Loads Of Renewable Energy Can Be Stored In The Air

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The idea of storing renewable energy in a tank of liquid air has been bubbling under the CleanTechnica radar ever since the UK firm Highview Power proposed building one such facility in Vermont back in 2019. That project never materialized, but the dream of air-sourced, long duration energy storage refuses to die. Highview is still in business and moving into greener pastures, and now the state-owned Chinese firm China Green Development Investment Group has leapfrogged into the action to the tune of 60 megawatts and 10 hours of storage.

Liquid Air Energy Storage In The Gobi Desert

As for why the liquid air energy storage dream refuses to die, that’s a good question, and 10 hours of storage is the answer. Lithium-ion batteries are already in widespread use for storing wind and solar energy, but they only last several hours at a time before running up against cost obtacles, which explains why they only account for a minuscule fraction of utility-scale energy storage. Here in the US, for example, pumped hydropower still dominates at around 95% of storage total capacity.

Compared to conventional batteries, liquid air and other alternative systems can offer more hours, economies of scale, longer lifespans, and a more onshore, less geopolitically fraught supply chain.

Since everyone is talking about the CGDG liquid air project, let’s get to that first. Described as a demonstration, the new facility is almost — though not quite — fully commissioned. CGDG decided to jump the gun with a public announcement earlier this week, aiming to set the stage for a breakthrough in economical, long duration energy storage systems.

“Liquid air has a density about 750 times that of ambient air and can be stored safely at atmospheric pressure. The equipment has a long service life and no geographical constraints, enabling stable operation even in extreme environments such as the Gobi Desert and high plateaus,” explains China’s state-owned news organization China Global Television Network.

Though the devil is in the details, the basic operation is straightforward. Located in the northwestern part of Qinghai Province, in the Gobi Desert city of Golmud, the CGDG project weighs in at 60 megawatts/600,000-kilowatt-hours. A nearby solar power plant of 25o megawatts provides surplus, zero emission electricity to run the facility’s compressor system during periods of low demand.

“Purified air is compressed into a high-pressure, high-temperature gas, cooled, and sent to a cold box for liquefaction, then stored in atmospheric-pressure cryogenic tanks,” CGDG explains. That sounds like a lot of energy-sucking is going on, and it is. The target temperature is -194 degrees Celsius (about -317 °F). The key, though, is the availability of excess solar power.

When electricity demand peaks, the system is called into action. The air is exposed to heat recovered from the compression process, transforming a liquid into a high pressure gas that is powerful enough to generate electricity in a turbine.

Here Comes The Liquid Air Energy Storage Revolution

A 60-megawatt facility is rather ambitiously scaled for a demonstration project, but the developer is confident that the new battery — billed as the largest project of its kind in the world — will deliver 10 hours of electricity as planned.

That remains to be seen. Though the basic technology dates back to the 1970s, the 21st-century task of scaling up to generate electricity at the 60-megawatt level presents a raft of engineering obstacles.

As described by CGTN, the developer collaborated with the Technical Institute of Physics and Chemistry branch of the Chinese Academy of Sciences to modulate the release of the air, among other challenges. “After countless tests, the team overcame a bottleneck in ultra-low-temperature cascade technology for cold storage, developed an atmospheric-pressure low-temperature storage system, and solved the core challenges of air storage and constant-pressure release,” CGTN recounted.

Don’t just take their word for it. In April, MIT News recapped the economic case for liquid air energy storage, as modeled by a new system developed under the Future Energy Systems Center at MIT. The big question is whether or not the technology can spark investor interest, and the research team has an answer.

The team assessed 18 locations in the US, cross-referenced with eight future decarbonization scenarios, based on a $60/MWh levelized cost of storage for a 100-megawatt system.

“Sensitivity analyses showed that policies providing a subsidy on capital expenses could make LAES systems economically viable in many locations,” MIT News summarized. “Further calculations showed that the cost of storing a given amount of electricity with LAES would be lower than with more familiar systems such as pumped hydro and lithium-ion batteries.”

MIT News is also among those pointing out that liquid air storage systems can be assembled from off-the-shelf components, commercially available in the US. “And the system can be sited almost anywhere, including near other industrial processes that produce waste heat or cold that can be used by the LAES system to increase its energy efficiency,” they emphasize.

In a particularly interesting finding, the model indicates that further improvements in energy efficiency will not significantly alter the economic case for liquid air energy storage. Instead, subsidies for capital expenditures will tip the balance.

Questions? Complete details are available in the journal Energy under the the title, “Evaluating economic feasibility of liquid air energy storage systems in future US electricity markets.”

Meanwhile, Over In The UK

Highview Power is not waiting around for subsidies to materialize in the US. The firm first introduced its technology in the UK back in 2011 before testing the waters in Vermont eight years later, in 2019. Highview sidelined the Vermont project in 2022 after the UK government came through with £10 million for the construction of a full scale plant at home, as a complement to the UK offshore wind industry.

If all goes according to plan, Highview will introduce two 3.2 gigawatt-hour facilities in the UK by 2030, one in Hunterston, Scotland, and one in Killingholme, Lincolnshire. In September, the company announced that Ofgem, the UK Office of Gas and Electricity Markets, has tapped both projects as “eligible” for support through the UK’s energy storage cap-and-floor platform, which provides investors with the security of a minimum revenue stream. The company is also constructing a 300 megawatt‑hour, six-hour duration facility in Carrington Manchester, which is expected to come online later this year.

“This is a significant step forward for Highview Power’s multi-billion pound LDES programme, indicating that the two projects meet the minimum criteria for deliverability by 2030, as part of the cap and floor scheme,” Highview explained. “It also marks the beginning of the next project assessment stage.” As eligible projects, the two facilities will undergo a customer benefit analysis conducted by Ofgem in collaboration with the National Energy System Operator.

Highview expects a final decision by midyear 2026, so stay tuned for more on that.

Image (cropped): The UK firm Highview Power is moving forward with plans to bring a total of 7 gigawatt-hours of renewable energy storage to the UK, deploying liquid air technology (courtesy of Highview Power via CleanTechnica archive).