If these blades are indestructible why do they need to even be replaced?
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Fatigue is the reason they need to be replaced on a regular basis..... and I suspect these bigger ones will have a need to be replaced on an even more frequent basis.
Offshore IWTs also have another problem... the experience with the offshore UK ones is that the blades have much higher erosion rates because of water droplets hitting the blades. I have looked at one application there in particular where they have gone to a much larger size... the blade erosion was so bad that the blades were done in just a bit over a year.
The ends of these blades move in incredible speeds.
If they hit anything, even rain droplets, it makes damage.
After a while, they are all chewed up.
Just like the farce of subsidized coal bed methane, there was absolutely no payout without subsidy, the insiders know the cold truth but will accept the technical challenge for what it is an make a living off the effective dole as long as they can.
The only coal bed methane that actually made a little money was either not really coal bed methane, San Juan Basin, or was an anomaly, Cedar Grove high pressure coal near Tuscaloosa. All the rest was just wishful or living on the dole.