Hello Adriaan,
I don't disagree with your comparison between blade pitch control and electrical modulation of the generator such as MPPT, but what I meant to compare was the clutch mechanism suggested in the OP with blade pitch control. Maybe I wasn't very clear about that so here is what I really mean: In a cost or complexity comparison between the 3 strategies, I would put pitch control in the middle between a clutch (more complex and expensive) and MPPT (cheapest and simplest). I should also note that reliability of the 3 strategies also follows the same trend. Expect a clutch to fail rather quickly on a wind turbine.
When I drive to work in the morning, I probably operate the clutch in my car about 100 times. Same on the way back home. I've had my car for 10 years, and replaced the clutch 3 times. I've put 300,000 km on it so let's say a clutch lasts 100,000 km on my car. Or I could say that a clutch lasts about 3 years. That's about 180,000 clutch operations before I have to replace it.
Put a clutch on a wind turbine, where it must close and release any time the wind passes through a given speed, and it will operate anywhere between 10 to 100 times in an hour. In a year that would be between 100,000 to 1 million operations. That clutch will probably fail in less than a year depending on the nature of the wind and the wind speed setting chosen for it to operate.
Sorry, Joe.
I can't get behind a clutch idea unless you have a variety that doesn't need friction. Actually, your idea is more like a sprag clutch, but I don't think they get more life, either. Also, a sprag fails abruptly, while a friction clutch fails progressively, getting slippy and noisy, which warns you of trouble before anything disastrous happens.