Which is not true in the venturi. I think we are in violent agreement here. To be clear: to sustain a case in which the wind speed doubles due to use of a venturi, power cannot increase as the cube of the wind velocity, because there will be a reduction in molecules of air with that velocity, such that energy is conserved. The power can not change, therefore something else has to change in the wind power equation. And that's the mass component of the kinetic energy. Conventionally, in the wind power equation it's stated as density, so I picked that one. Density has to vary in order to hold power constant while velocity changes. That's all I'm saying Russ, I'm only adding to your earlier remark, not detracting from it in any way. Again, to be clear, we are speaking of a turbine placed inside a venturi. As I gather from looking at the photo the cross section of the venturi is just large enough to accomodate the prop. Therefore, the swept area under consideration is exactly the same as the swept area of the free stream turbine. Got that, Russ. As you'll see from looking at their data, most of it is in the 2-4 mph range. No gripes there. I didn't mean to put you through the hoops. I was explaining that in the wind power calculation, the statement "power increases as the cube of velocity" is unconditionally true for the free stream case, but in the venturi, it is conditioned upon supplying a vacuum to account for the extra energy gained. The alternative, I said, (paraphrasing) was that power shall remain constant, hence the density of fast moving air (across the same area, the area swept by the prop) must drop to conserve energy. I think the only confusion here is that I did not draw a diagram, label it and make it clear where I was. I was inside the venturi at this juncture. Here is where the number of moles of air must drop by the inverse of the gain from velocity boost. I only brought up perpetual motion in reference to the erroneous interpretation of their results inferred by the statement "600% power gain". I merely said that to claim any increase in power (energy) without an external source is to claim a common mistake made by some of the craftier perpetual motion advocates: they destroy energy, which is harder for naive people to spot than the ones who claim to create it. Obviously they are the same thing. Here, and only in the mind of the erroneous thinker, they destroy the energy (pressure x volume = energy, ideally) at the backside by (in their mind) creating a vacuum which is not there. This vacuum unburdens the conservation of energy that reduced the number of moles in the venturi, and now they do actually (in their mind) achieve 600% power increase since the number of moles returns to the number of moles at ambient while the velocity nearly doubles (cube root of 6 is 1.82). All of this, I said, comes to a screeching halt when the naive person who thinks that (not me) is confronted with the backpressure at the tail pipe where we find no vacuum, no energy was destroyed after all, and hence the whole idea peters out. There never was any benefit to using a venturi. However, I did add that it probably improves efficiency a little by reducing turbulence. Other than that, it can't do what they said it does (run faster in the venturi, produce more watts than outside in the free stream.) Again, since I think we are in violent agreement, pictures may help. I am referring to the purported claim that the power increased inside the venturi. It did not, other than (1) some incidental improvement in efficiency, such as reducing turbulence at the prop, or (2) some accidental (not by design) vacuum at the tail pipe. Nor did they publish electrical power measurements. The closest we have to wind power measurements are the anemometers which (I think; it looks like it must be so) were plotted without the turbine installed. Therefore, the perpetual motion inferred by their numbers must be inferred only as a matter of erroneous interpretation, namely, if the reader erroneously assumes that the 9:7 velocity improvement in their published data (see their figure 3 below) produced an actual power gain (in this case closer to 2:1), then it would lead that erroneous person to conclude that the venturi is tantamount to, if not the actual implementation of, a perpetual motion machine (over unity). Of course I would turn them over to you so you could take them out to the woodshed. Please Register or Log in to view the hidden image! Sorry for all the confusion. In my mind I actually thought I said what I said clearly. Evidently not. As a hint, though, keep in mind that I'm aware you know what you're talking about, so my intent is to supplement, not contradict you. They actually said "600% power gain" which is where all this hooplah started. I have to admit I don't understand why you are speaking of the data differently than I interpret it. I'll repost it here for your convenience. Look again at the day of the anomaly, when they got the 9:7 velocity gain. If you wish, you can tell me whether you think I misunderstand what it says. That might clear up any lingering confusion, since I get the feeling you didn't look at this too closely (not sure; just seems that way). And to be clear I understand that this is a comparison of shaft encoder ticks converted to wind velocity. In the alternative, it might be voltage across a load, translated to velocity by some other fancy footwook. But it looks like raw data which is why I suspect it's an encoder. I'll admit I have no idea. Once someone tells me I'll be happy to adjust my thinking accordingly. Here you go. Once again: the data highly erratic, no clear conclusions can be drawn from it. And again: See figure 3, day 5. Then look at day 1, and the periods where it's a toss. Please Register or Log in to view the hidden image!