Using heavy objects to store energy

Gravity Energy Storage Technology, often abbreviated as GEST, operates on the principle of gravitational potential energy. It involves lifting heavy objects, such as massive weights or containers filled with materials, to a higher elevation when energy is abundant or inexpensive. [pdf]

Example of using water to compress air for solar container

Hydostor will store compressed air in a reservoir that''s partly filled with water to balance out the pressure. The whole system will hold up to 12 hours of energy for the grids where the two . [pdf]