Doubts about an unusual approach to turbine design have been proven right with the demise of Vortec Energy, launched in 1994 with strong hopes for its diffuser augmented wind turbine (DAWT) design. Strong financial interest raised NZ$25 million ($10.3 million) and there was talk of listings in the US and Europe alongside licensing deals in Australia and Spain. But the New Zealand company has admitted to shareholders that its technology is not commercially viable and Vortec Energy is being wound up. Geoff Henderson of the New Zealand Wind Energy Association is not surprised. "Vortec took a concept that had been known since the 1970s, was long ago abandoned by its US originators and was known to incur major weight and cost penalties," he comments. The critical economic issue is how much augmentation is achievable. A 7-metre Vortec prototype was based on achieving an augmentation of about nine, but a value of 2.4 was achieved. "Conventional fluid mechanics suggests that four is the theoretical limit, but even if it had achieved an augmentation of nine, it is doubtful whether the concept would be viable," says Henderson. "The diffuser itself is such a large, heavy structure that the economics were always questionable." Serious concerns had also been raised internally by an independent consultant, Jens Mueller, appointed by Vortec in June. There are hopes that the intellectual property can be sold to a new company with shares offered to existing Vortec Energy shareholders on a pro rata basis.