Natural refrigerants,

a complete solution - Latest technological advancements

Prof. Dr. Armin Hafner

No-7491 Trondheim

Norway

armin.hafner@ntnu.no

• Introduction

• Alternative Technologies for

heating and cooling

• Commercial refrigeration incl. Light commercial

• Industrial Refrigeration

• Mobile AC and Residential AC with CO2

• Transport refrigeration

• Summary

Content

Introduction

Norwegian Ice Export from 1860 to 1915

150 years ago: ICE = refrigeration

Introduction

Advertisement in ICE and REFRIGERATION, 1922, vol. 63

Working fluids history

Use of natural working fluids – Air, ethyl ether, SO2,

methyl chloride, ammonia, propane, isobutane,

CO2 etc

Introduction of synthetic working fluids, like

CFC12 and HCFC22

Montreal protocol established, CFC and HCFC

ozone depletion due to chloride/bromine.

Phasing out CFC (1995) and HCFC (2010)

Hydrogen-Fluor-Carbons (HFC) introduced

Kyoto protocol established, HFC regulated due to

high GWP factor

EUs F-gas directive – Phase down of high GWP fluids

Increasing focus on use of natural working fluids,

especially ammonia, hydrocarbons and CO2

1930

1930-50

1987

1987

1997

1990-now

2006/2007

HFC Emissions, example HFC-134a

0

200

400

600

800

1000

1200

1400

1600

1800

2000

MMTCO2e

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

year

Global reported cummulated Production and Release of R134a

in Million Metric Tons of CO2 equivalent

Production

Released

Source: AFEAS Alternative Fluorocarbons Acceptability Study 2006

More than half of all the refrigerant ever produced

is in the atmosphere!!!

Not a sustainable

solution

for Europe, nor for

the world

What next after Paris?

Source: AFEAS Alternative Fluorocarbons Acceptability Study 2006

Companies focusing on

Natural Working Fluids

will face no risk to invest into

technologies being on the phase

out agenda in the future

<=>

Safe & sustainable investment

SINTEF Energy Research

Alternative technologies:

(non vapour compression)

1

0

• Technologies successfully applied in other applications e.g. Cryogenic, in spaceshuttles, etc.

• Often theoretical comparisons

- Not looking into required heat transfer parameters

• Hypes supported by a small enthusiastic community and others (not) understanding that this prolongs current turnover…

SINTEF Energy Research

Magnetic cooling?

11

Fridge: required cooling capacity: Qo = 20-150 W -> on/off

- Thermal resistance of the magnetic cooling unit?

- Temperature level of the (cold and) hot side may vary at different locations

- Requires regenerator with different material configurations to achieve large temperature lift.

- Change in temperature gradient

- Off design operation?

- Complexity of the unit…

- Customer acceptance: Strong magnetic field (pacemaker?), benefit?

Challenge: What is the design point for a Magnetic Cooling domestic appliance with respect to:

• part load ? • maximum cooling capacity ?

• customer expectations ?

• Based on magnetocaloric effect (MCE) • Reversible temperature change when

magnetic field is applied adiabatically • MCE peaks around Curie temperature

of the alloy • max Dt ~ 3 K @ min capacity

Air Cycle – Made in Japan

Example from MAYEKAWA: Pascal Air

-60 ºC

Transport refrigeration vapour compression cycles

1

6

Containers

• Leading Danish container handling company -> R290

• Carrier has developed R744 refrigeration units placed inside several containers in service.

Application area with a high potential to PHASE-IN

natural refrigerants globally.

Truck & Trailer units

Similar challenges and possibilities as with the container unit.

• Konvekta has roof-mounted R744 refrigeration units for transport vehicles.

Transport refrigeration

1

7

Chamber 2

Chilled food

0 ⁰C

Chamber 1

Frozen food

-20 ⁰C

COP Comparison of Temperature inside the freezing chamber -20 ⁰C at 8 kW and inside the chilled food chamber 0 ⁰C at 6.5 kW

Two stage refrigeration cycles for medium- and low temperature applications.

Ambient temperature [⁰C ]

Ref.: Möhlenkamp et al. Proceeding of the DKV Meeting 2014

Germany Spain USA

An

nu

al e

lect

rica

l e

ne

rgy

usa

ge [

kWh

]

Water heating heat pumps a perfect application for CO2

1

8

Entropy, [kJ/kg K]

Tem

pera

ture

[°C

]

Compressor

GasCooler

Int. Heat

Exchanger

Throttle

Valve

Evaporator

Receiver

1

2

3

4

56

p= 1

50 b

ar

p= 2

0 ba

r

0

20

40

60

80

100

120

3.0 3.2 3.4 3.6 3.8 4.0 4.2

5

4

3

6

1

2

Water heating heat pumps

1

9

From Eiji Hihara, University of Tokyo (2004)

Compact systems

single gascooler: Compact systems

tripartite gascooler:

Chillers applying NR provide comfort AC in building complexes and commercial buildings

Split-Gascooler-Design

Simulation results show:

- COP increased by up to 20% to standard CO2 chiller.

- Additional 10-20% COP increase expected by applying ejectors.

A new PHASE-IN application until 2020!

2

1

Ref.: Jin, Zhequan; Eikevik, Trygve M.; Nekså, Petter; Hafner, Armin. Investigation on CO2 hybrid ground-coupled heat pumping system under warm climate. International journal of refrigeration 2015

Low cost reversible AC/HP RAC unit

Why not reversing the entire unit instead

of the refrigerant flow direction applying

complicated valves?

Simple solution

Low number of required components

2

2

Set-up (heating)

INDOOR

heating

OUTDOOR

cooling

Set-up (heating)

INDOOR

heating

OUTDOOR

cooling

Picture of the R744 turn-table ECU

This concept study showed that a turn-table residential AC-unit,

with R744 as working fluid, is a viable option for many global

areas, where both heating and cooling is required during a year.

HVAC units for public transport vehicles

Busses / Coaches

• Similar challenges as MAC

• Konvekta developed R744 operated Air Conditioning units for busses since 1997

• If MAC goes R744 -> buss AC will follow…

Trains

• Up to 30 % of their total energy consumption has to be spent to operate the HVAC units of the passenger trains in Germany. (Ref. DB)

2

6

R744 HVAC units for public transport vehicles

GC1GC2

IHX

Ejector EV1

EV2 Valve

Com

pre

ssor

Separa

tor

GC2

IHX

Ejector EV1

EV2 Valve

Com

pre

ssor

GC1

Separa

tor

AC-mode HP-mode

AC-mode

HP-mode

Potential train HVAC unit

R744 unit:

Including fixed

nozzle ejectors:

Boosting performance at

high ambient temperature

Transport refrigeration in Japan?

• Refrigerated transport of valuable food needs sustainable refrigeration technology to preserve the food and limit the environmental footprint. – Fishing vessels (HCFC 22 -> R 744)

– Road transport ( HFC xxx -> R 744)

• Public transport: – Train ( HFC xxx -> R 744 or air)

– Cars - MAC ( HFC 134a & HFC 123xxxx -> R 744)

2

9

3

0

The start: 1989-91 in Trondheim Main issue: Energy efficiency of R744 MAC system

R744 lab. prototype system (left) and

BMW 520 CFC-12 system (right)

Mobile Air-Conditioning

18 years ago! CO2 MAC in 1998: soon ready…

http://www.vda-wintermeeting.de/fileadmin/downloads2008/presentations/Christoph_Walter_Behr.pdf

Schwäbische Zeitung 4.April 1998

…the greenhouse gas effect of the car AC

system can be cut by a third when applying

carbon dioxide as a refrigerant

Courtesy, Denso

Worlds first CO2 Car AC system

Made in Japan

And even with a heat

pump option! Source:

NEDC

Ambient conditions: 25ºC @ 50% RH

no sun load; Mode: fresh air

FDC - Fix Displacement Compressor

EVDC- Externally controlled Variable Displacement Compressor

Off line for 2008 average

Fuel consumption due to drag torque, according to 99 / 100 7 EG

Total l/100km: 5,8

CO2-Emission: 156 g/km

Values without A/C

R-134a with EVDC

+ 0,1l/100km (off mode)

R-744 with EVDC

+ 0,05l/100km (off mode)

10 years ago: CO2 MAC: 30% lower fuel consumption

Cooling Cars with Less Fuel, Paris, October 2006

To

tal F

ue

l C

on

su

mp

tio

n l/

10

0k

m

R-1

34

a F

DC

R-7

44 E

VD

C

Gra

ms

CO

2

em

iss

ion

pe

r k

m d

rive

n

R-1

34

a E

VD

C

~ 35 ~1.3

~ 27 ~1.0

~ 19 ~0.7

0ff 0ff

Fuel consumption of a Toyota Yaris (MY 2006) with different

mobile AC systems when driving a NEDC at various ambient

temperatures,

VDA Alternate Refrigerant Winter Meeting 2007, Saalfelden, Austria.

-> 2020 ? Ref: www.daimler.com

"….Responsible risk management

Those who take responsibility in business are also prepared to weigh risks and to act accordingly even when this temporarily leads to problems. A well-functioning risk management system, which gives priority to the safety, health, and protection of lives of vehicle passengers and rescue staff, will pay off for all of us in the end. The refrigerants debate illustrates the high value assigned to responsible risk management at Daimler. Because of safety considerations the company has decided to use CO2 as a refrigerant in the future and to drive forward with rapid development to enable its use as quickly as possible – in the interest of making an effective contribution to improving climate protection and ensuring a high level of safety for customers and vehicle occupants….."

http://www.daimler.com/dccom/0-5-876574-1-1691213-1-0-0-1727129-0-1-8-0-0-0-0-0-0-0-0.html

Industrial refrigeration

CO2/NH3 cascade system

• Evaporation temp.

– Chilling -5°C

– Freeze -32°C

• Economy

– Marginal better than ammonia system with glycol as secondary fluid

• Energy efficiency

– considerably lower energy consumption, mainly due to lower pump work: - Glycol pumps 75 kW,

- CO2-pumps only 4 kW

• Health/Safety + No ammonia in public area

condenser

compressor

receiver

heat

exchanger

compressor

from freeze-room

from chilled-room

low-temp

receiver high-temp

receiver

to freeze-room

to chilled-room

Industrial CO2/NH3

cascade system MS Kvannøy (Norway)

• Design system

– 11 plate freezers, 9 RSW-tanks and one ice machine

– Refrigeration load 1350 kW at -48°C

• System

– Ammonia in top stage

– 6 piston compressors for CO2 – 2 screw compressors for ammonia

– Special built 50 bar CO2 piston compressor for hot gas defrosting

– Liquid separator equipped with ”cold finger" and pressure release valve

• Challenges

– Demanding dynamic in the interaction between the CO2 og NH3 screw compressors

• Operating experience

– Freezing time are reduced with 40% and corresponding increase in

freezing capacity

– Satisfactory safety in operation

3

8

Light commercial ref. units / standalone units

Important players are joining: They have installed more than 3.5 million units using natural refrigerants – both in developing and industrialised countries. This is real PHASE-IN of natural refrigerants! CONGRATULATIONS

Commercial Refrigeration (Supermarkets)

• In future: supermarket refrigeration system provides entire

energy flow and demand in the building (and surrounding) • Air Conditioning (direct or chilled water)

• heat recovery: hot water production, space heating, ice protection

• heat pump function & export of heat

• CO2 (R744) is the preferred alternative of the end-users

across Europe for new installations

• Predictable – no restrictions

• CO2 booster units are proven technology with potential to further

improve COP (parallel compression + ejector technology)

• Promising global perspectives for a successful Phase-in

The average annual refrigerant leakage rates:

• in Europe: 15-20 % of the total charge, mainly HFC-404A

• Worldwide about 30 % of the charge, mainly HCFC-22

Commercial Refrigeration (Supermarkets)

Evolution of R744 Commercial Refrigeration since 2003:

R744 simple Booster

Parallel

Compression

(PC)

Ejector System

(Supporting PC)

SEER + 10%

SEER + 10-20%

SEER: Seasonal Energy Efficiency Rating

Evolution of R744 Commercial

Refrigeration

R744 simple Booster

(Baseline)

• simple

• many units in the

market

• flash gas bypass

• low cost (below HFC

in Scandinavia)

• COP / SEER baseline

for moderate – cold

ambient temp.

Parallel

Compression

• advanced

system

• higher

investment

cost

• flash gas

(auxiliary)

compression

Ejector System

• advanced system

• flooded

evaporators: • possible

• simple (no pump)

• pre-

compression

• higher load on

auxiliary

compressors

SEER

+ 10% SEER

+ 10-20%

Example:

'Multi Ejector' Supermarkets in CH

Ref: Eric Wiedenmann, ATMOsphereEurope 2015

4

3

R744-PC with and without Ejector Field test results from Ibach / CH

Ejector system ≠ Ejector system

Classic Ejector

• High pressure control with

needle in motive nozzle

• High eff. at design point

• Part load operation

challenges

• Low motive flow rate and

• Large mixing chamber

• Requires oil return strategy

• Ejector off (low pumping

ability) – superheat

operation of evaporators

• Discontinues operations

Liquid Ejector

only

• Enables flooded

evaporators all year

• Applicable for

booster and parallel

compression system

• Simple on/off control

• Requires low

pressure accumulator

Ejector supported parallel

Compression

• Fixed nozzle ejectors:

designed for pumping

liquid and pre-

compressing vapour (ex:

Multi-Ejector block)

• Enables flooded

evaporators all year,

requires small low

pressure accumulator

• Higher load on auxiliary

compressors.

• Pressure lift can be

adapted to provide

efficient AC

Venturi type

• Part load challenges

GC

MT

Comp AC_Evap

to = +5°C

ref_

evaps ref_

evaps ref_

evaps MT_Evap

to = -2°C

HR

Parallel

Compressor MT

Comp

MT

Compressor

p = 48 bar

p = 33 bar p = 17 bar

LT_Evap

to = -25°C

GC

liquid

vapour

AC = Air Conditioning

MT = Medium temp cooling

LT = Low-temp freezing

GC = Gascooler

HR = Heat Recovery

LT Compressor

High pressure: up to 120 bar

Separator

AC Ejector

Multi-

Ejector

MT- Receiver

Next generation R744

com-ref unit

R744 ejector versus HFC404A

Performance of commercial

refrigeration systems

Ambient Temperature [°C]

CO

P

Ref: Finckh 2011

ICR 2011

Annual temperature bins

for selected cities

Source Meteonorm

North America

South America

South Europe

Africa India China Australia

Relative annual energy usage (exclusive AC part)

How to make real

systems?

• Ejectors are widely used in refrigeration systems to pump

lubricant inside compressors

• Since a few years many European OEM’s are developing

R744 ejectors for units with a cooling capacity above 5 kW:

• Supermarkets require high efficient systems with natural

working fluids all across Europe

• Laboratory and real pilot units are required for development

• More advanced system configuration requires good

understanding during the design and implementation

phase

Training and technology transfer is important

We will help you with pleasure!

– Modular design (ejector cartridges placed into a monoblock casing) developed by Danfoss in cooperation with SINTEF/NTNU

– Six fixed-geometry ejectors

– 6-100 kW cooling capacity

Example:

Multi-ejector module

Multi-ejector lab tests

Ejector efficiency for VEJ1

Multi-ejector

performance mapping

tevap = -8 °C, ∆tSH = 10 K, constant load, automated ejectors controlling

Multi-ejector

ejector efficiency

R744 ejector system for Japanese market applications

• R744 Ejector well known from EcoCutes in Japan

• Roll out of R744 systems for small supermarkets started successfully – integrated systems (ref, AC, HP, water heater)

• Performance boost with ejectors not utilized yet

• Flooded evaporator R744 systems should be developed for RAC applications including simple low cost ejectors

-> efficient low cost R744 RAC system

• Integration of EcoCute function and RAC might solve challenges and open new markets (even outside Japan)

• Reduced investment cost for the customer

• Only one outdoor unit (eco-cute + RAC)

5

7

Summary / conclusions / outlook (CO2 - R744)

• Tremendous development of CO2 technology since 1988

• Energy efficient CO2 systems have been introduced in the market

• CO2 systems enable flooded evaporators and offer to integrate: Ref. + HVAC + Eco-Cute

• Adapted ejector technology offer high system performances and COP's, even at high ambient

• CO2 is a viable natural refrigerant PHASE-IN candidate for many applications, globally 5

8

Summary / conclusions / outlook

• Natural Refrigerants are already ‘PHASED-IN’ in many applications -> there is more potential

• OEM’s with a clear strategy towards a fast introduction of NRs will gain market shares, not wasting investments towards intermediate solutions

• Authorities have to support the introduction of NRs despite the lobby attempts of chemical companies

• Knowledge transfer + Training is key

5

9

A wise man said

20 years ago

Prof. Gustav Lorentzen (1915-1995)

We have heard a great deal lately of the

harmful effects to the environment when

halocarbon refrigerants are lost to the

atmosphere. This should not really have come as a surprise since similar

problems have happened over and over again. Numerous cases are on

record where new chemicals, believed to be a benefit to man, have turned

out to be environmentally unacceptable, sometimes even in quite small

quantities (DDT, PCB, Pb etc.).

In the present situation, when the CFCs and in a little longer perspective the

HCFCs are being banned by international agreement, it does not seem very

logical to try to replace them by another family of related halocarbons, the

HFCs, equally foreign to nature.

International Journal of Refrigeration 9. Vol. 18, No. 3, pp 190 197, 1995