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Proceedings of Symposium on Energy Engineering in the 21<sup>st</sup> Century (SEE2000) Volume I-IV

ISSN:
1-56700-132-7 (Print)

THERMALLY DRIVEN HIGH-PERFORMANCE SORPTION HEAT PUMPS

Hans-Peter Klein
Institute for Nuclear Technology and Energy Systems University of Stuttgart

Eike Willers
Institute for Nuclear Technology and Energy Systems University of Stuttgart

Manfred Groll
Institute of Nuclear Technology and Energy Systems, University of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany

Abstract

Sorption Heat Pumps are promising devices for the rational and environmentally friendly use of energy. The commonly used working pairs have no Ozone layer Depletion Potential (ODP) and a negligible Global Warming Potential (GWP). In the field of liquid sorption, lithium bromide-water (LiBr-H20) and water-ammonia (H2O-NH3) machines are commercialized, while among the solid sorption machines only silicagel-water devices are produced in small series. To cover a larger fraction of the potential market, sorption devices need to have a performance close to the overall performance of compression devices, taking into account the efficiency of electricity generation. This is possible by coupling systems operating with different working pairs. A topping cycle allowing its waste heat to drive a bottoming device increases the efficiency significantly, and thus contributes to a higher competitiveness of the sorption technology. Some materials have the potential to be used in a topping cycle for providing simultaneously cold and high temperature waste heat to a bottoming cycle. Suitable materials are ammonia salts and metal hydrides, which cover a large temperature range from very low to very high temperatures. Favourable materials for bottoming cycles are silicagel-water and lithium bromide-water. In this paper various combinations of topping/bottoming cycles and machine schemes are compared.