Re: Energy Ball - A Cheap And Efficient Wind Turbine
09/23/2008 3:27 PM
There is not enough information provided to make any conclusions on this. They provide no efficiency data; no size of ball plus wind speed provides x amount of power etc so that it can be compared with anything else. It looks interesting to say the least, but when they start making statements like the wind flow pattern it generates is the Venturi Effect and that is why it is so efficient, the little alarm bells in my head start going off and screaming "Scam!" They again provide no information, no documentation and don't even make an attempt to describe or diagram the wind flow pattern.
The Venturi Effect has to do with incompressible flow getting constricted. There are two ways of looking at it. When water flows through a pipe at some given pressure, for example, it moves at some prescribed velocity. When it encounters a restriction in the pipe, all of that mass of water must get past the restriction quickly enough that it doesn't hinder the flow in the pipe (flow must not be choked or this doesn't work). The fluid therefore, must move more quickly. This faster flow results in a pressure drop at the restriction. That is the Venturi Effect. The alternate view is that the pressure drops and the energy tied up in the pressure is converted to kinetic energy so the fluid flows faster. One can imagine for wind that wind hits two skyscrapers and then funnels through the narrow space between them. The air pressure is lower and wind speed higher between the buildings than it is on the upwind side of the two buildings.
It is not obvious how our little turbine ball is going to be restricting the size of the wind flow path in any real way to change its pressure and speed significantly. Obviously, however, our turbine designers are indeed claiming that they are producing a wind flow pattern that causes a constriction in the wind and therefore a significant pressure drop resulting in faster wind speed through the turbine. That seems like a bit of circular logic to me - we use the turbine to change the wind speed so it will spin the turbine faster so we can change the wind some more. If it really is the case, we could have a runaway process even with a light breeze.
I think at best they don't understand the Venturi Effect and at worst, they are using the term to scam people so they can sell more. That doesn't necessarily mean that if some of you guys buy them they won't work just fine, but my bets are they are no better than what is already out there and may be worse since you have to move so much more blade mass - all out at the farthest distance from the hub.