Guidelines related to the use of an existing cavity (mine/quarry) as reservoir of a pumped storage hydroelectric facility

Underground mines/quarries or open pits are manmade earthworks resulting from previous extraction of natural resources. They were mostly abandoned after resources depletion but underground or surface excavations remain.
Pumped Storage Hydroelectricity (PSH) is one of the only efficient solutions for large scale energy storage. During peaks of energy production, water is pumped from a lower reservoir to an upper reservoir. On the other hand when demand peaks, energy is generated when water is transferred to the lower reservoir.
The objective of this work is to study the recovering of abandoned excavation volumes as lower reservoirs for pumped storage hydroelectricity. Underground Pumped Storage Hydroelectricity (UPSH) is a particular case where at least one of the reservoir lies below the surface.
Compare to classical PSH plants, using an existing cavity as a reservoir raises three main additional problems:
1) What are the water movements and thus discharge availability at the pump/turbine location depending on the reservoir (complex) geometry?
2) What are the exchanges between the reservoir (usually not watertight) and the surrounding medium?
3) How can the reservoir sides resist to cyclic loading imposed by the plant operation?
In the following, some simplified criteria and issues are provided to carry out feasibility assessments of such rehabilitation projects, from the existing reservoir point of view. These criteria do no replace a detailed and complete study but draws the attention on problems specific to PSH using existing cavities as reservoir. They do not concern problems existing for every PSH project, such as location of electricity transport lines, availability of water…