Air-powered electricity storage system at 700m deep seabed

BaroMar's system uses excess electricity to compress and direct air to tanks on the seabed, storing it there until needed.

Simulate the operation of an air-based power storage system on the seabed. (Video: BaroMar).

Israeli company BaroMar is preparing to test an energy storage system touted as the cheapest way to stabilize the renewable power grid in the long term, New Atlas reported on May 6. Specifically, BaroMar will use Compressed Air Energy Storage (CAES) technology to help store excess renewable electricity for later consumption, during the cold winter months.

CAES uses excess electricity to run compressors, pumping air into large tanks. Air is stored at high pressure, then released through a turbine that drives a generator. This technology is already cost-effective, but BaroMar says its new system can even surpass traditional systems for long-term electricity storage.

Essentially, BaroMar's plants will be located close to the coast with access to deep water. Instead of high-pressure tanks, BaroMar takes advantage of the pressure of the water column to store compressed air in much cheaper tanks.

These tanks are made of concrete and steel, above is a cage filled with rocks to keep the tank submerged at a depth of 200 - 700 m. They have many water valves around them and are initially filled with seawater. Compressor and generator systems are located close to each other on dry ground. When there is excess electricity to be stored, the compressor will send ambient air down to the tanks through pipes at a pressure of 20 - 70 bar, depending on the depth.

These containers are made of concrete and steel, and above are cages filled with rocks.

Compressed air will push the water out of the tank, but because the hydrostatic pressure of the water outside is in balance with the air pressure inside, the tank doesn't need to be as sturdy and expensive as a land-based one. On land, the air inside the tank is at very high pressure compared to the normal atmospheric pressure outside.

When energy needs to be discharged, the system will allow air to flow back through the duct, into the heat recovery system, followed by the expansion turbine to run the generator. At the other end, the water flows back into the tank and is ready to be ejected when the compressor runs.

A pilot project is being developed in Cyprus, the goal is to achieve a cycle efficiency of about 70% - equivalent to the efficiency of the world's largest CAES plant with a capacity of 100 MW, electricity storage capacity of 400 MWh in Truong Jiakou, northern China. This is very high efficiency compared to traditional compressed air systems. Of course, the pilot plant will be much smaller, storing only 4 MWh of electricity.

BaroMar claims that its system costs less than other Long Term Energy Storage (LDES) solutions thanks to cheap containers, long life, low to zero underwater maintenance costs. When operating With a 100 MW plant capable of storing 1 GWh for 350 days per year for 20 years, the company can deliver a Levelized Cost of Storage (LCoS) of $100 per MWh, while LDES technologies another cost about 131 USD/MWh.