Liquid-air start-up: a milestone for long-duration storage

19 July 2018

The world’s first grid-scale liquid-air energy storage (LAES) plant, Highview Power’s 5MW/15MWh Pilsworth facility, is finally in operation, with a switch-on ceremony held on 5 June (about three years later than originally planned).

The plant, a pre-commercial demonstrator, has been constructed alongside Viridor’s Pilsworth landfill gas generation plant at Bury in Greater Manchester, UK, and has been developed in partnership with Viridor, with financial support from the UK government.

Gareth Brett, CEO of Highview Power, described it as “the only large scale, true long-duration, locatable energy storage technology available today, at acceptable cost.”

“The adoption of LAES technology is now underway”, he noted, and Highview is already “in detailed negotiations to build plants ten times the size of this one for utility customers of several nationalities and for various different applications.”

The company estimates that 60% of the global energy storage market comprises long-duration, grid connected storage and thinks that its LAES technology is ready to meet almost half of this (45%).

Highview says LAES technology “can scale to hundreds of megawatts”, which “means that LAES plants could easily store enough clean electricity generated by a local windfarm to power a town like Bury (around 100 000 homes) for many days, not just a few hours.”

Highview believes that “true long-duration energy storage is critical to: enable the broader deployment of renewable energy; overcome the intermittency of solar and wind energy; help smooth peaks and troughs in demand; and provide...a stable and secure source of homegrown energy.”

Demand response aggregator KiWi Power has the role of providing the commercial interface for the Pilsworth demo facility’s grid service offerings, which include reserve, grid balancing and regulation services. Yoav Zingher, KiWi Power CEO, said “Given the high uptake of renewable energy in the UK this is the technology that will allow the future grid to maintain system inertia and ensure the lights stay on. By investing in LAES technology companies will also be able to earn a predictable, annual, recurring revenue through the ancillary services...”

For the Pilsworth demonstrator, turbine and generator were supplied by GE, heat exchangers by Heatric, thermal storage tanks by Metalcraft and cryogenic storage tanks by BOC.

Highview’s LAES system consists essentially of three basic processes: 1 - charging; 2 - energy storage; 3 - power recovery.

The charging system comprises an electrically driven air liquefier. The air is cleaned and cooled to subzero temperatures. 700 l of ambient air become 1 l of liquid air. In the case of the Pilsworth demonstrator, liquid air/nitrogen is being delivered to the plant rather than being liquefied on site.

The liquid air is stored in an insulated tank at low pressure, which functions as the energy store.

When power is required, liquid air is drawn from the tank. Stored heat from the air liquefier is applied to the liquid air via heat exchangers and an intermediate heat transfer fluid. This produces a high-pressure gas, which is used to drive a turbine.

The low boiling point of liquefied air means the round trip efficiency of the system can be improved with the introduction of any low grade waste heat that is available. Highview’s standard LAES system captures and stores heat produced during the liquefaction process and integrates this heat into the power recovery process. For the Pilsworth demonstrator, Highview is employing waste heat from GE Jenbacher gas engines at the Viridor landfill power generation facility.

Although the Pilsworth demonstrator does not have the liquefaction stage, the full process was tested in a 350 kW/2.5 MWh pilot plant from June 2011 to the end of 2014 at SSE’s Slough CHP facility. 

LAES, the basic concept
Storage capacity comparison

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