Abstract: An Underground Pumped Hydro Storage system may comprise a substrate, a large water-fillable bag, and an overburden causing pressure in the bag. The overburden may have nonuniformities of composition or dimension. Such nonuniformities may locally make overburden more flowable or gentle to the bag, at regions of relatively high shape change or flow during a cycle. Such nonuniformities may help prevent the overburden from freezing up in cold weather, or may enable a controlled progression of bag shapes. The overburden may have an irrigation hose buried in it. The bag edge joint may have any of various features that provide for a transition of local bending and load distribution near the joint between the bag upper and lower layers. An antechamber may be provided for access to the bag interior for robotic inspection or maintenance. The system may be deployed near a dam on a river.

Abstract: An energy or water storage system can comprise a storage reservoir, a discharge reservoir, a pump for charging the storage reservoir, and a turbine or similar discharge device. The storage reservoir can comprise a flexible bag covered by overburden that creates pressure inside the bag. Energy is stored by raising the overburden. The bag can comprise a shaped internal filler piece to prevent formation of a crease at the bag edge. Solar panels can be mounted above any bag to make additional use of the land. Solar panels mounted on overburden can have tracking mechanisms and controls suitable to achieve desired orientation regardless of the slope of overburden. Elevation difference between the storage reservoir and discharge reservoir can be used, including an underground cavity. The bag can have internal tethers to influence bag shape.