water heater powered directly from wind turbine

[sunbelt56]

I was reading a thread from physicsforum: (heating-water-with-a-wind-turbine)
because I was thinking what would be a quick and dirty way to test the output of a wind turbine. You would have to either have 3 separate water heaters or one with 3 elements. Or, just buy 3 heater elements and mount them so that they could be immersed in a 55 gal drum with some kind of overflow and circulate the water with a pump. Of course, I'd have to have fuses and possibly a 3 phase contactor to divert the power to a cc/inverter if the water got too hot. The elements  wouldn't care about the phase, just as long as volts and amps aren't exceeded.

[OperaHouse]

What you want to use is a shunt regulator which allows the gen to spin up to a speed at which it starts to provide useful power.  A proportional shunt regulator will draw only enough current to keep it spinning at a useful speed.  Something like a GHURD controller.  I do a similar thing with solar. panel voltage rises when the charge controller demand lowers.  The excess I send off to heat water.  You don't necessarily need 3 elements if the power is rectified.

[Adriaan Kragten]

The disadvantage of dissipating the generated power of a wind turbine generator directly in resistors is that the power absorbed by the resistors increases quadratic to the voltage. As the voltage increases linear to the rotational speed, the power increases quadratic to the rotational speed. However, the maximum power generated by a wind turbine increases to the cube of the rotational speed. This means that if the resistance is chosen such that the matching is good at a moderate wind speed, the rotor will be loaded too strongly at low wind speeds and so the load will brake down the rotor to almost stand still at low wind speeds. So you need an electronic device which changes the load such that the load resistance is high at a low rpm and that the load resistance is reduced at increasing rpm.

If the wind turbine is normally used to charge a battery, the charging voltage is increasing only a little at increasing power. However one needs a battery charge controller to prevent that a full battery is overloaded. On my website there is a manual of a 27.6 V, 200 W battery charge controller at the bottom of the menu KD-reports. The power is dissipated in two resistors and one power transistor. This battery charge controller can also be used without a battery and then it keeps the voltage at the adjusted constant voltage. So this is a device which can also be used to test a wind turbine without a battery. However, a constant voltage load has only a limited rpm range for which the matching in between rotor and generator is acceptable. At low wind speeds, the generated voltage is too low and the rotor will run unloaded.