> I've been expending a little mental energy on permanent magnet alternator= s > for "a while now". As have I. > Obvious problem is no inherent method of regulation, i.e. > output entirely dependent on shaft speed and load. > > Commonly found on motorcycles. Typical regulator circuit is (functionally= , > at least) a massive zener diode clamping at battery float charge voltage.= OK > ish for most engine based applications (lots of power to spare), not > acceptable for small, low-power, high efficiency applications. If you can tolerate the voltage you can let the bus float to whatever it wants and buck regulate it to desired output. Efficiency can be excellent. At light loads conversion efficiency is unimportant from an energy use point of view. When loaded heavily it approaches the loaded design value. Unless you boost, design Vout needs to be greater than system voltage - usually a battery - at all wind speeds where power is required. Otherwise a system which has say 10% Voltage headroom at 10 m/s may have -45% headroom (eg no charge) at 5 m/s. Simplistic systems use star delta switches and direct battery connection apart from a "switch" so that Vout is boosted at low speed (Star) and lowered above a certain point (Delta). Joe will tell you what fun these can be. As the need to dump energy or limit energy used usually occurs at high wind speeds you can consider PWM shorting the alternator. This produces variable braking and both partially removes V_alternator from adding to Vout and limits power by braking. If you are relying on shorting to keep WT speed down to prevent cubed law runaway you want to start "early enough". Above a certain speed short circuited braking energy does not match V^3 wind input and the gates of hell (nor Microsoft) shall generally prevail against attempts to prevent self destruction. Very low power systems can be over-engineered to TRY to survive serious overspeeding but the cbe law means that real world products usually need some other mechanism. This can be eg tilt back, tilt sideways, feathering, blade stalling, winch it down when a storm's coming, etc. Blade stalling is a good trick if you can manage it and an even better one if you can guarantee it come what may. The default speed regulation mechanism is fly-apart, which come in many interesting forms. MPPT Maximum Power Point Tracking) can be used with WTs with variable success. More challenging than solar due to, again, the cube law with Velocity energy input, the lack of a known energy level (unlike solar) and the addition of extra factors - eg solar has cloud pattern changes etc but HAWT (Horizontal Axis Wind Turbine) has slewing response, rotor inertia and energy storage, > Seems there would be a useful crossover from solar PV panel tech here. > Adding some variation of the Maximum Power Point controller could > improve efficiency markedly and allow useful generation over a much broad= er > range of wind conditions. Crystal ball lookahead helps in gusty conditions (especially with HAWT). Some have been known to use a ring of "incoming sensors". Sounds bizarre but makes sense as they get bigger. VAWT(Vertical Axis .....) regulation is often by wing stalling , or claimed to be (and you'd better hope so if you don't want to have to wonder where your blades have gone). Lift style VAWTs have most of the problems of prop-HAWTS and as an eg Darrieus VAWT can be designed to run at a TSR of up to about 5:1 they can get very exciting above max design wind speed. Power at wind speeds much below design for a site is low to very low and largely not worth putting much $ effort into. eg a 10 kW at 10 m/s system makes about 1.25 kW at 5 m/s (12%) and under 300 Watts (3%) at 3 m/s. At 1 m/s it would notionally make about 10 Watts but is unlikelt to turn and even less likely to start. Real people choose real sites* with a Weibull distribution that allows closish to design power a lot of the time and fewish periods with very low power. Sites with broad flat Weibull distributions make getting consistently good power out and not failing to fall down both hard. * Real sites are generally as high as possible, away from anything of similar height and thus well away from turbulent flow, not mounted on anything where acoustic coupling is liable to lead to midnight axe attack. Entrepreneurs, investors, starry eyed idealists and people who don't know how to use Gargoyle keep rediscovering VAWTs as the answer to everything. They proclaim their ability to work in low height turbulent urban locations, on roof lines, in courtyards and more. raise money, have fun and largely fade gently from the scene. Some people build real world VAWTS, charge really really really high prices for them and stay in business. Helix seem to have survived longer and done better than many. AFAICT, http://www.helixwind.com/en/S594.php The many http://www.google.co.nz/search?tbm=3Disch&hl=3Den&source=3Dhp&biw=3D1920= &bih=3D1042&q=3Dvawt&gbv=3D2&oq=3Dvawt&aq=3Df&aqi=3Dg10&aql=3Dundefined&gs_= sm=3De&gs_upl=3D3009l3718l0l4l4l0l0l0l0l575l575l5-1l1 Wow http://www.wrapwind.com/download/ Yee Ha http://www.alibaba.com/countrysearch/CN/vawt-10kw.html .... where vibration ... http://www.alibaba.com/product-gs/381872267/Small_vertical_wind_ge= nerator_VAWT.html Wow. Silly , but wow. http://www.fieldlines.com/board/index.php/topic,140042.html R --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .