ON the day that the launch of Scotland’s newest hydro electric scheme took place in the Highlands, plans were revealed for one of the largest hydro developments in Europe to be built in the Outer Hebrides.

The £12m three megawatt (3 MW) Cia Aig scheme on the Abhainn Chia-aig at the eastern end of Loch Arkaig, some 20 miles north of Fort William, had its official launch yesterday.

It is a substantial state-of-the-art run of river generating scheme, but it will be dwarfed by the £200 million development being proposed for Eishken on the Isle of Lewis.

The renewables industry was in a lather yesterday over the announcement of the Eishken plan, which is for a pumped storage scheme with a difference – it will be the first in the UK using sea water.

There are just four pumped storage hydro schemes in the UK, of which the most famous in Scotland is at Cruachan in Argyllshire.

They act almost as batteries, able to generate electricity quickly, and the proposed scheme on Lewis will act as a “battery” for the 162MW Muaitheabhal windfarm which already has planning permission.

At Cruachan the pumps and turbines are stored inside Ben Cruachan while water is pumped 1,300 ft from Loch Awe up to Cruachan reservoir at night, then released to generate electricity during the day.

The Eishken plan would see the sea around Lewis used as the base, with sea water being pumped up to a reservoir at off-peak times and then cascading through turbines, generating 300MW of power between it and the windfarm – 100 times more capability than is being expected at Cia Aig.

The Eishken scheme will effectively double the use of the Western Isles Link – the cable being installed by National Grid to export electricity generated from renewable energy sources on the islands, which in turn will guarantee power from the mainland to Lewis should it be needed.

Nick Oppenheim of Eishken Ltd 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.”

At the launch of Cia Aig, Energy Minister Paul Wheelhouse said: “Congratulations to RWE Innogy UK on the inauguration of their hydro power station.

“This 3MW hydro scheme will help contribute to the growing importance of hydro generation in Scotland – the largest source of renewable power in Scotland after onshore wind.

“I welcome RWE Innogy UK’s commitment to provide community benefit funding associated with their renewables schemes including their Cia Aig hydro development.

The Scottish Government is committed to supporting the development of renewables – including hydropower – as part of Scotland’s balanced energy portfolio, and we are already developing an overarching energy strategy, setting out what we can do to optimise the benefits of Scotland’s significant energy resources and expertise through to 2030.”

Simon Hamlyn, chief executive of British Hydropower Association said: “We are delighted that another of our member’s schemes is now in full operation and we welcome this opportunity to demonstrate to Scottish Government the positive impact the development of new hydropower has on Scottish communities.

“There is now more than 177 MW of small-scale hydropower available in Scotland with approximately 1,700 people working in the sector in Scotland and increasingly many local communities are taking a stake.”

Speaking about Cia Aig, 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 government support, hydro at all scales can continue to thrive, delivering economic benefits and helping us meet climate targets.”