SBGK wrote: > Rather confused thinking there about extracting energy by making the > wind turbulent. Turbulence creates drag, the last thing the windmill > designers want. >
Of course turbulence creates drag - that's obvious. However the above statement shows a lack of understanding about the basics of thermodynamics. The above seems to ignore the fundamentals of energy extraction. I see a complete lack of appreciation of entropy and its role in energy conversion. > > They want laminar flow creating variations in pressure as it flows over > the blades, thus creating thrust which is translated to angular motion. > > Of course everybody wants laminar flow in their wind machines and other airfoils, but that ignores the global consequences of extracting energy from a flow of air. One might be naive and think that the only way to extract energy from a flow of air is to slow it down. However an improved understanding of thermodynamics tells us that the overall method is based on increasing entropy. Perhaps the obsession with laminar flow over the airfoil has led to a lack of realization that the air that has passed over the airfoil by any means becomes more turbulent downstream of the area of laminar flow. > > this Harvard study seems to suggest that the wind does slow down and may > affect regional weather. > > http://wattsupwiththat.com/2013/02/25/rethinking-wind-power-harvard-study-shows-it-to-be-overestimated/ > That is a very imaginative reading! Let's be clear - there is no free lunch, never well be and that is the gist of what the article says. However, there are no actual findings of significant climatic changes in that article. At the most they are suggested, but only vaguely so. Of course the changes have to exist, but what they are needs to be quantified. If there is actual quantification, are please quote it I'm not finding it. Merely finding a change or different is what Golden Ear merchandisers do. It's called "Raising a concern". It is often actually just FUD. The evils of high end audio are largely based on unquantified effects that are actually microscopic and irrelevant to reliably perceived sound quality. > > "Each wind turbine creates behind it a wind shadow in which the air > has been slowed down by drag on the turbines blades. The ideal wind > farm strikes a balance, packing as many turbines onto the land as > possible, while also spacing them enough to reduce the impact of these > wind shadows. But as wind farms grow larger, they start to interact, and > the regional-scale wind patterns matter more." That would appear to be innuendo and statement of truisms, not actual identification or quantification of actual effects. I have no doubt that there are wind shadows. The relevance of the issue is highly dependent on what they are, not that they exist at all. Calling people Confused when the only evidence at hand is based on speculation and innuendo of unquantified effects suggests things like poor critical thinking or a desire to extract an emotional toll for the purposes of personal satisfaction. ------------------------------------------------------------------------ arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=104207
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