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Major pumped storage hydro scheme planned for Isle of Lewis

Plans have been unveiled for an innovative £200M water engineering project on the Isle of Lewis that will deliver a significant boost to energy production in Scotland.

The large pumped storage hydro (PSH) scheme on the Outer Hebrides island will be capable of generating 300MW of electricity – enough to power more than 200,000 homes. The scheme, being developed by Eishken Ltd, will store electricity generated by windfarms on Lewis and increase significantly (from 40% to 80%) the use of the Western Isles Link, the cable being installed by the 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 Wind Farm on the Isle of Lewis. It will permit part of the output of the wind farm to be stored until required allowing it to balance the sometime intermittent nature of wind.

Pumped storage facilities in essence 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 Limited said: “There are very few PSH 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 Ltd 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.

Author: James Brockett,
Topic: Energy/Water Nexus , Pumps & Pumping Systems , Sustainability & social value
Tags: electricity , storage , energy , reservoirs

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