IT purrs and growls just like the day it was installed a century ago, the colour of the bluebells that flourish in the nearby woods and every bit as “green”.

While across the country new hydropower schemes are helping to feed the revolution in renewables and clean energy, in a hut beside a babbling burn on an estate near Dundee, the forerunner of them all is efficiently and calmly still going about its business. 

Just as the rest of us might use the garden hut to store the family bikes, a few tools, the lawnmower and maybe mouldy camping gear, Duncan Stewart throws open the door to his workshop to reveal Scotland’s oldest working hydropower Turgo water turbine. 

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Installed in 1919 – just weeks after the first 30hp Turgo was fitted at Invergeldie Lodge, near Crieff – Mr Stewart’s personal 8kW hydropower system is not only generating energy to heat and provide hot water for his five-bedroom house in Burnside of Duntrune, there’s even enough left over for him to sell on to the National Grid.

As a result, Mr Stewart and his wife Pat not only live virtually energy bill-free thanks to the turbine, but they also derive some tax-free income from it.

“It is remarkable to think that something installed 100 years ago is working so well,” said Mr Stewart, 76. “As a result of it, most of our heating is free, it heats our water and powers a log splitter that provides me with logs for my wood-burning stove that keeps us warm in winter. It’s not just saving us money, it’s making money too.”

HeraldScotland:

Duncan Stewart with the hydropower turbine, which is generating energy after being installed in 1919.

The engineering treasure draws its water from the nearby Fithie Burn, which was dammed by workmen using shovels, horses and carts in the months after the First World War. 

However, water-driven power at the site dates back even earlier – to more than 400 years ago, when there was a mill with a water wheel in the area. 

The 4ft high, 9ft long turbine was originally installed in a workshop serving Duntrune Estate, powering a large circular saw and sending electricity to Duntrune House, nearby Craighill House and Burnside House, the former estate manager’s home.

When the Stewarts moved to Burnside House almost 40 years ago, the turbine was still providing electricity to the property – albeit via a quickly dismantled hazardous DC connection – alongside a mains connection. 

However, it eventually ground to a halt and was mothballed while the couple opted for more “modern” mains supply electricity and an oil-fired range cooker and boiler. 

It lay rusting until Mr Stewart met television presenter and engineer Lieutenant-Colonel Dick Strawbridge at an event and happened to mention the  turbine lurking in his shed. 

“He said, ‘get it fixed, it could be your pension’,” recalled Mr Stewart.

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Inspired, he dusted grime from the rusty turbine’s nameplate and discovered it was a Turgo turbine, manufactured by Cumbria-based Gilbert Gilkes & Gordon Ltd. Papers related to its commission and invoices confirmed it had been installed in 1919 – the same year the revolutionary turbine was designed by Eric Crewdson, who had outlined its features while serving in the trenches of the war.

Crewdson conceived the idea of a side-entry impulse turbine capable of running at twice the speed of a Pelton water-wheel turbine, with a higher efficiency across a broad flow range. 

Within months of returning from the war, his concept had been developed and the first Turgo turbine installed at a property in Crieff. 

However, it is no longer operational – making the Stewarts’ refurbished and repainted turbine the oldest operational example version of its type in Scotland. 

The refurbishment was carried out by the original manufacturers, while Mr Stewart set about removing a build-up of silt from the burn.

He added: “The turbine’s governor alone, which controls the flow of water and is a beautiful piece of engineering, must have weighed half a tonne – the new one only weighs around half a pound. Now it all works beautifully.”

The savings – and earnings – have been significant. Hydropower is used to heat the property’s water and radiators, enabling the Stewarts to reduce oil consumption, as well as powering the log splitter to feed the stove.  

“I now use about 1,500 to 2,000 litres of oil when a house this size would normally require 5,000 litres,” Mr Stewart added, “while I get paid for whatever energy is generated regardless of how much actually goes to the Grid. 

“It’s now part of our life.”

The only downside, he adds, is if a dry spell hits and the local farmers opt to use additional local water to irrigate their crops, leaving an insufficient flow to power the system.

Hydropower has recently surged in popularity, with dozens of community-run schemes now either in operation or in the planning stages. 

Hannah Smith, senior policy manager at Scottish Renewables, said: “Hydropower is one of Scotland’s great unsung heroes, using our notorious wet weather to provide 15 per cent of Scotland’s gross electricity demand while reducing the carbon emissions which cause climate change.

“Mr and Mrs Stewart’s turbine is one of Scotland’s oldest, and the fact it is still in service in its 100th year demonstrates how hydro delivers subsidy-free power long after support provided by government has ceased.”

She added that the Scottish Renewables Hydro Conference, in Perth on May 9, is set to explore further ways to ensure hydropower technology’s role in the future energy landscape, particularly in wake of the closure of the Feed-in Tariff scheme earlier this month.