EnergyDome Proposes to Use CO2 to Store Renewable Energy

We told you a while ago that China was testing compressed air as a means to store electricity produced by solar and wind power. The National Energy Large-Scale Physical Energy Storage Technology Research and Development Center just compresses air and liberates it when the grid needs additional energy to balance itself.

The principle is simple: when solar or wind power sources produce energy that no one needs, the Chinese power plant uses that energy to compress air. When more people need that energy, the compressed air moves a generator and gives the electricity back to the power grid. The EnergyDome solution is slightly different.

First of all, because it does not compress the air around us: it uses only carbon dioxide. It is a fantastic irony that it takes this gas out of the atmosphere to store renewable energy. It may not be enough to put the atmosphere back to the levels before human societies burned fossil fuels in a large scale. However, it may certainly help reduce this gas level in the atmosphere and, consequently, the greenhouse effect.

EnergyDome stores this CO2 in large domes with undisclosed capacity. What the Italian company says is that the largest system can deliver up to 200 MWh of storage. That’s five times what the Chinese compressed-air power plant could deliver. If it was able to power 3,000 houses per day, the largest EnergyDome system could power 15,000.

The Italian company has two products that work with carbon dioxide: the CO2 Battery and the CO2 ETCC (Energy Transition Combined Cycle). Both operate in a similar way: compressing carbon dioxide to store the energy and releasing it to recover it. The main difference is that they do not release that CO2 back to the atmosphere: it stays either as a liquid inside a vessel or as a gas inside the CO2 dome.

The CO2 Battery has an energy efficiency of 75%. That makes the CO2 ETCC a preferable solution in terms of efficiency: it can recover up to 80% of the energy used to compress the carbon dioxide. The secret is a boiler that recovers heat from the turbine that generates electricity with compressed CO2. The CO2 Battery does not have that boiler, but it is also cheaper, which may compensate depending on the applications it will have.

EnergyDome promises that it can scale the energy storage needs for whatever customers want. Five of its largest domes could store 1 GWh of renewable power. If the idea is economically feasible, we may soon see large CO2 energy storage systems installed worldwide.

The only concern the idea raises is with how safely the CO2 will be stored. In 1986, a sudden release of carbon dioxide killed 1,746 people and 3,500 livestock in Lake Nyos, Cameroon. About 300,000 tons of the gas suddenly displaced the air in that valley, cutting the oxygen supply of all the ones that died.

Although EnergyDome did not disclose how much carbon dioxide its largest dome can store, it must work with a lot less gas than the deadly quantities released by Lake Nyos. Anyway, safety must be a priority with such systems, and anyone interested in it should have that in mind. Again, it would be fantastic to see carbon dioxide play a role in cleaning the energy matrix and making the world a cooler place.