New materials improve solar air conditioning

Solar air conditioning could be more efficient and less expensive following new research being conducted in the UK and Australia.

Engineers from Warwick University will be helping a team at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) develop materials for adsorption chillers, which are used for converting collected solar heat into cool air.

The project will focus specifically on developing novel desiccant materials for adsorbing water vapour.

Once developed the material will be coated onto a rotating part of the solar air-conditioning device, known simply as ‘the wheel’.

Bob Critoph, a professor at Warwick’s school of engineering, said most of the work will be conducted at CSIRO, where the technology will be patented. It is later hoped the technology will contribute to the development of new higher-efficiency solar air-conditioning system with mass-market potential for commercial buildings. 

‘At the moment desiccant rotors are expensive bits of kit so if you could get a lower capital cost and efficient desiccant material onto this wheel that could increase its market potential,’ he said.

Dr Stephen White, who is leading the research at CSIRO, declined to give details about the technology being developed because patents have yet to be granted, but his research facility’s website gives some indication of how it will work.

According to White’s description, the system will take in outside air, dehumidify it and then evaporatively cool it in a way similar to how human skin is cooled by the evaporation of moisture from its surface. A solar thermal collector – such as a solar hot-water panel or a parabolic solar trough – gathers heat from the sun and uses it to drive the desiccant dehumidifier.

The market for solar-cooling technology has room to grow. A report by Solarnext, a German solar-cooling and heating system provider, states that, in 2006, approximately 12MW cooling capacity had been installed in Europe. This works out to about 100 to 120 solar-cooling systems. Germany has around 39.1 per cent of the systems, while Spain and Greece take up 27.5 per cent and 8.7 per cent respectively.

One key reason these systems are not more popular, points out Roberto Fedrizzi, a solar-cooling expert from Italian research centre EURAC, is that upfront costs are too high.

An 8kW adsorption solar-cooling system, he said, could cost as much as €40,000 (£33,000). While these systems save a significant amount on yearly electricity costs, Fedrizzi estimated that payback time without government incentives could be anywhere around 30 years.

Those involved in the Warwick and CSIRO project hope upfront expense will decrease as the market for solar-cooling technology matures and governments roll out incentives for investing in low-emission technology.