In central Sardinia, a massive balloon looms on the horizon. It is full of carbon dioxide, one of the main greenhouse gases causing dangerous changes to our climate. Yet the very gas driving global warming could be an important factor in the fight against climate change.
Energy Dome, a Milan-based start-up, uses the huge balloon, also known as “the dome”, as a critical part of their “CO2 Battery”.
“Renewables are currently taking the lead in terms of power production, but they come with a catch —the sun doesn’t always shine, and the wind is not always there,” says Paolo Cavallini, Energy Dome’s chief of staff. “At the same time, we need renewable electricity day and night. Hence, we need long-duration energy storage.”
Storage is the missing piece in the energy transition. Energy producers need to be able to store excess electricity produced by the wind or the sun so that it can be used at times of low production. Innovators are trying a number of different methods. Energy Dome’s is one of the most promising.
The company’s innovation can store energy for as long as 10 hours at a cost half that of lithium-ion batteries. “This duration is pivotal, as it makes it possible for renewables to replace fossil fuels and become up to 90% of Europe’s energy mix,” says Cavallini.
Energy Dome’s demo plant, the first of its kind, has been in operation for two years. A full-scale plant, with the potential of generating 200 MWh of electricity in one single discharge – equivalent to 2 439 Tesla Model 3 "Long Range" batteries – is under construction in the municipality of Ottana, Sardinia.
“Long-duration energy storage is the missing link in making the energy transition happen,” says Cavallini, “and we believe that with our technology we can lead this wave.”
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From negative to positive
During the day, the CO2 Battery uses excess energy from the local grid – normally supplied by solar power – to compress and liquify carbon dioxide, storing it in steel tanks. This exploits carbon dioxide’s ability to liquefy under high pressure at ambient temperature, unlike air. The compression also generates heat which is stored in special thermal energy storage units.
When electricity is needed, the process is reversed. The stored liquid carbon dioxide is heated through the storage units, turning it back into a gas. This gas then moves back to the dome. But before it gets there, it spins a turbine to produce electricity.
“The whole process is a closed loop, giving back to the grid 75% of the energy initially used during charging,” says Cavallini. “It can last 30 years without any kind of degradation, contrary to other electrochemical technologies that quickly degrade.”
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Supporting Europe’s green transition
To fight climate change, the European Union has an ambitious plan to transition to a carbon-neutral economy by 2050. To meet this goal, Europe will eventually have to shut down all its carbon-emitting coal and gas power stations. It will have to replace the lost generation capacity with emission-free sources, particularly renewable energies such as wind and solar.
Energy Dome’s storage solution is backed by the European Investment Bank and the Bill Gates-founded Breakthrough Energy Catalyst with combined funding of €60 million. Such solutions are critical for Europe’s climate goals.
Energy Dome
“This is an inspiring example of game-changing technology that we need more of in Europe and worldwide,“ says Alessandro Ronzoni, an investment officer of the EIB Cleantech Growth Capital Division at the European Investment Bank who worked on the deal. “This financing will help the construction of the site, deployment of the technology, and the mobilisation of private funds."
The future of long-duration storage
Energy Dome’s batteries are great for balancing the energy supply from renewable energy sources, and energy demand, as well as providing backup storage for several days to stabilize the grid during periods of poor weather that disrupt the generation of solar photovoltaic panels.
The affordability of carbon dioxide batteries is also what sets them apart. They’re made with eco-friendly materials and off-the-shelf components. This means they will have the potential to generate electricity for a lower price than lithium-ion batteries.
“Our plant in Sardinia is the first full-scale module of its kind and it's going to be a module that we are going to replicate all over the world,” says Cavallini. “Our domes can be operated in multiple sizes and configurations.”
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