“We said, ‘No, we’re not convinced this makes sense,’ ” says Larry Cundy, director of development at MPR. But CWind convinced MPR to do some basic analysis of the design, and eventually the engineering firm agreed to build the prototype. “It’s a very novel application, quite frankly,” Cundy says. “It’s really a stroke of genius.”
Cundy says the biggest advantage of CWind’s design is that it’s easier and less costly to maintain over the lifetime of the equipment. When a gearbox on a conventional turbine fails, the turbine is knocked completely out of service. Getting a replacement gearbox takes a long time, and removing the massive device from the wind turbine’s nacelle requires a large crane and many days of work. Every day the turbine isn’t generating electricity for the grid amounts to lost revenue for the operator.
“On a friction-drive system with multiple tires, if you lose a tire, the others are still there,” says Cundy, adding that replacing tires is quick–roughly a day’s work–and that future designs will allow maintenance while the turbine is still operating. The same redundancy applies to the generators–if one fails, the others can still function. Cundy says that the small, off-the-shelf generators used in CWind’s design can be obtained quickly and are installed fairly easily with the help of a small crane built into the nacelle.
Nayef says that the tires used are designed to last for three years, and replacing all the tires used on a two-megawatt wind turbine is expected to cost $30,000–or nearly $200,000 over 20 years. By contrast, gearboxes have an average life of six years and cost about $600,000 to replace, or nearly $2 million over 20 years. “We’re going to be competitively priced with conventional gearbox wind turbines, yet we have the advantages of high availability, high efficiency, and all of the advantages that come with serviceability.”
Last month CWind signed a manufacturing agreement with global auto parts maker Linamar, which has committed its McLaren Performance engineering team (of Formula 1 racing fame) to producing the two-megawatt prototype. As part of the 10-year contract, Linamar will also manufacture market-ready turbines, likely beginning in 2011. Nayef says work is already under way on five-megawatt and 7.5-megawatt designs aimed at the offshore wind market as well as remote onshore sites where easy maintenance becomes a key selling feature.