Propane (R290). Polarpure propane is mainly used in air conditioning systems, dryers and commercial refrigeration equipment. R290 is the best environmentally friendly alternative to R22.
Hydrocarbons (HC) are chemical compounds of the elements hydrogen and carbon
HYDROCARBONS AS REFRIGERANTS - PROPANE (R290)
Besides being environmentally friendly, hydrocarbons are economically beneficial in heating/cooling and freezing processes. HCs, which commonly replace hydrofluorocarbons (now considered harmful to the environment), can handle oils and other components found in many existing systems. In addition, they are not expensive and achieve significantly higher energy efficiency, which is reflected in lower operating costs.
Hydrocarbons (HC) are chemical compounds formed of hydrogen and carbon. These elements are present in nature, for example high concentrations are found in crude oil. As innovative and non-toxic refrigerants, hydrocarbons are an environmentally friendly alternative to ozone-depleting fluorocarbons (CFCs/HCFCs).
HCs are flammable, but propane (R290) is commonly used in cooking and heating. All users have to accept rules in order to use these materials safely.
Propane (R290) is mostly used in commercial heat pumps, air conditioners, refrigerators and freezers.
HYDROCARBONS AND THE ENVIRONMENT
HC refrigerants are not considered ozone-depleting compounds and for the most part have a global warming potential (GWP) of 3. In comparison, the synthetic refrigerant R404A (now commonly replaced by HC) has a very high GWP of 3260. Systems with HC refrigerants have a dual role in reducing harmful greenhouse gas levels. Firstly, due to the low GWP value of HCs, they significantly decrease direct greenhouse gas (GHG) emissions. For example, in an ordinary supermarket, between 5 and 10% of the total refrigerant is released locally into the atmosphere; using HC as a substitute refrigerant reduces gas emissions by many tonnes per year.
Secondly, the convergence of the physical properties of HC-based systems (lower liquefaction point, thermodynamic benefits and higher coefficient of performance (COP)) makes energy-efficient operation possible. For example, the use of propane (R290) to replace HFC-134a in an air conditioner leads to a reduction in greenhouse gas emissions of at least 80%.
Further benefits of HCs are their low-cost availability, since they are by-products of oil and gas extraction and processing, and the fact the multiple studies demonstrate that the use of HC systems results in actual energy savings. In this context, hydrocarbons have long proven to be good substitutes for fluorocarbons and other environmentally harmful refrigerants.
The importance of HCs has so far been clearly evident in household appliances and freezers, where isobutane refrigerant (R600a), first used in the GreenFreeze refrigerator, is now in use worldwide. The same can now be said for commercial refrigeration systems; in supermarkets and many other places, propane (R290) is mainly used to replace ozone-depleting refrigerants. There is similar situation in the field of air conditioning. Here we find HC in residential and office buildings. In addition, some groundwater heat pumps use energy-efficient propane (R290).
HC systems use the same cooling circuit as systems with synthetic refrigerants. Propane (R290) refrigerant is compatible with equipment and appliances designed for the traditional ozone-damaging synthetic refrigerant R22, making it a direct substitute with far superior performance to its synthetic competitor.
In summary, HC technology has the following benefits:
1. No destructive effect on the ozone layer
2. Significant reduction in greenhouse gas emissions
3. Low global warming potential and therefore lower global warming impact
4. Increase in energy efficiency
5. Ease of use
6. Migration to the new system requires a very low investment
Being a fire hazard, HCs are subject to international safety guidelines and laws. Use is limited to a charge of 150 g per system, but exceeding this value is officially permitted in Europe under certain favourable conditions. All HC system manufacturers must adhere to safety regulations and their employees must understand and apply the prescribed procedures on safe handling of HCs. Government safety regulations require leakage simulation tests and strict standards apply for insulation of electrical components near refrigerant flows. In addition, many household and commercial appliances, such as household refrigerators, freezers, heat pumps, and commercial refrigeration and compressors, are subject to international safety regulations.
Propane (R290) and other hydrocarbons are well established in commercial refrigeration, and similar developments are already underway in air conditioning.
FLAMMABLE REFRIGERANT R290
R600a and R290 are hydrocarbons. These refrigerants are flammable and may only be used in equipment that meets the requirements specified in the current revision of EN/IEC 60335-2-24 (dealing with potential hazards arising from the use of flammable refrigerants).
Consequently, R600a and R290 are the only refrigerants that can be used in household appliances because they meet the above-mentioned standards. R600a and R290 are heavier than air and the concentration is always the highest at ground level. R600a may only be stored and transported in approved containers and must be handled according to the guidelines in force.
- Household refrigerators and freezers
- Refrigerated drink holders
- Ice machines and refrigerated cabinets
- Commercial refrigeration equipment
- Beer coolers
- Beverage dispensers
- Heat pumps
ASHRAE safety designation and classification
R290 - Propane
Safety Group A3
- Air conditioning
- Commercial and household refrigeration
- Commercial refrigerated cabinets, walk-in freezers, commercial displays, ice machines, refrigerated vending machines, cold stores
- Household freezers and refrigerators
R290 or propane refrigerants, can replace other refrigerants with a high environmental impact in household/commercial refrigerators, heat pumps, air conditioners... It has zero ozone depletion potential (ODP) and negligible global warming potential (GWP). It is also a component of petroleum gases from natural sources. R290 refrigerant was used in the past and has now found widespread use for multiple applications in Europe. Given its worldwide availability, the use of propane as a replacement for CFCs/HFCs/HFOs has been widely discussed.
- This content is not explicitly specified in DIN 8960. Only impurities are listed and limited. The main content is the rest up to 100%.
- According to thermodynamic calculations, an R600/R600A isomer content of up to 5% in R290 propane is not critical, does not exceed the temperature creep criteria, and has an extremely low impact on pressure, with an evaporation temperature of less than -271.15 °C.
- R290 with an isobutane content of up to 1% is acceptable for compressors.
- This is the maximum value for each of the multiple unsaturated hydrocarbons.
- This is the maximum value for each aromatic compound.
- This is a preliminary value to be reviewed when more experience is available. Due to the higher pressure of the propane, the vapour phase will contain higher concentrations. To avoid demixing problems, charging must always be carried out from the liquid phase.
Table 4: Flammability of propane
Due to the flammability of propane in various concentration ranges, safety precautions are required on the appliance and in the production plant. The risk assessments underlying these two situations are very different. The main common starting point is that accidents arise from two essential conditions. One is a flammable mixture of gas and air and the other is an ignition source with a certain energy level or temperature. These two elements must both be present for combustion to occur, so this combination must be avoided.
|Lower explosive limit (LEL)||1.5 %||about 38 g/m3|
|Upper explosive limit (UEL)||8.5 %||about 203 g/m3|
|Minimum ignition temperature||460 °C|
Propane (HC-290) is used by some manufacturers for plug-in refrigerated beverage racks, chest freezers and catering display cabinets. These units usually have higher refrigeration capacities than household refrigerators, which require the higher pressure propane refrigerant. When the legal safety requirements (e.g. IEC 60335-2-89) are met, propane is the ideal refrigerant for such units. It can be used together with available components, mixes well with mineral oils, results in lower end-of-compression temperatures, and is often 10-15% more energy efficient than a comparable HFC unit. In addition, the ratios and pressure differences are lower than with HFC, resulting in lower noise emissions.
R290 (propane) can also be used as a replacement refrigerant. Being an organic compound (hydrocarbon), it has zero ozone-depleting potential and a negligible direct global warming effect.
Its pressure levels and refrigeration capacity are similar to those of R22, and its temperature behaviour is as advantageous as that of R134a.
There are no particular problems with materials. Unlike NH3, it is compatible with copper-based materials, so it can be used in semi-hermetic and hermetic compressors. The mineral oils common in HCFC systems can be used as lubricants in a wide range of applications. Polyol esters (POE) and polyalphaolefins (PAO) boast even more favourable properties.
Refrigeration systems with R290 have been in operation for many years all over the world, especially in industry: it is a “proven” refrigerant.
In parallel, the R290 is also used in smaller compact systems with low refrigerant charges, such as air conditioners and household heat pumps. Furthermore, there is a growing trend to use R290 in commercial refrigeration systems and chillers.
R290 is extremely suitable as a refrigerant in heat pumps and chillers. It can be used in many cooling and heating applications in air-water heat pumps (including with a wide capacity range), or when used in a brine chiller/refrigerator for comfort air conditioning, cooling industrial processes, preserving refrigerated products, cooling machinery and foodstuffs. It is generally used in cooling mode for all applications that require a system flow temperature from -40 °C to +20 °C. For uses below -15 °C, propene is more suitable. It is used in heating mode for heat pumps, which then operate efficiently even at very low ambient temperatures, with flow temperatures up to 65 °C for the entire range of applications.
- Very low GWP (3), zero ODP (0).
- Not affected by fluorinated gas legislation.
- Refrigerant that meets the needs of the future, available and inexpensive.
- Low service and operating costs.
- Low end-of-compression temperatures -> intensive evaporation with a single-phase system.
- Low filling quantity due to good density/heat of evaporation ratio.
- Good material compatibility.
- Working pressure.
- Non-hazardous to water.
With a further reduction of the GWP quota, refrigerant manufacturers will increasingly rely on the production of natural and low-GWP refrigerants to exploit their production capacity. Moreover, R290 is not patentable, so there will be no patent fees.
The EPA recommends that catering companies choose the R290 refrigerant (also known as hydrocarbon or HC), which is natural, non-toxic and does not damage the ozone layer. Approved in 2011, HC has a low GWP and is one of the most environmentally friendly and economical refrigerants available. R290 is also an excellent alternative to the hydroflurocarbon (HFC) refrigerants R134a (used in refrigerators) and R404a (used in freezers). Using this refrigerant can also reduce overall energy expenditure by up to 28%.
HC refrigerants can be produced domestically and, unlike HFCs, are not harmful if they come into contact with the skin or are inhaled. R290 also has a higher degree of purity than standard propane. Furthermore, its low moisture content ensures that it does not damage the refrigeration system and its components. More than 1.5 billion HC refrigerators and freezers are in use in homes on a global scale, and there are also 2 million commercial units in use.
While it was initially feared that these propane refrigerators could pose an explosion risk, studies show that the chance of this happening is less than 0.001%, even in gas kitchens. In fact, most R290 units contain less propane than common products such as lighters, air fresheners and spray paint. R290 systems can also be dispersed into the atmosphere, which means that the refrigerant does not have to be recovered. Please note that R290 can only be used on new equipment and cannot be retrofitted.
R290 is the common name for high-purity propane, which is extremely suitable for use as a refrigerant. It is already used as an alternative to HCFC refrigerants in medium- and low-temperature refrigeration and air conditioning systems.
The use of R290 is increasing due to its low environmental impact and excellent thermodynamic performance. It is non-toxic, has an ozone depletion potential (ODP) of 0 and a global warming potential (GWP) of 3.
The EU F-Gas Regulation aims to gradually reduce fluorinated gases and prevent their release into the atmosphere. R290 does not contain fluorine or chlorine and is therefore not affected by these regulations.
Because to its wide availability and low price, it is an appropriate solution to meet the needs of the future. It is also non-hazardous to water.
- Low GWP (3)
- Zero ODP (0)
- Refrigerant that meets the needs of the future, widely available and inexpensive
- Low end-of-compression temperatures resulting in intensive evaporation with a single-phase system
- Not affected by the EU F-Gas Regulation
- Low filling quantity due to good density/heat of evaporation ratio
- Good material compatibility
- Working pressure
- No risk of water contamination
As a refrigerant, propane offers users an alternative that avoids these obstacles while offering a number of benefits. Unlike ammonia, for example, it does not pose any problems for materials since it is compatible with copper and can also be used with semi-hermetic and hermetic compressors. Compatibility with the latter is essential if it is to be used in fully sealed systems.
Propane is environmentally friendly, highly efficient and offers high performance. In 2011, the EPA approved the use of propane in small quantities in stand-alone commercial refrigerators and freezers. Using it could effectively eliminate the EPA compliance problems that food retailers and others will face with refrigerants in the near future. An R-290 system needs a 40% lower refrigerant charge compared to systems of the same size using R-22 and R-134°. These refrigerants have a GWP of 1,810 and 1,430 respectively, compared to a GWP of only 3 for R-290. R-404A, an HFC currently in use, has a GWP of almost four thousand. Hydrocarbons generally operate at lower discharge temperatures, which improves system reliability. The relatively low mass flow of propane (about 55-60% compared to R-22) also allows a considerable reduction in refrigerant charge. However, it operates at similar pressures and refrigeration capacities to R-22. R-290 systems can therefore be designed to meet similar criteria, but with lower impact and higher efficiency.
Industrial refrigeration operators have long recognised these and other benefits. Systems around the world have been using R-290 in large-scale operations for many years, to the extent that a study by Bitzer (a compressor manufacturer quoted in ACHR News) called it “a proven refrigerant”.
In addition to industrial refrigeration applications, propane refrigeration is also used on a smaller scale. "R-290 can be used in smaller, compact systems with low refrigerant charges, such as household air conditioners and heat pumps", the report states. "In addition, there is an increasing trend towards its use in commercial refrigeration systems and chillers." It requires a relatively low mass flow (approx. 55-60% compared to R-22), so a lower refrigerant charge than R-22 is needed in similarly sized systems, and this can be taken into account when sizing components.
Benefits of R290
Interestingly, analysing the thermodynamic performance of R290 as a refrigerant reveals numerous benefits. Here are some of them:
- Gas discharge temperature from the compressor
R290 and especially R600a (isobutane) have a lower discharge temperature than other refrigerants. The benefit of a low discharge temperature is that it has a positive effect on compressor materials, components and oil stability. If the gas discharge temperature is too high, the lubricant oil decomposes.
- Higher heat exchange, low pressure ratio
The excellent thermodynamic properties of propane, such as higher heat exchange and low pressure ratio (condensation to evaporation pressure) make it is possible to design appliances with smaller heat exchangers, which could lead to a reduction in the physical space required, facilitating design and installation.
- Lower density
The density of propane is far lower than that of fluorocarbons (less than half that of R134a and R410a) and this, combined with the higher heat transfer, results in a much lower refrigerant charge. In this regard, several tests were carried out with reciprocating compressors; these showed a potential halving of the R290 charge compared to R32 and a reduction to almost one third compared to R134a.
- Efficiency comparison
Compared to R410A, the EER for R290 and R600a is 5% to 12% higher. This simplistic EER comparison is indicative of the strong energy efficiency potential for operations with HC systems.
- Compressor envelope comparison for different refrigerants
Here we can see that propane is an efficient and flexible refrigerant under a range of operating conditions. It can go from very low evaporation temperatures to high condensation temperatures.
This makes it possible to design a wide range of products, from chillers (high, medium and low temperature) to heat pumps.
Overall, these comparisons show that smaller compressors and heat exchangers can be used with propane. Even when considering medium GWP refrigerants such as R513a and low GWP options such as R1234ze and R1234yf, the comparison favours R290, even when considering the same reciprocating compressor model.
In conclusion, promoting an increase in the use of natural refrigerants such as R290 propane (GWP = 0.02) and R600a isobutane (GWP = 0.006) is one of the ways the HVAC sector can help save the planet.
The road is well mapped out, the industry is undoubtedly on it, and excellent results are expected from all major players in the market as soon as possible.
Hydrocarbons such as R290 (propane), R600a (isobutane) or R1270 (propene/propylene) are non-toxic, low-GWP natural refrigerants with excellent thermodynamic properties. They offer an energy-efficient and environmentally friendly alternative to HFCs in various applications, such as household and commercial refrigeration, air conditioning, heat pumps or ultra-low temperature applications.
Thermodynamic properties of hydrocarbons
Hydrocarbon refrigerants are chemically stable over a wide temperature range, non-toxic, and are environmentally friendly because they have an extremely low GWP and zero ODP. Hydrocarbons also boast excellent thermodynamic, physical and chemical properties that make them particularly energy efficient. In vapour compression refrigeration and air conditioning systems, the most commonly used hydrocarbon refrigerants include R290 (propane), R600a (isobutane), R1270 (propene/propylene)
Main thermodynamic and environmental properties of hydrocarbon refrigerants
|Ethene / Ethylene||R1150||CH2=CH2||28.1||-104||3.7||0|
|Propene / Propylene||R1270||C3H6||42.08||-48||<1||0|
Hydrocarbon refrigerant applications in refrigeration and air-conditioning systems
Hydrocarbons can be used either in a system specifically designed for their use or as a substitute for other refrigerants with some modifications to the equipment. In retrofitted equipment, it is of paramount importance that the lubricant and safety measures are compatible.
Hydrocarbons in household refrigeration and air conditioning
The use of HFCs in household air conditioners is still widespread in many countries. However, production lines are converting to R290 (propane) in China, South-East Asia and South America. The restrictive requirements of the safety regulations limit their introduction onto the market, with the exception of small and portable units. Hydrocarbon-based air-conditioning systems are on the market for low charge indoor applications, such as mini-splits, window and portable air conditioners, and more recently in split and ducted rooftop systems.
Flammable refrigerants such as propane can be used safely in window air conditioners due to their compact size and low refrigerant charge volume. In one study, R290 was used as a drop-in replacement in an HCFC-22 room air-conditioning system with the addition of a liquid-suction heat exchanger. A 38% increase in COP was achieved with the new system. In another study, a prototype high-efficiency window air conditioner with R290 achieved the same cooling capacity as a reference model with R410A, and achieved an EER 17% higher than that of units promoted by the US Environmental Protection Agency's Energy Star programme.
Hydrocarbons in commercial refrigeration
According to a recent review article, HCFC-22, HFC-404A and HFC-134a still dominate small retail refrigerated equipment. However, the adoption of hydrocarbons such as R290 and R600a in cabinets and freezers is gradually advancing thanks to charge reduction technologies. For example, a 28% reduction in energy consumption was recorded when using R290 in refrigerated beverage racks with glass doors compared to older HFC-134a beverage racks. In China, the results of a performance study showed a significant reduction in energy consumption when using R290 in a vertical display cabinet, in both freezing and chilling conditions.
Hydrocarbons in automotive air conditioning
Regional safety standards and charging requirements for the use of flammable refrigerants have not been standardised in automotive air conditioning. For example, according to the UNEP 2018 RTOC assessment report, hydrocarbon retrofits were legal in some Australian states but illegal in others and in the United States. Hydrocarbon refrigerants could be used in the new systems, provided that safety issues are reduced, e.g. by introducing a secondary loop circuit to separate flammable refrigerants and occupied spaces.
Hydrocarbons in ultra-low temperature applications
R170 (ethane) and R1150 (ethene) are the only hydrocarbon refrigerants with normal boiling points suitable for refrigeration at ultra-low temperatures (below -50°C). R170 is suitable for low-temperature and large commercial and industrial equipment. In a theoretical study, R170 and R1150 were used in the lowest stage of a cascade system. Compared to the other selected refrigerants, R170 performed better in terms of COP but not in terms of volumetric refrigeration capacity. Other studies that analysed the use of an ejector in an R290/R170 cascade refrigeration system found higher performance in terms of COP, refrigeration capacity and lower electricity consumption.
Hydrocarbons in heat pump applications
In large-capacity heat pumps, the use of hydrocarbons is limited by the maximum charge of 500 g required by the IEC standard, and HFOs are therefore more suitable. For small and medium capacity systems, however, compression heat pumps using hydrocarbon refrigerants have great potential for development in commercial applications.
According to the UNEP 2018 RTOC assessment report, a limited number of low-charge heat pump water heaters using R290 have been sold in Europe. However, a more recent report by UNEP indicates that R290 is rapidly growing in one-piece water heaters, where safety restrictions allow its use.
Energy efficiency and environmental impact of hydrocarbon refrigerants
Hydrocarbon refrigerants are an energy-efficient alternative to HFCs. Several studies have reported energy savings ranging from 4.4 to 18.7% when using hydrocarbons compared to HFC-134a, and from 2.65 to 13.5% compared to HCFC-22. Several studies also reported refrigerant charge reductions of 40-56% with hydrocarbons compared to HFC-134a and reductions of 12.9-58% compared to HCFC-22. This is due to the lower density of hydrocarbons compared to HFCs. A lower refrigerant charge helps to reduce refrigerant consumption and, consequently, possible CO2-eq emissions due to end-of-life leakage. In a recent study, the total equivalent warming impact (TEWI) was used to determine that using hydrocarbons instead of HFCs combined with optimised refrigeration system design reduced CO2-eq emissions.
Hydrocarbons are particularly suitable for smaller heat pumps, one-piece and mono-split air conditioners. They are suitable for collective systems (buildings and apartment blocks) and industrial applications, if appropriate risk management measures can be taken. Hydrocarbons are less suitable for large multi-split and VRF systems due to high costs and limitations due to the required safety measures.