Highview prepares for the next step in liquid air technology development29 February 2016
An important milestone in the development of liquid air energy storage is expected to be reached this spring with entry into operation of Highview’s 5 MW pre-commercial demonstrator, which is being constructed alongside Viridor’s Pilsworth landfill gas generation plant in Greater Manchester, UK. In addition to providing energy storage, the plant will convert low-grade waste heat to power.
The project is planned to demonstrate the capabilities of LAES in providing a number of balancing services, including Short Term Operating Reserve (STOR) and so-called "Triad avoidance" (supporting the grid during the winter peaks).
The project has received £8 million in funding from the UK Department of Energy and Climate Change (DECC).
Highview's Liquid Air Energy Storage (LAES) system comprises of three primary processes: 1 - charging; 2 - energy storage; 3 - power recovery.
• Stage 1, charging. 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 Viridor demonstrator project, liquid air/nitrogen will be delivered to the plant rather than being liquefied on site.
• Stage 2, energy storage. The liquid air is stored in an insulated tank at low pressure, which functions as the energy store.
• Stage 3, power recovery. When power is required, liquid air is drawn from the tank(s). 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 then 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 (stage 1) and integrates this heat into the power recovery process (stage 3). For the Viridor demonstrator project, Highview will integrate waste heat from GE Jenbacher gas engines at the landfill site.
Althouth the Viridor plant will 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 Heat & Power biomass plant in Greater London. This plant successfully completed a full testing regime, including performance testing for the US PJM electricity market. In practical terms, says Highview, the plant amassed operating hours equivalent to more than three years of UK Short Term Operating Reserve service.
The plant has now been relocated to the University of Birmingham's new centre for cryogenic energy storage for recommissioning and further testing and research.
(Originally published in MPS February 2016)