Seasonal thermal energy storage for large scale district heating

Seasonal thermal energy storage (STES) systems in combination with heat pumps can significantly reduce the impact of peak loads in large scale district heating systems and allow for the application of renewable heat sources in these networks. This paper investigates technologies with the highest potential for implementation in large scale district heating networks and identifies high temperature aquifer thermal energy storage (HT-ATES) as the most suitable technology. The HT-ATES has been applied at the primary side of the network (90 to 110 oC) and at the secondary side (72 to 92 oC). Suitable locations for the STES have then been identified. A control volume approach is used in Matlab to predict heat transfer and pressure drop in the HT-ATES wells considering porosity, permeability, grain size and geometry of the aquifer. The temperature distribution and extraction temperature are predicted as function of time. The yearly heating demand of a network has been used in combination with different operating modes to identify the required size of the HT-ATES. The simulations indicate that it will take 5 years to reach steady temperature supply.