A sequential approach for integration of multiple thermal energy storages with fixed mass and variable temperature

Heat recovery in industrial processes is gaining importance as climate goals push industries to increase their energy efficiency. But also potential economic benefits give incentives to increase waste heat recovery and thus energy efficiency. The various available thermal energy storage technologies yield high potentials to increase energy efficiency in industrial processes. However, storages with fixed mass and variable temperature are rarely considered for storage integration using process integration methods. In this paper, a sequential approach using mathematical programming formulations combined with insights from pinch-analysis is proposed that allows to find cost efficient heat recovery systems incorporating storages with fixed mass and variable temperature. The procedure is demonstrated by integration of pressurized water storages into two industrial process examples taken from literature. For both examples hot utility demand could be reduced by about 50% compared to solutions without storage integration.