The transition to renewable energy in the heating sector faces significant challenges, particularly the mismatch between the availability of renewable thermal energy sources and fluctuating demand. High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems offer a promising solution to mitigate this mismatch and further decarbonize heating systems by bridging the gap between supply and demand.

This thesis explores the integration of HT-ATES into the heating system at TU Delft, which is transitioning from gas-fired boilers and a combined heat and power plant to a geothermal well-based thermal energy system. During periods of low demand in summer, excess geothermal energy will be stored in the HT-ATES system, to be utilized during high-demand periods in winter when the geothermal well's capacity is exceeded. The objective is to meet 85% of the annual heating demand through sustainable thermal energy sources.

In this study, two design options for integrating the HT-ATES into the heating system are analyzed. Besides the geothermal well and the HT-ATES, the heating system also comprises a heat pump to reach the required supply temperatures. One option is to locate the HT-ATES behind the evaporator of the heat pump and therefore use the previously cooled down temperature to extract thermal energy from the HT-ATES. In the second option, the HT-ATES is located directly behind the heat sink in the system, using the return temperature of the consumers to discharge the HT-ATES.

An energy system model is set up using TESPy and coupled to a numerical model to simulate temperature changes in the HT-ATES. With the results of the model, the influence of the integration concept on the system performance is explained. Furthermore, the effect of varying input parameters such as supply and return temperatures as well as overall demands in the system are examined.

The results indicate that, when comparing the two design options with HT-ATES, locating the HT-ATES behind the evaporator yields the better results across all evaluated performance indicators – mainly a reduction of GHG emissions, an improved system SCOP and a better thermal recovery efficiency of the HT-ATES. However, compared to a base design without HT-ATES, the integration of a HT-ATES leads to additional financial costs and a substantial intervention into the subsurface. Due to its lowest electricity consumption, the base design also shows the best system SCOP.