New technologies for energy storage are being developed as the industry continues to mature. Energy Dome, an Italian energy storage technology company founded in 2019, recently announced it will use the proceeds from its $11 million Series A fundraising to complete construction of its “CO2 Battery” demonstration project in Sardinia, Italy, and to accelerate the growth of the company’s business. Energy Dome officials in a recent meeting with POWER at the Energy Storage Association’s conference in Phoenix, Arizona, provided insight into the company’s technology, which along with providing a new concept for energy storage could also advance efforts to capture and reuse carbon from the industrial and power generation sectors. The system also could support the growth of renewable energy through grid stability efforts.

Claudio Spadacini, founder and CEO of Energy Dome, told POWER, “Grid systems across the world need effective, low-cost storage to pair with renewable energy. We’re excited to be leveraging this investment and agreement to accelerate our deployment of this transformational technology.” Spadacini told POWER that the CO2 Battery has an optimal charge/discharge cycle of four to 24 hours, enabling daily and intra-day cycling. The battery can be charged during daylight hours, taking advantage of greater solar power generation, and then dispatched during “evening and next-morning peaks.” A key consideration, though, is that the storage can enable dispatch of solar and wind power generation 24 hours a day. Spadacini also said his company is committed to fighting climate change, noting Energy Dome’s goal is “new technology capable of drastically reducing greenhouse gas emissions into the atmosphere,” with a focus on supporting renewable energy and “decarbonizing the energy industry.”

Spadacini told POWER that Energy Dome’s system could achieve a levelized cost of storage (LCOS) of $50 to $60 per MWh in the next few years, less than half the current LCOS of systems using lithium-ion batteries, according to energy industry analysts. The company’s 2.5-MW/4-MWh demonstration plant is under construction in Sardinia, with testing and validation expected in the current quarter.

1. This rendering of an Energy Dome installation shows the company’s “dome,” an inflatable atmospheric gas holder filled with carbon dioxide in its gaseous form. Courtesy: Energy Dome

Spadacini, who prior to founding Energy Dome led Exergy S.p.A., a developer of geothermal, waste heat recovery, and concentrated solar power plants, said Energy Dome is advancing a more cost-effective form of energy storage by using CO2 in a closed-loop, thermodynamic process where it changes from gas, to liquid, and back to gas. The company’s “dome” is an inflatable atmospheric gas holder filled with CO2 in its gaseous form (Figure 1).

The company in its documentation for the system said that during the charging phase, “the system draws electrical power from the electric grid, which feeds a motor. The motor drives a compressor which draws CO2 from the dome and compresses it, generating heat which is stored in a thermal energy storage device. The CO2 is then liquefied under pressure and stored in liquid CO2 vessels, at ambient temperature, to complete the charging cycle.”

When discharging, “the cycle is reversed by evaporating the liquid CO2, recovering the heat from the thermal energy storage system, and expanding the hot CO2 into a turbine, which drives a generator. Electricity is returned to the grid and the CO2 re-inflates the dome without emissions to the atmosphere, ready for the next charging cycle. The system components are standardized and modular, allowing for up to 200 MWh in storage capacity, and targeting a wide range of customers including utilities, independent power producers, grid operators, industrial applications and remote mining operations.”

Spadacini and Gianpaolo Volpe Pasini, marketing manager at Energy Dome, said that the group uses CO2 because it can be converted into liquid under pressure at 30C, compared to minus 150C for air. Both said that makes Energy Dome’s system more cost-effective and brings a higher roundtrip efficiency of as much as 75% to 80%. They also said that unlike lithium-ion batteries, which can have significant performance degradation during their lifecycle, Energy Dome’s CO2 Battery will maintain its performance during its expected 25-year operational life.

“Consequently, the cost of storing energy will be about half of the cost of storing with similar-sized lithium-ion batteries,” said Spadacini, who told POWER his group has “calculated an LCOS already below $100/MWh with the first commercial plant we are going to build, which is 25 MW/200 MWh,” what he said is Energy Dome’s standard module. Spadacini said the company projects “that we can quickly reduce the cost of the technology… we are aiming to be far below $60/MWh in a few years, close to $50/MWh.”

Energy Dome’s system has been compared to other compressed air energy storage, or CAES, installations, including those of UK-based Highview Power. Javier Cavada, Highview’s then-CEO (Cavada is now president and CEO of Mitsubishi Power of Europe, the Middle East, and Africa), has discussed his company’s cryogenic energy storage technology with POWER, including a system at a 50-MW plant in the Atacama Desert in Chile. Highview has touted its cryogenic technology as a good fit for data centers, saying it can “store power from air for hours to even days.” Highview has said it wants to achieve an LCOS of $50/MWh by 2030.

Echogen, an Ohio-based energy company, also has said it could hit an LCOS of $50/MWh to $60/MWh from its supercritical CO2 -based power cycle technology. Echogen’s solution turns thermal energy into electricity, with sand as the storage medium. The Echogen process uses a CO2 heat pump cycle to convert electricity into thermal energy by heating a sand-based reservoir. The thermal energy is then converted back into electricity on demand. Echogen has received funding from the U.S. Department of Energy as part of the DAYS program, or “Duration Addition to electricitY Storage.”

Spadacini said Energy Dome’s system is designed to be modular and scalable, depending on a client’s needs. Pasini told POWER, “A 100-MWh system needs a few hundred MT [metric tons] industrial grade CO2 for a one-time charge. This is a relatively small amount, compared to the 2M [2 million] tons that a medium-sized, gas-fired power station emits into the atmosphere every year.”

Pasini said Energy Dome expects to have a steady supply of CO2. “Sourcing this CO2 will not be an issue as there is a choice of industrial gas providers willing and able to supply,” he said. “And, with carbon capture on the increase, if anything, folks may be happy that we take it off their hands.” He added, “We don’t anticipate having to do much re-filling. There might be marginal dissipation of CO2 during maintenance and a very occasional top-up might be required during the 25-year lifecycle of the plant.”

A2A, an Italian company active in the energy sector, has entered a memorandum of understanding with Energy Dome to deploy the company’s first commercial project, which Pasini said would be a 100-MWh system. A2A has said that system could support increased use of renewable energy and provide additional energy storage for the power grid. A2A participated in Energy Dome’s recent funding, through a partnership with the round’s lead investor, 360 Capital, a technology venture capital firm.

Darrell Proctor is a senior associate editor for POWER (@POWERmagazine).