All ten Vestas 3 MW turbines at the 30 MW East Point Wind Plant on Prince Edward Island, Canada, are being fitted with new gearboxes for the second time in just over a year. The turbine manufacturer says the machines are now receiving an "improved validated version" of the gearbox that corrects a problem with the planet bearing.
Two of the East Point turbines underwent repairs in July after an inspection showed signs of wear significant enough to warrant replacement, says Ron Estabrooks, an energy adviser at government-owned PEI Energy Corporation (PEIEC), which owns the wind farm. The project went online in February 2007.
Vestas is also replacing the gearboxes on the remaining eight turbines. "Hopefully they can get this done before we are into serious wind conditions," says Estabrooks. Vestas says the gearboxes will be replaced this autumn before the site is covered with snow. The decision to refit all ten turbines is a preventive plan, the company says.
"As the site is located on an island in Canada where the mobilisation cost of a crane is considerable, and where the weather windows during winter time are quite narrow and site works and roads during summer are soft, Vestas has decided to replace the remaining eight gearboxes of the previous version to the improved gearbox solution in one preventive operation," Vestas says. "The power production from the project and the total cost for Vestas will be less affected by this preventive plan."
This is the second time turbines at East Point have undergone a retrofit. Six turbines were taken offline in March and April 2008 after gearbox damage was discovered (Windpower Monthly, June 2008). When two more then started showing signs of similar wear, says Estabrooks, PEIEC asked Vestas to replace all ten. "The replacement started towards the end of May 2008 and I believe was pretty well done by the end of August," he says. "Now we're back where we were, in some respects."
Gearboxes in the offshore version of the Vestas 3 MW machine installed in the 90 MW Kentish Flats wind farm off the east coast of England suffered a series failure in 2006, requiring replacement of the component. In early 2007, the offshore 3 MW machine was pulled off the market, to be reintroduced again in May 2008 (Windpower Monthly, June 2008).
When the gearboxes on the East Point turbines were replaced last year, it was with a version that was "generally the same" as the original. "This was done in order to ensure the turbines remained operational until the improved validated version of the gearbox was ready for use in the field," the company says.
"The improved solution gearbox has been tested and validated by our supplier and certified by Det Norske Veritas as a third party. We do not expect any future gearbox failures of the V90 3 MW," Vestas says, adding that offshore projects now under construction using V90 machines have the improved version of the gearbox.
Estabrooks says PEIEC is fortunate to have a very good contract with Vestas for operations and maintenance. The East Point turbines are covered by a five-year warranty, for which PEIEC pays about C$1 million a year. The agreement guarantees 95% turbine availability and pays liquidated, or pre-determined, damages for lost production. But it does not cover the C$0.01/kWh loss of revenue that would have been made under the Canadian government's ecoEnergy for Renewable Power programme, says Estabrooks.
The problems, Estabrooks continues, have reinforced his concerns about the long-term cost of turbine operation and maintenance. "I don't know if anybody really knows what it's going to be ten years from now," he says. "It's been a learning experience for us. I guess when you first get into this business and you don't know too much about it, you figure you are going to put a turbine up for twenty years and just basically stand back and watch it go. But that's not true."