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Using CO2 as energy storage

A plant for compressing carbon dioxide as a way to store energy in an effective and affordable manner. Image credit: Energy Dome

Production of power and its consumption are not in synch. This means that there is a need to store surplus production to be used when there is a surplus demand. Storage of energy sources is practical for some, tricky for others. Storing fossil fuels is straightforward (they have been stored for millennia on the Planet!) whilst storage of electricity is costly.

Actually storing electricity can only be done use capacitors and they can store very little amount at a relatively high cost. Hence, the storage of electricity is done by converting it into a different form of energy, like chemical energy using batteries or potential energy using pumps to move water to higher levels -hydropower, converting it into inertial energy by spinning big masses …

Each of these alternative ways of storing electrical energy have advantages and disadvantage. Researchers are at work to look for solutions that can be both effective and affordable.

One way of storing energy is by compressing air. You convert electricity using a pump into high pressurised air that can be stored in a tank. On demand you can tap onto that pressurised air to spin a turbine and generate electricity.

CAES, Compressed Air Energy Storage, is not an ideal form of storage because the energy density is pretty low and it makes practical sense only if you have huge containers available, like natural caverns. On the contrary LAES, Liquid Air Energy Storage, has a much higher energy density, hence you can store significant amount of energy in reasonably smaller tanks, but to keep air in a liquid form you need to operate at very low (cryogenic) temperatures and that makes the system complicated and expensive.

An Italian company, Energy Dome, has come up with an energy storage based on CO2. This provides for high energy density and storage at ambient temperature (thus getting rid of complexity and cost).

They have created a trial plant, ideally to be positioned in the vicinity of some renewable source, like wind power and solar power. When there is excess production this excess is used to liquify, by pressurisation, CO2 storing it into a steel tank. The pressurisation produces heat that is also stored (there are various ways of storing heat basically by heating some substance that is isolated from the environment so that the heat is not radiated and depleted). Once there is need to tap onto the stored energy the heat is used to warm up the liquid CO2. That produces gaseous CO2 that can spin a turbine to produce electricity.

As mentioned, so far they have built a trial plant. There are still engineering hurdles to overcome, not in terms of making it work, rather in terms of making it affordable.

Anyhow, the idea is interesting, and with their plant they have already proved that it is more than a “concept”. It works. Now the challenge is to make it competitive.

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the New Initiative Committee and co-chairs the Digital Reality Initiative. He is a member of the IEEE in 2050 Ad Hoc Committee. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.

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