Clean energy journalism for a cooler tomorrow

Energy Dome is on the brink of a long-duration storage breakthrough

This Italian startup is speeding to market, unlike many of its competitors in the long-duration energy storage sector.
By Julian Spector

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A large white industrial bubble next to a metal silo-type structure
(Energy Dome)

Startups making bold claims about their ability to change the world is nothing special. But it’s notable when a company chases its promises with concrete actions.

Italian startup Energy Dome accomplished that this week. The company vowed last year that it would successfully demonstrate its novel technique for storing vast amounts of clean electricity and use it to build a full-scale power plant. Earlier this month, it completed a 2.5-megawatt/4-megawatt-hour unit in Sardinia. Then on Tuesday, Energy Dome announced it raised $11 million in bridge funding to buy equipment for a 20-megawatt/200-megawatt-hour facility for major Italian utility A2A.

That project is in permitting now, and Energy Dome aims to complete it by late 2023 or early 2024, CEO Claudio Spadacini told Canary Media by email Monday.

Our intention is to proceed at high speed because climate change does not wait,” Spadacini noted. The market needs a solution for [long-duration energy storage] that is quickly available, efficient and reliable.”

These preliminary successes make Energy Dome a contender to watch in the emerging long-duration energy storage industry. This sector is dedicated to turning the ups and downs of wind and solar power into a reliable, round-the-clock electricity source. To do this, companies must store power for many hours up to many days at exponentially lower cost than today’s go-to grid storage technology, lithium-ion batteries.

Long-duration storage has recently attracted billions of dollars in investment, and the space now includes several publicly traded companies with collective market caps in the billions of dollars. But it’s hard to find any operational projects capable of discharging 20 megawatts of power for 10 hours straight, as Energy Dome says its next project will be able to do. Indeed, simply cracking into megawatt-scale territory with a commercial storage plant remains a rare feat for the long-duration field.

CDP Venture Capital Sgr, the venture arm of Italian sovereign wealth fund CDP Equity, led the convertible funding with Barclays Sustainable Impact Capital. Previous investor Novum Capital Partners also joined the investment.

That money is crucial because a newfangled technology is all but impossible to finance; Energy Dome needs to spend the money it raised to build initial projects and develop a track record of performance to support future financing.

Because our technology is now proven and the team has demonstrated our capabilities, we are willing to support the financing of our first commercial projects and back our customers with performance guarantees to reduce their risk premiums,” Spadacini said.

Energy Dome’s novel approach to long-duration energy storage dispenses with batteries altogether. Instead, the company erects enclosures that resemble tennis bubbles and fills them with carbon dioxide gas. Excess electricity can be used to pressurize the gas into liquid form, storing energy; turning the liquid back into a gas releases that energy, turning a turbine and regenerating electricity.

As detailed in Canary Media’s previous reporting, this approach has a few advantages relative to other long-duration storage attempts:

  • It uses off-the-shelf equipment from mature industrial supply chains. That means Energy Dome doesn’t need to build its own factory, a capital-intensive step that other long-duration startups needed to do. It also means Energy Dome doesn’t need to spend years on laboratory science — it just needs to prove that the equipment all works together the way it’s supposed to.
  • The dome is supposed to deliver round-trip efficiency of 75 percent, meaning 75 percent of the energy that goes into the process comes back out at the end. That’s less than typical battery efficiency but a lot better than many long-duration storage contenders.
  • Carbon dioxide is easier to compress and store at ambient temperature and atmospheric pressure compared to other gaseous storage vehicles, like hydrogen or air.

The commercial plant in Sardinia puts these theoretical advantages to the test. It’s been operating successfully in stand-alone testing mode so far, Spadacini said, but it’s connected to an industrial grid that in turn connects to the national high-voltage transmission network. Energy Dome plans to deliver energy and ancillary services to the national grid once testing is done.

Energy Dome chose 2.5 megawatts of power capacity because that was the smallest size it could build with the same kind of integrally geared compressors that a full-scale plant will use. The rest of the plant components are the same as those that will go into bigger plants; Energy Dome will multiply those components in parallel and in series to deliver much greater storage capacity.

The real-world testing has helped Energy Dome engineers shield the system’s performance quality from fluctuations in ambient temperature, as well as improve the construction design for the thermal energy storage components, Spadacini said.

Energy Dome previously raised an $11 million Series A late last year from Novum, Barclays and Third Derivative, a climatetech accelerator launched by think tank RMI and New Energy Nexus. (Canary Media is an independent affiliate of RMI.)

Julian Spector is a senior reporter at Canary Media. He reports on batteries, long-duration energy storage, low-carbon hydrogen and clean energy breakthroughs around the world.