I guess the Savonius type is too easy for me - I like a challenge! As for efficiency, I don't have that much wind, but probably enough... but for me efficiency isn't about getting something for nothing (so who cares about efficiency, right?) it's about getting as much as I can from the smallest possible machine. In any case a Darrieus will be far better than a Savonius in this respect, at least as far as I can glean from the literature so far.
I agree about the centrifugal forces - that's why I assume my blades have to be built light, but I think I can handle that.[ Parent ]
But is a six foot hunk of wood flying at maybe three hundred miles per hour when your mill comes apart in a 50 MPH wind one of the things you want to get from it?
A Sandia Savonius can get about 2/3 of the energy there is to get from the wind. So if it's half-again as big as your Darrieus it will beat it. In that same 50 MPH wind the outer edge will be going only about 40 MPH - and the mill will be MUCH stronger.
If you have a severe limit on the size of your mill it means you can't site it 'way over THERE, where the flying pieces probably won't make it through your window and easy chair. So I'd strongly suggest you accept the size penalty and build a Savonius. A Darrieus needs a BIG no-man's-land to be safe.
Of course if you have 80 acres or so, and want to play with the Darrieus design for the geek value, go for it! B-)[ Parent ]
Well... no ;-) but is that figure of three hundred realistic, or plucked out of thin air (pun intended)? This is the sort of thing I want to know - how do I calculate the actual turbine speed from aerofoil data and other parameters? If I can calculate the approximate RPM, I can work on how beefy the thing needs to be built. Also, arranging a brake to avoid overspeeding/overstressing should be easy enough.
Of course if you have 80 acres or so
Well, I have 8... and a good third of it is one big clear area which apart from a few cows is unused. It's hard to imagine that even the most catastrophic failure would really be all that bad (as long as no-one is too close at the time). Ever seen a caravan overturn? That's how I sort of imagine it - vapourising into matchwood.... Of course I hope it doesn't come to that.[ Parent ]
