Propane is an environmentally friendly, natural hydrocarbon refrigerant, otherwise known as R-290. While it can be used as a refrigerant in a range of applications, propane is of particular interest to the heat pump and chiller markets. Indeed, with F-Gas Regulations restricting Hydrofluorocarbon (HFC) refrigerants for heat pump use, and savvy chiller manufacturers keen to stay ahead of future regulatory change, R-290 is viewed as a future-proof refrigerant option, especially for small to medium applications.
Why are we returning to natural refrigerants?
Natural refrigerants were used in the very first refrigeration systems. As technology evolved, they were replaced by man-made, synthetic refrigerants, engineered to overcome issues such as flammability, toxicity and corrosion. However, it was discovered the synthetic refrigerants Chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs), had a disastrous impact on the ozone layer. It was then found that HFCs (the refrigerants designed to replace CFCs and HCFCs), contributed towards global warming. Under the Montreal Protocol, a number of countries agreed to phase out CFCs and HCFCs. Subsequently, under the Kigali Amendment, countries committed to a gradual phase down of HFCs, with the aim for a 80-85% reduction by the late 2040s.
Legislation has been enacted worldwide to ensure the phase out and phase down of harmful refrigerants. CFCs and HCFCs are banned in the European Union (EU), with HFCs being controlled by the F-Gas regulations. These regulations are aiming to cut fluorinated gas emissions by two-thirds by 2030 compared to 2014 levels, under a phased approach, starting with the most environmentally harmful according to Global Warming Potential (GWP). The aim is to drive out high GWP HFC refrigerants and replace them with low GWP natural refrigerants, Hydrofluoroolefins (HFOs) and refrigerant blends.
The EU is considering amending the F-Gas Regulations further to enforce a quicker and even more comprehensive HFC ban. This may prove disastrous to the roll out of heat pumps using refrigerants with GWPs higher than those being considered under the amendments. The industry has to find ways to adapt, and propane could provide the answer.
The advantages of using propane
Certified manufacturers are leading the way when it comes to using propane as a refrigerant in both chillers and heat pumps. Not only does R-290 flex some impressive green credentials, but it also has excellent thermodynamic properties:
- It has a low environmental impact, with a GWP of 3 and an ODP of 0
- R-290 is non-toxic
- Compared to HCFCs and HFCs, propane has a lower system pressure drop and higher heat transfer performance
- R-290 also has lower density, resulting in a lower refrigerant charge
- It has excellent thermodynamic performance, as it can go from a very low evaporating temperature to a high condensing temperature
- It has good compatibility with materials
- Unlike HFOs, it doesn’t break down in the environment into trifluoroacetic acid (TFA) or other harmful substances
- Propane is easy to procure and relatively cheap in price
- It’s proven, as one of the original refrigerants.
Swegon is a certified manufacturer taking a lead on propane development. Keen to hear from the front lines of innovation, Eurovent Certita Certification (ECC) spoke to Swegon’s Product Management Manager in the Cooling & Heating Business Development Department, Fabio Polo, on the uses and benefits of R-290. Fabio raised several points, “Propane, if compared to synthetic refrigerants, has the benefit of being in line with the upcoming requirements of the F-Gas revision, thanks to its negligible GWP (0.02 GWP (AR6), pursuant to IPCC VI, evaluated over a span of 100 years). Also it will be not limited by the upcoming REACH Restriction proposal on PFAS. This means whatever the outcome of those legislative processes, Propane offers a future-proof solution.”
“Propane also has excellent thermodynamic properties and can be used in a wide variety of HVAC appliances. It is particularly suited to high temperature heat pumps thanks to its pressure/temperature diagram.” Indeed, propane could offer a real solution to speeding up the switch from gas boilers to heat pumps. Traditional heat pumps operate at 50oC to 55oC max. High temperature heat pumps can deliver hot water at up to 70oC making them more compatible to pre-existing radiator wet central heating systems and offering higher domestic hot water temperatures.
The disadvantages of using propane
While we can marvel at the benefits of propane and its long proven refrigerant capabilities, we can’t ignore its main disadvantage, and that is flammability. Propane is more dense than air, meaning that it will drop to the lowest point. This results in a risk of explosion (especially in enclosed areas) if the leaked propane comes into contact with a flame, spark or other source of ignition. It’s also an issue that makes retrofitting impossible as systems have to be built with flammability in mind. Those already using flammable substances such as LPG or natural gas to heat buildings may be unfazed at propane’s combustibility, but for others it is a sticking point.
Fabio continued, “From a theoretical perspective, with its thermodynamic properties, propane can be used in lot of applications. However, at the moment there are limitations due to its flammability. This means that it’s more straightforward to use it as a refrigerant in small to medium external monobloc systems, where there is no risk of propane leaking into a confined area. Currently, large units suffer some limitations due to component availability, as well as some nervousness from end users on having higher charges.”
“Internal units (like water-to-water chillers/heat pumps) can use propane in smaller capacities than external units, at least if keeping the installation requirements at a minimum level. At the moment, the highest limitations apply to air-to-air units treating air for occupied spaces. Propane is not always going to be suitable for these types of applications.”
ECC is keen to dispel some of the myths around this versatile refrigerant, by looking into the ways in which manufacturers have acted to minimise risk when it comes to the manufacture, installation, servicing and maintenance of propane systems.
Fabio continued, “Swegon has already upgraded our production lines to handle propane flammability in the right way. We invested heavily to make sure we can produce and test units safely. We also invested in the proper training of the staff manufacturing the units, in order to have them ready to manage A3 refrigerant circuits.”
“Installation is for sure one of the key points. We made the choice not to avoid or ignore the topic of flammability. The purpose is not to re-write the rule book, but to provide guidance from the very start of the process, to allow the one who designs the project to enter into the right mindset and make sure the potential risks are evaluated immediately. The sooner, in this case, the better.”
“It's also important to underline that the site requirements will vary based upon the system design and choices made by the unit manufacturer. One of the key targets we follow in our product design is to minimise (whenever possible) the constraints imposed upon propane systems, and to ensure we meet regulatory requirements along with the requirements of the final customer and the local installation.”
When it comes to servicing and maintenance, Swegon emphasise that working on a unit using A3 refrigerant is different to a unit with A1 or A2L refrigerants. “For this reason we not only developed products using propane, we also launched the ZERO Academy. A training and knowledge sharing platform linked to the use of flammable refrigerants in air conditioning applications, with the aim to help in this key transition. We have created specific documentation including an A3 Refrigerants guidebook, where we explain our view, and also link in to installation and servicing. We also educate all our service engineers and partner engineers at the time of the first sales in each country.”
Last but not least, Swegon highlighted that the rules around transportation of propane are pretty clear (depending on the charge and the type of transport), as flammable substances have been transported all over the world for many years. Shipping companies can help with information on transportation. In addition, Swegon is available to help find the right solution in specific projects where there are obstacles to overcome.
Other considerations of R-290
With flammability tackled, we switched onto the other considerations of propane. As mentioned, propane cannot be retrofitted, as systems have to be specially designed to use the refrigerant. While most components remain the same to those used in systems with HFC refrigerants, one of the big design changes is to the compressor, where pressure and temperature limits must be in line with propane, and also electrical components manufactured to reduce the risk of ignition. Components such as heat exchangers and expansions devices may also be designed differently for propane systems. Leak detection control equipment should be fitted.
Fabio also pointed out that from a theorical point of view, he would expect most propane units to be bigger than R-32 for a similar capacity and a similar level of efficiency. Adding, “At the moment EN 378 clearly drives some specific installation requirements and accessibility restrictions which differentiate A3 from A2L refrigerants. So this transition will go beyond the pure product - it will impact the whole industry. That’s why we launched the idea of ZERO Academy. The idea is to generate documentation, provide seminars and to share our expertise to reach as many people as possible with the message that this transition is possible and feasible, but we need to make it happen.”
Changing the subject to energy efficiency, Fabio said, “Associating the efficiency of a product solely with the refrigerant is incorrect, it is a shortcut that can lead to mistakes. The unit’s resulting efficiency derives from many factors including the product design and the available technologies. Indeed it is often a trade-off between different project targets such as compactness, silence, cost, etc. Therefore, you cannot compare products purely on unit overall figures and refrigerants, that leads to a gross simplification.”
Luckily ECC know a thing or two when it comes to product data. From energy efficiency to acoustics, certification tests the performance of products reliably, independently and impartially. This is why it gives free access to HVAC specifiers, designers, professionals, buyers and those in charge of the operation of systems, to its online certified product directory. Web users can view and compare thousands of certified heat pump and chiller products at the touch of a button at www.eurovent-certification.com.
Propane: A natural solution for chillers and heat pumps
The use of propane is going to grow in many areas of the HVAC and refrigeration industry, with the chiller and heat pump markets leading the way. The reasons are plentiful, from its excellent thermodynamic characteristics, through to its green credentials. Forward thinking manufactures have embraced its use and have been developing products that will abide by regulations for years to come. Manufacturers like Swegon started the development of propane products far before the legislative processes to ban HFCs started in earnest, and the company firmly believes that propane will be one of the main refrigerants of the future.
While low GWP HFOs and refrigerant blends will need to cover applications where flammability is an issue, it is no loophole to continue using synthetic refrigerants. Fabio concludes, “It’s quite the opposite. We see a future where the ratio between synthetic and natural refrigerants will be the opposite to today. So let’s get ready, because it’s not a matter of “if” but only of “when”. Let’s use propane as refrigerant and make sure no single gram of fossil fuel is used in a boiler system. That’s one of the most important targets our industry will have in the coming years.”
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