Archimedes screws power up on Ettrick Water

Hydro electric generator at Selkirk Cauld.
Hydro electric generator at Selkirk Cauld.

PHILIPHAUGH Estate’s hydro-electricity generator is up and running, with the capacity to power more than 200 homes.

The construction on the Ettrick Water at Murray Cauld, Selkirk, is the first of its kind on the Tweed river system. When the two Archimedes screw turbines are running at maximum capacity, they can generate 904,000kW hours per year – enough electricity to power 225 homes. Each turbine can produce 110kW per hour, but the turbines will only produce power when there is a minimum of three cubic metres per second of water going through them. The turbines operate most efficiently when 12 cubic metres of water per second are running through them.

Philiphaugh Estate, which oversaw and funded the £1.3million, two-year project to revamp the 165-year-old cauld head, said protection of the native species was its number one priority.

Philiphaugh Trust’s Julie Nock said: “To ensure the free passage of wildlife, we have worked closely with Scottish Natural Heritage and SEPA throughout the project. A new Larinier state-of-the-art salmon pass, and a combined eel, lamprey and smolt chute have been installed beside the turbines, so fish, eels, lampreys and smoults can ascend and descend the cauld. Screens also prevent otters and larger fish from entering the turbines.

“We closely monitor the river level to ensure that the salmon pass and mill lade get a constant flow of water. Two electronic sensors have been placed in the river above and below the cauld to measure water flow and height. These sensors can close off the turbines when water is low or if an obstruction to the flow occurs. Our first priority is to ensure that water can run down the fish passes, the second is to ensure that water descends the mill lade to protect this sensitive environment.”

She added: “We have installed four cameras, one overhead and three underwater, which transmit live video feed to the Salmon Viewing Centre. The underwater cameras are situated within the salmon pass and at its exit. Visitors to the Salmon Viewing Centre will now have a wide choice of viewing options to observe returning Atlantic salmon in their natural habitat.”