Revisiting the role of thermal energy storage in low-temperature electrified district heating systems

Abstract

Decarbonising the energy supply system is crucial to mitigate climate challenges. An emerging type of the multi-energy system, that is, the low-temperature electrified district heating system is gaining increasing popularity as a potential solution for future low-carbon heat supply. This paper investigated its operational optimisation with thermal energy storage (TES) installed at building sides. The optimisation model was to obtain the minimum operation costs of all heat pumps in this system. The TES was meant to achieve energy arbitrage through load shift, but it was observed from the optimised results that the TES did not play an active role in the optimisation. Five possible causes were identified and further investigated to reveal their impacts on the optimisation process. Results showed that the thermal capacitance, thermal resistance, and indoor temperature range of the building were major influencing factors, while the electricity price tariff and heat loss parameters of TES were minor ones. The results indicate that there is no need to equip the TES for operational optimisation purposes when the building thermal capacitance is larger than a threshold value, the thermal resistance is smaller than a threshold value, or the indoor temperature range is broader than a threshold value. These threshold values are case-specific and can be determined with the simulation model and method developed in this paper.