Energy Cache is working to develop a flexible, responsive, low-cost, grid-scale energy storage solution to improve grid reliability, improve the electrical transmission network and enable the wide-spread adoption of renewable energy. Energy Cache is developing a mechanical battery that they anticipate will beat the cost and performance of pumped hydro, compressed air and other “geologic” energy storage solutions.
One of the most common forms of energy storage by utilities is pumped hydro where energy is used to pump water up a hill and then when energy is needed, the water is released to flow back down the hill. This is one of the cheapest forms of energy storage – much less expensive than a big battery farm. The Electric Power Research Institute (EPRI) says that there is at least 127,000 MW of pumped hydro energy storage projects globally, and pumped hydro makes up a 99% (!) of the world’s energy storage technologies.
One problem with pumped hydro technology is it can only be used in very specific locations that have both a certain level of elevation and reservoirs for water (a problem in drought prone Los Angeles). Pumped hydro also lacks flexibility when it comes to being able to provide quick bursts of power to the grid.
Energy Cache’s idea is based on pumped hydro, but uses a motor and a cheap solid material instead of a liquid so that the system can be built in more locations and react quickly. The result is a system of buckets on a line that picks up gravel at the bottom of a hill, and moves the gravel to the top of the hill; when the process is reversed the gravel moves back down the hill and powers a generator to produce energy.