F’ing Windmills
It is good to see FRIAMers enthusiastically holding forth on another area of their whimsy – the effectiveness of wind turbine arrays. Wind Energy can provide a significant contribution to our energy supply. Understanding it helps. Commenters might be interested in the first seminal paper, Energy Effectiveness of Arrays of Wind Energy Collection Systems, (1976), by a clown, name of Lissaman. This paper has been referenced and improved upon many times in the last 30 years. The most recent revision, by the same author, appears in the book, Wind Turbine Technology, published by NASA, and reprinted by ASME in 2009. It’s ancient, but the principles, and our planetary boundary layer have not changed. The article in Science Magazine is an example of bad science reporting, illustrating the red neck passion to simplify subtle issues into easily understandable syllogisms (see contemporary Republican politics). The reporter discusses “new” vertical axis machines! The Darrieus Vertical Axis Wind Turbine was new in 1971, while the Savonius VAWT goes back to 1931. So much for the writer’s research! That history is in most encyclopedias. In 1976, I gave a paper at the International Wind Energy Congress in Cambridge , England , funded by US DOE, noting that the then new VAWTs were not cost effective compared with the propeller type. I think that’s still true. The FRIAM response seems a little like superficial science; thinking things that “look like” or “sound like” something are that thing. An intelligent, but untutored, opinion may be interesting in philosophy, it usually isn’t in science. FRIAM is supposed to be a place where knowledgeable folks can share it. For those interested: On complex terrain there are locations that have strong flows. This is a function of topography and wind direction. One would like to install Wind Energy Collection Systems at these locations. Usually space is limited, so some WECS units will be in wind shadows, sometimes. The array can be designed to maximize the annual energy capture. This requires annual detailed wind records, a model to compute the flow over complex terrain and a turbine model describing the turbulent wake and its dissipation -- indeed a complicated process well suited to modern computers, and dependent still on poorly known fluid physics, especially atmospheric turbulence. The economic trade enters next, where costs are reconciled with the reduced revenue of units in dense arrays. From hence cometh the most effective array – not always the max. capture case. And, because costs are time variant, different each year! The ideas are simple, the execution exceeding tiresome! In the dark ages of wind energy, with funding from SBIR and DOE, Lissaman and Quinlan developed, and AeroVironment marketed, a software model, AVENU, by which one could take a contour map of a site, define a wind speed and direction, place multiple turbines on it and compute the total energy capture, including interference. One could then drag the turbines to putatively better locations, and observe the effect. Easy on a computer, not so in the cruel world! I always thought that the verb “drag” was especially vivid here, having actually, with a cursing crew, moved 30-ton turbines by dragging them from one piece of California low desert to another. We sold the software here and abroad for $25,000 a crack, including a free Mac II, since our European customers were PC operators. It was not a successful product financially, but has been used extensively in array design for the last 30 years. I have not read my friend John Dabiri’s Caltech report, but have put in a call to chat to him. I taught wind turbine stuff at Caltech to grad classes when John was in grade school, and expect that his will be an excellent contribution. I will report on same to FRIAM when I have studied the paper itself. My title, “f’ing”, referred to “flocking”, certainly a very interesting phenomenon, as is the other possible adjective. One can achieve favorable array interference in water, air or on land. I have made technical contributions to all: wet, dry and dirty flocking. The conclusions are sometimes surprising. For example, in a Vee formation of migrating geese the leader, at the tip of the Vee, experiences the most favorable interference. It’s nothing like “breaking the trail”, the magical anthropomorphical explanation! Since I published this in 1970, folks have asked why the strongest Alpha animal would take the easiest position. My reply is, “They ain’t Boy Scouts! If you were the strongest member of the team, wouldn’t you take the easiest job?” I would, and do, as does every FRIAMer who employs a gardener! Peter Lissaman, Da Vinci Ventures Expertise is not knowing everything, but knowing what to look for. 1454 Miracerros Loop South, Santa Fe, New Mexico 87505,USA tel:(505)983-7728
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