Integration of an industrial heat pump for a TES-based power-to-heat system : A techno-economic assessment

Abstract: This work aims to investigate the potential electricity savings, as well as the potential decrease in LCoH and OPEX, that an integration of an industrial heat pump can have on a molten salt-based power-to-heat system with integrated thermal energy storage. The original system uses an electric heater to heat up molten salt, which acts as the heat transfer fluid of the system, from which heated steam can be produced and delivered at the output. The idea of integrating an industrial heat pump into this power-to-heat system is that it would heat up the molten salt for a certain temperature range in the beginning of the heating phase, while the electric heater would be used for the later part of the heating phase of the molten salt.  First, a background section is presented in order to provide background information about the topic at hand, primarily focusing on heat pump theory and avaliable process- and waste heat that could be used by an industrial heat pump. After that, a system configutaion is presented of the investigated power-to-heat system with all the components in it thoroughly explained. The methodology followed throughout this work is then presented, which includes the description of a mixed-integer linear program that is of fundamental importance in relations to this work, and used for conducting simulations from which much of the results is derived from.  When using a waste heat tempreture of 100°C and a sink temprerature of 250°C for the industrial heat pump, results show that the electrical power used in the system without an industrial heat pump can be decreased by 15,6%. Moreover, a maximum decrease of 13,4% of the LCoH and 16,6% of the OPEX can be achieved by the integration of the industrial heat pump. The biggest decrease, in regard to the LCoH and the OPEX, were for the countries with the highest average electricity prices, while a smaller decrease was shown for the countries with lower average electricity prices.  A cost increase for the industrial heat pump, which would affect the CAPEX of the system, was shown to have a small outcome for the LCoH savings, the major contributor was the OPEX of the system. If any impactful change for this particular power-to-heat system is desired, it's going to have to decrease the OPEX for best result, which is what the integration of an industrial heat pump aims at doing.