What is a venturi wind turbine?
A venturi wind turbine is a wind turbine in which the wind first passes through a funnel or constriction, so the wind speed at the rotor increases. It is also called a shrouded or ducted turbine, or a DAWT (diffuser augmented wind turbine). In Dutch it is a ‘venturi-windmolen’. Turbines with a wing-shaped shroud or rim around the rotor go by the same name, although they have little to do with a true venturi.
How it works
Because the rotor sits in the constriction, the blades can be smaller, and several small turbines can be placed one behind the other. The funnel turns into the wind on a rotating platform. Claimed benefits include a lower cut-in wind speed, blades enclosed by the shroud (safer for birds and people) and possibly less noise. One known design with a wing-shaped rim, the Donqi, is no longer available.
An honest assessment
- Little real-world evidence: according to the Dutch reference site joostdevree.nl there are hardly any built examples, and it is unknown whether the principle beats a few separate small turbines. A study of a venturi turbine on a hotel roof found an unfavourable ratio of yield to investment.
- Buildings are a poor wind site: buildings slow the wind and make it turbulent. In a large UK field trial (Energy Saving Trust, 2009), no building-mounted small turbine at an urban or suburban site generated more than 200 kWh a year.
- Structure and nuisance: the high air speed in the constriction puts heavy loads on the structure, and on a building you must allow for noise and vibration.
Tips
- Ask for measured output at a comparable site, not calculated figures at ideal wind speeds.
- Compare the cost with solar panels on the same roof.
- Check planning rules with your local authority before installing any turbine.
Related terms
- Windmill
- Photovoltaic
- Sustainable construction
- Noise nuisance
- Construction vibration
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