this amount of water at maximum efficiency is

determined by dividing Va by the optimum flow rate (Qopt) corresponding to the maximum

turbine efficiency which is obtained from the efficiency -flow characteristic curve for each plant.

The energy (Eopt), which could be generated by operating the plant for time T was calculated by

using the following equation.

In the same manner, the actual energy (Ea) generated in the particular month was calculated using

the following formula for comparison with Ea.

25

4 Analysis of data

4.1 Data collected from Ella Pita Ella Small hydro plant:

Installed capacity -600 kW Cross flow type turbine

Penstock line Diameter = 30 cm H- Head (m) = 70 m

Table 4.1 – Summary of data from Ella Pita Ella Small Hydro Plant

Power (kW) Flow(m3/h)(Test 1)

Flow(m3/h)(Test 2)

Flow(m3/h)(Test 3)

Flow(m3/h) (Average)

100 820 770 890 827

200 1490 1500 1500 1497

300 2140 2170 2190 2167

400 2840 2820 2940 2867

500 3730 3620 3780 3710

600 4840 4850 4800 4830

4.2 Data collected from Kebilladowa Small hydro plant:

Installed capacity -900 kW Pelton wheel type turbine

Penstock line Diameter = 35 cm H- Head (m) = 145 m

Table 4.2 – Summary of data from Kebilladowa Small Hydro Plant

Power (kW)Flow(m3/h)

(Test 1)Flow(m3/h)

(Test 2)Flow(m3/h)

(Test 3)Flow(m3/h) (Average)

100 360 371 382 371

200 682 685 682 683

300 950 975 985 970

400 1245 1280 1285 1270

500 1600 1620 1622 1614

600 2063 2098 2094 2085

700 2505 2525 2518 2516

800 2900 2925 2950 2925

900 3250 3320 3375 3315

26

4.3 Data collected from Watawala Small hydro plant:

Installed capacity -1MWx2 Turgo Impulse type turbine

Penstock line Diameter = 40 cm H- Head (m) = 98 m

Table 4.3 – Summary of data from Watawala Small Hydro Plant

Power (kW) Flow(m3/h)(Test 1)

Flow(m3/h)(Test 2)

Flow(m3/h)(Test 3)

Flow(m3/h) (Average)

100 745 738 740 741

200 1376 1398 1360 1378

300 1900 1938 1940 1926

400 2370 2390 2359 2373

500 2710 2752 2740 2734

600 3082 3070 3076 3076

700 3652 3640 3637 3643

800 4241 4230 4231 4234

900 4886 4826 4856 4856

1000 5393 5441 5402 5412

4.4 Electrical power – flow rate curves

Table 4.4 Electrical Power and Average Flow Rate data

Electrical Power (kW)

Flow(m3/h) (Average)

Ella Pita Ella Kebilladowa Watawala

100 827 371 741200 1497 683 1378300 2167 970 1926400 2867 1270 2373500 3710 1614 2734600 4830 2085 3076700 - 2516 3643800 - 2925 4234900 - 3315 4856

1000 - - 5412

27

Figure 4.4 Electrical Power Vs. Average Flow Rate

4.5 Turbine efficiency – flow rate curves

The efficiency values were calculated using the equation (3.1) for all three plants.

Table 4.5.1 – Summary of overall efficiency calculation for Ella Pita Ella Power Plant

Power (kW) Flow (m3/h)Mechanical Power (kW)

Overall Efficiency (%)

100 827 158 63.4200 1497 285 70.1300 2167 413 72.6400 2867 547 73.2500 3710 708 70.7600 4830 921 65.1

Table 4.5.2 – Summary of overall efficiency calculation for Kebilladowa Power Plant

Power (kW) Flow (m3/h)Mechanical Power (kW)

Overall Efficiency (%)

100 371 147 68.2200 683 270 74.1300 970 383 78.3400 1270 502 79.7500 1614 638 78.4600 2085 824 72.8700 2516 994 70.4800 2925 1156 69.2900 3315 1310 68.7

28

Table 4.5.3 – Summary of overall efficiency calculation for Watawala Power Plant

Power (kW) Flow (m3/h)Hydraulic

Power (kW)Overall

Efficiency (%)

100 741 197.88 50.5200 1378 367.99 54.3300 1926 514.34 58.3400 2373 633.71 63.1500 2734 730.11 68.5600 3076 821.45 73.0700 3643 972.86 72.0800 4234 1130.69 70.8900 4856 1296.79 69.4

1000 5412 1445.27 69.2

Figure 4.5.1 Turbine Efficiency vs. Flow Rate curve for Ella Pita Ella SHPP

Maximum point:

Turbine Efficiency, ηt =73.3%

Flow Rate, Q (m3/h) =2700

29

Figure 4.5.2 Turbine Efficiency vs. Flow Rate curve for Kebilladowa SHPP

Maximum point:

Turbine Efficiency, ηt =79.9%

Flow Rate, Q (m3/h) =1270

Figure 4.5.3 Turbine Efficiency vs. Flow Rate curve for Watawala SHPP

Maximum point:

Turbine Efficiency, ηt =73%

Flow Rate, Q (m3/h) =3076

30

4.6 Maximum energy from the available water

4.6.1 Kebilladowa Plant

The maximum or optimum energy generation from the available water in each month calculated

using the equations 3.2, 3.3 and 3.4. The following is the sample calculation carried out for the

Kebilladowa plant for month of January.

Water volume

No. of hours for utilizing this amount of water at optimum flow of 1270m3/h = T

Actual efficiency is taken from the Efficiency Vs. flow rate curve in Fig 4.5.2.

Actual Energy

Energy at optimum operating condition,

31

Table 4.6.1.1 below gives the calculated values for and for all months. Figure 4.6.1.1

compares the actual flow with the optimum flow rate in order to achieve the maximum

efficiency. Also Figure 4.6.1.2 and Figure 4.6.1.3 illustrate the variations of month actual energy

with the optimum values and the “losses” or water energy not converted to electrical energy

respectively.

Table 4.6.1.1 Details calculation results of Kebilladowa SHPP

Month Qa (m3/h) Va(m3) T (h) ηa Ea(GWh)Eopt

(GWh)

loss

(GWh)

January 3104.73 2235405.6 1760.16189 0.69 0.609 0.707 0.097

February 1929.2 1389024 1093.719685 0.74 0.406 0.439 0.033

March 179.25 129060 101.6220472 0.67 0.034 0.041 0.007

April 1483.73 1068285.6 841.1697638 0.79 0.333 0.338 0.004

May 385.06 277243.2 218.3017323 0.68 0.074 0.088 0.013

June 128.01 92167.2 72.57259843 0.66 0.024 0.029 0.005

July 801.55 577116 454.4220472 0.77 0.176 0.182 0.007

August 153 110160 86.74015748 0.66 0.029 0.035 0.006

September 761.87 548546.4 431.9262992 0.72 0.156 0.173 0.017

October 2382.15 1715148 1350.510236 0.71 0.481 0.542 0.061

November 1752.75 1261980 993.6850394 0.77 0.384 0.399 0.015

December 937.76 675187.2 531.6434646 0.78 0.208 0.213 0.005

Figure 4.6.1.1 Comparison of actual flow rate and optimum flow rate on monthly basis for Kebilladowa SHPP

Optimum flow rate, 1270m3/h

32

Figure 4.6.1.2 Actual generation of energy and the optimum generation on monthly basis for Kebilladowa SHPP

Figure 4.6.1.3 Loss of generation due to non-operation of the plant at optimum efficiency for Kebilladowa SHPP

33

4.6.2 Watawala Plant

Similar calculations as for the Kebilladowa plant carried out for the Watawala plant and results are

given in the Table 4.6.2.1.

Table 4.6.2.1 Detail calculation results of Watawala SHPP

Month Q a (m3/h) Va(m3) T (h) ηa Ea(GWh)Eopt

(GWh)

loss

(GWh)

January 2880.19 2073736.8 674.16671 0.70 0.388 0.443 0.055

February 1936.87 1394546.4 453.3635891 0.58 0.216 0.298 0.082

March 1039.14 748180.8 243.2317295 0.52 0.104 0.160 0.056

April 5188.45 3735684 1214.461638 0.69 0.688 0.798 0.110

May 5037.95 3627324 1179.23407 0.69 0.668 0.775 0.107

June 4984.96 3589171.2 1166.830689 0.69 0.661 0.767 0.105

July 5375.02 3870014.4 1258.13212 0.69 0.713 0.827 0.114

August 4569.23 3289845.6 1069.520676 0.70 0.615 0.703 0.088

September 5592.18 4026369.6 1308.962809 0.69 0.742 0.860 0.118

October 2662.95 1917324 623.3172952 0.67 0.343 0.410 0.067

November 2275.63 1638453.6 532.6572172 0.61 0.267 0.350 0.083

December 994.87 716306.4 232.8694408 0.52 0.099 0.153 0.054

Figure 4.6.2.1 Comparison of actual flow rate and optimum flow rate on monthly basis for Watawala SHPP

34

Figure 4.6.2.2 Actual generation of energy and the optimum generation on monthly basis for Watawala SHPP

Figure 4.6.2.3 Loss of generation due to non-operation of the plant at optimum efficiency for Watawala SHPP

35

5 Conclusions and futurework

Sri Lanka relies mainly on hydro power and thermal power that utilizes imported fossil fuels.

According to the CEB annual report 2010, in that year the hydro power generation was 5720

GWh and thermal power generation was 4955 GWh. The research has shown that hydro power

generation using large rivers is limited, and by now Sri Lanka has utilized all such possibilities.

This situation naturally leads to thermal power as a convenient alternative, but with high cost in

the backdrop of ever increasing fuel prices. By the mid of 2011 Sri Lanka has commissioned and

commercially startup first ever coal power plant in puttalam area with the collaboration of

Chinese government. The number of Thermal power plant increasing means more adverse effect

on economy as well as socio environmental conditions of Sri Lanka. The next option available is

to explore the renewable energy sources like solar, wind and biomass, and micro or small hydro

power generation using small streams of water ways. Apart from renewable energy sources such

as solar and wind, small hydro power generation is one of the promising renewable energy

sources to be explored in the country with the reaching of maximum utilization of hydro power

generation using large rivers. It has been identified that about 600 small scale hydro power plants

capable of adding about 500MW of power to the national grid are available in the country [4]. On

the other hand existing power plant performances have to check and using possible methods it

should improve to enhance energy output from a particular water resource.

In a recent study carried out to determine the performance of Small hydro power plants in the

country revealed that they did not reach the expected targets. According to the findings of

previous researchers, major issues which severely affected the plant performance were found to

operational issues and the improper or lack of maintenance. In design stage faults also

contributed to reduced generation capacity as well [4]. The objective of the research activity was

to investigate selected Small hydro power plants to determine the actual performance and the

possibilities of improvements. Three Small hydro plants were selected for the study.

According to the literature review findings Electricity generation sector of Sri Lanka enrich with

substantially higher amount of hydro power generation. Ceylon Electricity Board and Sri Lanka

government further planned to extend hydro power generation with the aids of foreign countries

like Japan and China. On the other hand most of the existing hydro power plant in Sri Lanka

exceeds more than 25 years of their life span and their performance level differ from original

design condition. In order to find out their optimum operating conditions power plant authorities

may have to perform actual testing work with some analysis.

36

Hydro power plants of Sri Lanka vary from Pico hydro power station (Up to 10 kW) to large

scale hydro power station (Above 10 MW). Here this research activity mainly focuses on Small

hydro power plants and with the measurements taken during actual operating condition possible

energy saving was calculated. Based on the results Kebilladowa Small hydro power plant and

Watawala Small Hydro Plants have potential to improve energy extraction up to 5% ~10% from

annual generation. This would however require additional costs for the improvement of water

storage capabilities in the evaluated case studies.

With a proper utilization of water resources by means of storage system there is possibility to

improve hydro power sector efficiency. This type of interventions could help avoiding the

requirement of new thermal power plant installation. 1kWh of thermal energy generation

replacement by renewable energy means it’s reduces 2 lbs CO2 emission to the environment (As

can be seen in figure 1.2.1). In order to enhance green technology and make human friendly

environment these research findings could be helpful to the Sri Lanka.

37

References

[1] http://www.need.org/needpdf/infobook_activities/SecInfo/HydroS.pdf (01/09/2013)

[2] http://en.wikipedia.org/wiki/D._J._Wimalasurendra (01/09/2013)

[3] Ceylon Electricity Board Annual Report 2010.

[4] D.H.G.S.R. Somasundara, A.M.A.J. Abeywardana, I.U. Attanayake and N.S. Senanayake

“Problems associated with mini hydro power plants for successful operation- a case study in

Sri Lanka”.

[5] Blyashko, Ya. I. Modern Trends in the Development of Small Hydro Power around the

World and in Russia, Thermal Engineering, 2010, Vol. 57, No. 11, pp. 953 – 960.

[6] Jessica Brandt and Jay Doering, Towards of improved model for predicting hydraulic

turbine efficiency, University of Manitoba.

[7] HAP best practices catalogue – Francis turbine, Prepared by MESA ASSOCIATE INC,

Chattanooga.

[8] Short-cut design of small hydroelectric plants, N.G. Voros, C.T. Kiranoudis and Z.B.

Maroulis, Department of Chemical Engineering, National Technical University of Athens,

Polytechnioupoli,Zografou,Athens.

[9] M. Borota, Mini Hydro Power Plants—Green Power for Users, Directorate for Water

Management , Ministry of Agriculture, Forestry and Water Management, MeritaBorota,

Serbia, 2008.

[10] L.H. Sheldon, “Field testing and optimizing efficiency of hydro turbines”, water power &

Dam Construction January 1982.

[11] http://en.wikipedia.org/wiki/Renewable_energy (20/02/2014)

38

Annexure A: Rain fall data of Nuwara Eliya (1981-2011)

Source: Department of Meteorology Sri Lanka

39

Annexure B: Rain fall data of Watawala (1993-2012)

Source: Department of Meteorology Sri Lanka

YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

1993 0.0 47.8 NA 219.6 1016.5 1505.6 845.0 484.2 218.8 1101.1 424.2 326.21994 91.8 149.2 28.4 312.6 646.7 410.5 707.2 508.1 481.1 854.6 235.6 35.61995 NA NA NA 610.5 776.6 1187.3 NA NA NA NA NA NA1996 161.7 135.7 22.3 300.0 100.9 503.7 714.3 856.8 1054.0 515.6 171.5 89.92002 NA 54.3 191.4 951.3 810.9 744.6 633.5 509.1 102.0 598.3 322.6 762.52003 226.9 40.3 349.2 636.3 786.8 385.9 652.3 669.5 676.8 381.7 327.8 44.92004 26.0 34.1 108.3 570.3 824.4 753.7 555.1 304.6 448.4 582.2 216.3 189.02005 77.1 124.6 261.9 184.6 216.5 746.5 1169.5 649.3 697.3 1133.9 962.7 358.02006 152.3 47.5 302.0 205.6 571.8 584.6 465.5 350.4 184.7 425.7 470.9 106.92007 96.4 123.7 123.5 423.8 315.0 428.0 501.0 436.0 586.0 626.0 384.0 84.02008 71.0 221.0 494.0 776.0 481.0 405.0 687.0 NA 294.0 732.0 390.0 135.02009 4.0 21.0 334.0 192.0 878.0 632.0 448.0 414.0 628.0 450.0 346.0 314.02010 58.0 24.0 154.0 410.0 854.0 909.0 728.0 731.0 485.0 619.0 556.0 472.02011 271.0 199.0 132.0 495.0 874.0 516.0 512.0 440.0 488.0 232.0 190.0 90.02012 22.7 NA NA 266.5 114.9 374.7 481.4 438.8 NA 576.9 NA NA

Avg 96.8 94.0 208.4 436.9 617.9 672.5 650.0 522.4 488.0 630.6 384.4 231.4

NA- Not Available

40

Annexure C: US 300PM Protable Ultrasonic Flow Meter Catalogue

41

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44

45

46

47

48

49

50