Nowadays, the fundamental idea of district heating (DH) is to utilize local heat resources to satisfy local heat demands, otherwise those resources would be wasted. However, the mismatch between the achievable resources and fluctuating demand is challenging. This study analyzed the possibilities to solve this problem by introducing a short-term thermal storage and a seasonal thermal storage. A water tank (WT) and a borehole thermal storage (BTS) were chosen as the thermal storages. The DH system of a Norwegian university campus was selected as the case study. A high order system model was built in Modelica language. The results showed that the mismatch might be solved. The BTS brought about 3 GWh annual heat saving, and the WT brought about 110 kW average peak load shaving. However, around 0.8 GWh/year electricity was used by heat pump to recover the stored heat in the ground.
Keywords 4th generation district heating, waste heat, ground source heat pump, seasonal thermal storage, water tank