Optimize prosumers' economic performance by using water tank as thermal energy storage

Heat prosumers will become important participants for future district heating (DH) systems. However, the current unidirectional heating price models reduce interest in prosumers and hinder the promotion of prosumers in DH systems, because the prosumers gain no economic benefit from supplying heat to the central DH system. This study aimed to break this economic barrier by introducing water tank thermal energy storage (WTTES) and optimizing the operation of heat prosumers with WTTESs, considering the widely used heating price models in Norway. Firstly, a generalized heating price model was introduced, which could represent the current widely used heating price models in Norway. Secondly, the WTTES was integrated into the heat prosumer to improve the self-utilization rate of the prosumer's heat supply from its distributed heat sources, meanwhile, shave the prosumer's peak load. Afterwards, an optimization framework was formulated to optimize the operation of the prosumer with the WTTES under the generalized heating price model. Finally, a numerical method for solving the proposed nonlinear optimization problem was given. A case study showed that the proposed method could cut the prosumer's annual heating cost by 7%, and the investment of WTTES could be recovered in four years.