Storing high temperature solar thermal energy in shallow depth artificial reservoir for space heating

The discontinuous and unstable characteristics of solar energy limit its application in the space heating field, while aquifer thermal energy storage (ATES), as a seasonal thermal energy storage pattern, is a feasible way of solving these problems faced by solar space heating and however, low temperature ATES must not exceed 25–30 °C while high temperature ATES has low recovery efficiency. Here a novel scheme of storing high temperature solar thermal energy into a shallow depth artificial reservoir (SDAR) is proposed. By innovatively storing thermal energy into rocks rather than aquifer, the recovery efficiency improves from 46% for ATES to 90% for SDAR, and the thermal power increases from 309 kW for deep borehole heat exchanger to 1970 kW for SDAR. SDAR has no special requirement to rock temperature and can thus be created in shallow buried depth rocks, leading not only to a reduction of engineering cost but also an expansion of application scope. To further avoid risk of induced seismicity caused by hydraulic fracturing and reduce cost, the abandoned oil and gas fields and mines can be reused as the artificial reservoir.