Hi DaveS,

You said about the Sharp Intermeshing VAWT concept:

"It seems as if the intermeshed VAWT pair depicted has the same overall solidity, rather than a true doubling of downwind solidity."

Nonsense. You are measuring the solidity ratio of the intermeshing middle section incorrectly. State your method and your calculations.

The solidity ratio of the intermeshing middle section is the sum of the separate solidity ratios. So if the separate rotors have a solidity ratio of 0.2, the intermeshing middle section will have a solidity ratio of 0.2 plus 0.2 equals 0.4.

The optimum solidity ratio of the original two rotors might be more like 0.15 so as to insure that the operating tip speed ratio of the Intermeshing VAWT stayed above 3.0.

" In any case, no VAWT blade aligned in upwind or downwind phases is helping, but adding drag."

Nonsense. “Phase” in this context refers to 180 azimuth angle degrees of blade travel, either to windward or to leeward. Lift-type VAWT blades, due to their circular orbit, are always traveling either to windward or to leeward -- except for the very brief transition points at the most-upwind and most-downwind points. So your statement claims that no lift-type VAWT blades can convert any energy -- except at the two very brief points where the blades are moving directly across the wind. But obviously, they do.

When VAWT blades are briefly heading directly upwind or downwind, they do create only drag and no lift. That is obvious. But the losses due to that drag are typically small for a well-designed VAWT with good streamlining. Consider this analogous flawed-argument: The solidity ratio of the HAWT blades near the hub is typically far too low to be efficient, so HAWT are inefficient. The premise is true, but the conclusion is not. That is because the losses near the hub are minor as compared to the major gains near the blade tips, due to the very large difference in swept area. You are incorrectly assuming that a minor disadvantage of VAWT is a major disadvantage of VAWT.

"Differing predictions that this is the "most efficient wind turbine" or that a parasitic VAWT drag factor reduces power-to-weight, compared to a HAWT rotor, awaits testing."

Nonsense. There are no “differing predictions”. If you insist that there are, then identify them and cite your references. As yet, there is only my prediction. If you wish to present a differing prediction for a Sharp Intermeshing VAWT, then please do so, along with your supporting reasoning and calculations.

Your statement is based on an illogical argument, which is this: Because most VAWT have more sources of drag than HAWT, and that because most VAWT rotors weigh more than most HAWT rotors, therefore VAWT cannot achieve a higher coefficient of performance than HAWT. That is like saying that because women are, on average, smaller and slower than men; therefore women are not able to bear children better than men. Women have characteristics that men do not have. VAWT have characteristics that HAWT do not have. Your false conclusion does not follow from your true premises. The VAWT disadvantages simply do not preclude VAWT from converting more energy than HAWT. If you insist that they do, then please present your reasoning in detail and cite your evidence.

New VAWT advantages continue to emerge. Intermeshing may be a new one. Those VAWT advantages can be translated into higher performance than HAWT. That is in spite of the disadvantages that most VAWT have. The advantages that VAWT have over HAWT could be stated negatively as the inherent disadvantages, faults, or limitations of HAWT. There are many. Can you list them? If not, then that would suggest that you have not evaluated the differences between VAWT and HAWT impartially.

You call for the testing of my theoretical prediction. But that is what theoretical predictions are for…!? So your recommendation is redundant. That is like telling someone who has written a shopping list that they should go to the store.

I have noticed that you immediately call for testing concepts or devices I present when you don’t understand them. But if you don’t understand what is being tested, you won’t be able to interpret the test results. For example, assume two Sharp VAWT (Cp = 0.45) are combined to create an Intermeshing VAWT with a predicted Cp of 0.60. Testing determines that the Cp is 0.50. Is my hypothesis supported, unsupported, or indeterminate? Explain your decision.

Your immediate call for testing implies that you assume that theory has little value until tested. Theory and testing are two sides of the same inseparable, scientific coin. Both are equally valuable and mutually indispensable. Without theory (specifically, an hypothesis, which is a prediction based on a theory), there is nothing to test. Theories also serve to provoke refinements or replacements of themselves. In other words, they raise new questions and possibilities, and they encourage skepticism about existing assumptions. In science, that is valuable, even without testing.

Most likely, the next step in evaluating an Intermeshing VAWT would be to run a simulation using intermeshing fixed-blade VAWT for simplicity. That is because Sharp VAWT are extremely difficult, and extremely expensive, to simulate due to their passive pitching. Then a wind tunnel test using fixed-blade VAWT models could be done to confirm the simulation if it produced sufficiently positive results. However, the extra width of an Intermeshing VAWT might preclude wind tunnel testing due to anticipated blockage effects. Testing wind turbines can be a lot more difficult than most people realize. And it can be quite expensive. Even simulations can be quite expensive. So going directly from theory to physical testing is seldom a practical strategy. In other words, to immediately call for (physical) testing is usually naive. And to call for testing before even understanding the theory to be tested is nonsensical.

PeterS