As the use of renewable energy sources grows in the world, whose share exceeds for the first time coal, there is also a growing need to store this energy for times when the sun is not shining and the wind is not blowing.
While some are turning to high-capacity lithium battery systems, others reversible hydroelectric power plants, a small but growing industry believes there is an even better solution - air storage.
Near the village of Carrington in northwest England, the foundations are being laid for the world's largest commercial energy storage facility based on liquid air technology.
The stored energy can later be delivered to the electricity grid when demand exceeds supply.
If the project is successful, more such facilities will be built.
This technology is currently expensive.
But as the need for clean energy storage grows, the company Highview Power, which is developing liquid air technology, believes that the scales will tip in favor of this method.
Watch the video: Why we store liquid air
The transition to renewable energy sources is essential if the world is to reduce greenhouse gas emissions and avoid the worst consequences of climate change, but such a shift poses challenges for electricity grids.
Fossil fuel power plants, such as coal and gas, can be turned on and off as needed, and therefore provide a predictable supply of electricity that can be matched to demand.
Unlike fossil fuels, renewable energy sources are variable, as they depend on weather conditions.
This means that sometimes not enough electricity is produced, which poses a risk of power outages, and sometimes too much is produced, for example during very windy days, which can cause disruptions in the power grid.
A big step towards solving this problem is storing excess energy, which can be delivered to the grid when needed.
This can ensure a more reliable supply and reduce the risk of system disruptions.
For decades they have Reversible hydroelectric power plants are the main solution for energy storage.
When there is excess electricity, it is used to pump water into the upper reservoir (lake), and when electricity is needed, that water is released through turbines and produces electricity.
It's 2021 in the world. there were 160 gigawatts from reversible hydroelectric power plants.
More recently, as the demand for energy storage grows, large-capacity battery systems have been built to store energy.
Capacity of large battery systems connected to the electricity grid grew from 1 GW (gigawatt) in 2013 to more than 85 GW in 2023, and more than 40 GW was added in that year, according to the International Energy Agency.
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The solution is liquid air technology
Energy storage technology using liquid air is relatively new.
The basic idea exists since 1977, but it was not given much attention until this century.
The process takes place in three phases.
In the first, air from the environment is taken in and purified.
The air is then compressed multiple times until it reaches a very high pressure.
In the final stage, the air is cooled to a liquid state. using a heat exchanger system, devices that are used to transfer heat from one fluid (liquid or gas) to another.
"This process uses excess renewable energy from the grid," explains Shailene Setigen of the Massachusetts Institute of Technology (MIT), who studies energy storage systems.
When the network needs energy, the liquid air is pumped out of the tank, evaporated, and returned to a gaseous state.
During this process, it drives turbines that produce electricity, and the air is released back into the atmosphere.
The main challenge is to build enough of this kind of storage capacity to accelerate the green transition in a purposeful way.
Watch the video: Will the world embrace wind energy?
Solution for temporary power supply
The facility being built near the village of Carrington will be the largest commercial facility of its kind in the world.
It is being built by a company. Highview Power, which has been developing liquid air energy storage technology for 20 years.
The facility will be able to store 300 megawatt-hours of electricity, when needed to deliver 50 megawatts to the grid for six hours, which will "provide enough stored clean, renewable energy to (temporarily) meet the needs of 480.000 households," the company explains.
The plant's commissioning is planned in two phases, says Richard Butland, CEO.
The turbine is scheduled to start operating in August 2026.
In this phase, the plant will not produce electricity, but will only be used to stabilize the power grid.
Grid operators now periodically turn on gas-fired power plants to stabilize the system, says Butland.
"It's a huge cost to the system," he points out.
He adds that his company offers an alternative, and can "prevent them from doing it."
In the second phase, planned for 2027, the plant will store energy and deliver it to the grid.
The company Highview Power plans to generate revenue by selling electricity to the grid during periods of high demand.
See: Are solar farms the solution to climate change?
Conclusion
Although energy storage is a key technology, the question of cost-effectiveness arises, says Setigen.
For a study published in March, she and colleagues investigated the economic feasibility of using liquid air. for energy storage in 18 US states.
They compared eight different decarbonization scenarios with different levels of renewable energy deployment.
In all cases, they estimated how much the project could earn by buying and selling electricity over its 40-year lifespan.
Liquid air energy storage technology would be cost-effective in Florida and Texas, but not in any other state analyzed, and only in the most ambitious decarbonization scenario.
"For the other decarbonization scenarios, we did not see any system that would be economically viable," says Setigen.
While this could be superficially interpreted as a "negative finding," she emphasizes that it doesn't mean that storing energy using liquid air is a bad idea.
To begin with, it deliberately applied conservative methods, and the study showed that other energy storage methods, such as reversible hydroelectric power plants and batteries, are even less economically viable.
The biggest problem is that storage facilities would not be able to generate large profits in the first years of operation, because the American power grid does not yet have enough electricity from renewable sources, which drives large fluctuations in electricity prices.
"The system would not be used enough in the first years of operation," she says.
Owners of liquid air energy storage facilities could wait a few years until renewable energy drives greater fluctuations in electricity prices, but that would slow down the energy transition, Setigen says.
Instead, she believes that governments should support this technology.
Government subsidies for the initial costs of building the system "could be a viable approach to achieving economic viability in the short term," she says.
In addition, faster introduction of renewables into the grid would encourage greater fluctuations in electricity prices, making energy storage more economically viable.
Setigen presents the final argument in favor of storing energy using liquid air - it's cheap.
Energy storage technologies are often evaluated according to the "levelized cost of storage," which estimates how much each unit of stored energy costs over the life of the project.
For liquid air, that cost can be as little as $45 (around €38.8) per megawatt-hour, compared to $120 (€103.6) for reversible hydropower and $175 (€151,1) for lithium-ion batteries.
"While none of these storage methods are currently likely to be cost-effective without government support, liquid air energy storage stands out as a particularly attractive option for large-scale facilities," says Setigen.
Batland expects that power grids will rely on a combination of different energy storage technologies.
Reversible hydroelectric power plants are extremely efficient and last for decades, but they cannot be built everywhere because they require a water supply.
The batteries are very efficient and can be placed almost anywhere, but their lifespan is about 10 years.
The advantage of energy storage based on liquid air technology is that it can store energy for longer than batteries, with minimal losses.
Every country that begins a green transition must adapt its electricity system to incorporate renewable sources.
"We are rebuilding all the power grids around the world to connect new energy sources," says Butland.
And that could very likely mean building a lot of liquid air energy storage facilities.
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