A UK consortium has developed the Prisma system, which stores thermal energy in liquid air form to provide onsite compressed air, via a latent energy cold storage tank filled with a phase-change material. It is expected to have a levelized cost of storage of GBP 114 ($143.10)/MWh.

The UK Department for Business, Energy and Industrial Strategy (BEIS) recently granted GBP 350,000 to a consortium featuring the Birmingham Centre for Energy Storage (BCES), Aggregate Industries, and Innovatium, a developer of liquid air energy storage (LAES) systems.

“The funding will be used to take the innovative Peak Reduction by Integrated Storage and Management of Air (Prisma) system from laboratory scale testing to demonstration level at Aggregate Industries’ Cauldon Cement Works in Staffordshire,” the BCES said in a statement. “This will be a key step in the Prisma system’s journey to full commercialization.”

The Prisma systems will be manufactured in northeastern England, with the aim of installing the first industrial-scale, behind-the- meter system in early 2023. “On the back of the demonstration at Aggregate Industries, Innovatium have currently closed an investment round of GBP 900,000 for product development of Prisma,” the director of the BCES, Yulong Ding, told pv magazine.

The LAES system stores thermal energy in liquid air form to provide onsite compressed air and works through a latent energy cold storage tank filled with a phase-change material (PCM) designed and tested by Innovatium, in partnership with the University of Birmingham. It is applied in an existing compressed air network operated by Aggregate Industries. PCMs can absorb, store and release large amounts of latent heat over a defined temperature range and have often been used, at the research level, for PV module cooling.

The PCM materials used for liquid air energy storage operate at cryogenic temperatures below -150 C. They store and discharge huge amounts of thermal energy between the freezing and melting cycle.

“Innovatium’s is currently working with researchers at Birmingham and Strathclyde University to develop a special formulation that does not degrade over time and is safer and environmentally friendlier than conventional batteries,” Ding said.

Two PCMs were developed with phase-change temperatures of around -100 C and -160 C. The PCMs are composite materials, typically made of a PCM, a structural stabilization material and a heat transfer enhancement material.

During the charging phase, which takes place in off-peak hours, the system utilizes excess electricity from renewable energy sources and stores it in the form of liquid air through an air liquefaction process. During this process, liquid air is compressed, cooled down by a packed bed cold store, liquified by the stored cold in the PCM store and, eventually, during discharge it is expanded to produce compressed air for the client’s factory.

The cold energy of liquid air is also stored during discharge for re-use in the liquefaction process to reduce power consumption. This technology can be applied to generate electricity in an air expansion turbine when combined with a heat store or heat source.

The Prisma system uses liquid air as its energy storage medium that is 700 times as dense as ambient air.

“This system can provide hours of backup compressed air to industrial consumers and act as a large buffer store that allows air compressors to run more efficiently by reducing the part-load inefficiencies that are common to all compressed air systems,” Ding emphasized.

The consortium said the system design and the integration of the equipment and components has never been attempted for the provision of compressed air in an industrial setting. The fully developed system has a targeted installed cost of GBP 400/kWh.

“Innovatium do point out however that there is no degradation or limit to cycling that gives an expected levelized cost of storage of GBP 114/MWh. Their feedback from the market suggests that the commercial offering would suit a PPA especially when coupled with a solar PPA,” Ding concluded. “Our estimated LCOE is $0.15/kWh to $0.30/kWh.”