New long duration, large scale compressed air energy storage system leverages simple water pressure to cut costs.

Long Duration Energy Storage From Thin Air: Just Add Water

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The carbon neutral goal is an elusive one, but progress has been reported in some unexpected spots. One of those is the European nation of Cyprus, which was hovering around rock bottom for renewable energy just a few years ago. Now the country has been picking up steam. In the latest development, Cyprus is trialing a new large scale, long duration compressed air energy storage system that leverages the water pressure of the ocean for maximum effectiveness.

Long Duration Energy Storage For More Renewable Energy

Among European nations, Iceland hit the 100% renewable energy target all the way back in 2015. However, since Iceland is not a member of the European Union, the race to be the first EU nation to ditch fossil fuels from the power generation landscape is still wide open.

For a while there it looked like Cyprus was almost ready to give up the ghost. Nevertheless, on February 24 the Guardian took note of renewable energy progress in the EU, listing Cyprus among the nations reporting big gains.

There is still a long way to go, as the Guardian puts it. A rundown of the data from 2022 shows EU electricity consumption averaging about 41% from renewable resources, with Sweden and Denmark leading the pack at 83.3% and 77.2% respectively. Down at the bottom were Malta (10.1%), Hungary (15.3%), the Czech Republic (15.5%), and Luxembourg (15.9%), with Cyprus easing ahead of the bottom-dwellers at 18%.

A healthy dose of long duration energy storage would help nations like Cyprus climb the renewable energy ladder more quickly. Unlike lithium-ion battery systems that typically last about 4-6 hours, a long duration energy storage system can produce clean kilowatts for longer periods, lasting up to full days, weeks, or even seasons. At that level, intermittent sources — namely, wind and solar energy — could provide for nuclear-style stability, continuity, and reliability at a fraction of the cost of a new nuclear power plant.

A Different Kind Of Compressed Air Energy Storage System

The long duration energy storage field has been attracting furious activity on the part of investors and innovators, with some of the latest activity focusing on new long duration technologies that deploy the physics of heat transfer.

The natural systems of the Earth are also rich territory for long duration innovators. Pumped hydropower, for example, has been getting a second look in recent years. This decades-old, mature technology is a perfect fit for wind and solar power. It relies on the force of gravity to shunt water from an upper reservoir to a lower generating station. Ideally, the upper reservoir is refilled only when excess renewable energy is available to run the pumps (see our long duration archive here).

Compressed air is another long duration technology that has been getting a workout in the 2000s. Some of the earlier compressed air attempts have fallen by the wayside, but new iterations keep popping up.

Compressed air systems can leverage underground rock formations or human-made structures as storage platforms, though each has drawbacks. In underground storage the containerization is durable and readymade, and there is less potential conflict with land use on the surface. However, rock formations are geo-specific. Human-made platforms can potentially cover a much wider range of site options, but they are expensive and can run into roadblocks from competing land uses.

Compressed Air Energy Storage: Just Add Water

One solution that has crossed the CleanTechnica radar is underwater storage. Back in 2022 we took note of a bladder-based energy storage system that is sort of an underwater version of pumped hydro, leveraging water pressure instead of gravity.

Another take on deploying water pressure for energy storage comes from the Israeli startup BaroMar, which has come up with a simple sounding tank-based compressed air system. The system is designed for use at coastal areas and islands adjacent to deep water. The plan is to locate the tanks in depths of around 500 feet, where the water pressure is sufficient and conflicts with marine life are less in evidence.

“The hydrostatic pressure of the surrounding water enables construction of long-lasting large tanks at very low cost,” BaroMar explains. Also assisting on the cost-cutting end of things is a design strategy focusing on eliminating underwater moving parts and subsystems. The tanks are constructed on shore, using marine-proven concrete and steel, then towed into place.

That sounds simple enough, though the devil is in the details. Earlier this week, the engineering firm Jacobs let word slip that it BaroMar selected it to produce the preliminary design for the Cyprus project, billed as a “first-of-its-kind underwater large-scale, long-duration energy storage pilot project.”

Jacobs observes that BaroMar’s energy storage solution deploys mature technologies in the fields of power, energy, and marine engineering. However, combining them with the hydrostatic pressure of seawater is a delicate act.

“This project requires extensive geophysical, geotechnical and bathymetric surveying, investigation, feasibility studying and permitting for tank installation at deep depths for onshore mechanical and electrical equipment needs,” explained Jacobs Vice President Fiachra Ó Cléirigh.

How Does It Work?

As described by Jacobs, the Cyprus project will consist of large, rigid tanks ballasted on the seabed with a combined capacity of 4 megawatt-hours.

“The tanks are designed to resist loads imposed by the marine environment as well as the compressed air and hydrostatic water pressure, during both installation and operational conditions,” Jacobs adds.

Excess electricity from wind and solar resources will be shunted by subsea cable to the tanks, where it feeds compressors. When more electricity is needed, the compressed air is fed back to land where it is expanded and fed into a generator.

Last September the nonprofit organization ISRAEL21c interviewed BaroMar founder Yonadav Buber, who explained that undersea tanks are less expensive to construct because the pressure of seawater acts as a stabilizer. Though site selection is limited to coasts and islands, these same locations are notoriously crowded. Opportunities for large scale, land-based energy storage are difficult to find.

“This is a really genius solution, because it circumvents the problem in a very elegant way. It also creates the possibility of more or less endless energy storage, because we’re talking about the seabed, which is not exactly hot real estate,” Buber told ISRAEL21c writer Naama Barak.

Buber emphasized that the technology components are mature and are not in need of extensive development, unlike some of the other new long duration energy storage technologies emerging today. He noted that marine-related regulatory and engineering requirements are the main challenges that lie between the pilot project and commercial deployment.

100% Renewable Energy For Cyprus By 2030, With An Energy Storage Assist

When Buber spoke to ISRAEL21c last fall, he indicated that Cyprus meets the three main client categories targeted by BaroMar. One consists of renewable energy producers with surpluses on hand, and the second consists of large scale energy consumers including port facilities and other large industrial complexes.

“And our third type of customer is governments,” Buber added. “We’re in discussions, for example, with the government of Cyprus, to make them the first member state of the European Union to run on 100 percent renewable energy by 2030.”

Whether or not that ambitious goal is possible remains to be seen. However, in February our friends over at PV Magazine reported that Cyprus already expects to curtail a good 28% of its renewable energy production in 2024, so it clearly has a hefty surplus on hand.

PV Magazine cited a lack of energy storage facilities and the absence of sufficient interconnections with other countries as the main drivers of renewable energy overproduction in Cyprus.

If you’re thinking green hydrogen could help soak up some of those excess clean kilowatts, Cyprus is one step ahead of you. In 2022 Cyprus earned the title of “laggard” in a rundown of EU national hydrogen strategies, but the very next year a consortium of 27 nations organized to tap Cyprus to host the EU’s first “Hydrogen Valley” in Cyprus. We’ll be keeping an eye out for next steps but so far the focus is on green hydrogen sourced from water, leveraging power from renewable resources.

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Image (screenshot, via YouTube): New long duration, compressed air energy storage system deploys water pressure to cut costs (courtesy of BaroMar).


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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

Tina Casey has 3326 posts and counting. See all posts by Tina Casey