Wind turbine generators are used primarily for electricity generation. The power used can be stored in a battery bank or connected to the mains supply using a suitable grid tie inverter. In very strong winds, and/or when the batteries are fully charged a wind turbine may generate more current than the batteries can handle. Therefore a dump load is often used to divert the extra energy to heat water so it is not wasted and so that the wind turbine does not spin so quickly that it is damaged.
Diversion Load Water Heating
Pictured above is a typical 12V water heating element (200 Watt power) which can be screwed into an immersion heater draincock hole. When used as a diversion (dump) load, such an element is connected to the batteries via a charge regulator. When the regulator detects that the batteries are fully charged, it diverts the generated electricity to the element which heats water.
Direct Wind Turbine Water Heating
It is not usually possible to connect a 12 Volt water heating element directly to the output from a wind turbine. The voltages generated by a 12 Volt wind turbine are typically far in excess of their nominal 12 Volt rating – with values of over 50 Volts often recorded in heavy winds. These high voltages would rapidly burn out the heating element when you need it most. A 12 Volt heating element should be used with just 12-15 Volts, a 24V heating element with just 24-30 Volts.
In order to prevent the heating element from receiving fluctuating over-voltages a small battery should be used as a buffer between the wind turbine output and the heating element. A 12V motorcycle battery is perfect for this task (for 12V immersion elements) – no more powerful than 4 amp hours / 50 cold cranking amps, and it should be a lead-acid battery which can be refilled with water. A sealed gel type battery or dry cell should not be used.
The heating element chosen must be closely matched to the typical power output of the wind turbine. If the element is too large (high wattage), the wind turbine will not be able to start up spinning unless the wind is very strong. If the element has a low wattage, nothing will be damaged since the small battery will limit the voltage to around 12v, but heat will be dissipated in the wind turbine generator and cables rather than used to heat water.
If the heating element is poorly matched then there is the risk of a large voltage drop between the wind turbine generator and the immersion heating element causing the cable between them to melt. In this eventuality the wind turbine would then freewheel at very high RPM and could easily be damaged to destroyed.
Buy an Immersion Heater Element for a Wind Turbine
Click here to view our new article Immersion Heater Elements for Wind Turbines in which we present some of the latest 12V, 24V, 36V, and 48V immersion heater elements on the market.