Major pumped storage hydro scheme planned in Outer Hebrides

Plans have been unveiled for a new £200 million water engineering project on the Isle of Lewis in the Outer Hebrides, which will deliver a “significant boost” to energy production in Scotland.

The large pumped storage hydro scheme on the Outer Hebrides island will be capable of generating 300MW of electricity.

The scheme, being developed by Eishken Limited, will store electricity generated by windfarms on Lewis and double the use of the Western Isles Link – the cable being installed by National Grid to export and import electricity generated from renewable energy sources on the islands. 

The proposed scheme will be adjacent to and form part of the already consented 162MW Muaitheabhal windfarm on the Isle of Lewis. It will permit part of the output of the windfarm to be stored until required, allowing it to balance the intermittent nature of wind.

Pumped storage facilities act like huge batteries storing electricity. Water is pumped uphill from a lower reservoir to a second reservoir at a higher level. When demand for electricity is high, the stored water is released through generators situated at the foot of the hill into the lower reservoir.

The technology is proven and has been in use for nearly a century although none have been built in the UK for the last 30 years. At present, such facilities operate commercially without government financial assistance schemes.

The proposed scheme is innovative because it is intended that the lower reservoir from which the water is extracted and to which it is returned will be the sea. This will have a much lower environmental impact than would be caused by creating a second reservoir, and will make the scheme easier, cheaper and quicker to build.

Nick Oppenheim of Eishken said: “There are very few [pumped hydro storage] schemes throughout the UK and what we are proposing is particularly innovative given the use of the sea as the lower reservoir.

“This scheme will not only materially enhance the benefits to be derived from the Western Isles Link but will make a material difference in the supply of energy to the mainland. It will also be a key element in the Scotland’s renewable energy armoury.”

Although using the sea as the lower reservoir is new to the UK, it has been successfully implemented in schemes in Asia.

Eishken is expected to seek consent for the scheme – which would take 3-5 years to construct – later this year. AECOM, the international infrastructure design and engineering consultancy, is advising Eishken on the technical aspects of the project.

A version of this article originally appeared on wwtonline

RWE Innogy is expected to officially unveil its 3MW Cia Aig hydropower plant today (24 August) at 2pm by Scottish energy minister Paul Wheelhouse, following two years of construction work.

Speaking about the scheme, Scottish Renewables policy officer Hannah Smith said: “Scotland’s Highlands are synonymous with hydropower and developments like Cia Aig, which continue to make the most of the area’s superb natural resources, are to be welcomed.

“This technology already provides more than a quarter of the renewable electricity generated in Scotland, and with the right support from government hydro at all scales can continue to thrive, delivering economic benefits and helping us meet our climate targets.”