Currently, pit storages are not built in Switzerland, mainly due to challenges regarding land use, costs,  implementation barriers, and societal factors. SP6 aims at finding solutions for multipurpose pit storage to overcome these barriers and to set the basis for a national dissemination of PTES. 

Xiang et al. (2022) provides a comprehensive overview of the state of the art of PTES. The biggest challenge is the inability to use the space above the pit. In conventional PTES, the cover is a compromise between cost, heat loss and vapor diffusion into the insulation material, resulting in cover designs which are unsuitable for additional use. If PTES are located in urban areas and, particularly in the Swiss context of high land prices, it is crucial that the area above can be used for applications like energy production, agriculture, public space or ecological compensation area, thus leading to increased social and political acceptance and reduced overall costs.

SP6 aims to develop a novel technology for PIT storage to allow for a multi-purpose use of the above surface. New concepts and constructive systems such as the combination of cable and floating technologies, car park building design, and green roof systems are evaluated and iterated (i). The use of PTES covers for solar energy production is addressed based on the development of a mounting system for solar energy production (ii). Additionally, we investigate how far the angle of inclination of the walls of the pit can be increased to maximize volume for a given surface (iii).

Furthermore, we develop concepts and investigate how gravel mining and landfill can be combined to construct energy and cost efficient PTES in these sites (iv), as in Switzerland, about 45 million m3 of gravel is extracted annually from ~ 500 gravel pits (FSKB 2022).