Underground pumped hydro-energy storage in Wallonia (Belgium) using old mines – Potential and challenges

Pumped Storage Hydroelectricity (PSH) is a well-known and efficient technology to store various amounts of electricity. In most parts of Europe, appropriate sites for new classical PSH plants are getting scarce. An alternative consists in using underground volumes as lower reservoirs to build so-called Underground Pumping Storage Hydroelectricity (UPSH) plants. The paper presents the main results of a research project currently investigating the potential and feasibility of such innovative plants in the context of Wallonia, where numerous abandoned mines and quarries are located all over the territory.
After a description of the main types of reservoir configurations existing in the considered region and the evaluation of their expected energy storage potential, the tools and methodology developed in the scope of the project are presented. Their application to the case of an underground slates quarry and an open pit chalk mine helps in identifying the remaining challenges