With all the emphasis on how important wind power is to the future of energy supply, it is surprising to me that we haven’t seen a variety of dedicated generator designs. There are a few, but only a few. Maybe this is because the magnetics of generator design are not a popular topic in engineering schools. It is difficult to find a physics professor who is knowledgeable on this subject.
Consider the basic operating requirements. Horizontal wind rotors turn at low speed, typically between 7 and 23 RPM. Very low speed for an electric motor or generator when the industry norm is 1200 to 1800 rpm.
Basically the wind industry has attempted to take existing motor designs at 500kW and above and make them work, even though wind power is not what those machines were designed to do. Using an “off the shelf” generator would make sense during early prototyping to avoid the expense of producing a new generator design. But where there is ongoing manufacturing, GE claims to have 16,500 turbines installed, the investment would be justified.
The power electronics guys are having to deal with the exact same problem when it comes to making inverters for the wind industry. Turning dc power into 60 cycle ac power is not news, but having wildly varying input power changes the solution dramatically. There are dozens of suppliers in the solar market with inverters 500kW and up to 2MW who have successful solved this problem for their markets.
To come up with a unique wind generator requires a clean sheet of paper. Just as Tesla insisted on it’s own custom motor with copper bars to increase driving range, the solution to a generator for the wind industry is starting from scratch and focusing on the needs of the application.
Boulder Wind has a large diameter circumferential generator so it can be directly driven by the propeller blades of a standard horizontal wind turbine. The design is high pole count so that it runs efficiently at low speed. The new unit is already showing increased efficiency in early testing and should be deployed in wind turbines by 2017.
General Electric has been demonstrating a 4MW PM direct drive wind turbine and planning a 10MW superconducting generator for the wind industry. Among the earliest and most innovative designs for onshore and offshore application, these systems eliminate the gearbox cost, weight and inertia making direct drive a significant improvement in wind power.
These improvements are all the result of the same thing; Motor Centric Design, examining the application of a motor or generator and looking for optimized solutions. Without this kind of starting point it is hard to image that wind power will ever become profitable.
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