1. What are hydrocarbons?
Hydrocarbon refrigerants are environmentally friendly, non-toxic, non-ozone-depleting replacements for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). From a chemical point of view, a hydrocarbon is the simplest organic compound, consisting entirely of hydrogen and carbon.
Hydrocarbons (HC) are naturally occurring substances. The majority can be found in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen.
2. Which hydrocarbons can be used as a refrigerant?
The following hydrocarbons can be used as a refrigerant in cooling & heating applications:
- R170 - ETHANE - C2H6
- R290 - PROPANE (Dimethylmethane) - C3H8
- R600 - BUTANE (N-Butane, Butane) - C4H10
- R600a - ISOBUTANE (2-Methylpropane) - C4H10
- R1270 - PROPYLENE (Propene) - C3H6
- R1150 - ETHYLENE - C2H4
However, the most commonly used HC refrigerants are propane (mainly in commercial and industrial freezers, air conditioning and heat pumps), and isobutane (in domestic refrigerators and freezers).
3. What are their main advantages?
Hydrocarbons are one of the most climate-friendly and cost-efficient refrigerants for heating, cooling and freezeing:
- Non-ozone depleting: Ozone Depletion Potential = 0
- Not climate damaging: Global Warming Potential = for most HCs below 3
- Safe: with proper handling
- Energy-efficient: usually better energy efficiency than CFC or HFC systems
- Easy replacement: able to replace many F-gases in existing systems without the need to change components or oils
- Cost-efficient: low refrigerant purchase price as well as lower system running costs
4. Are hydrocarbons safe?
Yes, with proper handling. Since hydrocarbons are flammable, some basic safety rules, which may differ slightly depending on the application, need to be respected by manufacturers, installers and users. As long as these rules are respected, it is perfectly safe to use hydrocarbons as refrigerants. Propane, for example, is used universally for heating and cooking. Hydrocarbons’ safe handling practices are well understood and practiced by the general global population. This makes them an appropriate alternative to climate damaging chemical refrigerants, also in developing countries.
5. Are hydrocarbons flammable?
Yes. However, adhering to the safety guidelines that exist for any application using flammable refrigerants, the risks of using hydrocarbons can be kept to a minimum, thereby avoiding any threat to human health and safety. Many of the hydrocarbon employing components used for commercial refrigerated appliances already meet safety standard requirements.
6. Are HCs toxic?
No. Hydrocarbons are not toxic for human beings and other living organisms.
7. Do HCs have an impact on the ozone layer?
No. Hydrocarbons do not contribute in any way to the depletion of the ozone layer.
8. Do HCs contribute to global warming?
No. Most hydrocarbons used as refrigerants have a Global Warming Potential (GWP) of below 3, meaning that, in small concentrations, they don’t pose a threat to the earth’s climate. By contrast, R404a, one of the chemical refrigerants hydrocarbons can replace, has a GWP of 3,260. To demonstrate this figure: 1 kg of released HFC-404a heats the atmosphere at a rate equal to 1.1 tonnes of propane or isobutane!
9. How does a HC system reduce greenhouse gas emissions?
There are two factors involved: Firstly, using hydrocarbons reduces the Direct greenhouse gas (GHG) emissions. This is due to HCs’ low Global Warming Potential (GWP) of just 3, compared to a GWP of 1,410 for HFC-134a, and even higher values for other chemical refrigerants. Why is this important? For example, from a typical supermarket refrigeration system, 5 to 10% of the total refrigerant charge is emitted to the atmosphere every year. Assuming that leakage rates are the same, hydrocarbons will thus, compared to any other chemical refrigerant currently used, spare the planet tons of greenhouse gases.
Secondly, HCs also lower the Indirect GHG emissions by maximising energy efficiency through a combination of factors, including their favourable thermodynamic characteristics, a higher Coefficient of Performance (COP), and a low condensing temperature. As an example, even when used in a secondary loop Mobile Air Conditioning system - to overcome any outstanding safety concerns - hydrocarbons (propane as the best choice in this case) would still represent a net savings of at least 80% of greenhouse gas emissions associated with current HFC-134a systems.
10. Which chemicals refrigerants can be replaced by hydrocarbons?
Hydrocarbons can replace many obsolete CFCs, HCFCs, and HFCs, including the ozone-depleting refrigerants R12, R13, and R22 in domestic, commercial and industrial refrigeration, and car air conditioning. It is also a future-proof substitute for R134a, R404a, R407c or R507a in fridges, freezers, cascade supermarket systems, heat pumps, and chillers.
Moreover, hydrocarbons can replace harmful insulation foam blowing agents. The hydrocarbon cyclopentane is now used as a viable alternative in HC domestic refrigerators.
11. Where do the HCs used as a refrigerant come from?
Hydrocarbon refrigerants are naturally occurring substances obtained when oil and gas are produced. They are easily available, globally, at extremely low costs.
12. Are HCs totally new refrigerants?
No. Propane (R290) has a long history in refrigeration. It has been in use since before ozone-depleting CFCs were developed and was re-introduced for use in heat pumps after the CFC phaseout. Its thermodynamic data, efficiency, and material compatibility are well known. In some countries, appliance manufacturers and food producers began using R290 as a replacement for R404A or R134a in appliances shortly after 2000, due to environmental concerns.
13. How energy-efficient are HCs?
Hydrocarbons are more energy-efficient than most conventional HFC or CFC systems. Used in residential air conditioning units, hydrocarbons have been reported to be 20-30% more efficient than synthetic refrigerants. A CO2-propane cascade supermarket system can save around 5% of energy, compared to an equivalent R404a system. In Mobile Air Conditioning, studies hint at a 35% higher energy efficiency than HFC-based MAC. Field tests with large A/C chillers have shown that all energy efficiency measures combined can result in a potential energy savings in excess of 50% for chillers that operate year round, when compared to minimum initial cost chillers that lack energy saving features.
14. In which applications are HCs used?
Hydrocarbons are suitable for use in the following applications:
- Domestic Refrigerators & Freezers: By far the largest application for hydrocarbon refrigerant to date. For example, R600a (isobutane) is used in more than 300 million so-called “Greenfreeze” fridges and freezers worldwide.
- Commercial Refrigeration: R290 (propane) is mostly used as a replacement for the ozone-depleting substance R22 and HFCs in ice cream freezers & cabinets, commercial freezers & refrigerators (walk-in-freezers, meat freezer, salad coolers), ice cube machines, bottle coolers, vending machines, cascade supermarket refrigeration systems, or water coolers.
- Air Conditioning: Split AC for office and domestic use, portable AC, water-air AC, air-air AC, AC chillers, and dehumidifiers can use hydrocarbons.
- Mobile Air Conditioning (MAC): As a retrofit for the currently used high global warming refrigerant HFC-134a, HCs are mainly used by drivers in Australia and North America as a more efficient, cheaper alternative. HCs can work as a primary MAC system refrigerant, or in secondary loop systems to ensure safer use. Some companies use HCs for cooling the drivers compartments in buses.
- Heat Pumps: Propane (R290) can be used in water-to-water low-charge heat pumps.
15. How much do I need in different applications?
A typical car air conditioning system contains about a coffee cup full of liquid refrigerant, and a small refrigerator contains about an eggcup full. An ice cream cabinet uses 100 g of HCs, half the amount needed of climate damaging HFCs. A mid-sized car with an HC secondary loop air conditioning would use 200 grams of propane. Split-system air conditioners for office and domestic use do not use more than 300 grams of HCs. Depending on the capacity, a heat pump could use from 500 g to 5 kg of propane.
16. How does a HC system work?
A system using hydrocarbons works in exactly the same way as systems currently using synthetic refrigerants. The basic refrigeration cycle remains the same, and only the charge of the system (exact amount of refrigerant) varies.
17. Can I replace HFC systems with HCs?
Yes. Components for the ozone-depleting chemical refrigerant R22 (e.g. compressors) are massively available in the market. The hydrocarbon refrigerant propane (R290) can use the same technology and is compatible with the most commonly used heat exchangers and materials. It is therefore the most cost-efficient replacement for harmful substances in many commercial refrigeration uses. Compressors developed specifically for R290 have been available since 2000. Other than propane (R290), no single refrigerant has such similar thermodynamic behaviour to R22. In high ambient temperatures, R290 performs better than R22 in terms of discharge temperature and pressure. This makes it the best replacement option for the ozone-depleting and high global warming R22.
18. What are the major benefits of using HCs?
The two main advantages of hydrocarbon refrigerants are lower environmental impact and economic gains. First, hydrocarbons do not damage the ozone layer. Moreover, hydrocarbons can significantly reduce emission of greenhouse gases from refrigeration and air conditioning equipment. Because of their very low global warming potential, their impact on global warming from direct emissions is much lower. Hydrocarbons typically lead to much higher efficiency than traditional chemical refrigerants, thereby reducing energy consumption and greenhouse gas emissions related to them. In terms of economic benefits, besides energy-related savings, hydrocarbons can be easily implemented in conventional cooling systems, requiring minimal investment in components and design.
19. Are there any legal requirements when using HCs?
As hydrocarbons are classified as flammable in international safety standards, their use in charges of up to 150 grammes per systems must follow certain guidelines. Guidelines for designing appliances for flammable refrigerants are available to meet the safety standards at any time. They specify that appliance producers manufacturing HC systems must be equipped accordingly, and service technicians must be trained in safe handling procedures. Safety standards cover leakage simulation tests and specifications for the sealing of several electrical components which may come into contact with leaking HCs. There are international standards on electrical safety in place, for the following applications: household refrigerators and freezers, motor compressors, commercial refrigerators and freezers, heat pumps, air conditioners and dehumidifiers.
However, a major problem for the global application of hydrocarbons is the lack of consistency from country to country, with some posing weaker or stricter legal requirements, and others still completely banning HCs from certain applications. The USA might serve as the best example of a world market currently in the process of lifting bans on the use of HCs in applications other than industrial process refrigeration.
20. Where can I not use HCs?
Household and some similar type appliances are limited to a maximum charge of 150 g. Within Europe, EN378:2008 (Refrigerating systems and heat pumps - safety and environmental requirements) allows larger charge sizes dependent on the occupancy of the area being cooled, the location of the refrigeration equipment and the practical limit. For example, typically up to 1.5 kg HC charge per separate circuit would be allowed on a supermarket shop floor, but a chiller located outside in an authorised access area with a vented secondary circuit could have an unlimited HC charge. You should consult the relevant local standards to check how much HC refrigerant can be used.
21. What are the key markets for HCs today?
Domestic Refrigeration: By far, the biggest markets for HCs at the moment are domestic refrigerators and freezers. Isobutane is used in 100% of all new home fridges in Germany, and in 50% of all new Chinese models. HC refrigerators are also sold in Western Europe, Argentina, Australia, Brazil, Cuba, India, Indonesia, Japan, Pakistan, and Russia. Overall, there are more than 300 million HC refrigerators running worldwide (2008).
Commercial Refrigeration: Propane (R290) and CO2 (R744) are used together in cascade supermarket refrigeration systems to provide high temperature and low temperature cooling for foodstuff. HCs have been used in supermarkets, dairies, institutes, and hospitals.
Air Conditioning: A large Italian manufacturer has been marketing propane cooled portable air conditioners since 1995, and has now expanded the HC product range to split system air conditioners for office and domestic use. A/Cs using HCs also operate reliably in universities, hospitals, and public institutions.
Mobile Air Conditioning (MAC): In Australia, over 300,000 vehicles are cooled with hydrocarbons in the air conditioning system. A similar figure can be found for the USA, where HCs are refilled by drivers in existing HFC-based MAC systems, however, without regulatory approval.
22. What could be future markets for HCs?
USA: The USA is the only major world market where HCs are still banned by law from domestic refrigeration. The first U.S. manufacturers, including white goods manufacturer GE and ice cream maker Ben & Jerry’s, have requested approval for isobutane and propane in domestic refrigerators and ice cream freezers. If granted by the U.S. Environmental Protection Agency, the USA is likely to become a key market for HCs in domestic and commercial refrigeration.
Globally: The global initiative “Refrigerants, Naturally!,” uniting some of the world’s leading consumer brands, might open up additional channels for hydrocarbons. Here, Unilever and McDonalds have both reiterated their commitment to using HCs in ice cream cabinets and in fast food restaurants respectively.