On the back of the announcement of a new 50 MW/250 MWh cryogenic energy storage plant for northern England, we asked readers of The Engineer which type of grid-scale storage they favoured for the UK.
There are several possible technologies available or in development:
- Conventional batteries (by which we mean large-capacity lithium-ion systems used at facilities such as Australia’s “mega battery”)
- Other battery technologies, such as redox flow, which are capable of storing energy for longer but may be more expensive at the moment.
- Pumped hydro storage is in use in the UK, such as at the Dinorwig “Electric Mountain” in Snowdonia, but is curtailed by geography so more new capacity may not be practical.
- Gravity storage, where excess power is used to hoist weights to the top of defunct coal-mine shafts which are then dropped to regenerate the energy when needed.
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Despite some of the challenges the technology faces, pumped hydro was the most popular option amongst our readers, garnering 31 per cent of the vote. Cryogenic grid-scale storage came in second with 20 per cent. Just 8 per cent felt lithium-ion batteries were the best fit for the UK, with readers slightly more convinced by redox flow battery technology (12 per cent). Gravity-based systems were backed by 13 per cent of respondents, while 16 per cent chose the ‘other’ option.
“Cryogenic storage is very promising and well worth developing,” wrote Jack Broughton. “However, pumped storage is the only proven large scale system of those listed, for GWh level storage.
“The other storage technology that is proven at this scale is Compressed Air Energy Storage, CAES. There are two of these that have been in very long term use and the design is proven.”
“The big issue in storage is the length of time storage technology can support the grid,” said Phillip Owen. “Is it a question of a few minutes frequency support? Is it a question of a few hours for reducing peak requirements? Is it a question of 10 days demand for the entire United Kingdom on a cold January or February anticyclone when the wind doesn’t blow and the days are short and foggy? To provide cover for 10 days with renewable resources would require tidal energy and perhaps a six-hour storage period.”
Readers are invited to continue the debate in the comments section of our news piece on Highview Power’s new cryogenic storage project or indeed kick off a brand new conversation below the line here in response to the poll results. As ever, we ask people to familiarise themselves with our guidelines for the content of comments before submitting and remind them that all comments are moderated for length, style and clarity.
Really surprised that pumped hydro was highest. For anything more than a few hours this will not really work. And the time to pump water back uphill is a lot longer than to drain it! It is attractively simple and low tech yes, but consumes vast amounts of land and as with wind is usually a long way from the highest consumption locations and hence incurs significant transmission losses. Used successfully for decades as a short term gap filler but for anything longer not that useful.
The great advantage of pumped storage is that the generators can be run on spinning reserve which adds inertia to the system and stability. Provided the control systems are quick enough full output can be in seconds. I remember Ffestiniog power up was controlled by the speed of the penstock valves and the check systems. As a young control engineer I had the job of fault tracing the the gate control system which was causing problems.
At the time in the early 1960’s it was said there were only a few potential sites available that would be economic to create pumped storage. At full output as I remember it could contribute a few hours supply.
It was built to take the output of the local Nuclear power station in an emergency or to load lop its output at high system loads and take power at low system demand. Nuclear power plants were base load full output devices only. Varying the output was very difficult and slow as the Russians found out .
Gas cooled nuclear plant are slow to react as the power density is very low (Magnox 0.7MW/m3, AGR 1MW/m3), which was one of their advantages. At privatisation, otherwise ignorant finance people thought we could two-shift the AGRs and had to be taught a little physics. But this doesn’t hold for other coolants. Military PWRs (~100MW/m3) can achieve almost instant output with large negative reactivity (MW/Cdeg) so I assume the same is true in principle for civilian plant and also for other technologies that have a similar higher power density.
I have research and published a lot about the fantastic pumped hydro potential of the UK and Scotland in particular, yet because of the failure of the popular science media to report my research many people are still unaware of the scale of the potential and keep downing playing it in the fashion of idle gossip.
Here are the links to my blog posts about pumped hydro potential.
“Search for sites to build new pumped-storage hydroelectricity schemes”
https://scottishscientist.wordpress.com/2019/04/04/search-for-sites-to-build-new-pumped-storage-hydroelectricity-schemes/
“World’s biggest-ever pumped-storage hydro-scheme, for Scotland?”
https://scottishscientist.wordpress.com/2015/04/15/worlds-biggest-ever-pumped-storage-hydro-scheme-for-scotland/
“Glasa Morie Glass Pumped-Storage Hydro Scheme”
https://scottishscientist.wordpress.com/2019/04/10/glasa-morie-glass-pumped-storage-hydro-scheme/
I can also provide links to other people’s research if that’s OK?