Heat recovery in energy production from low temperature heat sources

Low-temperature (<100 degrees C) heat sources have the potential to provide renewable and clean energy. Traditional technologies (thermal engines and thermoelectric solid-state devices) are not economic in this temperature range. Innovative methods have been recently proposed. In some of them, a process of "heat recovery" has been proposed: it consists in the reuse of the heat provided by the heat source more than one time. Here, we perform a thermodynamic analysis of the heat recovery process. We found that, in the considered temperature range, the temperature difference across the heat exchangers has a major impact on the efficiency, being the main cause of entropy production. By evaluating the efficiency and the surface of heat exchangers needed for producing one unit of power, we found that fundamental processes operating on large temperature difference should be preferred, in order to minimize the capital cost and volumetric dimension of the heat recovery system. (c) 2018 American Institute of Chemical Engineers AIChE J, 65: 980-991, 2019