Compressing gases to store energy isn’t new: for decades, a few facilities around the world have been pumping air into huge underground caverns under pressure and then using it to generate electricity in a natural gas power plant. But Energy Dome turned to carbon dioxide because of its physics.
Carbon dioxide, when squeezed to high enough pressures, turns into a liquid, which air does not do unless cooled down to ultra-low temperatures. The liquid carbon dioxide can fit into smaller steel tanks close to where renewable energy is generated and used.
In Energy Dome’s designs, a flexible membrane holds the carbon dioxide in a huge dome at low pressure. When excess electricity is available, the gas goes through a compressor to reach high pressure. This process also generates heat, which is stored too.
Then, when energy is needed, the stored heat is used to warm up the carbon dioxide, which decompresses and turns a turbine, generating electricity.