AWES materials

This topic is about what is satisfactory and what can be improved in AWES components such like fabrics and rigid materials for the wings or the blades, ground stations, generators, anchors, tethers, and so on.

Below are some topics or comments concerning some aspects of materials:

There’s a long history of people trying aluminum blades on wind turbines, going way back to the early days when people “assumed” aerospace companies were the natural best fit to develop utility-scale wind turbines. I believe it was Boeing that built an early large turbine like an airliner. I think it did not last too long. The reasons why fiberglass composites are used instead of aluminum include weight, metal fatigue (cracking over time), and the fact that when bent, metal can take a permanent “set” (bend), whereas composites “bounce back” or break fibers. The broken fibers and slow decomposition and adhesion breakdown of the resin matrix and the fiber reinforcement are why wind turbine blades still have a finite life and must eventually be replaced. Most people have no idea of the level of torture wind turbine blades undergo during their service life. I would still not rule out aluminum for various roles in turbine blades, but so far it has never worked out. I even remember one small turbine company from Canada that utilized extruded aluminum blades. Met them at an AWEA-sponsored “Windpower” trade show. A Dad and son team. I thought it might work out, but even if someone has a good (survivable) product, which almost never happens, business execution may be lacking. And of course, due to the cubic power in the wind, overspeed controil is usually lacking in any new product. What looks foolproof on the trade-show floor, typically melts its generator or otherwise self-destructs in the first good storm.

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I glanced at a discussion about aluminum autogiro rotors. 2000 to 3000 h, that is about 3 to 4 months (it is very little for a wind turbine use!), while “Composite rotors could be good forever or for any of those numbers.”

Concerning a crosswind AWES rigid kite, a question is if it works like a plane or rather like a wind turbine. Intuitively I will go for the latter, given the forces transmitted by the tether and the attachment of the bridle on the wing. This leads to a possible preference for composite materials rather than aluminum which would risk working too much under such constraints.