The Difference Between Solar and Wind

Wind turbine supplies AC output which must first be rectified to DC, where a solar panel already produces DC. This is sometimes true, but the phrase, "charge controller," is the key. Most commercially available wind turbines for home use do produce unregulated AC power, meaning the frequency changes with the speed of the rotor. This does have to be rectified to DC, but the charge controller has nothing to do with this. Most wind turbines have a rectifier bank either in their control box that comes with the turbine, or in the turbine unit itself. The TESUP London 2kW is a good example of this, it is rectified to DC in the tower unit, then is fed to the battery bank without any "charge controlling." You can add a controller if you want to protect your batteries from overcharging.

A solar charge controller works by disconnecting the power from the panels to the battery when the battery voltage reaches a point that indicates they are fully charged. Some do this second to second, others on a longer time schedule. A wind turbine charge controller works by taking battery power from the batteries and feeding it into a "dump controller" when the battery voltage begins to get too high. Once the dump load is running, the battery voltage comes down slightly, and the controller turns the dump load off again. This cycling will continue as long as necessary to protect the batteries from reaching too high a voltage. The rectifying of the turbines AC power to DC is done first before the dump controller even sees it.

The weblink that Ji listed is a good example of this, take a look at all of the various models of wind controllers, each lists which dump load comes with it. Now look at solar controllers at the same web page, you won't see any dump loads included or even mentioned, that is the primary difference between the two.

The reason for this is simple. You can simply switch off the circuit between a solar panel and the battery without any problem, the panel simply backs up to its open circuit voltage and no electricity flows until the controller turns back on again. In a wind turbine, the torque the turbine is generating has to go somplace all the time. Switching off the feed from the turbine to the battery would be like opening the throttle on your car all the way while you are in nuetral, the engine would overspeed in seconds and be destroyed. A wind turbine would do the same thing, so a dump load is used to dispose of the unwanted electricity. The turbine has no idea where the power is going, it is just producing it all the time when the wind is blowing.