The New Zealand promoter of a "diffuser augmented" wind turbine design being marketed under the name Vortec has still to prove that its "technology indeed works and that it has not given birth to a white elephant," reports WindStats Newsletter, a sister publication to Windpower Monthly. In an article describing the development history of the turbine concept and its technical advantages and drawbacks, WindStats points out that experiments with a 1 MW prototype, the Vortec 7, were apparently inconclusive. "Claims of a six to eight fold increase in energy yield compared to conventional free flow horizontal axis wind turbines with the same rotor size never materialised," writes author Eize de Vries. The theory behind diffuser technology is that the diffuser creates a sub-atmospheric pressure which draws more air through the blades and thus generates more power than a conventional turbine with the same blade diameter. Vortec promises it can thus provide a 20% reduction in wind energy generating costs. Despite not having yet provided detailed data to prove that the theory works in practice, Vortec Energy has "daring plans to launch a 1 MW machine, followed by its 3.5 MW turbine, and only limited field references with a much smaller prototype to go by," says WindStats. In doing so, "Vortec is taking considerable risks."
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Senior Renewable Energy Analyst (WindGEMINI Product Lead) DNV GL Bristol (City Centre), City of Bristol