Page 65 - Energize March 2022

TECHNICAL

compression, heat is removed and stored
in a thermal storage system and later
integrated into the power recovery process.
The low boiling point of liquefied air means
that the round trip efficiency of the system
can be improved with the introduction
of heat above ambient temperature. The
system can also integrate waste heat from
industrial processes at the evaporation
stage, recovering additional energy.

Features
The engineering systems required to
produce, handle and store gas for cryogenic
gas storage are well established and
readily available in the temperature range
Figure 2: Layout of a practical LAES system (Highview)
of liquefied air. Systems are modular in
nature and can be expanded by adding
• Power recovery: Liquid air is drawn from the tanks and raised to a high pressure. The air is extra modules. Systems can operate in
evaporated and heated to ambient temperature (or higher). This produces a high-pressure standalone mode with heat and cold
gas, which is then expanded through a multistage turbine with interstage heating, to storage, or as a hybrid system integrated
produce electricity. The layout of a practical system is given in Figure 2. with industrial processes, exchanging heat
and cold with other systems.
Heat production and absorption A lifetime in excess of 30 years is
Heat is produced during compression and must be removed, and air cools when it is estimated, based on the lifetime of
expanded, so additional heat is needed to assist the process. This removal and addition of existing cryogenic systems. Cost at the
heat gives the system a rather low turnaround efficiency. Storage and reuse of heat and cold current state of development is estimated
produced in the process would improve efficiency significantly. Alternatively, waste heat to be in the range €1270 to €2090 per
from adjacent industrial processes could be used. (If the LAES is used for industrial bulk kW and €300 and €600 per kWh. Size of
electricity storage this becomes practical). planned systems extends from around
Referring to Figure 1, during evaporation very cold air is removed and captured by a cold 5 MW to 100s of MW, with a storage
storage device. This will be used at a later time during the liquefaction process. Alternatively, capacity of 100s of MWh. Furthermore,
the system can integrate waste cold from industrial processes such as LNG terminals. During since capacity and energy are decoupled,
the systems are very well suited to long
duration applications

State of the technology
A number of commercial plants are in the
planning stage. One of the first large-scale
commercial plants in the UK has recently
been announced. The new 50 MW storage
facility will become one of the largest
battery storage systems in Europe, with a
minimum projected output of 250 MWh,
which could be easily scaled up.
In South Africa, gas company DNG has
stated an interest in developing liquefied
air electricity storage systems.

Reference
1. O O’Callagan: “Liquid air energy storage
systems: A review” RaSER, 2021.

Send your comments to
Figure 3: Highview power storage 350 kW/2,5 MWh pilot plant (Highview) rogerl@nowmedia.co.za

energize | March 2022 | 63