Another Headache For Fossil Fuels: Liquid Air Energy Storage
Whatever happened to liquid air energy storage? The UK startup Highview Power was going to bring its new liquid air system to the US back in 2019, providing the kind of scaled-up and long duration energy storage needed to support more wind and solar power on the grid. Highview switched gears and headed back home where the grass is greener. Our loss is the UK’s gain…
Long Duration Energy Storage From Thin (But Liquid) Air
Highview first surfaced on the CleanTechnica radar all the way back in 2011, when the company let word slip that it was developing a new “liquid air” battery capable of storing electricity in bulk, and discharging it over a longer period of time compared to conventional lithium-ion battery arrays.
The long duration angle is a critical piece of the renewable energy transition puzzle. Today’s Li-ion batteries last around four hours, enough to fulfill daily grid balancing tasks. For a future grid saturated with wind and solar power, though, the US Department of Energy is seeking diurnal (all-day) systems of at least 10 hours, towards the ultimate goal of storing renewable energy for days, weeks, or entire seasons.
Liquid air energy storage fits the long duration bill, but it is actually not a new concept. The foundational technology is attributed to a UK engineering team spearheaded by University of Newcastle upon Tyne researcher E.M. Smith, who was pursuing the idea of a compressed air storage system capable of filling in for power plants during periods of peak electricity demand. Patented in 1977, Smith’s system is adiabatic, meaning that no heat is added or subtracted from the air as it is compressed and released.
By 2019, Highview was readying itself to test its long duration system in the US state of Vermont. However, in 2022 the firm decided to shelve the Vermont storage project and concentrate on developing its technology for use in the UK.
The Wind Energy Connection
One factor that may have figured into Highview’s decision is the potential for co-locating its storage system with offshore wind farms. Vermont has no coast, though it does sit near the wind-rich Atlantic seabed.
Perhaps it’s just as well that Highview dropped its US plans when it did. Offshore wind stakeholders in the US were just beginning to find their footing along the Atlantic coast when President Trump took office on January 20 and promptly sent the offshore industry into a death spiral.
Having left Vermont behind, in 2023 Highview joined with the leading offshore wind firm Ørsted to build the case for investing in the UK’s offshore wind industry. With liquid air technology, offshore wind farms could shunt excess capacity to a storage facility on shore, making use of their turbines instead of having to curtail operations during periods of low demand.
“Highview’s liquid air battery literally uses liquid air as a storage medium,” CleanTechnica observed in 2023. “The system deploys electricity to supercool ambient air down to -196 C, at which point it becomes compressed as a liquid. There it stays in a cryogenic state until electricity is needed, when heat is applied to restore the liquid to a gas, which goes through a turbine to generate clean kilowatts.”
Highview and Ørsted took their case to Parliament, where they apparently received a favorable reception. Last fall Highview announced that it will construct suite of four liquid air storage facilities in the UK by 2030, weighing in at 2.5 gigawatt-hours each.
Hunterston, Scotland, will host the first facility to be constructed, with a second to follow. The other two will be located in England.
“Two of the 2.5GWh plants will deliver more storage than all of the UK’s existing battery storage, using 100% sustainable technology, with a 40-year lifespan,” Highview noted. “The addition of these four plants by 2030 means the government’s target to achieve a net zero grid by 2030 is achievable.”
“Each 2.5GWh liquid air energy storage (LAES) plant will have the ability to power 650,000 homes for over 12.5 hours,” the firm elaborated. “The plants are strategically placed to ensure the balance of supply and demand and reduce energy curtailment.”
More Liquid Air Energy Storage For The USA
Presidents come and go, but the renewable energy transition is here to stay. With that in mind, let’s take a look at the investor case for backing liquid air energy storage here in the US, if not at the present time then perhaps 3.75 years from now, when the current occupant of the White House leaves office peacefully, as required by the US Constitution.
Among those making the case for liquid air energy storage in the US is a research team at MIT. They have just published a study in the journal Energy examining the economic feasibility of liquid air storage in 18 regions of the US, and they concluded with a thumbs-up.
The researchers draw comparisons between liquid air and two other mature forms of long duration energy storage, compressed air and pumped hydropower. Both of these have limited application because they depend on the availability of underground caverns or elevation differentials. In contrast, liquid air storage facilities consist mainly of above-ground tanks, which can be located practically anywhere.
Among other advantages of liquid air, the researchers cite the ability to generate electrical, mechanical, and thermal energy, as well as opportunities to integrate with other sources of heat or cold to improve efficiency.
“Liquid air energy storage is a clean, long-duration grid-scale energy storage technology, capable of providing multiple gigawatt-hours of storage capacity. Its inherent locatability unlocks nearly universal siting opportunities, making it suitable for diverse geographical contexts,” the research team summarizes.
More Green Energy For Deep Red States
The MIT team employed a mixed-integer linear programming model to arrive at a conservative estimate of economic viability, taking into consideration the future state of electricity markets.
“The results identify Texas and Florida as the most promising markets for deployment and suggest that a levelized cost of storage of approximately $60/MWh is achievable across all decarbonization scenarios, which is significantly lower than literature-reported values for alternative technologies, such as pumped hydro energy storage and lithium-ion battery energy storage,” they concluded.
Despite its red state politics, Texas has had a grip on the #1 slot for installed wind capacity among all 50 US states, and it is closing in on California for installed solar capacity as well. Wind resources in Florida are less than optimal, which is a feature of the southeast region. However, the state is taking full advantage of its solar resources.
For next steps, the MIT team will apply its methodology to assess the long term economic potential of pumped hydropower and Li-ion under the same decarbonization scenarios, aiming to achieve a more direct comparison with liquid air systems.
Image (cropped): The UK firm Highview Power is bringing its liquid air energy storage system to four locations in Scotland and England, providing long duration storage for wind and solar energy (courtesy of Highview Power).
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