High-efficiency solar cooling

How efficiently can solar radiation realistically be converted into cooling power? With recent advances in the solar and chiller fields, net coefficients of performance (COPs) of 100% and above should be attainable (i.e. 1 kW of incident solar radiation yielding 1 kW or more of cooling power) with existing technologies. The performance leap, relative to current state-of-the-art solar cooling systems, stems from the introduction of solar fiber-optic mini-dish systems that can deliver high-temperature heat at high solar-to-thermal conversion efficiencies. Driving efficient commercially-available double-stage absorption chillers, solar mini-dish systems should be able to realize net COPs of around 1.0. A further boost in net COP to around 1.4 can be achieved by modifying the conventional scheme to a thermodynamic cascade that takes maximal advantage of high-temperature input heat. The cascade comprises a solar-fired gas micro-turbine producing electricity that drives a mechanical chiller, with turbine heat rejection running an absorption chiller. An additional virtue is that the energy of concentrated sunlight can be stored compactly as ice produced at a retrofitted evaporator of the mechanical chiller. The compactness and modularity of solar mini-dish systems opens the possibility for small-scale ultra-high-performance solar cooling systems. (C) 2000 Elsevier Science Ltd. All rights reserved.