Latent heat and thermochemical storage as enablers for waste heat-to-power and heat-upgrade: A general approach

Most excess heat/cold in industrial processes is unrecovered due to intermittency and variability in grades (due to e.g. temperatures) and amounts (due to e.g. flow rates), which complicates the heat-to-power conversion and heat upgrade using traditional technologies. The decoupling of heat sources/sinks and thermal power utilisation via generation/heat upgrade enabled by the integration of a suitable storage system has the potential to address the challenges. The aim of this study is to develop a framework based on heat storage (latent and thermochemical), heat-to-power (organic/steam Rankine cycle, Kalina cycle, etc.) and/or heat upgrade (heat pumps, etc.) options, already available or nearly ready for the market, for the utilization of the industrial waste heat. A wide temperature range is considered which spans applications to as wide as the food and steel sectors. Based on an extensive literature survey, mutual links are established on the basis of temperature and illustrated in maps. This facilitates the primary screening of the latent heat and thermochemical storage systems for heat to power and heat upgrade applications. With such generalized maps, the application of the Rankine cycle (both direct and reverse) using refrigerants in relationship to the thermal energy storage technologies is discussed.