TL: ALTERNATIVE TECHNOLOGIES TO REFRIGERATION AND AIR CONDITIONING (GP) SO: Greenpeace International DT: 1992 Keywords: atmosphere ozone refrigerants greenpeace groups gp cfcs uk europe / GREENPEACE BRIEFING APRIL 1992 INTRODUCTION Refrigeration and air conditioning is the largest sector of CFC use in the UK (weighted by ODP); in 1989 it was 31%, whereas in 1986 this sector only accounted for 11% of CFC use (1). The CFC consumption of the UK refrigeration and air conditioning sectors in 1989 was 9,700 tonnes, divided, as shown below, between four main applications (DTI, 1989). Domestic refrigeration 3% Retail food distribution and storage 29% Industrial refrigeration 54% Air conditioning 14% Transport 1% Additionally, there is an estimated 'bank' (ie. CFCs in equipment currently in use) of 32,000 tonnes of CFCs (1). However, this is an underestimate as CFCs are also contained in the foams which act as insulation in fridges. In a typical fridge, 150g of CFCs would be used as coolant and 500g would be in the foam (2). ALTERNATIVES Refrigeration technology was first developed in the nineteenth century but it was not until early this century that commercial systems became available. Early refrigeration commonly used refrigerants such as ammonia and propane, but these were superseded in many applications by the development on CFCs in the 1930s. It is clearly desirable that alternative refrigerants have energy efficiencies similar to or better than those of the CFCs to be replaced. However, it is clear that the best way to minimise energy consumption is to minimise the amount of cooling we use, for example, less air conditioning. When planning new buildings, optimum building design, air circulation and ventilation should be actively investigated as alternatives to air conditioning. The refrigeration and refrigerant industries are presently advocating alternative halocarbon compounds as substitutes for CFCs in refrigeration and air conditioning. The chemical industry is spending large sums of money testing substitutes such as HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons) for toxicity and suitability as refrigerants (3). However, the HCFCs are ozone depleting substances and both HFCs and HCFCs are powerful global warming gases (4). This brief discusses other possible refrigeration alternatives which do not rely on the production or use of halocarbons. The list below is by no means exhaustive but highlights refrigerants and refrigerating techniques which could be of long term value. Some of these alternative refrigerants are already available in developing as well as developed countries, unlike halocarbon technologies. Greenpeace does not advocate any one technique but is calling for increased and urgent research into, and implementation of, ozone benign and environmentally sound techniques which can replace halocarbons. Many of the refrigeration alternatives included below are readily available but are being ignored by the industry, and by the bodies on which industry is represented. Industry clearly perceives greater profits being made from the halocarbon industry. The investment into halocarbon alternatives is being made at the expense of other readily available technologies. Clearly the halocarbon industry stands to profit more from the patenting and marketing of new chemicals than it does through promoting existing alternatives. NON-HALOCARBON ALTERNATIVES TO CFCS IN REFRIGERATION Non-halocarbon alternatives are already used and are thus readily available. Some are well known and require minimum development and testing to determine their suitability. COMPRESSION SYSTEMS The most common refrigeration system is the compression system which is found in most domestic, retail and many large refrigeration applications. This uses electrical energy to pump the refrigerant between the gaseous and liquid phases thus causing a cooling effect as the gas condenses to form liquid. The efficiency of the system depends on the system design, which needs to be optimised for a particular refrigerant, and on the properties of the refrigerant. The two refrigerants discussed below are in use for certain applications and are readily available already. AMMONIA Ammonia has been successfully used for industrial refrigeration for more than 100 years, and it has demonstrated excellent system efficiency and reliability (5). The cost is typically 4% of HFC 134a, is technically superior to HFC, and has obvious benefits for developing countries. Most large scale chilling, freezing and cold storage plants use ammonia. In the USA, 81% of refrigerated warehouses are run on ammonia (5). In Germany, nearly two thirds of the present systems of cold storage and food processing use ammonia, compared to only 7% for CFCs. A similar trend is seen in the Nordic countries, and ammonia is the most widely used refrigerant in Eastern Europe and in most developed countries (5). Ammonia is used as a refrigerant in both compression and absorption systems. Compression driven ammonia systems are currently widely used in the food storage, in processing industries and in the chemical industry. Compression is particularly useful where large areas, such as supermarkets and wholesale food depots, need to be kept at low temperatures (6). The widespread use of ammonia results from its excellent thermodynamic properties and easy availability: Research has found it to have a greater efficiency at most temperatures than HCFC-22, to have several operational advantages over HCFC-22 as well as being cheaper and more readily available (6, 7). Two areas in which it has been proposed that ammonia compression systems could readily replace halocarbon systems are air conditioning systems which circulate chilled water around a building, and supermarket refrigeration (6,8). British Standard BS 4434 details the precautions which need to be taken with ammonia. Ammonia gas is toxic at low concentrations in the atmosphere but is not persistent in the environment. Therefore, great care needs to be taken with the installation and maintenance of equipment, which in turn will result in smaller losses of refrigerant (9). It is easy to detect leaks of ammonia because of its pungent smell, and given appropriate design, the toxicity of ammonia should not restrict its use. Safety considerations dictate that large systems should generally be isolated from an occupied rooms and cool a secondary medium which can be circulated to facilitate cooling (8). Ammonia was used in domestic fridges in the past, but this ceased because of the perceived benefits of CFCs. However, the use of small quantities (about 100g) and the use of hermetically sealed units in appropriated corrosion free-materials should present few problems. A DTI report in 1990, noted that 'there is no technical reason why ammonia cannot be used again in domestic refrigeration equipment' (1). UK supermarket chain William Low are one example of ammonia refrigerant use in the UK. The two main cold stores have the equivalent capacity of 75,000 large family sized freezers (10). In Germany, the company Aerotech is developing systems which could supply supermarkets with all their cooling requirements such as frozen food storage, cool cabinets and counters for sales, meat cutting rooms and general air conditioning. In this situation a secondary cooling medium, such as water or brine, is circulated around the building and the ammonia compression unit is isolated from the public are.l of the store (8). HYDROCARBONS Although little known among the public and the press, hydrocarbons are well established as refrigerants and were, like ammonia, used extensively in domestic and small commercial facilities in the past (11). Hydrocarbons are now commonly used as refrigerants on industrial sites where the facilities are already set up to meet the standards concerning the use of flammable substances. Propane is extensively used by York International all over the world, in a range of industrial installations (12). A range of hydrocarbons can be used for refrigeration such as propane and isobutane. Thermodynamic assessment of this family of compounds shows many of them to have efficiencies similar to or better than the commonly used CFCs and other halocarbons for refrigeration and freezing. This has also been demonstrated in practical tests (11). The similarity of propane and propylene to CFC-502 makes them excellent candidates for replacing the CFCs in small retail freezer cabinets in both existing and new systems. As described in Appendix A, scientists from the South Bank Polytechnic have retrofitted a domestic fridge with propane and found even without design changes that good performance was possible (12). The efficiency is likely to be improved if the system is optimised for use with propane. They found that no problems were encountered with compressor lubrication (which can result in problems with substitution of halocarbon compounds) and that hydrocarbon gases cost only 2% of the price of compounds such as HFC-134a. The use of hydrocarbons in small facilities ceased in the 1930s as a result of hypothetical concerns about the flammability of these compounds. However, even in those days despite the poorer technical ability and the greater quantity of refrigerant required (possibly 1,500g) the safety record was excellent (11, 12). In fact, in 1930 the US National Fire Protection Agency stated that 'to date the fire record of mechanical refrigeration has been exceptionally good' (11). Considering this, the improved technical abilities and smaller volumes of refrigerant required (50-100g similar to the amount found in a lighter refill container) it seems surprising that the DTI report stately perfunctorily and without explanation that 'British Standard BS 4434 prevents the use of hydrocarbons as refrigerants within the occupancy categories of industrial, public assembly and residential' (1). This seems extraordinary considering that the same compounds are permitted to be used in aerosols where they are sprayed into the air, for example as a hairspray. In a typical domestic fridge about 50-100g of propane would be contained in a hermetically sealed unit. Numerous experts have noted that the added hazard represented by a hydrocarbon fridge in a typical kitchen would be insignificant (11,12). Tests for flammability of propane in domestic fridges have been carried at the Fire Services College test facility in Moreton, Gloucester to look at both the likelihood of the propane causing a fire and the result were the fridge to be involved in a fire (12). The first test, which allowed the propane to leak into the refrigerated space before it was ignited, produced an explosion so small that it was not sufficient to start a fire within the fridge. The second test, in which the whole refrigerator was burnt, showed very little difference between the CFC-filled and propane-filled fridges. By far the worst effect was the choking smoke and toxic fumes caused by the CFC filled foam burning - these would include choking smoke, phosgene and cyanides (12). System optimisation and technology changes, such as designs which prevent the refrigerant charge leaking into the cold space will require minimum time and investment when compared to the use of an entirely new system (12). A critical point in favour of refrigerants such as hydrocarbons is their ready availability and low cost, making them ideal for all areas of the world. According to Star Refrigeration Ltd, 'in the short term domestic refrigerators and deep freezers could be run on propane with negligible risk provided the charge were kept below 100g and there were no in-built sources of ignition in the appliances. What is lacking is the will to do it.' (13). Also, the Institute of Refrigeration state that "it would appear sensible in the short term to use propane as the refrigerant for domestic fridges and to use CO2 blown polyurethane as the insulation" (14) WATER Water can be used as the refrigerant in a compression system to cool to temperatures down to 0OC (15). These systems operate at very low pressures and thus use two stage compression, and also require large-sized refrigeration plants because of the thermodynamic properties of water. However, the use of water improves energy efficiency; by up to 50%, and of course water is an 'environmentally friendly' refrigerant (15). Refrigeration systems which use water as the refrigerant available under the name 'Ecochiller', are manufactured by Integral Technology GmbH, and these have been used for air conditioning and as heat pumps for many years (15). The plant for refrigeration systems using water can be relatively simple in design and maintenance, cost no more than a conventional system and as such may be especially appropriate for developing countries (15). ABSORPTION SYSTEMS Absorption systems are available which can use simple refrigerants such as water and ammonia. These use heat, from a gas flame for example, to drive the refrigerant between the liquid and gaseous phase (instead of a compressor) and thus to cause the cooling effect. Absorption systems are currently used in domestic, caravan, industrial refrigeration and air conditioning applications (9). If primary heat, or better still waste heat from a combined heat and power unit, is used the efficiency of energy generation is comparable to that of a compression system. It has been suggested that it is advantageous to use absorption refrigeration for all applications where there are plans to use primary energy in the medium to long term (7). Two absorbtion systems are widely used at present. Ammonia Ammonia absorption refrigerators are currently used widely in mobile homes, hotel rooms and hospitals and make up about 5% of the German household market (7). They typically have a better energy efficiency than conventional compressor fridges when run using gas, which is readily available in most kitchens, or on waste heat. There are very few moving parts in a absorption fridge and so operation is almost completely silent and free from vibration (7). Small fridges contain about 200 grammes of ammonia and concerns are sometimes raised over their safety. However, as with the compression systems the small quantity of refrigerant required and the engineering techniques available should be able to minimise any risks. Such absorption systems are proposed by the United Nations Environment Programme as immediately usable alternatives for domestic refrigeration and chilling (16). Absorption fridges and fridge/freezers which utilise ammonia are marketed in the UK by Electrolux in sizes varying from 25 to 170 litres (17) . Some only operate using electricity but many can be switched between 12V, 240V and gas operation. They are commonly used in caravans and boats, as mini bars in hotel rooms and for the storage of vaccines and insulins in doctors dispensaries, pharmacies and clinics (18, 19). Ammonia heater/chiller appliances have been developed by Servel and British Gas for air conditioning of buildings and have been found to offer an improved efficiency and lower capital costs. Ammonia absorption chillers are used widely in air conditioning which has been supplied by Servel to banks, local authorities, restaurants, and gas and rail companies (20). Water and lithium bromide Water can be used as the refrigerant in a lithium bromide solid adsorbent refrigeration system (9). These are usually used to cool water or a similar substance for air conditioning and water chillers. Water itself cannot cool to a temperature below 0OC but the addition of other chemicals such as glycols means that colder temperatures can be reached. These systems are fairly widely used for air conditioning large buildings such as hospitals and office blocks especially where waste heat is available; Carrier Corporation market lithium bromide chilling systems to cool process water for industrial applications and for air conditioning in hospitals (21). Air conditioning systems using lithium bromide and water are engineered by York International. Lithium bromide and water absorption systems have been called the 'state of the art' technology in air conditioning (7). OTHER ALTERNATIVES This section discusses briefly some specialist alternatives and others under development. These vary in sophistication and in the areas of refrigeration in which they may be applied. Expendable refrigerant system. This system which is used in refrigerated lorries and containers, is basically an extension of the ice room principle where ice would be stored in a well insulated box with the food to be cooled. The expendable refrigerant system involves spraying into the refrigerated area a pre-cooled liquid which evaporates and causes cooling (9). The liquids, such as carbon dioxide or nitrogen which turn from liquid to gas at - 197OC and -78.5OC respectively, are cooled and liquefied at a depot and stored in a large 'vacuum flask'. The temperature in the container is controlled by the rate at which the gases are released. The term expendable refrigerant is a little misleading as in fact the gases will be cooled by some conventional system before being supplied to the lorry and the cooled gases such as nitrogen would be discharged into the cool space. The transport of frozen and chilled foods uses around 1% of CFCs currently used for cooling operations in the UK (1). Expendable refrigerant is said to be fairly common internationally and of use for a variety of transport methods such as trains and containers (9). Safety precautions are required to prohibit the liquid being vapourised in the presence of people, but the use of these gases is rapidly expanding (9). It is also possible to use ice or dry ice in this way but temperature control is more difficult with these. Water zeolite air conditioning A water-zeolite system is being developed for use in automobiles which can be used either to heat or cool the interior of the car (22). Zeolite is made up of aluminosilicate materials which are widely used by industry and are thus readily available at reasonable cost. These systems can be run using waste heat from car exhaust enabling considerable savings in costs and emissions. A company called Zeotech is developing this technology. Other systems employing metal compounds, which would use heat to recharge the cooling system, are also being developed for automobile air conditioning (7). Stirling Cycle The principle of the Stirling cycle was developed in the mid- nineteenth century and has been used intermittently for heat pumps and engines ever since (23). The Stirling cycle works using two opposing pistons to compress and expand a working fluid such as helium which is passed through a regenerator matrix in the middle, which acts like a heat exchanger. This enables the Stirling cycle to be very efficient but in the past technical difficulties have limited its use. The Stirling cycle is currently used in refrigeration installations which operate at temperatures between -800C and - 1840C where it offers excellent efficiency. Using more than one unit in combination can enable temperatures of -4500C to be reached (9). Interest in the use of the Stirling Cycle for other types of refrigeration has now been revived and a company called Sunpower in Ohio have completed prototype tests on a domestic Stirling cycle refrigerator. Sunpower predict that the efficiency will be better than for a standard household fridge and that costs will be comparable (23). Air Cycles Air can be used as a refrigerant in a variety of cycles and has obvious advantages for various applications. Air cycle refrigeration has been used extensively in the past, especially for ships, and is used to air condition aircraft (24, 25). The efficiency of these systems depends very much on the machinery used. Compressors used in the past were inefficient such as compressors, which historically were inefficient and unreliable. However, improvements have now been made and it has been proposed that these systems could be applied to food processing where temperatures of around -20 to-800C are required (25). The Institute of Food Research, Bristol Laboratory at Bristol University has done a considerable amount of research into air cycle refrigeration and considers that 'it has a great future' (24). The Institute is especially interested in the application of this technology to low temperature food freezing but suggest that air cycle cooling could also be used in transport applications (trains and lorries), for air conditioning where heating is also required and in supermarkets (24). Refrigerated Backpack The Cranfield Institute of Technology has developed a refrigerated back pack which is a kerosene-fired absorption unit. It was designed to keep life-saving vaccines cold as they are transported to remote villages in Nepal (26). 'Acoustic' fridge A wide range of other technologies are also being investigated. For example, an 'acoustic' fridge has recently been developed by scientists at the Los Alamos National Laboratory in New Mexico (27). In this fridge the compressor uses sound instead of a conventional piston pump. This means that CFCs, which are used because of their compatibility with the lubricating oils, may be readily substituted. References 1. CFCs and Halons. Alternatives, the scope for recovery for recycling and destruction, DTI, HMSO, 1990. 2. Cold Comfort for the Ozone Layer: Local Authority Recovery and Recycling of CFCs from Domestic Refrigeration Equipment, Friends of the Earth, October 1991. 3. Harris, M. Programme for Alternative Fluorocarbon Toxicity Testing. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 4. WMO. Scientific Assessment of Stratospheric Ozone, 1989, Vol 1 World Meteorological Organisation, Geneva. 5. UNEP, Report of the Refrigeration, Air Conditioning and Heat Pumps Technical Options Committee, December 1991. 6. Stoecker, WF. Growing opportunities for ammonia refrigeration. In 'CFCs: time of transition' Am. Soc. of Heating, Refrigeration and Air Conditioning Engineers, Atlanta, p.128-139, 1989. 7. Umwelt Bundes Amt. Responsibility means doing without - how to rescue the ozone layer. The Federal Environment Agency, 1989. 8. Schmidt, HG. Ammonia in supermarkets. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 9. Althouse, DA, Tumquist, CH and Braceliano, AF, Modern refrigeration and air conditioning, Goodheart Willcox, Illinois, 1992. 10. Air Conditioning and Refrigeration News, February 1991. Taking the High Road to Distribution. 11. Haukas, HT. Halogen free hydrocarbons as refrigerants. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 12. James, RW and Missenden JF. The use of propane in Domestic refrigerators, Inst. J. Refrig. 15, 95-100. 13. Letter from SF Pearson, Star Refrigeration Ltd to Greenpeace, 1 May 1991. 14. Environmental effects of refrigerants. Institute of Refrigeration, 1991. 15. Paul, J. Water as a refrigerant and coolant. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 16. UNEP. Report of the Technology and Assessment Panel, 1992. 17. The Electrolux Guide to refrigeration on the road, 1991. 18. Minicool. Cool comfort within easy reach, Electrolux ,1988. 19. Minibars by Electrolux, 1990. 20. CFC-free with gas. Heating and Ventilating Review, August 1990. 21. Streaffield, B. The absorption option, Refrigeration and Air Conditioning, July 1991. 22. Hoppler, R and Schwartz, J: Air conditioning in automobiles based on zeolite and water. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 23. Clery, D, 19th Century Engines refrigerates without CFCs. New Scientist 1 September 1990. 24. Gigiel, AF, Air as a refrigerant. Air Conditioning and Refrigeration Today, February 1990. 25. Kruse, H. The cold gas process as an alternative technology. Presented to International Conference on Alternatives to CFCs and Halons, Berlin, 24-26 February 1992. 26. O'Callaghan, PW. Refrigerated backpack, Cranfield Institute of Technology, 1992. 27. Clery, D, Acoustic fridges sounds good for the ozone layer, New Scientist 4 April 1992. Appendix A THE PRODUCTION OF A CFC-FREE FRIDGE FOR GREENPEACE The refrigeration group of the Institute of Environmental Engineering, South Bank Polytechnic, was engaged by Greenpeace to build a demonstration fridge which is CFC free and to audit this fridge in terms of composition, energy efficiency and health aspects. This was done by replacing CFC-12 refrigerant with propane gas, and CFC-11 foam with carbon dioxide blown foam in a domestic fridge. A typical domestic fridge uses about 150g of CFC-12 as a refrigerant and 500g of CFC-11 as the blowing agent to make the rigid closed cell polyurethane foam used as cabinet insulation. Two standard fridges (Make: Hotpoint - 8221) were obtained, one fridge (Unit A) was modified and the other fridge (Unit B) remained unchanged to provide a basis of comparison. Energy consumption was measured for both units before and after the changes, so that energy comparisons could be made. This report briefly covers the details of the refrigerant and insulation change and presents the results of energy consumption tests. Replacement of CFC-12 with Propane A programme of research work concerning the application of propane in domestic refrigerators has been undertaken by the Polytechnic (see eg 1, 2, 3). The global warming influence of propane is zero (4) and its ozone depletion potential is zero. Propane presents an attractive alternative to current CFCs in small systems such as domestic refrigerators if given correct technical application for operational and safety factors. Propane was therefore chosen to replace CFC-12 for Unit A. The fridge was originally charged with 90g of CFC-12 which was recycled using a refrigerant reclamation unit. 29g of propane was found to be the required replacement charge. Changing the Insulation The current insulation material for domestic refrigerators uses CFC-11 as blowing agent. We identified a rigid carbon dioxide blown foam which has little different thermal conductivity. The carbon dioxide blown foam has an initial thermal conductivity (at 20øC) of 0.0228 W/mK. (Manufacturer: Liquid Polymers, Newhouse Road, Huncoat, Accrington, Lancashire, BB5 6NT, UK.) The thermal conductivity for CFC foam is about 0.021 to 0.023 W/mK. CFC foam was mechanically removed from Unit A. All the parts were cleaned and the carbon dioxide blown foam was injected into the wall cavities where it provided both insulation and support. A thin layer of mineral wool (Rock wool) was used together with a piece of aluminium sheet to seal the fridge at the rear, to maintain water vapour exclusion. Energy Consumption Tests Before the changes, an energy consumption test was conducted for each fridge operating with R12 using a standard kilowatt-hour meter. The two units were placed together in a large space of known isothermal characteristics. The first test lasted for seven days (From 15:05, 27th of February to 15:05, 5th of March). A 60 W light-bulb was placed inside the compartment of each unit and switched on for 60 min in every two hours to a simulate identical cyclical loads. The second test was repeated in like manner after the changes for Unit A were conducted (Tested from 11:30, 2nd of April to 11:30, 9th of April). Results of tests are shown in the following table. It will be noted that there are differences in energy consumption between the two tests because of the differing environments, ie the ambient temperature of the room. ENERGY CONSUMPTION TEST RESULTS first test second test (before change) (after change) kWh kWh Unit A 7.6 7.5 Unit B 6.8 8.5 Discussion and Conclusion The energy efficiency test results showed that the change of refrigerant and insulation did not result in an increase in relative energy consumption by the altered Unit A. Indeed, the CFC free unit showed an improvement in energy consumption in line with previous tests on other comparative refrigerator pairs. However the differences which may exist between serially produced items must be borne in mind, only large scale statistically significant tests can items must be borne in mind, only large scale statistically significant tests can fully demonstrate the differences. The test results reflect the calculations of thermodynamic performance expected. The system efficiency is expected to be further improved by component optimisation such as use of a larger condenser and an appropriate compressor. The thermal conductivity of carbon dioxide foam used might increase with age, possibly ending at about 0.0274 W/møK. However optimisation of overall cabinet design including insulation thicknesses is desirable on other grounds i.e. in reducing life costs. John Missenden Institute of Environmental Engineering, South Bank Polytechnic. April 1992 References 1. Missenden JF, James RW, Wong AKW, "Propane for systems with small refrigerant change." Paper presented at the Anglo-Swedish Conference of the AICVF at Sophia Antipolis, France. March 1990 2. James RW, Eftekhari M, Missenden JF, "Propane: the environmentally friendly refrigerant." Research Memorandum 127, Institute of Environmental Engineering, South Bank Polytechnic, October 1990. 3. James R and Missenden J, "The use of Propane in Domestic Refrigerators", International J. of Refrigeration. Vol. 15, March, 1992. 4. Fischer G and Olliff M, "Climatic Impact of Chlorofluorocarbons and their possible replacement", Paper presented in Ozone Protection for The 90's, Australia, March 1992.