Refrigerants are substances that can be used in the refrigeration cycle of air conditioning and refrigeration equipment because of their thermodynamic properties. It is a liquid or a gas with a very low boiling point. Refrigerants such as hydrofluorocarbons (HFCs) are powerful greenhouse gases (GHGs) with GWPs hundreds to thousands of times more potent per pound than carbon dioxide (CO2 ); however, more low-GWP alternatives are becoming available. At the same time, especially in Africa, the rapidly expanding middle class and changing lifestyles translate into growing demand for refrigeration and air-conditioning.
- Refrigeration and air conditioning are responsible for emissions of approx. 4,8 GT CO2eq which will rise to above 12 GT CO2eq by 2030 under a business as usual scenario.
- About 1/3 of these emissions are caused by the use of refrigerants and 2/3 by energy consumption.
In order to mitigate both direct and indirect emissions from the cooling sector, the introduction and diffusion of green cooling technologies is of paramount importance. Green Cooling is environmentally friendly air-conditioning and refrigeration (RAC) with minimum negative impacts on the environment. The negative environmental effects of cooling appliances are due to their direct and indirect emissions. To avoid emissions, green cooling RAC equipment involves two main factors: Climate-friendly refrigerant and high energy efficiency.
Responds to the following needs
- Cleaner cooling
- Reduced GHG emissions
- Reduced ozone depletion
- Domestic use (appliances)
- Cooling of buildings and offices
- Automotive industry
- Transport refrigeration industry
Relevant CTCN Technical Assistance
- Chile: To support the replacement of F-refrigerants used in refrigeration system in food processing production and exports (fruits and vegetables)
- Ghana, Kenya, Mauritius, Namibia: Green Cooling Africa Initiative (GCAI)
- Papua New Guinea: Energy Effeciency on Refrigeration and Air Conditioning Sector Regulations Development options for Papua New Guinea
A coolant is a fluid which flows through or around a device to prevent the device from overheating, transferring the heat produced by the device to other devices that either use or dissipate it. While the term coolant is commonly used in automotive and HVAC applications, in industrial processing 'heat transfer fluid' is one technical term more often used in high temperature as well as low temperature manufacturing applications A much used coolant is water, or a water-glycol solution if the temperature of the process is close to 0°C. For lower temperatures CO2 is also used as a cooling agent. Coolants are for example used in vehicles where it keeps the engine from overheating. It does this by keeping the temperature at a constant so it runs more efficiently. The coolant is a 50/50 mixture of water and antifreeze. When you start your engine, a water pump circulates the coolant through the engine and radiator. Once the engine has reached a certain temperature, a thermostat opens to control the flow of coolant through the radiator. The thermostat stops the flow of coolant on a cold engine to allow quicker warm ups, and then opens as needed to keep the engine’s temperature constant. The use of CO2 is considered an environmentally friendly method.
A refrigerant is a liquid or a gas with a very low boiling point. Where water normally boils at 212 degrees Fahrenheit (and freezes at 32 degrees), a refrigerant like R-134a boils at 15 degrees below zero (and freezes at -154). The refrigerant in an A/C system cools the air by absorbing heat. Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are synthetic substances used as refrigerants. These halogenated refrigerants have to be chemically synthesized as they either do not occur in nature at all or only in trace concentrations. CFCs and HCFCs are being phased out under the Montreal Protocol, an international agreement to protect the ozone layer. They have been controlled by the Montreal Protocol since 1987 because of their ozone depleting potential and high global warming potentials. Environmental organisations such Greenpeace advocate the uptake of environmentally sustainable natural refrigerants such as CO2, hydrocarbons, ammonia, water and air.
- Unsaturated HFC's: Consumption of HFCs is growing dramatically world-wide due to their function as replacement substances for CFCs and HCFCs. Nevertheless HFCs are greenhouse gases. Their use should be avoided in order to slow global warming. Unsaturated HFCs (u-HFCs, also marketed as hydrofluoroolefins, or “HFOs”) are synthetically made HFCs with no ODP and low GWP that have been developed specifically to fulfil regulations that prohibit HFCs with higher GWP (e.g., above 150). Some are slightly flammable and combustion can form hydrogen fluoride. In the atmosphere their decomposition leads to the formation of trifluoroacetic acid (TFA), which is a strong acid with toxicity to some organisms. There is no known degradation mechanism for TFA.
- HFO's: The chemical industry is promoting substances called ‘Hydrofluoroolefins’ or HFOs, as HFC replacements. Chemically, HFOs are a form of HFCs, but due to the negative connotations that HFCs have acquired, this new class of chemicals is being marketed under a different name. While HFOs have lower GWPs than the earlier generation of HFCs they continue to have negative effects on the environment as HCFCs are used to make the most prominent HFO's, HFO blends have high GWP and they produce toxic by-products upon their production and decomposition.
- Natural refrigerants: Natural refrigerants are more climate friendly. They have a very low or zero global warming potential and zero ozone depletion potential; they are part of the natural biogeochemical cycles and do not form persistent wastes in the atmosphere, water or biosphere. Natural refrigerants are the naturally occurring substances CO2, ammonia, water, air and hydrocarbons such as propane, isobutene and propene/propylene. Their production is not energy intensive as even the hydrocarbons can be obtained without chemical transformation by separation. Natural refrigerants are widely used in some RAC applications, for example isobutane in domestic refrigerators and ammonia in large cooling processes. Natural refrigerants are relatively cheap because they are mass produced for a wide range of uses and are readily available if distribution structures are present. Natural refrigerants can often be sourced as by-products from other processes. Recycling or disposal after use in cooling systems is easier than with CFCs, HCFCs and HFCs. For an extensive survey of companies around the world working with cooling technologies using natural substances see the interactive database www.cooltechnologies.org.
Mobile air conditioning
Mobile air conditioning (MAC) systems are installed in cars to keep drivers comfortable and cool while driving safely. Vehicles can heat up significantly in hot weather or under direct influence from sunlight, which is the reason why the capacity of MACs in passenger cars lies in the range of around 5 kW – enough to cool a small flat. In 2006, 20 % of the global refrigerant emissions were from MAC systems in passenger cars. These direct emissions result from leakage during manufacturing, operation, servicing, repair and at end-of-life. Indirect emissions are due to increased fuel consumption caused by MAC operation.
- Main refrigerants used: HFC-134a, u-HFC-1234yf. Charge size approx. 600 g
- Natural refrigerant alternative: R-744 (CO2). HC-290 is sometimes used in the aftermarket
- Growth rate/future demand: High. Strong market increase especially in emerging economies such as China and India.
Unitary air conditioning
The subsector unitary air conditioning (UAC) contains ductless split, ducted split and rooftop ACs as well as variable refrigerant flow (VRF) systems and self-contained units, which are movable ACs and window/through-the-wall units. Typically one unit is installed to cool one room with the exception of VRF systems and multi-splits, both of which can be used for several rooms. In reversible ACs, the cycle can be reversed and used for heating. The most common UACs, split residential ACs consist of two modules, one of which contains the compressor, outdoor heat exchanger and expansion device and is installed outside. The other module with the indoor heat exchanger is placed inside in the room. Inverter technology is used in many new units as they can help with improving the energy efficiency during part load operation. Inverters enable the control of the compressor speed according to the cooling demand, thereby reducing the so-called cycling losses that are present with on-off control.
- Main refrigerants used: HFC-410A, HCFC-22
- Natural refrigerant alternative: HC-290 (propane), HC-1270 (propene)
- Growth rate/ future demand: High. In Southeast Asia, air-conditioning sales are growing by about 20 % per year. Roughly two-thirds of the global UAC market is located in Asia and SE Asia and the highest growth rates in 2012 were also found in this region. Nonetheless, air conditioner penetration in key markets is still low (e.g., India 4%, Thailand 14%, Indonesia 7%, Vietnam 6%, Philippines 11%)
Chillers contain water, which is cooled, and is then distributed over longer distances, for example to cool whole buildings (air-conditioning chillers) or industrial processes such as plastics and rubber manufacturing and food processing (process chillers). The cooling capacity in chillers ranges from as little as 1.75 kW for air cooled chillers up to several MW for water cooled chillers. Different capacity chillers are equipped with different compressors. Typically, process chillers have a lower COP because these chillers need to generate lower temperatures.
- Main refrigerants used: HFC-134a, HFC-410a, HFC-407c, HCFC-22
- Natural refrigerant alternative: HC-290 (propane), HC-1270 (propene), R-717 (ammonia), R-744 (CO2)
- Growth rate/future demand: Continuously growing market, especially in emerging economies such as China and India
Refrigerators are often the first electrical appliance a household buys. Fridges and freezers are often responsible for a large proportion of a household’s energy consumption. For example in Brazil this is on average 30%. Domestic refrigeration is the subsector with the highest number of units. The global stock is estimated to be approaching 1,500 million units. 100 million units are produced annually. On a more industrial level: if one would like to reduce the amount of refrigerant in the cooling system and limit the fluctuations in temperature of the fresh produce, the cold of the refrigerant could be transferred to a cooling agent. The refrigerant will then only be found in the machine room and the cooling agent transports the cooling capacity through the building and to the cold rooms.
- Main refrigerants used: HFC-134a (60% of existing units), 50 to 250 g
- Natural refrigerant alternative: HC-290 (propane) and HC-600a (isobutane) are used in 50% of newly produced refrigerators. Hydrocarbon (HC) refrigerators need less refrigerant than HFC refrigerators and a typical HC refrigerator with a volume of ca. 250 l contains ca. 55 g HC-600a. R-441A (a blend of ethane, propane, butane, and isobutane), R-450A (an HFO/ HFC blend), and R-513A (an HFO/HFC blend). None of these alternatives deplete the ozone layer and all have significantly lower impacts to the climate system than CFCs, HCFCs, and HFCs.
- Growth rate/future demand: Growth rates depend on the region, as saturation rates are already above 100% in some developed countries like the US or in Western Europe, but are still as low as around 20% in some developing countries.
Transport refrigeration is a vital part of every cold chain: Perishable goods, mainly food but also medical supplies and other goods, have to be refrigerated on their way from harvest or production to the consumer. Refrigerated transport increases food safety and prevents economic losses due to spoilage. Trucks and trailers are in many parts of the world the main mode of transport for refrigerated goods. Different requirements for long-distance transport in trailers and distribution traffic in smaller vehicles leads to a range of cooling capacities from 4 to 20 kW. Similar to mobile ACs in passenger cars, the refrigerant leakage is high. These are in particular caused through constant vibrations during operation and at times when difficult road conditions lead to loose connections. Leakage rates can be as high as 20-30% per year.
- Main refrigerants used: HFC-134a, HFC-404a, HFC-410a. Short-term replacement R-452a. Charge size 1.5-7.5 kg average depending on cooling capacity
- Natural refrigerant alternative: HC-290, R-744 (CO2). Cryogenic: liquid CO2 or N2
- Growth rate/future demand: Continuously growing market especially in emerging economies as importance of temperature-controlled transport is recognized widely
Examples of products
- Low GWP refrigerants:
- 111223344-Nonafluoro-4-Methoxybutane [Eco-Patent Commons]
References and relevant publications
- GIZ Proklima: Operación de equipo de aire acondicionado tipo split con hidrocarburos Una guía de reconversion para técnicos, instructores e ingenieros de refrigeración
- GIZ Proklima: Refrigeration Management Projects in Africa (MLF)
- GIZ Proklima: Climate-friendly room air-conditioners on hydrocarbon technology and new standards for natural refrigerants in China
- HFO's: The new generation of F-gases
- Factsheet: Green Cooling Initiative
- The Green Cooling Initiative
- Transitioning to Low-GWP Alternatives in Domestic Refrigeration
See the related webinar by our partner Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ): Green Cooling Technologies – Reducing Emissions from Refrigeration and Air-Conditioning Sectors