Pumped storage in outline © RK Gupta
Managing when the wind isn't blowing
Schemes such Loch an Earba or Loch Fearna / Loch Quoich store 40 GWh of electricity, 500 times as much as the proposed battery site at Airyhall. But even 40 GWh is a small proportion of UK daily demand of say 800 GWh. Hence, pumped storage can help to manage daily cycles in demand but won“t do anything to help manage sustained periods of low wind.
The best way of managing electricity supply when the wind isn't blowing is to
- build interconnectors (as is currently happening). The statistical frequency of anti-cyclonic days where there is little wind is considerably reduced when the UK is combined with the Netherlands and Germany
- develop hydrogen/compressed air storage in underground caverns.
Future Trends in Storage
As noted above, an individual pumped storage scheme is a small fraction of total UK daily demand. However, both as more schemes get built, and demand is smoothed by e.g. charging of electric cars at night, we will see a trend of pumped storage being used to support electricity supply on low wind days. You can already see the start of this trend when driving past our existing small hydro schemes, which are being used differently to the past when they were filled in the winter and emptied during the summer. Now, they are increasingly used to balance low wind days if they have available capacity.
Pumped storage schemes need a large height difference as found only in mountainous areas and are expensive and risky. Based on the published Corrie Glas price tag of £1.5 billion, the schemes at Loch an Earba and Loch Fearna are likely to cost in the order of £2 billion each. The tunnel failure at Glendoe, costing over £100 million, shows that pumped storage schemes are risky.
Hydrogen might have a role to play in the future. It can be compressed and stored underground in suitable rock formations. However, handling and using hydrogen involves a number of issues where technology needs to be developed. Storing compressed air in underground caverns is even further down the technological road.
In the past, the Government would have produced a strategy for what storage was needed and how to produce it. Now, these matters are left to individual companies to look for profitable schemes and then build them. There are many developments ongoing simultaneously, e.g. solar panels with associated batteries on individual houses, "borrowing" power from car batteries during charging at night, battery units at sub stations, the increase of electric car batteries typically charged at night, further development of interconnectors between continents, the replacement or not of our existing nuclear power stations. How all these factors will interact is difficult to predict. However, the need for medium term storage = pumped storage is likely to be around for some time.
As noted above, this picture is likely to change as hydrogen and or compressed air storage technology develops.
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