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July 19, 2001
Geoff Henderson

Vortec closure no surprise


Comments on the Closure of Vortec by Geoff Henderson, Windflow Technology, Christchurch, New Zealand.

Auckland based R&D company, Vortec, which was trying to demonstrate an unorthodox windmill design, has closed its doors. After receiving some media inquiries for comments we (WindFlow)decided to issue the following media release. If you would like further background on this, we have correspondence on file since 1997 and earlier, which we would be happy to make available.


The announcement this week that Vortec is closing comes as no surprise to Windflow Technology chief executive, Geoff Henderson. Windflow Technology Ltd is raising $3 million to establish local manufacturing of its Windflow design.

New Zealand is recognised as one of the most suitable countries in the world for developing wind power from its large renewable wind resource. Wind is the natural complement to our existing hydro resource, which has again been put under great pressure this winter. As our gas resources are rapidly depleted, wind power is our largest and environmentally friendliest renewable solution to the constantly rising demand for electricity. Windflow is tackling that challenge with proven technology.

"The aim of wind turbine designers for many years has been to come up with ways of increasing turbine size without incurring major weight and cost penalties," Mr Henderson said. "The Windflow design is an example of such an approach and uses well proven technologies to do so."

"Vortec by contrast took a concept that had been known since the 1970's, was long ago abandoned by its US originators and was known to incur major weight and cost penalties. They haven't been able to achieve a feasible result."

The Windflow design is based on two technologies that reduce fatigue loads in wind turbines and provide a 30 50% reduction in turbine weight. Both of these technologies have been proven in projects led by Geoff Henderson in Britain. These involved full scale turbines (25 and 33 metre respectively) which have been running since 1988 and 1990. The design is an evolutionary, rather than a revolutionary, step from existing designs.

By contrast Vortec has been trying to demonstrate a radical wind turbine design called the diffuser augmented wind turbine (DAWT) since the mid 1990's. This involves building a shroud, or "diffuser", which is about twice the diameter of the turbine rotor. The diffuser surrounds the rotor and is a large structure that must be supported at rotor height and be able to be oriented to face the wind. It increases the wind speed through the turbine and thus "augments" the power output. The critical issue for the economics of the design is how much augmentation is achieved.

Vortec's 1997 prospectus claimed that US wind tunnel tests on a 0.5 metre model had achieved an augmentation of 5.5. It implied that higher augmentation was achievable, and stated that a minimum of 4 would be required for the concept to be viable. The design of its 7 metre prototype at Waikaretu, south of Auckland, was based on an augmentation of about 9.

Published test data by Vortec since 1997 has shown that only 2.4 was achieved.

"Conventional fluid mechanics suggests that 4 is the theoretical limit, but even if it had achieved an augmentation of 9, it is doubtful whether the concept would be viable", said Mr Henderson. "The diffuser itself is such a large, heavy structure that the economics were always questionable. And the yaw system to orient the diffuser becomes a nightmare to design. The pay off might have been there if very high augmentation factors could be achieved. They weren't, so the venture has apparently been unsuccessful."

Windflow Technology Ltd has recently re opened its initial share offering. The technologies underlying the Windflow design are conventional, and have been used at full scale in wind turbines in Britain since 1988 and 1990.

 

Further information: www.windflow.co.nz


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