----- Original Message ----- From: "Lars Bloch Gravengaard" > > ----- Original Message ----- > From: "Peter" > >> >> But the most efficient turbine is the two-blade 'propeller' type, by >> far. >> > > Are you sure ? Why is that 'ALL' wind turbines is the 3 blade type ! > > Lars http://www.windpower.org/en/tour/design/concepts.htm "Two-bladed wind turbine designs have the advantage of saving the cost of one rotor blade and its weight, of course. However, they tend to have difficulty in penetrating the market, partly because they require higher rotational speed to yield the same energy output. This is a disadvantage both in regard to noise and visual intrusion. Lately, several traditional manufacturers of two-bladed machines have switched to three-bladed designs." "Yes, one-bladed wind turbines do exist, and indeed, they save the cost of another rotor blade! If anything can be built, engineers will do it. One-bladed wind turbines are not very widespread commercially, however, because the same problems that are mentioned under the two-bladed design apply to an even larger extent to one-bladed machines." The bedst :-) "The Danish Three-Bladed Concept Most modern wind turbines are three-bladed designs with the rotor position maintained upwind (on the windy side of the tower) using electrical motors in their yaw mechanism. This design is usually called the classical Danish concept , and tends to be a standard against which other concepts are evaluated. The vast majority of the turbines sold in world markets have this design." Lars -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist