Technology developed by an ancient Greek is helping a farmer in the heart of Aberdeenshire generate electricity.
The Archimedes’ screw used by John and Jacqueline Riley at Strathdon, however, works in the opposite direction from that for which it was designed.
Greek polymath Archimedes of Syracuse is said to have developed the screw in the third century BC to lift water from low-lying areas into irrigation channels so food crops could be grown. Its use has since spiralled, but the concept still remains the same in that it has a spiral screw within the metal casing to move the water.
Today, the Rileys feed water into the top of theirs and let gravity do the rest as it pulls the liquid down, making the screw turn.
That is the theory, at least. Dry weather this summer has meant the screw has been out of action for more than three months as there has been insufficient water in the River Don to allow them to operate it.
That said the screw has, since its installation in 2007 and commissioning in December that year, helped them generate an average annual output in excess of 322,000 kilowatts, enough electricity every year for 176 homes.
The Rileys farm 300 acres at nearby Semeil Farm, where they grow malting barley and oats. Mr Riley works in the oil industry and had always had the ambition of farming, a dream he realised on the purchase of Semeil in 1985.
The screw is housed in a redundant hydro power plant built in 1946 by Strathdon’s Candacraig Estate. It generated electricity for the community until National Grid supplies finally arrived in 1974.
The Rileys make use of the weir the estate built at the same time to dam the Don to provide the original plant with water. But they had to install their own intake as they were unable to use the original in the weir as it is not in their ownership.
The new intake is controlled by an automatic hydraulic sluice which only lets water through when there is a sufficient flow and water depth in the river.
It takes the water through pipes into the original feed-in channel to the generation plant, which the Rileys bought in 1996 along with the land surrounding it. But they pay a penalty for that diversion as it slows the speed of the water entering the channel because of the corners it now has to pass through.
Mrs Riley said: “Do you make use of hydro power or cover the countryside in windfarms? We use the water for 200m and it then goes back into the river for someone else to produce the same or more electricity if they wanted using the same water downstream. That’s the true meaning of renewable energy as the water can be used over and over again.”
Mrs Riley admitted that operating the screw has not been without its challenges, particularly those thrown at them by the Don District Salmon Fishery Board which has the statutory duty for protecting and enhancing salmon and sea trout stocks in the river.
Mr Riley sits on the board as a riparian owner as he controls the north bank beats directly upstream and downstream from his generation plant.
But Mrs Riley said views on hydro needed to be updated and the emotion taken out of the debate, particularly when there were ever-growing demands for more power generation from renewables.
She added: “We don’t want to do anything that upsets the fish. Hydro is as near a truly renewable energy that you can get. I completely agree that hydro has a bad history and that the dams and big hydro reservoirs built in the 1940s, 50s and 60s did take their toll on migratory fish. But the world has moved on.
“My husband takes the view that he needs to be responsible, just as we all should be if we are to look after this Earth for future generations.
“A major part of his vision for this was that he found a fish-friendly turbine because he has been a life-long fisherman and has for years worked to improve the habitat of the fish.”
Barriers have been installed in the out channel to avoid fish entering the screw. The channel mouth has also been widened so as to slow the speed of the water returning to the Don. That should detract migratory species entering the channel as they should stay in the faster-flowing water of the Don.
Mr Riley has also been attempting to improve the fish ladder on the weir so that more salmon make use of it. And he supports the work of the River Don Trust, a charitable group charged with conserving and enhancing the river and its tributaries.
Mrs Riley said the hatred that some had of hydro was an unreasonable position as everything had to be done to secure the planet not just for the current population, but all subsequent generations.
Mr Riley takes conservation seriously. He has in recent years planted seven miles of hedges on the farm. He has also sown wild flower margins in his arable fields.
Semeil is home to many bird species, including lapwings and snow buntings which have a keen following among local ornithologists.
And if they had to start again from scratch? Absolutely. “We’d still go with an Archimedes’ screw because of the fish friendliness of it,” said Mrs Riley.