Cobham and Boulder accelerate revolutionary wind turbine technology 23 October 2012

Cobham Technical Services and Boulder Wind Power (BPW) are collaborating on what they describe as revolutionary wind turbine technology capable of delivering "a 20% reduction in the cost of wind-generated electricity".

According to Brian Sullivan, principal electromagnetics engineer at BWP, it uses a direct-drive permanent magnet generator and an axial flux, air-core architecture.

Sullivan says this increases efficiency and reliability, and will ultimately reduce the cost of wind generated electricity to compete at parity with fossil fuels.

BWP used the Opera advanced electromagnetic design simulator, from the Vector Fields Software range of Cobham Technical Services.

Like all permanent magnet direct drive wind turbines, the generator rotor of BWP's 3.0MW design turns at about 13rpm, necessitating a high pole count. Opera's software allowed high periodicity to be leveraged, so that the analytical model could be a fraction of the size of the complete generator – significantly reducing simulation times.

This is particularly important for BWP because it makes exclusive use of the 3D version of Opera, which is necessarily more computationally demanding than the 2D version.

Sullivan explains that, while many wind turbine designers employ 2D simulation for the main components in a generator, and only use 3D for elements such as the end turns on windings, BWP's designers had to use full 3D at every stage, to model the generator's novel architecture.

"The physics engine and computational solvers in Opera-3D provide an excellent foundation for the detailed analyses that we perform for our design optimisation," states Sullivan.

"Combined with Opera's extensive scripting capabilities, which are far more flexible than the pre-programmed templates offered by competitive packages, this software is enabling us to develop new analytical techniques for our machine architecture," he continues.

"The results obtained from prototype testing have shown a high degree of correlation with our analyses... As an example, our predictive models for open circuit voltage in Opera were within 2% of measured data.

"We are now working with Cobham to build on these results by enhancing dynamic and transient modelling capabilities, which will enable us to take the next big step in accelerating our design analysis and optimisation."

Unlike conventional permanent magnet generators, the air-core stator in the BWP design does not use electrical steel laminations wound with conductors, and contains no ferromagnetic materials.

This breakthrough has several advantages, including eliminating iron losses associated with flux reversals in the stator and obviating the magnetic attraction between the generator's rotor and stator. Together these enable higher efficiencies and higher torque levels for a given mass of generator, says Sullivan.

According to Andris Cukurs, CEO of BWP: "Having proven the fundamental design approach for our generator and validated our design tools, we are now in the process of designing units to be incorporated in our clients' multi-megawatt wind turbine designs for prototype testing.

"We believe our technology will provide wind turbine manufacturers with the innovative design advantages they are looking for to better compete in the global wind market."

Brian Tinham

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