Adsorption refrigeration - An efficient way to make good use of waste heat and solar energy

This paper presents the achievements gained in solid sorption refrigeration prototypes since the end of the 1970s, when interest in sorption systems was renewed. The applications included are ice making and air conditioning. The latter includes not only cooling and heating, but also dehumidification by desiccant systems. The prototypes presented were designed to use waste heat or solar energy as the main heat source. The waste heat could be from diesel engines or from power plants, in combined cooling, heating and power systems (CCHP). The current technology of adsorption solar-powered icemakers allows a daily ice production of between 4 and 7 kg m(-2) of. solar collector, with a solar coefficient of performance (COP) between 0.10 and 0.16. The silica gel-water chillers studied can be powered by hot water warmer than 55 degrees C. The COP is usually around 0.2-0.6, and in some commercially produced machines, it can be up to 0.7. The utilization of such chillers in CCHP systems, hospitals, buildings and grain depots are discussed. Despite their advantages, solid sorption systems still present some drawbacks such as low specific cooling power (SCP) and COP. Thus, some techniques to overcome these problems are also contemplated, together with the perspectives for their broad commercialisation. Among these techniques, a special attention was devoted to innovative adsorbent materials, to advanced cycles and to heat pipes, which are suitable devices not only to improve the heat transfer but also can help to avoid corrosion in the adsorbers. Recent experiments performed by the research group of the authors with machines that employ composite adsorbent material and heat pipes showed that it is possible to achieve a SCP of 770 W kg(-1) of salt and COP of 0.39 at evaporation temperatures of -20 degrees C and generation temperature of 115 degrees C. (C) 2006 Elsevier Ltd. All rights reserved.