Underground Pumped-Storage Hydropower (UPSH) at the Martelange Mine (Belgium): Interactions with Groundwater Flow

Abstract

Underground pumped-storage hydropower (UPSH) is a promising technology to manage the electricity production in flat regions. UPSH plants consist of an underground and surface reservoirs. The energy is stored by pumping water from the underground to the surface reservoir and is produced by discharging water from the surface to the underground reservoir. The underground reservoir can be drilled, but a more efficient alternative, considered here, consists in using an abandoned mine. Given that mines are rarely waterproofed, there are concerns about the consequences (on the efficiency and the environment) of water exchanges between the underground reservoir and the surrounding medium. This work investigates numerically such water exchanges and their consequences. Numerical models are based on a real abandoned mine located in Belgium (Martelange slate mine) that is considered as a potential site to construct an UPSH plant. The model integrates the geometrical complexity of the mine, adopts an operation scenario based on actual electricity prices, simulates the behavior of the system during one year and considers two realistic scenarios of initial conditions with the underground reservoir being either completely full or totally drained. The results show that (1) water exchanges may have important consequences in terms of efficiency and environmental impacts, (2) the influence of the initial conditions is only relevant during early times, and (3), an important factor controlling the water exchanges and their consequences may be the relative location of the natural piezometric head with respect the underground reservoir.

The Impact of Hydrogeological Features on the Performance of Underground Pumped-Storage Hydropower (UPSH)

“…Certain authors considered that, initially, the underground reservoir must be empty [50] because previous works needed to adapt the mine to be used as an underground reservoir, and this adaptation requires dewatering it. However, it was proven in a previous investigation that the differences between considering a previous pumping or not are negligible and only occur during the early periods [33].…”

“…Recently, researchers observed that water exchanges may progressively fill the underground reservoir, reducing η. Occasionally, a volume of pumped water could actually not be fully discharged into the underground reservoir because the latter has been partially filled by underground water exchanges [33]. In addition, this volume of water must then be discharged into surface water systems, which could alter their quality because mine water is often not of an appropriate quality.…”

Underground Pumped-Storage Hydropower (UPSH) at the Martelange Mine (Belgium): Underground Reservoir Hydraulics

“…No operations were scheduled in the 14 hours that were left in a 24-hour period. Such discharge patterns were also generated for the summer and spring periods of 2013 [29]; however, only the discharge curve from the winter period was presented in this study. More detailed explanation on the generation of the discharge patterns is provided by Pujades et al [29].…”

“…Such discharge patterns were also generated for the summer and spring periods of 2013 [29]; however, only the discharge curve from the winter period was presented in this study. More detailed explanation on the generation of the discharge patterns is provided by Pujades et al [29]. Due to the fact that in the present study the discharge cycle needed to start with turbining, the first six hours of the original winter discharge time-series, corresponding to a pumping phase [29], were moved to the end of the time-series.…”

“…A hydraulic numerical model has been developed to analyze (a) the effect of the cross sectional area of the connecting galleries and the subsequent inertia effects due to their limited discharge capacity and (b) the effect of aeration of the underground chambers on the water levels. The effect of groundwater exchanges is analyzed separately in a companion paper focusing on the same site [29].…”