How the “CO2 batteries” work, an alternative to lithium for the accumulation of energy

A CO battery₂ It is technically defined as long -lasting energy accumulation (Long Duration Energy StorageLDDES) in which thecarbon dioxide to a thermodynamic cycle in which the CO₂ He liquefies during the office and returns gaseous in the discharge phase. Like other types of accumulations, these systems are fundamental for the energy transition because they allow to accumulate the non -programmable energy produced by renewable sources and return it in the periods when this is not available, for example for solar energy during the night, or for wind energy when the wind falls, without producing emissions of any kind. Energy Domean Italian company that creates systems of this type, has recently signed an agreement with Google To provide carbon dioxide storage systems that feed the operations of the Mountain View giant with a more sustainable environmental technology.

CO batteries₂ they do not produce emissions because they operate through a closed cycle. There must be an accumulation of gaseous carbon dioxide, called the Cathedral or dome In English, from which the cycle begins. The electricity produced by a renewable source is used to feed a compressor which compresses carbon dioxide so that it warms up. Later it is sent to a thermal accumulator in which the accumulated heat is released through a cooling water capacitor. At this point the carbon dioxide, having cooled and having increased its pressure, passes to liquid status. Co storage₂ Liquida takes place in steel cylinders appropriately isolated against heat and resistant to the pressure necessary for this type of storage.

When it is necessary to consume the accumulated energy, the system works exactly oppositely. Liquid carbon dioxide begins to escape from the cylinders, is preheated with the water heat exchanger and enters one turbine. This is nothing more than the opposite machine compared to the compressor, because in this case it is the gas, i.e. the co₂which gives up its energy to the turbine and allows it to generate electricity. At this point the carbon dioxide, once returned to the gaseous state, accumulated again in the Cathedral.

The efficiency of the cycle is around values ​​of the About 75%: In other words, for every 100 kWh of renewable energy produced and “stored”, about 75 kWh of energy are obtained when this is actually requested. Energy storage in the form of liquid carbon dioxide can last from 8 to 24 hours, making this system that is almost automatically accoped to a photovoltaic system. Lithium batteries can have a few hundred megawattora storage capacity and generation of dozens of megawatts.

The efficiency of an energy storage system with carbon dioxide is lower than that of lithium batteries, which reach an efficiency of 85-90%, a value which, however, degrades rather quickly as the charging cycles increase. CO batteries₂ Instead they degrade much less quickly: The useful life of such a system seems to be over 30 years old. The cost is also advantageous compared to lithium: with the same energy produced, the cost of lithium batteries also seems to be greater than 70% than that of an co -A system₂. In addition, carbon dioxide batteries do not require critical components such as rare lands or other materials difficult to extract.