Quidnet Energy from the US has proposed a low-cost alternative to pumped-storage hydroelectric energy storage. Instead of lifting water to a height and then lowering it through turbines, Quidnet’s technology involves pumping water under pressure into the earth’s interior – mines and caves. In February 2025, the technology was tested in Texas at a megawatt-hour energy storage scale and proved its readiness for widespread implementation.
Image source: Quidnet Energy
Quidnet was founded in 2015 and has raised more than $60 million in funding to date from companies like Hunt Energy Network, Prime, and Bill Gates’ Breakthrough Energy. The Microsoft founder gave Quidnet $10 million in 2020 to develop and prepare a demonstration project at megawatt-hour scale for energy storage. The experiment was eventually conducted at Quidnet’s Texas site near Dallas.
The creation of traditional pumped storage capacities requires the organization of a huge dam at a considerable height. To store a sufficient volume of energy in water raised to a height, truly cyclopean structures are needed, which by definition cannot be cheap.
Quidnet Energy’s idea is to pump water into underground reservoirs, either natural or specially created. According to calculations, the cost of creating such underground energy storage facilities per kilowatt will be at least two times lower than the cost of building traditional pumped storage reservoirs.
Like pumped-storage storage, Quidnet’s geomechanical accumulator uses excess energy from renewable sources to pump water underground under pressure. However, the process is much simpler: water is pumped into the mine under pressure from a nearby reservoir (pond). Since water is virtually incompressible, energy is stored by increasing the mechanical stress in the rock—the walls of the improvised reservoir. Ideally, the reservoir should have a lens-shaped structure, but almost any will do to reduce the cost of the project.
After the water is pumped underground, the valve is closed and opened only when electricity generation is needed. The water passes through turbines and returns to the surface reservoir, from where it can be pumped underground again. Due to the closed cycle, water loss is minimal.
Quidnet emphasizes that the creation of such storage devices has already been practically debugged by drillers: all processes and procedures — from drilling to laying pipes — are standardized and have an industrial base. This is an important factor for the mass implementation of such geomechanical accumulators. Inspired by the results of the experiment, the developers are ready to begin a large-scale project to integrate the system into the national power distribution network.