High-efficiency solar cooling

Abstract

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. © 2000 Elsevier Science Ltd. All rights reserved.