“uåX˜äŠÊ˜·³Ç

A prototype vertical axis wind turbine (VAWT) named the Turby designed for mounting on the roofs of buildings over 20 metres high is due for installation this month in the Netherlands. The unit has already shown promising results in wind tunnel tests at the Technical University Delft, reports its creator, Dik Sidley of Dutch energy consultancy and development concern Core-International. Further testing will now continue with a prototype Turby in the university's wind turbine test area.

The 2.5 kW Darrieus-rotor design Turby is intended for operation in the strategically important built-up environment, says its inventor. If the Turby can overcome noise and vibration problems which affected earlier models, Sidley believes his invention can tap a vast potential market.

Early tests in the wind tunnel are encouraging, he says, especially on noise. "So far they've shown that at a wind speed of 10 m/s we're just over 70 dB(a), which means that it will not be noticeable at a distance of 15 to 20 metres. Plus all the indications are that it is vibration free, with virtually no peaks."

Control problems -- also a feature of earlier VAWTs -- will be solved through a signal from the converter which is positive when everything is in order, but can cut out the generator in the event of problems. "The rotor will keep turning," says Sidley. "For those who want it we can also supply a mechanical braking system but we'd rather not."

The model, due to be installed at the TU Delft on February 25, will be a production standard turbine, "although the electronics will be a bit laboratory-ish," says Sidley. "If that goes well, 20 prototypes will be built and installed throughout the Netherlands. If they do as well as expected, we are looking to start full scale commercial production next year."

The Turby, which has a nominal output of 1.2-2 kW at 5 m/s, is estimated to produce some 3000 -- 5000 kWh a year. Mounted on a ten metre mast and requiring no lifting machinery, installation is simple and the unit is intended for private energy generation rather than grid supply. The prototype cost NLG 25,000 to develop and the estimated price for production models is NLG 15,000. "This means the turbine would be paid off in ten years, making it considerably cheaper than solar panels," says Sidley. Although not suited to every roof top -- some 25 % of Dutch buildings, or 100,000 rooftops, are higher than 20 metres -- its price at least puts it in reach of every householder, believes its inventor. Read more about urban turbines in “uåX˜äŠÊ˜·³Ç's sister publication, WindStats Newsletter.