A giant dome filled with 1000 tonnes of carbon dioxide could be the answer to a growing headache for the electricity sector.
Huge growth in wind and solar energy has provided a source of plentiful green power, but during sunny, windy days across Europe, there is often more electricity than the grid needs.
Grid operators and renewable plant owners are racing to find a cheap way to store this excess power so it can be used when energy demand peaks in the evening, or when the wind drops and the sun doesn鈥檛 shine.
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An Italian company called Energy Dome says it has the answer: a giant gasholder filled with CO2. When green power is plentiful, the CO2 is pumped into a compressor, where the gas is heated and compressed into a liquid, then kept in carbon-steel tanks. Heat from the process is stored in the plant for later reuse. The company refused to provide details of how it does this.
When power is required, the liquid CO2 is run through an evaporator to turn it back into a pressurised gas, which is reheated and used to drive a turbine, generating electricity. The CO2 gas is returned to the dome.
The plant can store power for 8 to 24 hours at a time, says Energy Dome鈥檚 , making it perfect for medium-term energy storage.
鈥淲hat we provide is a technology which is intended to be in the daily storage market. It means to switch energy from day to night, from today to tomorrow,鈥� he says. 鈥淭hat is the main need you have with a wind and solar-dominated grid.鈥�
Backed by funding from Breakthrough Energy Catalyst, Bill Gates鈥檚 climate-focused investment vehicle, and the European Investment Bank, Energy Dome will open its first commercial plant in Sardinia later this year. The company didn鈥檛 disclose how big the plant would be, but Spadacini says it takes up about the same amount of land as a 3 to 4-megawatt solar farm, which would typically be between 5 and 10 hectares (12 to 25 acres).
The site will provide 20 megawatts of storage capacity at a build cost comparable to lithium-ion batteries with equivalent capacity, says Spadacini. A 鈥渧ery large, well-known global utility鈥� has signed a deal to operate the storage capacity for the next 10 years, he says.
Energy Dome says it has 鈥渞eceived a lot of requests鈥� from other utilities and wind and solar plant developers that are interested in building a dome on their sites to avoid the penalties of ultra-low, or even negative, power prices.
However, at University College London says the CO2 dome will struggle to compete against traditional batteries for storage, partly because batteries are already being manufactured at scale and costs are still falling. 鈥淲ith batteries, you can build great big factories that churn them out, and they are modular and easy to install and so on. With a CO2 dome, it鈥檚 a big electrical chemical plant, basically, that you can鈥檛 wheel out of a factory,鈥� he says. 鈥淚f I was betting, I wouldn鈥檛 put my money on the CO2 dome.鈥�
