Invelox wind turbine, does it work?
The Invelox wind turbine on the roof looks like a Vuvuzela, popular and hated at the World Cup in South Africa in 2010.
Michael Dubelaar hopes that it will be an alternative to the classical wind turbines. Recently, NedPowerSWH has installed a prototype.
The Invelox (INcreased VELOcity) was invented by the American Daryoush Allaei and his company SheerWind. The funnel has been built for the Venturi effect: constrictions in the flow passage should accelerate the wind.
The Invelox – 21 meters long, an intake of 4.5 meters and an output of 7 meters – should yield 600 to 800,000 kWh per year. Enough power to supply 200 households. NedPowerSWH bought a license from the Americans. According to project leader Dubeling, it will be the first roof installation in the world. A little ‘brother’ has been installed in Polynesia. And two ground installations are under construction in the US and China.
Does the Venturi effect work out well?
The Strata tower in London is the first skyscraper with three wind turbines expected to generate 8 percent of the power needed for the 147 meter high tower.
The aerodynamic shape of the walls should make the turbines extra efficient. But the rotors hardly ever run. And if they do it, the residents on the top floors are complaining about the noise.
“A failed prestige project”, professor Bert Blocken, aerodynamica expert at the University Eindhoven judges. “Because of the hyped stories, many investors aren’t fond of wind power in the city. It leads to cynicism: You see, it does not work.”
The Bahrain World Trade Center – two sail-shaped towers of 240 meters high with three turbines in between – are generating 1.1 gigawatt hours per year. And it could have been even better.
If the turbines had been placed exactly opposite, the yield of the turbines had been nearly 15 % higher. And if the turbines were placed further back, even 31 percent.
Blocken: But that part was counterintuitive because engineers were thinking they had to funnel the wind in a V-shape.
The Invelox in the Netherlands is not ready to generate green power. At this time, the wind speed is measured with sensors. In April, three generators will be placed in the narrowest part of the funnel: the place where the wind blows six times as hard, according to inventor Daryoush Allaei.
“If this will be four or five times, it is still interesting,” says project leader Dubelaar. He admits inventor Allaei has no practical data.
We will find out. The municipality is interested because they do not want any more classic wind turbines.
Will the Invelox succeed? Harry Hoeijmakers, emeritus professor of engineering fluid mechanics at the University Twente reacts:
Theoretically it is possible, but I don’t think so. If the wind flow isn’t guided, you even accelerate less speed than placing a rotor in the wind. A wind acceleration of six times, seems an awful lot.”
The problem: the Venturi effect will work in closed systems such as paint spray and water jet pumps, but not in the open air. The wind always will choose the path of least resistance.
Bert Blocken: “In 2006 there have been scientific debates wether the Venturi effect also works in the atmosphere. The conclusion was: No.
Still Dubelaar remains optimistic. “It’s an experiment, it can fail but our investors want to take the risk.” That investor is Reikon Management, a company with a biblical vision. A sympathetic approach, Bert Blocken admits.
“Remember: the wind turbines as we know them now, have been developed in decades. That also was trial and error.”
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