Thermal electricity storage inspired by hang-gliders

UK‑firm ‘Isentropic’ has developed a pumped heat electricity storage (PHES) system for cheap and convenient distributed grid storage, with a projected levelised cost of storage (LCOS) below industry‑leading hydroelectric storage.

Founding member and Technical Director, Jonathan Howes, credits hang‑glider thermals as the inspiration behind the technology. Rather than store electricity in the form of a potential difference (i.e. voltage), as is the case with batteries, PHES systems maintain thermal gradients between materials to store potential energy.

Thermal electricity storage hang-gliders

A combination compressor-generator is used to transfer heat from a ‘cold’ thermal storage silo–filled with gravel and inert argon gas–to the other ‘hot’ thermal storage silo in order to store energy. The work done by the heat pump creates a temperature difference between regions of the thermal storage silos. The process is reversed when extracting electricity, allowing the argon gas to expand and drive the generator-compressor in the reverse cycle. Isentropic quote a round‑trip efficiency of 72–80%, depending on the size of the system.

Isentropic Energy Storage

Gas flows and temperature gradients within the PHES system. Image Credit: Isentropic

If successful, the technology is claimed to enable the lowest cost of any electricity storage device, with a levelised cost of storage of less than US$35 per megawatt‑hour – approximately one‑third of the cost of pumped hydroelectric storage.

In addition, PHES systems are modular, scalable and are designed for unit sizes as small as 2 megawatts, making them relatively portable and suitable for road transport. PHES uses non‑toxic, common materials and operates at non‑explosive pressures, adding to its safe and environmentally‑friendly appeal.

The technology is currently in an advanced prototyping phase, receiving US$22M worth of funding from the Energy Technologies Institute (ETI) to develop a 6 megawatt‑hour electricity storage unit for deployment at UK primary substations.

Headlines are abuzz with electricity storage advancements, the vogue topic and ‘next big thing’ in renewable energy systems. And despite countless attacks by the Coalition government, renewable energy combined with innovative storage solutions are set to change the Australian electricity landscape at all levels.

Top Image Credit: Isentropic

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John Rodriguez

John regularly contributes original technology articles to Solar Choice News. He is a PhD candidate in solar PV engineering at the University of New South Wales (UNSW), having graduated with First Class Honours in a Bachelor of Engineering (UNSW, specialising in PV). His knowledge of and passion for renewables technology led to him receiving the federally-funded Australian Postgraduate Award and Engineering Research Award for research excellence, in addition to being a Co-operative Program scholar during his undergraduate studies. John also works as an energy efficiency and process engineer and analyst.
John Rodriguez