Dutch startup Ocean Grazer has designed an ocean battery that uses excess renewable energy to pump 20 million litres of low pressure water from a concrete reservoir on the sea bed into a flexible bladder. When energy is needed, the bladder releases the water back into the reservoir using the force the ocean above it, driving water turbines and generating up to 10MWh of electricity as it passes back into the reservoir, at an efficiency rate of between 70 and 80 percent.
