Paul Blacklock
Calor Gas Ltd Athena Drive,
Tachbrook Park
CV34 6RL
Warwick
Warks United
Kingdom
Tel. + 44 1926 330088
Fax. + 44 1926 318718 E-mail:
pblacklo@calorgas.co.uk
http://www.care-refrigerants.co.uk/

(reduced, recovered, destroyed, replaced, avoided)

The most common non-fluorinated refrigerants used are ammonia, hydrocarbons, carbon dioxide (CO₂), water and air. NIK technologies include absorption, desiccant, evaporative cooling, Stirling cycle¹⁹ and thermoelectric.

HFCs are powerful global warming gases with global warming potentials (GWPs) typically thousands of times higher than non-fluorocarbon alternatives². The non-HFC technologies identified above have either zero or negligible GWPs. This is important as most of the damage from HFCs arises through their leakage and venting during the lifetime of RAC equipment. In 1996 some 80% of HFCs were used for topping up leaking systems³.

HFC Leakage Rates
Historical halocarbon annual leakage rates were high as 25% for distributed systems (e.g. supermarkets, cold stores etc), refrigerated transport and mobile a/c, and 10% for central chillers⁹ in 1995. These high leakage rates are due to the fact that the containment of fluorocarbon refrigerants has traditionally been a low priority during equipment design, manufacture, installation, use and disposal. There has of course also been a strong commercial incentive, particularly amongst the fluid suppliers and maintenance contractors, for systems to leak.

These attitudes are spread widely within the RAC industry. This was evidenced by the poor response that the UK Government received to its voluntary agreement with the UK RAC industry to limit HFC emissions. Of the more than 7000 companies in the UK industry only around 200 (less than 3%) have formally signed up to the agreement⁴.

The average loss of charge on the disposal of RAC equipment has also been traditionally high - despite the existence in many countries of mandatory recovery and recycling schemes. Disposal losses have been typically 75% for distributed systems, 25% for central chillers and 100% for refrigerated transport and mobile a/c⁵.

Control through public policy is made all the more difficult by the sheer number of systems involved (over 1 billion) and the fact that the vast majority of systems are sited in private premises far away from law enforcement authorities.

Impacts from HFC Manufacture
HFCs also have a global warming impact arising from their manufacture⁶. This is as a result of fugitive emissions from the manufacturing process and due to the energy consumed during manufacturing. This compares unfavourably with the non-HFC alternatives. For example, the total process related CO₂ arising from the manufacture of HFC134a is more than 160 times greater than that required to manufacture isobutane⁷.

Energy Efficiency
The issue of energy efficiency is of crucial importance in relation to the indirect global warming impact from CO₂ emissions arising during energy production. Using a non-HFC substance or technology may have an important influence on energy usage. In some cases the effect can be beneficial. However, in other situations there is an energy penalty, which can actually lead to an increase in CO₂ emissions that outweigh the benefits of reduced HFC emissions. These effects are strongly application and design dependent and must be carefully taken into account when considering HFC emission reduction strategies. This is a topic of intense discussion as there is no general rule because refrigerants and refrigeration technologies can behave differently in different systems under different conditions. However, numerous research work has illustrated that non-HFC technologies can provide more efficient refrigeration cycles than those using HFCs.

NOTE: See "ADDITIONAL REFERENCES" below.

Emission Forecasts.
It is extremely difficult to forecast the future emissions of HFCs. This is because any forecast is dependent upon a number of factors. These include the future volumes of HFCs in the market, leakage rates, recovery rates and the take up of non-HFC technologies. These will vary from country to country. These variables mean that there are already substantial variations in the forecasts for future HFC emissions - even when they are based upon the same data. For example, current estimates for UK HFC emissions vary from >1% to 4%^8,9 of total UK greenhouse gas emissions.

It should be noted that it is impossible to achieve zero leakage with any refrigerant in any kind of equipment.

(e.g. toxicity, flammability or other air emissions)

HFC production can leak toxic chemicals. The manufacture of HFCs releases vinyl chloride, ethylene dichloride (both carcinogens), other chlorinated organics, HFCs and HCFCs into the atmosphere. Liquid traces include heavy chlorinated residues likely to contain traces of dioxins as well as chromium in catalyst wastes⁶.

In addition, HFCs have been shown to have toxic effects on refrigeration technicians whilst handling these refrigerants, leading to skin and stomach disorders and other effects such as headaches and dizziness¹⁶. Within a fire situation, HFCs produce poisonous, toxic and corrosive substances when burned¹⁷.

HCs as Volatile Organic Compounds
The issue of Volatile Organic Compounds (VOCs) is often raised in respect of the use of hydrocarbon aerosol propellants and there have been attempts to extend this to the use of hydrocarbons as refrigerants. However, it is already recognised that the VOC issue is very limited in respect of its impact on the use of hydrocarbons - even in 100% emissive applications such as aerosols¹⁰.

It has been calculated that if the entire UK refrigerant bank converted to hydrocarbons this would equate to approximately 10,000 tonnes. Even if this were then to leak at current leak rates this would equate to only 0.09% of all UK manmade VOC emissions.

Refrigerant Flammability and toxicity
It is widely known and recognised that hydrocarbons are flammable. Ammonia is less flammable, but is toxic. However, these safety issues have already been addressed in a number of international and national standards. It should be remembered that society already makes wide and safe use of such flammable substances as petrol, natural gas, LPG, paraffin and diesel. Ammonia has been used safely as a refrigerant for more then 100 years.

CO₂ is neither flammable nor toxic and can then thereby serve as a good alternative in applications where this is beneficial.

(cost)

• Type of equipment
• Application
• Availability of technical support
• Commercial availability of alternatives
• Safety requirements
• Legal environment
• Life costs - this includes the cost of energy, capital, maintenance and disposal.

Training has not been included in this list as there will be an equal requirement to train - whether to use ammonia/hydrocarbons safely or HFCs responsibly. Training to achieve and maintain a high system performance during operation will be the same for all refrigerants.

It is only once all these factors have been taken into account that the economic impacts can be properly calculated and the UNFCCC is counselled against accepting any 'rule of thumb' measures or sweeping generalisations. It is a simple fact that in some cases the use of HFC alternatives will reduce costs and in other circumstances costs will increase.

One positive benefit of switching to non-HFC solutions now is that it will avoid the costs involved with any possible HFC phase-outs in the future. Some countries have already proposed a phase-out of HFCs and this is against a background where much of the RAC industry is still using vast quantities of CFCs and HCFCs. It will obviously be more economically prudent for these users of CFCs and HCFCs to switch straight into non-HFC solutions. This will completely avoid the need for any possible costly conversions in the future should end users decide to go down the HFC route. This issue is particularly pertinent in Article 5 countries that are in the process of phasing out CFCs and HCFCs.

Economic Instruments
It is already widely recognised that there is a role for economic instruments to reduce the emissions of greenhouse gases such as HFCs. Many countries are either applying or proposing specific energy taxes per given quantity of carbon or energy, applied in the form of downstream taxes on end users.

This is certainly a model that could be followed in order to encourage a shift to more environmentally benign non-HFC technologies such as ammonia, hydrocarbons and CO₂. Denmark has been in the forefront of this and has already proposed a tax relating to the consumption of refrigerants and weighted according to their respective global warming potentials¹¹. For example:

Since refrigerants are sold for thousands of US dollars per tonne any tax has to be of an appropriate order of magnitude if it is to have an effective influence on buying behaviour.

Such an economic instrument would encourage all of the main technical opportunities that are available to reduce HFC emissions. These being (a) Use a zero/low GWP non-fluorinated refrigerant (b) Use NIK technology (c) Reduce emissions throughout the life cycle of the product.

A tax based on the GWP of refrigerants has the following benefits:

• It is simpler and less bureaucratic to implement and administer than any leakage monitoring system.
• It would give strong signals to business considering investments in RAC equipment.
• It would provide revenue streams that could be used to support proper reclaim and recycling schemes and incentives for investments in non-HFC technology.

An HFC tax would certainly encourage a controlled and phased transition to non-HFC refrigerants. It would also ensure that the use of HFCs is restricted to those non-RAC applications where there are currently no alternatives commercially available.

Components for CO2 technology are becoming available at the moment and commercial systems are expected to be available by 2000.

The main aspect to be considered in respect of timing is that the longer that any substantive action to control the use of HFCs is delayed the greater the cost of any future compliance.

ACP Consult
Klovervangen 60
8541 Skodstrup
Denmark
alex@pachai.com
(Alexander Cohr Pachai)

Association for Environmentally Conscious Builders
Nant-y-Garreg Farm
Saron Llandyssul Dyfed UK
Admin@aecb.net
(Keith Hall)

Bonus Energi AB
PO Box 32
S-370 10 Brakne-Hoby
Sweden
tony@bonusenergi.se
(Tony Andersson).

Boral Refrigerants,
Esanty Australia
Dominic.drenen@esanty.com.au
(Dominic Drenen)

David Butler
Principal Project Engineer
Environmental & Fire Dynamics Centre
Building Research Establishment
Garston
Watford WD2 7JR
UK
Butlerd@bre.co.uk

Professor Donald Cleland
Massey University
Private Bag 11-222
Palmerston
North New Zealand
d.cleland@massey.ac.nz

Cool Concerns
18 Newbury Lane
Compton
Berks RG20 6PB
UK
Janeg@coolconcerns.co.uk
(Jane Gartshore)

Danish Technological Institute
Teknologiparken
DK-8000 Arhus C
Denmark
Michael.kauffeld@teknologisk.dk
(Dr Michael Kauffeld)

Delft University of Technology
Laboratory for Refrigerating Engineering
Mekelweg 2
NKL 2628 CD Delft
The Netherlands
c.h.m.machielsen@wbmt.tudelft.nl
(Assoc. Prof. Cees H.M. Machielsen)

De' Longhi S.p.A.
31100 Treviso
Italy (S. Zanolin) (Fax - + 39 0422 413654)

Earthcare Products
Conbar House
Mead Lane
Hertford SG13 7AP
UK
Nickcox@dial.pipex.com
(Nicholas Cox)

Ecozone Ltd
Network of Climate Safe Cooling
The Netherlands
ecozone@antenna.nl
(E.F.S. Dijkstra, MSc)

Elgas Limited
PO Box 818
Milsons Point NSW 2061
Australia
kevin.sansome@elgas.com.au
(Kevin Sansome)

European Business Council for a Sustainable Energy Future (e5)
Stalen Enk 45
NL - 6881 BN Velp
The Netherlands
Pemetz@worldonline.nl
(Paul Metz)

Friends of the Earth
1025 Vermont Ave., NW
Washington, DC 20005
USA
JVallette@foe.org
(Jessica Vallette)

Global Cooling b.v.
P.O. Box 4202, NL-7200 BE Zutphen,
The Netherlands
info@globalcooling.nl
(Geert Klok)

Hopkins Catering Equipment
151 Kent Road
Pudsey
Leeds LS28 9NF
UK
Chris@hopkins-catering.co.uk
(Chris Hopkins)

INFRAS
Gerechigkeitsgasse 20
CH-8002
Zurich
Switzerland
oschwank@infras.ch
(Dr O. Schwank)

International Secondary Refrigerants Association (ISRA)
PO Box 1015
3180 AA Rozenburg
The Netherlands
Nina.liem@kemira.com
(Secretary: Ms S.L.N. Liem)

Kemira Chemicals
PO Box 1015
3180 AA Rozenburg
The Netherlands
Nina.liem@kemira.com
(Nina Liem)

Yasuko Matsumoto
Associate Professor
Suwa Junior College
Science University of Tokyo
5000-1 Toyohira,
Chino-City Nagano Prefecture,
Japan 391-0292
yasuko@sk.suwa.sut.ac.jp

NTNU Norwegian University of Science and Technology
N-7491Trondheim Norway
Petter.neksa@energy.sintef.no
(Petter Neksa)

SHV Energy India
T-220, J/1, Savitri Nagar
Nr Malviya Nagar
New Delhi 110 107
India
Supergas@del3.vsnl.net.in
(J. Bhatia)

SINTEF Energy Research
N-7465 Trondheim
Norway
trude.tokle@energy.sintef.no
(Trude Tokle)

The Netherlands Organisation for Applied Scientific Research TNO,
Department of Refrigeration and Heat Pump Technology
Laan van Westenenk 501 PO Box 342
7300 AH Apeldoorn
The Netherlands
r.j.m.vangerwen@mep.tno.nl
(R.J.M. van Gerwen M.Sc.)

University College London
Dept. of Mechanical Engineering
Gower St
London WC1E 6BT
K_suen@meng.ucl.ac.uk
(Dr William Suen)

University of New South Wales
School of Mechanical and Manufacturing Engineering
Sydney
NSW Australia 2052
Ian@ilm.mech.unsw.edu.au
(Prof I. Maclaine-cross)

Northern Ireland Centre for Energy Research & Technology
University of Ulster
Coleraine, Co.
Londonderry,
Northern Ireland, BT52 1SA
United Kingdom
Nj.hewitt@ulst.ac.uk
(Dr Neil J Hewitt)

University of Warwick
School of Engineering
Coventry CV4 7AL
UK
Esrec@eng.warwick.ac.uk
(Dr B. Critoph)

(what and where)

1. Colbourne, D., Blacklock, P. 'Limiting HFC emissions through the use of non-HFC technologies.' Proc. IPCC/TEAP Joint Expert Meeting, Petten May 1999
2. IPCC Second Assessment Report. 1996
3. Building Services Research and Information Association. 'UK & European Market for Refrigerants.' Status Report 121471/1. Sept 1998.
4. Environmental Data Services. Issue No 252 pp31-32. January 1996.
5. UK Department for the Environment, Transport and the Regions. 'Proposed New Controls on CFCs, HCFCs,1,1,1-Trichloroethane and Carbon Tetrachloride, UK Costs and Compliance Study. Sept 1998.
6. Banks, R.E., Sharratt, P.N. ' Environmental Impacts of the Manufacture of HFC134a.' UMIST November 1996.
7. McCulloch, A., Campbell, N.J. 'The climate change implications of producing refrigerants.' Proc. IIR Conf. Natural Working Fluids '98.Oslo
8. Johnson, E. 'Global Warming from HFC.' Environmental Impact Assessment Review. November 1998.
9. March Consulting. 'UK Emissions of HFCs, PFCs and SF6 and Potential Emission Reduction Options.' 1999.
10. Campbell, N. ' Technical, Pesticide, Cosmetic, Convenience and Novelty Aerosol Products. Proc. IPCC/TEAP Joint Expert Meeting, Petten May 1999
11. Lindegaard, E. Speech to IIR Natural Working Fluids Conference. Aarhus 1996 12. Pedersen, P.H. 'Ways of Reducing Consumption and emission of potent greenhouse gases (HFCs, PFCs and SF6). Project for the Nordic Council of Ministers. DTI Energy December 1998.
13. Powell, L., Blacklock, P. 'Experience of using Hydrocarbons in refrigeration and air-conditioning applications in Europe. Proc. AIRAH Conf. Sydney April 1997. 14. Greenpeace video. ' Cool Technologies - working without HFCs.' Shown at the UNFCCC/TEAP Conference. Petten May 1999.
15. Website of Calor Gas Refrigeration. www.care-refrigerants.co.uk
16. Hansen, B., "Arbejdsmilio, olier og kolemidler", Dansk Koledag, 1998.
17. Anon, "Beware! Decomposing Refrigerants", Industrial Fire World, USA, Nov/Dec 1997.
18. Nyvad, J., Lund, S. ' Indirect cooling with ammonia in supermarkets.' IIR Conf. Applications for Natural Refrigerants '96.
19. Berchowitz, D.M. ' Maximised Performance of Stirling-Cycle refrigerators.' Proc. Conf IIR Natural Working Fluids Oslo. 1998
20. Stene, J., 1998: "Compression Systems with Natural Working Fluids - Results and Conclusions from IEA Annex 22 (1995-1998)", Natural Working Fluids '98, IIR - Gustav Lorentzen Conference, Oslo, Norway, IIR, p. 129-137.
21. Nekså, P., S. Girotto, et al., 1998: "Commercial Refrigeration Using CO2 as Refrigerant - System Design and Experimental Results", Natural Working Fluids '98, IIR - Gustav Lorentzen Conference, Oslo, Norway, IIR, p. 227-236.
22. Nekså, P. , 1999: "CO2 Heat Pump Systems", Heat Pumps - a Benefit for the Environment. 6th International Energy Agency Heat Pump Conference, Berlin Germany, May 31 - June 2, 1999.

ADDITIONAL REFERENCES

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Agarwal, RS, "Isobutane as refrigerant for domestic refrigeration in developing countries", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996

Arnvig, M, "Technical options in industrialised countries", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

Baz, P Meyerson, K Lagatis, D, Hydrocarbon Technology Yearbook 1995, GTZ (Deutsche Gesellscaft fur Technische Zusammenarbeit. 1995

Bitzer GmbH, "Application of propane (R290) with semi-hermetic compresors", Technical information booklet KT-660-1

Brendeng, E., A. Christensen, et al., 1997: "CO2 in the Low Temperature Stage of Large Industrial Refrigerating Plants". CO2 Technology in Refrigeration, Heat Pumps & Air Conditioning Systems, Trondheim, Norway, IEA Heat Pump Centre, p.

Butler, D. J. G., "Replacing R22 in existing DX Liquid Chillers" Proc. Conf. R22 Phase Out, Institute of Refrigeration, London, 1998.

Castle, T, "Status of natural refrigerants within the UK", IEA Annex 22: UK Country report, EA Technology Ltd, 1995.

Charters, WWS Megler, VR Urma, J Aye, L, "Propane as a working fluid in domestic heat pumps, "Proceedings of IIR Commission E2: Refrigeration, climate control and energy conservation, Melbourne, Australia 11-14 Feb 1996

Choi, DK Domanski, PA Didion, D, "Evaluation of flammable refrigerants for use in water-to-water residential heat pumps", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996

Cleland, D.J. & Keedwell, R.W. (1998) Use of hydrocarbon refrigerants in on-farm milk cooling equipment, AIRAH J. 52 (7) 19-23.

Dijkstra, E Machielsen, C Menard, D, "Cooling of a bulk milk tank with R290/R600a in the Netherlands", International Conference on Ozone protection technologies, 1996.

Frehn, B, "Hydrocarbons as alternative refrigerants for heat pumps - initial operational experience", RWE Energie, Essen, Germany.

Gentner, H., 1998: "Passenger Car Air Conditioning Using Carbon Dioxide as Refrigerant", Natural Working Fluids '98, IIR - Gustav Lorentzen Conference, Oslo, Norway, IIR, p. 259-268

Gerwen, R.J.M., "Air Cycle Heat Pump Developments and Applications", 6th IEA Heat Pump Conference, Berlin, Germany, 1999

Gerwen, R.J.M. van, "Air as Refrigerant - Prospects and Challenges", IEA Annex 22 Workshop Compression Systems with Natural Working Fluids, Gatlinburg, USA, 1997

Gerwen, R.J.M. van, "Quantification and evaluation of safety risks related to the use of ammonia and hydrocarbon refrigerants", IEA Annex 22 Workshop Compression Systems with Natural Working Fluids, Gatlinburg, USA, 1997.

Gerwen, R.J.M., "Natural Refrigerants: applications and risks", 19th International Congress of Refrigeration, IIR/IIF, The Hague, 1995.

Gerwen, R.J.M. van, "Dutch Regulations for Reduction of Refrigerant Emissions: Experiences with a Unique Approach over the period 1993-1998", ASERCOM Symposium, Nuremberg, Germany, 1998.

Gomez, ML, "Hydrocarbon technologies in Argentina: present situation and future applications", Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995.

Haaf, S Mall, K Rinne, F, "Natural fluids in supermarket applications. Linde's solutions for tomorrow today available Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995

Halozan, H, "Practical experience with direct-expansion propane heat pumps in Austria", Annex 22 - HPP-AN22-1: Workshop Proceedings "Natural working fluids - Applications, experience and developments", 1996

Halozan, H, "Propane for heat pumps", Proceedings of 19th international congress of refrigeration 20-25 August 1995, vol Iva.

Halozan, H Ebner, T Lawatsch, H, "Propane - a realistic alternative", Proceedings IIR Commission B2: New applications of natural working fluids in refrigeration and air conditioning, Hannover, Germany, 10-13 May 1994

Halozan, F, "Natural refrigerants - an option for heat pumps", Proceedings of IIR Commission E2: Refrigeration, climate control and energy conservation, Melbourne, Australia 11-14 Feb 1996

Haukas, HT, "Practical performance of alternatives to R12 and R502 in refrigerators and freezers", Proceedings of Institute of Refrigeration conference on CFC alternatives: User experience and update, Novermber 1992.

Jakobsen, A. and P. Nekså, 1998: "Carbon Dioxide in Marine Refrigeration Applications", Earth Technologies Forum 98, Washington D.C., USA.

James, RW Missenden, JF, "The use of propane in domestic refrigerators", International Journal of Refrigeration, Vol. 15, No. 2, pp 95-100, 1992.

Kauffeld, M, "Breakthroughs in mobile hydrocarbon refrigeration and cooling", Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995.

Kauffeld, M., "Breakthroughs in Mobile hydrocarbon refrigeration and cooling", Danish Technological Institute, 1995

Kauffeld, M. ' Emerging Alternatives for HCFC in RAC technologies', Proc. HCFC Workshop, OEWG. Geneva. May 1999

Keedwell, R.W. & Cleland, D.J. (1998) Use of hydrocarbon refrigerants to replace HCFC-22 in on-farm milk cooling equipment, Proceedings IRHACE Technical Conference, Nelson, April 1998, p. 10-18.

Kim, MH., Lim, BH Chu, ES Moon, JH Park, YS, "Performance evaluations of HC refrigerant in a frost free refrigerator/freezer", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

Kim, MS., Chang, YS Ro, ST, "Performance and heat transfer of hydrocarbon refrigerants and their mixtures in a heat pump system", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996

Köhler, J., M. Sonnekalb, et al. 1998: "Kohlendioxid als Kältemittel für Bus-Klimaanlagen", 194-197.

Kraft, R, "The use of hydrocarbons in supermarkets", Proceedings of international conference on ozone protection technologies, 21-23 October 1996, Washington DC, 1996.

Kruse, H, "Current status of natural working fluids in refrigeration, air conditioning and heat pump systems", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

Kruse, H, "Energy savings when using hydrocarbons as refrigerant", Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995

Lorentzen, G, "The use of natural refrigerants: a complete solution to the CFC/HCFC predicament", International journal of refrigeration, Vol. 18, no. 3, pp. 190-197, 1995

Lorentzen, G. 1988: "Ammonia : an Excellent Alternative*", International Journal of Refrigeration, vol. 11, no. July, p. 248-252.

Lystad, T, "Testing of a heat pump with propane as working fluid Annex 22 - HPP-AN22-1: Workshop Proceedings "Natural working fluids - Applications, experience and developments", 1996.

Machielsen, C.H.M., Dijktra, E.F.S., and Weber, H., Hydrocarbons as Refrigerant in Bulk Milk Tanks, Practical Experience in Indonesia and the Netherlands, Proc. of Int. Conference on Fluid and Thermal Energy Conversion, July 21-24, 1997, Yogyakarta, Indonesia.

Machielsen, C.H.M. and Dijkstra, E.F.S., International Standards and the Dutch Code of Practice for the application of flammable refrigerants, seminar on ODS Phase-Out: Solution for the Refrigeration Sector, May 5-7, 1999, Bali, Indonesia.

McLaine-Cross, IL Leonardi, E, "Comparative performance of hydrocarbon refrigerants", Proceedings of IIR Commission E2: Refrigeration, climate control and energy conservation, Melbourne, Australia 11-14 Feb 1996

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Nekså, P., 1999: "CO2 Heat Pump Systems", Heat Pumps - a Benefit for the Environment. 6th International Energy Agency Heat Pump Conference, Berlin Germany, May 31 - June 2, 1999.

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Nekså, P., H. Rekstad, et al., 1998: "CO2-Heat Pump Water Heater: Characteristics System Design and Experimental Results", Int. Journal of Refrigeration, vol. 21, no. 172-179.

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Nielsen, OR Schreiber, J, "Propane as refrigerant in commercial refrigerating - an example in practice", Proceedings of 19th international congress of refrigeration 20-25 August 1995, vol Iva.

Oellrich, LR, "Propane and butane as possible alternatives to R12 and R22, R502 - some experimental results in the power range of commercial refrigeration and their discussion", Proceedings IIR Commission B2: New applications of natural working fluids in refrigeration and air conditioning, Hannover, Germany, 10-13 May 1994.

Patil, A. S., 1998: "Natural Working Fluids - Military Advantages and Opportunities", Natural Working Fluids '98, IIR - Gustav Lorentzen Conference, Oslo, Norway, IIR, p. 247-250.

Paul, J, "Hydrocarbons and commercial refrigeration. Experience from applications in Germany", Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995.

Pearson, SF, "Uses of hydrocarbon refrigerants", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

Pedersen, P. H., "Substitutes for Potent Greenhouse Gases (HFCs, PFCs & SF6)", Report of Danish Technological Institute, 1998.

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Pettersen, J., R. Aarlien, et al., 1996: "A Comparative Evaluation of CO2 and HCFC-22 Residential Air-Conditioning Systems in a Japanese Climate", Trondheim, Norway, SINTEF.

Petz, M Wolf, R, "Performance tests of a vehicle refrigerant compressor with R12, R134a, R290 and R600a", Hydrocarbons and other progressive answers to refrigeration/Greenpeace, 1995

Petz, M Wolf, R, "Performance tests of a vehicle refrigerant compressor with R12, R134a, R290 and R600a", Low temperature climatology transfer centre, University of Karlsruhe, 1997.

Powell, L, "Field experience of HC's in commercial applications", Proceedings of International conference on ozone protection technologies, 21-23 October 1996, Washington DC, 1996.

Richardson, RN, "Performance comparison of R12, R134a, R290 (propane) and R290/R600a (propane/isobutane) mixtures in a fully instrumentated hermetic test circuit.", Institute of Cryogenics, Southampton University

Richardson, RN Butterworth, JS, "The performance of propane/isobutane mixtures in a vapour-compression refrigeration system", International Journal of Refrigeration, Vol. 18, No. 1, pp 58-62, 1995.

Richardson, RN Castle, TP, "Performance testing of CARE 30 Refrigerant in a simulated automotive air-conditioning system", Institute of Cryogenics, Southampton University, 1994

Richardson, RN Ritter, TJ, "The performance of hydrocarbon alternatives to R12 and R22", AIRAH Journal August 1996, pp21-28, 1996.

Rieberer, R. and H. Halozan, 1998: "CO2 Heat Pumps in Controlled Ventilation Systems", Natural Working Fluids '98. IIR - Gustav Lorentzen Conference, Oslo, Norway, IIR, p. 167-176.

Ritter, TJ, "Experiences with hydrocarbon blends in the UK market", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

Rolfsman, L., 1995: "Low Charge Ammonia Chiller Units for Air Conditioning and Commercial Refrigeration", Natural working Fluids - Applications, Experiences and Developments, Trondheim, Norway, IEA Heat Pump Programme, p. 87-92.

Schmidt, E. L., K. Klöcker, et al. 1998: "Applying the Transcritical CO2 Process to a Drying Heat Pump", 21, no. 202-211.

Stene, J, "IEA Annex 22 - compression systems with natural working fluids. Status and outlook for the project", Proceedings of Applications for Natural Refrigerants/IIR Commissions B1, B2, E1, E2/DTI, Aarhus, Denmark, 1996.

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