October 24, 2023

Liquid Air Energy Storage (LAES)

With the ever - increasing demand for power and the limited availability of conventional resources, man has turned to renewable energy sources. These renewable sources include wind, solar, tidal, geothermal and the like. Their contribution to the global power demand has been increasing steadily with the advancement in technology.

Among thermo-mechanical storage, LAES is an emerging concept where electricity is stored in the form of liquid air (or nitrogen) at cryogenic temperatures. A schematic of its operating principle is depicted in Figure 1, where three key sub-processes can be highlighted, namely charge, storage and discharge.

During charge, ambient air is first purified, compressed using excess electricity and finally cooled down to reach the liquid phase; liquid air is then stored in near-atmospheric pressure vessels. Despite the cryogenic temperatures (liquefaction temperature for Nitrogen at ambient pressure is -196°C), vacuum or perlite insulation is very effective in limiting boiloff at this stage to only 0.1-0.07% per day.

When discharging, the required electricity is retrieved by pumping, evaporation and expansion of the liquid air stream through a set of turbines, in the power recovery unit (PRU). During the operation of LAES, hot and cold thermal streams are produced, respectively, during air compression (charge) and evaporation (discharge). As illustrated in Fig. 1, and discussed in greater detail later on in the review, such streams can be harnessed and reused within the process itself to improve plant energy efficiency. For this reason, the storage section of LAES typically comprises also thermal energy storage (TES) devices – a hot and a high-grade cold one – in addition to the liquid air tanks.

Fig. 1. Liquid air energy storage (LAES) process.

LAES is a thermo-mechanical storage solution currently near to market and ready to be deployed in real operational environments. LAES exhibits significant advantages with respect to competing solutions: energy density is 1 to 2 orders of magnitude above the alternatives and no site constraints limit its deployment. Because of the cryogenic temperatures of liquid air, the power generation cycle can be driven by largely available heat sources at ambient temperature.

Not only this eliminates the need for combustion and associated carbon emissions, but it also allows the recovery of low-temperature streams such as waste heat within the LAES process. Integration with external sources of heat and/or cold enables energy synergies and symbiosis with other processes, such as industrial sites near the location of LAES process. Underpinned by such compelling features and technical potential, endeavours towards the increase of LAES conversion efficiency – long been identified as a key drawback – and LAES commercialisation have achieved significant milestones in the latest years.

The concept of storing energy by means of liquid air was first proposed in 1977, but experimentally investigated only several years later by Mitsubishi Heavy Industries and Hitachi. A 2.6 MW air-driven Rankine cycle was successfully operated by Kishimoto et al. showing excellent stability characteristics for power generation, while researchers from Hitachi focussed on a layout including a gas combustor and a concrete regenerator to enhance gas liquefaction. Efficiencies as high as 70% were predicted for the system.

Few years later, a joint venture between Highview Power and the University of Leeds, UK, led to the design and construction of the first fully integrated LAES plant in the world. The 350 kW, 2.5 MWh pilot-scale plant was commissioned in 2010 and successfully tested in 2013, when it was relocated to the University of Birmingham for further research and development. This system established a cornerstone for LAES development, stimulating great research interest in the technology.

Source: Highview Enterprises Limited

A further 5 MW, 15 MWh pre-commercial plant by Highview Power was operated in June 2018, leading to the deployment of two LAES 50 MW plants (named CRYOBattery) in the UK and US, recently unveiled from the same company; these will be the first grid-connected LAES plants worldwide. Alongside commercial development, a number of international projects (e.g. the CryoHub project, and the IEA Energy Storage Task 36) have been established to further investigate, characterise and develop LAES technology.

Recent cases

LAES, GPP and much more

October 25, 2023
Orsted Signs Up to Study Liquid Air Storage for Offshore Wind Power

Offshore wind giant Orsted is working with a UK-based startup in an effort to solve one of the most persistent problems for offshore wind power: storage. In stormy weather, offshore turbines can produce so much electricity that they have to be curtailed so as not to overwhelm the grid; in light airs, however, they produce […]

October 24, 2023
Battery storage takes central role in powering net zero

State backing for renewable investments fuels growth but western nations remain dependent on Asia for supply. Often overshadowed by their counterparts in flashy electric cars, batteries for renewable energy storage are becoming increasingly important to countries’ net zero ambitions. While solar and wind energy have the benefit of reducing reliance on carbon-emitting fossil fuels, the […]

October 24, 2023
Drilling commences for deep geothermal research at Weisweiler site in Germany

Drilling has started for the deep geothermal research project as part of the DGE-Rollout at the site of the Weisweiler power plant in NRW, Germany. Drilling has officially started for the first exploratory borehole for deep geothermal energy at the site of the Weisweiler lignite-fired power plant in Eschweiler at North Rhine-Westphalia (NRW), Germany. Power […]

menu-circlechevron-up-circle linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram