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Large Wind Turbines

May 23, 2009
Paul Gipe

Energy Ball--A Review

Energy Ball in a greenwashing application at the Southern California Edison training center in Rosemead, California, 2011.

I've been putting off writing anything about the "Energy Ball" simply because there are too many of these "inventions" for one person to track, analyze, and report on. Like many of these contraptions, and that's the best I can say about such devices, it's a distraction from more serious endeavors.

The Energy Ball is a novel 1.1 meter diameter wind turbine that sweeps 1 m2 of the wind stream. For those knowledgeable about wind energy that should tell you all you need to know. If you don't know why I say that then you need to do some homework. In short, there's not much there, there.

This is a micro wind turbine, equivalent to the Air Breeze, which also sweeps about 1 m2. At a standard power rating for small wind turbines of 200 W/m2, a turbine of this size should be "rated" at 200 watts.

The Energy Ball's promoters don't use exactly the same term as "rated power" used in the Anglophone world and this could be due to a poor translation of the original Dutch. The term used by the Dutch firm, "Measured Yield", is incorrect in English.

Energy Ball's promoters don't make any truly off-the-wall claim. The promoters say the Energy Ball has a "Measured Yield" of 100 W at 10 m/s. For a machine of this size that's a reasonable number. Of course, there's no documentation of this "measured yield".

The company's flyers do emphasize that the "turbine" will generate 500 kWh per year at wind speed of 25 km/h. That's equivalent to 7 m/s. The promoters hedge their claims sufficiently by noting that this yield is for atop a tower 12 meters high in an open area. This estimate is actually lower than claims for most other micro turbines in this size class, so it's entirely within reason.

Yet the company touts the turbine for rooftop applications. I don't know of any rooftops in the world where the measured wind speed is 7 m/s. Maybe there's a roof in Punta Arenas, Chile with that kind of wind speed, but there's unlikely one anywhere in the Netherlands where this turbine comes from.

Then the brochure goes on to make the claim that this wind turbine will "generate a significant amount of your home or small office's electrical needs". No way. For a typical northern European home 500 kWh/yr is only 1/6 of consumption and for a typical Canadian home that's only 5% of consumption. In neither case is that "significant".

Worse, experience to date is that the winds on rooftops are much lower than elsewhere. At an average wind speed of 5 m/s, the turbine is expected to produce only 200 kWh/yr. However, Eize de Vries, a Dutch authority on wind energy, says that it's unlikely that a rooftop wind turbine in the Netherlands will ever see such wind speeds. He suggest that it's more likely that the wind speed on a residential rooftop will average 2-3.5 m/s. At that average wind speed a turbine this size would be hard pressed to produce as much as 100 kWh/yr at best.

At the Delta test site in the Netherlands the Energy Ball generated only 21 kWh from April through September, 2008. This obviously included the windy months of April and May. Let's give it the benefit of the doubt. For this test site, on a tower not a rooftop, this turbine would likely only produce 100 kWh per year.

For the cost of the turbine tested by Delta, £3,400 (about $5,000 CAD) you'd be better off buying Southwest Windpower's Air Breeze. For $1,000 CAD you can buy the Air Breeze and add a modest tower for another $1,000 CAD and you're still at half the cost of the Energy Ball in the Dutch field tests.

As explained in my new book, Wind Energy Basics, the Dutch and the British have been plagued with inventions of this type. The reason for this is that both the Dutch and the British have no effective renewable energy policy and this results in inventors preying on the public's deep-seated desire to do something about climate change. The public wants to take action now and the only way for them to do so is to put a micro wind turbine on their roof or in their backyard.

Ian Woofenden, who gives workshops on how to best use small wind turbines, says "The urban resource is very poor, and where it may be OK on very tall buildings, the size of turbines you can install on these buildings will have a very small impact on the energy load." In other words, small rooftop wind turbines like the Energy Ball are a waste of time and money.


Will it do what it claims? Yes it may, but so what. It doesn't claim to do much, not much at all.

Is it a revolutionary new device? No. It doesn't do any more than other micro turbines.

Is it cheaper than other micro turbines? No. It's not cheaper by any significant amount. In fact, it appears more expensive.

Is there published data on its performance? There's some data, but it's of limited duration. See Dutch small wind turbine trial suffers low wind speeds.

What should it be used for? It would make a great lawn ornament or a conversation piece.

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