Wind News

Friday 06 March 2009

Cornwall Light and Power said that it has learnt some painful lessons, but has now installed a blade monitor that will prevent the turbine shedding ice in future

A wind developer that became a "lightning rod" for the industry when one of its turbines started shedding ice in December, has revealed its latest strategy for dealing with ice build-up, writes Rachel Johnson.

Cornwall Light and Power told delegates at the British Wind Association's Health and Safety conference in Brighton on Wednesday that it is planning to invest in ice-detection technology for its turbines, and revealed the lessons that it had learnt.

And the firm called for an industry code of practice that would prevent this kind of incident occurring again.

The company had come under public scrutiny in December when its single Vestas V90 1.8MW turbine at Whittlesey, Cambridgeshire, began hurling ice into the local area (see this New Energy Focus story).

"Lightening rod"

According to Cornwall Light and Power, a local businessman reported a "four foot javelin" of ice falling into his car park 100m away.

Dr Martin Comer, operations and technology manager at Pure Energy Professionals, the firm that consulted on the Whittlesey project, said that the incident had been a PR disaster.

"We realised pretty quickly that we would become a lightning rod for the industry," he said. "In fact our sister company in Canada is now having to deal with objector groups who are citing our turbine as an example."

But he told delegates that although the learning process was "painful", the company has now got a better picture of what went wrong, and has put in place a strategy to deal with icing on turbines.

"We knew icing would occur but believed our turbines would stop in the event of an ice build up," he said.

The investigation revealed that the most widely available guidelines on icing, including those from the BWEA, had said that wind turbines are designed to shut down in the event of an ice build up.

According to the guidelines, the turbines are able to use in-built vibration sensors that measure any imbalance between the blades that occur in the event of ice build up.

But Dr Comer said that the Whittlesey experience proved the guidelines to be untrue, as in this case ice built up equally on all three blades, keeping it well balanced and bypassing the vibration sensor.

To illustrate the point, he revealed that from 5am to 10am, when the ice build up was at its worst, the turbine attempted to start up and connect to the grid 30 times.

Blade monitoring

So to combat the deficiency in the vibration monitor, the company is planning to install a blade monitoring system that can detect ice on the turbine rotor blades.

Cornwall Light and Power is considering both the BladeControl solutions from German-owned IGUS-ITS, and the Rotor Monitoring System (RMS) from UK firm Insensys.

The Insensys RMS device monitors the condition of the blade, and can sense 4kg of ice on a 10,000kg blade, using fibre optics.

Dr Comer, who called for a code of practice on icing for developers, went on to say that in order to combat ice-build up, developers must assess the risk while developing the wind farm early on.

He said: "Ask, are members of the public able to approach your turbine when there is a risk of ice? What protection do you rely on during icy conditions?"

"Planners must be informed of the risk," he added. "Get the planners involved early on. And speak to the turbine's manufacturers about ice prevention systems."

Whittlesey, which has been operational since September last year, is located near Peterborough.

Cornwall Light and Power has in operation or development 14 wind farms around the UK, in Cornwall and northern and midland England.