Natural refrigerants: The future of low carbon cooling

It is ironic that the very substance implicated in destroying the planet could also be its saviour… or at least be a powerful weapon in the fight against climate change.

Carbon dioxide (CO2) is a significant greenhouse gas and a big contributor to global warming. However, using this ubiquitous chemical compound as a coolant for air conditioning systems can help save energy and reduce the carbon emissions that increase the likelihood of global warming.

Following the 2020 update to the F-Gas Regulations, R32 refrigerant is regarded as the most practical and efficiency low-GWP cooling option for heat pumps. But a global warming potential (GWP) of 675 makes it 675 times more harmful to the environment than CO2 (which boasts a GWP of just 1).

This makes for a compelling argument in favour of CO2 as a green alternative to traditional refrigerant-based cooling media favoured for many air conditioning and heat pump applications.

Japan has been leading the research and product development of heat pumps suitable for buildings of a range of scales down to individual dwellings and this research is promising. However, there are also limitations of using natural refrigerants.

The case against CO2

The main drawback of carbon dioxide as a refrigerant is its high working pressure. This makes it necessary to redesign and strengthen components to cope with CO2 cycles.

The problem is that newly designed components can only be manufactured at reasonable prices if they are mass-produced. This can be a big hurdle to surmount before CO2 technology is introduced in refrigeration, air conditioning, and heat pump systems.

If, for instance, the automotive and transport industries decided to move to this technology, other fields would benefit from mass-produced low-price components.

Because their componentry must be redesigned, CO2-based systems tend more complex to ensure safety of the overall system. On top of this, specialist training is required to safely handle, service, maintain and install CO2 systems.

Besides, existing heat pumps can’t easily be switched to CO2 as a refrigerant; the system must be designed to cope with the significantly higher pressures than traditional heat pumps.

Furthermore, CO2 heat pumps generally require large temperature differences in the fluid used to remove heat from the heat pump, typically requiring a significant reconfiguring of the building heat distribution system.

The case for CO2

However, there remains a strong case in favour of CO2 systems. Indeed, there is increasing interest and development going into heat pumps using CO2 as a refrigerant, according to an influential report published in 2020.

The ‘LETI Climate Emergency Design Guide – How new buildings can meet UK climate change targets’, says: “Besides having zero Ozone Depletion Potential, CO2 also has an ultra-low GWP of 1 (unlike most currently used refrigerants, the most common of which typically have GWPs in the range of 1,400 to 2,100), is non-flammable (unlike almost all other natural refrigerants) and is non-toxic (unlike ammonia, which is often used as a refrigerant in large scale industrial applications).

“But perhaps of most interest in the context of Future Heat for buildings is the ability of CO2 heat pumps to deliver domestic hot water (DHW) temperatures at relatively high efficiencies compared with most currently available heat pumps.”

Since CO2 is a naturally occurring substance, it forms part of natural biogeochemical cycles and does not therefore create persistent waste in the atmosphere, water or biosphere. Moreover, CO2 is neither toxic nor flammable, is relatively cheap, and is sustainable and future-proof. It is also far easier and cheaper to dispose of than manmade refrigerants.

So, selecting the right refrigerant for the job inevitably involves a compromise – perhaps, for example, sacrificing 100% non-flammability for a low GWP.

Why green refrigerants make sense

The cooling processes creates both direct and indirect emissions. By using natural refrigerants such as CO2 in high energy efficiency appliances, it is possible to cut both types of emissions substantially.

Direct emissions result from the release of refrigerants to atmosphere. This can occur during normal operation due to leaks in pipes and components or during maintenance and dismantling. Although the quantity of a refrigerant might be small, the high GWP of typical refrigerant gases can have a devastating impact on the environment.

Indirect emissions are related to the energy consumption of cooling appliances so they rely on the source of the electricity and the amount of CO2 emitted during its production. Indirect emissions can be reduced by increasing the energy efficiency of a product or by decarbonising electricity generation, a process that has made great strides in the UK over the past five years.

The importance of the heat pump technology

However, it is not just the refrigerant that matters when it comes to selecting a heat pump. The right technology is also crucial. That’s why it pays to specify a high efficiency unit such as Enerblue’s HP90 – HP90W heat pump.

With a heating capacity of 14.5 to 133.2kW, this versatile range is designed for most commercial / industrial sectors.

This CO2 refrigerant gas-based range can heat water to temperatures up to 90 dec C with an external temperature of -20 deg C.

It boasts a host of features including semi-hermetic reciprocating compressors, axial fans, total cool recovery and the ability to provide heating.

The natural choice

Enerblue’s environmentally-friendly air conditioning solutions – including its innovative, tried and tested heat pump technology – is supported and distributed in the UK by Klima-Therm. Email us at or call +44 (0) 20 8971 4195.