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Analysis: Boulder's change in direction explained

UNITED STATES: Boulder Wind Power is in the midst a dramatic change of direction, with the release of a number of different designs for generators. Windpower Monthly spoke to the company's CEO Andy Cukurs about what prompted this move.

The three generators and power conversion unit
The three generators and power conversion unit

Boulder made its name with a design for a radically different direct-drive generator that relies on a printed circuit board stator and sits outside the turbine's nacelle. However, it has now released an array of new products, including a geared generator.

One reason for this diversification is the lack of appetite within the wind industry for designs that break with convention, Cukurs said.

"Any time that you are introducing new technology, the closer it is to what the industry is used to, the easier it is to have it accepted. There are some hurdles to overcome with our low-speed turbine, such as 'do I want to do permanent magnet?' and 'do I want to go with direct drive?', and then there's the fact that we're a new company with a radically different design."

These fears, along with the significant adaptions of turbine nacelles necessary to accommodate the generator, have meant that the company is yet to find a commercial partner for the generator – although Cukurs said that an agreement with a European manufacturer is "imminent".

And so the company has added to its portfolio with the introduction of a medium-speed geared turbine that can fit within existing nacelles.

"What we realised was that even though technically it's not better to go towards a smaller diameter, from a marketing standpoint it would be a lot easier. We broadened the portfolio so that we could appeal to a much larger audience," said Cukurs.

But the new generator is not totally abandoning Boulder's innovative direction. It also features a printed circuit board stator which means it has no iron and as such no attractive forces between stator and rotor, meaning it can be made much lighter than other generators.

Cukurs claims that there has been a "tremendous amount of interest" in this new model and that Boulder is in talks with three companies about the use of the generator in their turbines. Two of these are for 3MW turbines, while the other is "quite a bit larger".

Asia has proved the happiest hunting ground, he added: "It is a more receptive market. The manufacturers are generally newer to the market and don't necessarily have years and years of experience producing the same machines."

The company is also marketing the medium-speed generator to the retrofit market. "There are a lot of older turbines that could be performing well. Why not put a larger rotor on these turbines? But considering noise constraints and the like you're going to have to slow down the rotor and with this generator you can create very high torque at a lower speed," Cukurs explains.

As well as moving into medium-speed generators, the company has also taken a step in the other direction, with the design of an ultra-low speed generator. This would be suited to sites that have "very low wind regimes". The generator is similar in design to the low-speed model, but has a lighter weight structural design as it won't have to deal with the same kinds of fatigue issues and maximum forces.

On top of this, Boulder has developed a new power converter that allows conversion to direct current (DC) within the generator. The new technology allows the power conversion process to be distributed across the generator. This could lead to an improvement in efficiency, possibly of up to 2%, the company said.

"Because Boulder generators are naturally segmented, we can combine our circuit board stators with power conversion components in a modular fashion and can optimise system voltage to meet customer requirements," said Cukurs.

So while the company is still looking to tread an innovative path, it has been forced to reign in its imagination somewhat by the realities of the wind industry. The installation of one of its generators in a turbine will be the next crutial step.

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