The Windmax MPPT controllers are modular, built from 500W units, with capacity up to 2.5kW. These controllers have built-in protection against over-voltage when the battery is full, diverting surplus power to a dedicated heating element.
Mostly when people ask me about using heaters directly on their wind turbines, I offer them a Solar Converters LDR circuit. This acts a bit like a battery because it works at a fixed voltage. Sometimes I recommend putting a heater in series with the supply cable from turbine to LDR. This allows the voltage to rise and achieves a low cost MPPT effect. But you need to have two heaters: one for the LDR control and one in series.
Schams also offer an MPPT heating controller for those who don’t need to charge a battery or connect their wind turbine to the grid. It’s not on the web page but it is reasonably priced. If you are interested then please contact Schams Electronic. This controller provides MPPT control of the wind turbine and puts the output into a single heater.