System puts the air into air conditioning

The world’s first building air conditioning system to use air as the refrigerant was unveiled this week at Bristol University.

It is the result of two years’ work by the university and the Building Research Establishment, supported by the DTI and a number of industry partners, to develop an air conditioning system that does not use ozone depleting refrigerants or greenhouse gases.

The system is based on the principle that when a gas expands it gets cold and when it is compressed it gets hot. Air – which is free, safe and harmless – can be compressed and expanded in a continuous cycle to provide simultaneous heating and cooling. It is ideal for buildings where there are both heating and cooling requirements most of the time, particularly hospitals.

The packaged unit demonstrated this week uses existing heat exchanger technology, and aerospace compressors and turbines to provide hot water at 80 degrees C and chilled water at 6 degrees C. It can be connected directly into standard heating and cooling systems.

In tests against conventional gas-fired boilers and vapour-compression water chillers, the Bristol unit cut overall energy consumption and CO2 emissions in buildings where there was a high proportion of simultaneous heating and cooling demand.

It will now be used to provide air conditioning for the conference suite in the university’s Food Refrigeration and Process Engineering Research Centre.