Liquid Air Energy Storage – Using liquefied air to create a potent energy reserve.

Liquid Air Energy Storage (LAES) uses electricity to cool air until it liquefies, stores the liquid air in a tank, brings the liquid air back to a gaseous state (by exposure to ambient air or with waste heat from an industrial process) and uses that gas to turn a turbine and generate electricity.   LAES systems use off the shelf components with long lifetimes (30 years +), resulting in low technology risk. Liquid Air Energy Storage (LAES) is sometimes referred to as Cryogenic Energy Storage (CES). The word “cryogenic” refers to the production of very low temperatures.

Executive Summary

Liquid Air Energy Storage (LAES), also referred to as Cryogenic Energy Storage (CES), is a long duration, large scale energy storage technology that can be located at the point of demand. The working fluid is liquefied air or liquid nitrogen (~78% of air). LAES systems share performance characteristics with pumped hydro and can harness industrial low-grade waste heat/waste cold from co-located processes. Size extends from around 5MW to 100s+MWs and, with capacity and energy being de-coupled, the systems are very well suited to long duration applications. 

Discussion

Although novel at a system level, the LAES process uses components and sub-systems that are mature technologies available from major OEMs. The technology draws heavily on established processes from the power generation and industrial gas sectors, with known costs, performance and life cycles all ensuring a low technology risk.

LAES involves three core processes:

  • Stage 1. Charging the system
    The charging system is an air liquefier, which uses electrical energy to draw air from the surrounding environment, clean it and then cool the air to subzero temperatures until the air liquefies. 700 litres of ambient air become 1 litre of liquid air.
  • Stage 2. Energy Store
    The liquid air is stored in an insulated tank at low pressure, which functions as the energy store. This equipment is already globally deployed for bulk storage of liquid nitrogen, oxygen and LNG. The tanks used within industry have the potential to hold GWh of stored energy.
  • Stage 3. Power Recovery
    When power is required, liquid air is drawn from the tank(s) and pumped to high pressure. The air is evaporated and superheated to ambient temperature. This produces a high-pressure gas, which is then used to drive a turbine.

Raising efficiencies:

Cold Recycle – During stage 3, very cold air is exhausted and captured by a proprietary high-grade cold store. This is used at a later time during the liquefaction process to enhance the efficiency. Alternatively, the system can integrate waste cold from industrial processes such as LNG terminals.

Thermal store – The low boiling point of liquefied air means the round trip efficiencyof the system can be improved with the introduction of above ambient heat. Highview Power Storage’s standard LAES system captures and stores heat produced during the liquefaction process (stage 1) and integrates this heat to the power recovery process (stage 3). The system can also integrate waste heat from industrial processes, such as thermal power generation or steel mills, at stage 3, recovering additional energy.

Take a virtual tour of Highview Power Storage’s 350KW/2.5MWh pilot plant

Conclusion

LAES plants can provide large-scale, long-duration energy storage, with 100s of MWs output. LAES systems can use industrial waste heat/cold from applications such as thermal generation plants, steel mills and LNG terminals to improve system efficiency. LAES uses existing and mature components with proven long-life times (30 years +), performance, and O&M costs.

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