Although renewable energy is very useful, they need a storage system as a backup to deliver energy even when there is no sun or wind. Marine battery is a new energy storage system design, which functions a bit like an undersea hydroelectric dam.
Developed by Dutch startup Ocean GRAZER, Marine Battery is designed to install offshore renewable energy generators such as wind turbines, floating solar farms, and tidal and wave energy systems on the seafloor. It consists of three parts, and its function principle is similar to that of a dam.
Specifically, buried at the bottom of the sea is a concrete reservoir that can store up to 20 million liters (5.3 million gallons) of fresh water at low pressure. A system of pumps and turbines connects the reservoir to a flexible bag on the ocean floor. The excess electricity from renewable resources can be used to pump water from the reservoir into the bag. When energy is needed, the bag is released and driven by the pressure of the sea water above it to squeeze the water back into the reservoir, then rotate the turbine on the way to transmit the generated electricity to Electroweb.
The Ocean Grazer team says the system is between 70 and 80 per cent efficient and should be able to run unlimited cycles over a life span of more than 20 years. It also has considerable scalability-each concrete reservoir has a capacity of 10 megawatts, so adding more such reservoirs can increase the overall capacity. If more energy is needed, additional pump and turbine equipment can be added to increase power output.
The concept of "marine battery" is interesting, but it is far from the only ongoing marine battery design. Subhydro, an innovative undersea technology company, has come up with a similar idea of pumping sea water from a tank placed on the ocean floor and then turning the turbine to fill the tank when electricity is needed. The Massachusetts Institute of Technology describes a similar concept with hollow concrete balls. Another recent design takes advantage of buoyancy, using electricity to drag balloon-shaped containers and secure them underwater, and then release them to generate electricity.
However, there is no solution for every situation, so solving global problems such as renewable energy storage is likely to require a host of different, creative ideas.
