Meet the CO2 battery cozying up with a wind energy giant

There’s a new CO2 battery in the energy game, and it just might be the assist turbines need to harness the full power of the wind. The technology uses carbon dioxide to store energy in the form of pressure and heat. It’s a relatively straightforward solution that gives the CO2 battery some more flexibility than more traditional alternatives, like lithium-ion batteries.

Lithium-ion batteries have become ubiquitous companions to solar panels. But the new CO2 battery could have an edge when it comes to storing energy from winds, which can be even more temperamental than the sun. Energy Dome, the company that developed the CO2 battery, announced a new partnership with global wind giant Ørsted last month.

The two companies plan to run a feasibility study on a 20MW storage facility that can dispatch energy for at least 10 hours at a time at “one or more” Ørsted sites in Europe. If all goes well, construction on the first storage facility using Energy Dome’s CO2 battery could begin in 2024.

It’s an early test of whether the CO2 batteries and wind turbines could become another iconic pair in renewable energy. Ørsted prides itself on having built more offshore wind farms across the world than any other company.

“We consider the CO2 Battery solution to be a really promising alternative for long-duration energy storage,” Kieran White, vice president Europe onshore at Ørsted, said in the press announcement.

The CO2 battery is made primarily with off-the-shelf industrial parts like compressors and turbines. And the way it works is relatively simple. CO2 is stored in a dome in gas form. When charging, the system pulls gas from that dome and compresses it down into a liquid. To discharge, the liquid is heated up to turn it back into a gas. As the CO2 expands from a liquid to a gas, it turns a turbine to generate electricity.

It’s actually a twist on what’s called compressed air energy storage, which encompasses a similar process that uses air instead of just CO2. Excess energy is used to compress the air, which is then stored underground, perhaps in a salt cavern or depleted natural gas reservoir. Energy Dome CEO and founder Claudio Spadacini, with experience as an engineer, says he got the idea for using CO2 instead of air because CO2 will liquify at ambient temperatures (at 31 degrees Celsius or 87.8 degrees Fahrenheit). “This makes it possible to store a huge amount of energy in a relatively small pressure vessel, which makes the technology very competitive in terms of cost,” Spadacini says.

It also frees up the technology from some of the geographic constraints with compressed air energy storage. So while you probably won’t be seeing little domes filled with CO2 paired with home solar panels anytime soon, CO2 batteries could pop up alongside larger solar and wind farms ushering in a cleaner future for the electricity grid.

Long-duration storage is the endgame for a grid that runs on renewable energy. Wind and solar power can be fickle, depending on the weather. Solar panels need to soak up energy on sunny days and turbines need to make the most of strong gales before they weaken. The problem is that there isn’t much storage on the grid yet, which can hold excess solar and wind energy and then dispatch it when the sun sets and winds die down.

The thing with wind is that it doesn’t ebb and flow quite as predictably as solar energy. The sun rises and sets each day, and lithium-ion batteries excel within this short time frame — quickly charging and discharging over several hours. A strong wind event, on the other hand, might last several hours or much longer than a day. And lithium-ion batteries become much less cost-competitive when it comes to storing and discharging energy for longer periods of time.

That’s where the CO2 battery could come in handy. Its sweet spot, when it comes to how long it can either store or dispatch power, is between four hours and a full day, says Spadacini. If it needs to, the CO2 battery can stretch that duration out to even a week or longer. That broad range means that the CO2 battery can go head-to-head against lithium-ion for solar energy storage — but it can potentially outcompete its rival for the longer-term needs of wind energy.

“Having storage that is able to cost effectively [charge up] over several days, and then discharge over several days — this is probably a better complement to wind than lithium-ion batteries,” says Eric Hittinger, an associate professor at the Rochester Institute of Technology who studies energy storage. That could become an important niche for an alternative energy storage company like Energy Dome, Hittinger points out, since lithium-ion batteries have already become so dominant in the solar industry.

Spadacini points to another edge he sees his startup having over lithium-ion batteries. It doesn’t need lithium or hard to come by minerals plagued by supply chain disruptions and allegations of labor and human rights abuses.

“The CO2 Battery is made only out of steel. We don’t use any kind of strange metal or rare metal,” Spadacini tells The Verge, which he says makes the CO2 battery cheaper and easier to produce in comparison to lithium-ion cells.

In that technological arms race, Energy Dome is going to need to milk every advantage it has. More than 40 startups in the growing long duration storage business raised over $1 billion of funding in total in 2021, according to BloombergNEF, which also named Energy Dome one of its BNEF Pioneers for “game-changing” innovation in 2022. Another startup developing iron-air batteries has also made waves for its potential to store and discharge renewable energy for days using simple materials. And older technologies like lithium-ion batteries and compressed air energy storage will continue to give startups like Energy Dome a run for their money.

In the end, there doesn’t need to be one winner — and that’s probably for the best so that our future energy system isn’t reliant on any one technology or set of materials. “Diversification in energy, in anything, is usually a good strategy,” Hittinger says. “The process of trying out a lot of alternatives is a healthy one.”