NB: In our intelligence brief, we incorrectly stated that L’Azienda Elettrica Ticinese had pulled its investment out of ALACAES and that Airlight Energy had run into technical problems. This version corrects both statements.

By Jason Deign

ALACAES, of Lugano, Switzerland, is seeking institutional partners and investors to create the world’s first high-pressure advanced adiabatic compressed air energy storage (CAES) plant.

The company is looking for between USD$4m and $6m in funding to build a demonstration plant operating at 90 to 100 bar after proving its technology with a 7-bar pilot last year.

The 2016 pilot, with a capacity of 1MWh and a power rating of 600kW, was the first adiabatic CAES plant in the world, according to ALACAES.

On its website, the US Energy Storage Association (ESA) notes: “Advanced-adiabatic compressed air energy storage (AA-CAES) is an evolution of traditional CAES, designed to deliver higher efficiencies.

“Operation is similar to traditional CAES in that energy is stored by compressing air with turbomachinery and storing in an underground cavern. The difference lies in the treatment of the heat of compression.”



Traditional CAES technologies

While traditional CAES technologies extract and dispense with heat from the air before compression, and need more heat for expansion, “AA-CAES instead aims to remove the heat and store it separately,” says the ESA.

“This has potential to substantially increase the round-trip efficiency of the process.”

ALACAES’s technology uses mountain rock caverns as a pressure reservoir. The design includes a proprietary thermal energy storage (TES) system in the pressure zone.

This “drastically” reduces the cost and complexity of the TES system, said ALACAES’s managing director, Giw Zanganeh.

“For the pilot plant, we used a 120m section of a 5m-diameter tunnel, sealed on the two sides by two 5m-thick concrete plugs,” he explained.

Various academic institutions

In tests carried out alongside “various academic institutions” with air at 7 bar and 550°C, the system achieved mechanical-to-mechanical round-trip efficiencies of 70% to 80%, he said.

“We showed that the TES effectively cools down the incoming air and heats it up again for the discharging, and that no air leakage occurs from the mountain.”

The pilot, in a tunnel north of Biasca in Switzerland, cost $4m, 40% of which came from the Swiss Federal Office of Energy.

“We are now trying to establish partnerships with main stakeholders of the technology to build a scale-up demonstration plant with a pressure of 90 to 100 bar,” Zanganeh said.

These partners could include construction companies, turbomachinery suppliers and utilities, he said. ALACAES is understood to be interested in potential allies in Switzerland and Germany, but also as far afield as the US and India.

One un-named partner on board

The company already has one, un-named partner on board, which Zanganeh said was a world leader in underground gas storage construction “interested in the technology and ready to collaborate for the next phase.”

ALACAES also expects to be able to gain further government funding, he said.

If the company is successful in taking its technology to commercialisation, it could help launch a category of large-scale storage that has so far remained elusive.

Currently there are just two existing large-scale plants in operation. Both rely on diabatic CAES, where the heat of compression is lost to the atmosphere.

One, in Huntorf, Germany, has been in operation since 1978, with a round-trip efficiency of 29%. The second, in McIntosh, Alabama, USA, has an efficiency of 54%.

Several other projects in the works

Several other CAES projects are said to be in the works, including a €90m, 330MW plant being developed by Dresser-Rand and Gaelectric in Larne, Northern Ireland, and a UK AA-CAES development by Storelectric.

The German utility RWE is also known to be pursuing an AA-CAES project called ADELE (for ‘Adiabater Druckluftspeicher für die Elektrizitätsversorgung’, or adiabatic compressed air storage systems for electricity supply).

The project, supported by General Electric, Züblin and the German Aerospace Center, DLR, was due to go live last year but RWE has been silent on progress since announcing the venture in 2010.

Perhaps the most newsworthy CAES initiative to date, however, is from US developer LightSail Energy, co-founded by former child prodigy Danielle Fong.

LightSail attracted investors including Bill Gates, Peter Thiel, Khosla Ventures and Total Energy Ventures with the promise of a novel AA-CAES technology using water to capture the heat of compression.

Keeping a low profile

But the company laid off a third of its workforce last April and has since kept a low profile.

ALACAES itself hasn’t been immune to challenges, but it has fared better than its former sister company, Airlight Energy, which focused on the solar thermal industry.

One of Airlight’s investors, Swiss electricity wholesaler L’Azienda Elettrica Ticinese, transferred its backing on ALACAES in 2012.

And Airlight’s commercially available thermal storage technology was incorporated into the ALACAES portfolio after Airlight ran into financial problems and had to close in 2016.

Today, ALACAES’s hopes for CAES remain alive and well. And as other developers struggle to get to market, success in this field is no longer just important for ALACAES, but also for the credibility of AA-CAES in general.