Distributed Liquid Air Energy Storage (LAES) systems and behind-the-meter energy storage

Liquid Air Energy Storage stores exergy in very cold liquid air at ambient pressure. The idea is that off-peak or low-cost electricity is used to liquefy air (by way of a compressor, cooler and then expander), that is then stored in an exergy dense cold liquid form. When electricity is required the cold liquid air is pumped (using a special cryogenic pump) to increase its pressure, super-heated in a heat exchanger using either ambient or low-grade industrial waste heat and then expanded through a turbine generating useful electricity. I use the term exergy instead of energy, as the cold liquid air isn’t itself a store of energy, rather it stores the ability to do work when the temperature of the air is returned to the ambient temperature. The liquid air energy storage process is depicted in the diagram below.

Cryogenic Energy Storage

Schematic diagram of the Liquid Air Energy Storage (LAES) process

At the University of Birmingham’s Centre for Energy Storage there is a pilot LAES plant which has been transferred from Highview Power Storage (shown in the photo below). The plant has a rated power of 350 kW and can provide this power for 8 hours when fully charged. Similar to my research in Energy Storage and Electricity Markets, my research in distributed LAES involved quantifying the revenue streams available to distributed LAES systems. Considering the pilot LAES plant at the University of Birmingham’s main campus, I carried out an analysis of how the plant could be used in order to generate the most value. This involved fully understanding and recreating the University’s electricity bill and analysing the campus electricity demand, as well as understanding the functionality of the pilot LAES plant. We then considered how to minimise the bill by using the LAES to minimise the University’s Transmission Use of System charges (also known as TRIAD charges) and the capacity charges. We also considered what the effect of waste heat availability would be and how this varied with the temperature.

This work is being used to help schedule the operation of the pilot LAES plant.

LAES Pilot plant now located at the University of Birmingham's Centre for Energy Storage

LAES Pilot plant now located at the University of Birmingham’s Centre for Energy Storage