Cam: Wind power seems like the obvious choice on a boat designed to reap the wind. I'm a big fan myself, having lived the past four years solely by wind and solar power. But.... I can see why boaters would shy away from wind power, and I'd say it's dangerous to rely on wind power alone. Some reasons why I'd be leery:
1) Turbines need clean air to work well. Turbulence reduces output and destroys them mechanically. Winds aloft are much more powerful than those near decks. So the obvious place for a turbine is at the masthead. But even a small turbine weighs 30 lbs or so -- that's a lot of weight aloft.
2) A sailboat turbine needs to be small and lightweight. But small turbines produce very little energy -- output is roughly proportional to swept area, and a 4' diameter turbine like the AirX won't really produce more than 1 kWh per day. (I know AirX owners
living in a Class 6 wind area who got 0.75 kWh/day, on the odd occasion the things were working.) The manufacturer's claims of 400 peak watts should not be used in calculating daily or monthly power output. Since output~swept area=r^2, a turbune half as large can produce at most one quarter the power. Downsizing quickly renders them toys.
3) Additionally, a boat-sized turbine generally has a small 'can', or rotor-stator arrangement, usually employing permanent magnets and laminations. The power curve flattens very quickly. To compensate, such turbines use very light, sharply-tapered blades with high tip-speed ratios (up to 13.5 times windspeed.) These airfoils sacrifice solidity and have a very narrow window of efficiency. Wider, slower blades are better, but they require a much heftier alternator. Higher RPMs also = noise, vibration, and shorter life. Small alternators spun fast is a proven recipe for ruin.
4) Small turbines are prone to damage in sustained high winds when the coils melt. Also, when batteries are full, a turbine needs someplace to put the excess juice. Letting it freewheel is bad for the mechanics; ought to held under load at all times. Bigger turbys use variable blade pitch; not realistic on a thirty-pound unit. So some turn out of the wind and stall the blades; others use alternating braking. The first method (furling) causes hysteresis, noise, and ungodly fatigue on the mechanicals; the second method (shorting the leads) inevitably burns up the stator.
5) So it's not a question of IF your small turbine will fail, but WHEN. The likeliest answer is "100 miles from Antigua". They are brute simple to repair, but you had better carry a full turbine's worth of spare parts on your boat, doubling up on rectifiers, stators, and bearings. That money and weight would buy some nice PV panels.
6) A rapidly-spinning propeller near the deck of a heaving boat full of tired people and many ropes. Paging Isadora Duncan....
7) Some people would argue the above list recommends a Vertical Axis Wind Turbine, like the ten thousand variants on the Darrius or Savonius designs. But VAWTs are lousy for generating electricity
and always will be. Every two years, someone comes out with a better mousetrap that stands on its end and goes round and round; and every one turns out to be a flop. As sailors, people here can easily understand why (50% beam reach, 25% beating, 25% DDW). Japan, Germany, and GE have some really good engineers. They build and install three-bladed, horizontal-axis wind turbines. If there was a better way to catch mice, they would know -- and sell it.
Solar panels on a sailboat are problematic, but so are small wind turbines. Asking inherently underweight and overstressed machines to survive in a gyrating salt-water environment is a stiff request. I love windpower, but here's a few pix showing why I wouldn't favor it over solar:
Nine major failures in less than four years. And this is a robust 8.2' turbine, rather heftier than most boat-sized ones. (Tho if I was was buying one, it would be similar to the D400 or Rutland: stout little 5-bladed HAWTs. Sacrifice swept area for solidity.)
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... the boat is, well, another story...
