The owners of more than 600 small wind turbines have been told to shut them down amid fears of catastrophic mechanical failure.
Experts said last night that blades could fly off the Proven 35-2 generators, which are dotted all over the north, in the worst-case scenario.
The troubled manufacturer of the turbines has suspended all sales and warned its biggest investor – the London-based Low Carbon Accelerator (LCA) fund – that it will not be able to cope with its current losses unless it gets another cash injection.
Proven Energy revealed drive shafts in the 35-2 model had an “acute” defect and told owners that the machines – which can produce up to 12.1kilowatts and cost up to £70,000 – should be left stationary, with the “parking brake” applied. The advice to stop the turbines follows so-far unspecified problems with three machines.
Engineers said a shaft problem potentially could cause built-in braking systems to fail and the turbine blades to fly off if they were turning faster than they were designed to cope with.
About 500 of the generators have been put up in Scotland on 50ft towers. Many of them are owned by farmers.
Three Aberdeenshire farmers said they were “surprised” and “gobsmacked” yesterday when the P&J told them the problem. Fred Hendry, of Byth Stone, and John McGrimmond, of Ladysheets, both Alvah, near Banff, each has a turbine but said they knew nothing about the plea to turn on the brakes.
Another farmer, who did not want to be named, has just had three of them installed on his land.
Mr Hendry said his machine started generating on June 1 last year. “It was a lot of money for me, roughly about £50,000,” he said. “I’ve a lot of questions about what happens now as it is supposed to be under guarantee. I’m absolutely surprised.”
Mr McGrimmond’s turbine went into operation in March. He said: “This is the first I’ve heard of this. It has been working OK up to now. I went for it to get the feed-in tariff (subsidy) as it seemed a good thing at the time.”
The farmer, who has three of the generators, said none of his machines had been fully installed yet.
Mr McGrimmond added: “They’re braked at the moment and it now looks as if the brake is going to kept on. They only went up in August. I presume, and hope, it will now be up to Proven to rectify this problem as soon as possible.”
LCA told the London Stock Exchange it expected to make either a substantial or total write-down of the £11.15million it had invested so far in Proven, which has offices in East Kilbride and Stewarton, Ayrshire.
LCA, which owns 81% of Proven, put £500,000 into the business only four weeks ago.
Proven described the shaft problem as a “potential defect” but LCA told the stock exchange it was “recent and acute”.
The defect does not affect the Proven 7 and Proven 11 turbines.
Only the home page on Proven’s website was working yesterday. The company could not be contacted for comment.
A message on the website said it was investigating the problem. Work had already shown that a “significant number of shafts” may be affected across multiple manufacturing batches.
Farmers’ union NFU Scotland said it had been unable to contact Proven but urged members with the machines to heed the advice to turn the brakes on. An NFU spokesman said it had noted the financial issues disclosed by Proven’s biggest investor.
He added: “This is clearly an evolving situation that will worry many of those who have installed or have been planning to install Proven Energy turbines. We have spoken to one major supplier of Proven equipment and he hopes to be in a position to write to all his customers next week clarifying the situation.”
The Scottish Government said it was aware of a manufacturing defect in the turbines, adding anyone with concerns should check Proven’s website.
The Proven 35-2 turbine is the largest by the firm. It is among the few small machines that qualify for the UK Government’s feed-in tariff.