Experimental investigation of the effect of thermal cycling loading on physical properties of a sandstone from the Upper Rhine Graben

Thermal energy storage can help to bridge temporal fluctuations of renewable energy provision, e.g. from wind and solar energy,  and demand, e.g. to avoid system shutdown and associated negative effects on technical equipment and reservoir in geothermal energy production.

Storing thermal energy in rocks or rock beds is interesting as the material is abundant and inexpensive. In addition, rock has good, suitable thermal properties and is available directly where it is needed.

We investigated the effect of cyclic thermal energy storage a sandstone (Buntsandstein) from the Upper Rhine Graben, a region in Germany with high geothermal gradient and therefore a target region for present and future geothermal projects. To characterise the rock before and after different cyclic thermal loading conditions, the sandstone specimens were subjected to an initial temperature of 150 °C in a muffle furnace,  then heated to 200 °C, 500 °C or 600 °C, and finally cooled to 100 °C in varying numbers of thermal cycles (2, 5, 10, 25 or 35).

After thermal treatment the sandstone showed changes e.g. in uniaxial and triaxial compressive strength, and P-wave velocity.