Solar Thermal Energy Could Keep Buildings Cool

A University of Florida engineering researcher has received $1 million in federal stimulus funds for a research project aimed at developing small refrigeration systems powered by solar thermal energy or waste heat. If successful, solar-powered cooling and heating of residential buildings could become economically viable.

Assistant Professor Saeed Moghaddams project was among 43 green energy projects funded with $92 million in stimulus funds from the U.S. Department of Energys Advanced Research Projects Agency.

University of Floridas Nanostructured Energy Systems group, directed by Moghaddam, is developing small-scale absorption refrigeration systems that, with reasonable efficiency, harness low-quality heat energy that cannot be converted to electricity. The systems use refrigerants such as water that have no global warming potential.

Absorption refrigeration systems have long been used to convert heat to a cooling effect but have been limited to large scales (hundreds of tons), where the economy of scale justifies their high cost and the boilers and cooling towers they require.

Moghaddam says that two-thirds of the fuel energy used for generating electricity is being wasted in the form of waste heat. And solar energy is only 10 to 15% efficient, with the rest mostly turning into waste heat. Absorption refrigeration systems could use this waste heat or could be powered by solar thermal energy, but manufacturing low-cost, small, and robust systems has been a challenge.

Economically viable solar-powered absorption refrigeration systems for buildings have the potential to harness solar thermal energy with efficiencies of 50 to 70%, far beyond the reach of photovoltaic cells, says Moghaddam. An inexpensive small-scale absorption refrigeration system coupled with solar collectors and a natural gas-fired heater could provide an economically viable route for year-round cooling, heating, and hot water generation in typical buildings while also reducing energy demand and greenhouse gas emission

Written by: Nancy Lamontage 22 July 2010,  Solar Novus Today