Carbon coolers

Carbon dioxide is set to replace harmful hydrofluorocarbons in fridges and air conditioning units.


Hydrofluorocarbon (HFC) refrigerants used in fridges and air conditioning units could soon be replaced with more environmentally benign CO2 combined with various sorbents.

The technology to achieve this is being developed by UK refrigerant specialist, Thermal Energy Systems (TESL), which has raised £300,000 from a consortium of investors including NESTA, the Liverpool Seed Fund and Enterprise Ventures.

TESL director John Poole and technical director Dick Powell said their concept uses commercially available components, which eliminates the need to retool production facilities with expensive new equipment.

‘By using known materials and components that are already proven, we avoid safety problems that would be associated with new compounds,’ said Powell.

He added that the successful use of CO2 as a replacement for HFC rests on achieving pressure levels that can accommodate CO2.

‘Carbon dioxide can be as high as 150 bar, whereas a typical hydroflurocarbon ranges from 15 to 30 bar,’ he said. ‘Existing refrigeration equipment is rated at 30 bar.’

Powell and Poole have developed a method to reduce the pressure level equal to that used by HFCs using unnamed sorbents to absorb the CO2 to levels that help achieve the correct pressure rating. It is waiting for a patent.

Powell would not specify how TESL’s absorption process works, but likened it to the absorption process in refrigeration applications where ammonia is used as a coolant. In one part of the fridges’ cycle, Powell said, ammonia is absorbed in water to reduce its pressure. While some refrigerant specialists have suggested ammonia as a good replacement for HFCs on a wider scale, its main drawback is that it is flammable and toxic. Also, equipment using it costs more than equipment using HFCs.

Carbon dioxide, on the other hand, ‘is relatively low toxicity, inflammable and cheap,’ said Powell.

TESL will concentrate on bringing its technology to air conditioning units before refrigerators because Powell said it is slightly easier to tackle from a technical point of view.

‘The temperature changes we have to deal with in air conditioning units are not as great as those we have to deal with in refrigeration,’ he said.

Powell and Poole are building a prototype customer rig that will be ready to demonstrate the technology to interested industry partners next month.

Powell said the development was a timely one as some European countries, notably in Scandinavia, have put a high tax on HFCs and therefore easy and inexpensive replacements are becoming more important.

‘It’s close to a 90 per cent tax in Scandinavia now,’ he said. ‘So a kilo of refrigerants that would normally cost about £10 a kilo will cost £50 to £70 a kilo.’

In addition, he said, there is a strong move to phase out HFCs entirely, as they have been linked with global warming.

Powell said that starting in 2011, the EU will ban the use of HFCs for air conditioning fluid in all new models of cars.

Siobhan Wagner