DC Water Heating Elements with Wind Turbine Generators or Solar Panels
Wind turbine generators are mainly used for electricity generation. The power used can be stored in a battery bank or connected to the main 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. In that case, 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.
In the video below, Jeff explains the types of dump divert loads that are safe and suitable for wind turbine (and solar panel) applications.
Dump Loads / Divert Loads Explained
Hooking a DC Water Heating Element Directly to a Wind Turbine
Why it might not be a good idea.
It is not usually possible to connect a 12 Volt water heating element directly to a wind turbine. The voltage generated by a 12 Volt wind turbine is typically far above the nominal 12 Volt rating, sometimes over 50 Volts in heavy winds. These high voltages would rapidly burn out the water heating element when you need it most. A 12 Volt DC water heating element should be used with just 12-15 Volts, a 24V DC water heating element with just 24-30 Volts.
A small battery should be used as a buffer between the wind turbine output and the heating element to prevent the water heating element from receiving fluctuating over-voltages.
A 12V motorcycle battery is perfect for this task (for 12 Volt DC submersible water heating elements) – no more powerful than 4 amp hours / 50 cold cranking amps, and 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 DC water heating element chosen must be closely matched to the typical power output of the wind turbine. If the element is too large (too high wattage rating), the wind turbine will not be able to start spinning unless the wind is very strong. If the water heating element wattage is too low, nothing will be damaged since the small battery will limit the voltage to around 12 volts, but heat will be dissipated in the wind turbine generator and cables rather than used to heat water.
If the DC water heating element is poorly matched, then there is the risk of a large voltage drop between the wind turbine generator and the element causing the cable between them to melt. In this case, the wind turbine would then freewheel at very high RPM and could easily be damaged to destroyed.
How to Connect a Solar Panel Directly to the DC Water Heating Element