Home Wind Generators, Charge controllers and Dump Loads
With rising energy costs, the interest in home wind generators has increased. This article explains the use of small wind turbines and what’s needed to use them as wind turbines for the home.
Most home wind generators are permanent magnet alternators. They produce three phase, wild, high voltage AC (alternating current). Wild, meaning that the voltage changes with the wind speed. Without controlling this voltage, it can’t be used.
To control this current, it’s converted to DC (direct current) with the use of a bridge rectifier. Once converted, the power is connected to a diversion charge controller. The primary job of the diversion controller is to maintain a constant voltage range that can be used for battery charging, or tying into the grid.
The secondary job of a charge controller for home wind generators is the diversion mode. Small wind turbines must be kept under load at all times. The constant load keeps them from spinning too fast. Without a load they can spin fast enough to damage themselves.
When wind turbines for the home are used for charging batteries, the current has to be diverted away from the batteries once they have reached full charge. Without doing this, the batteries would be damaged by being over charged.
When home wind generators are used with grid tie inverters, the inverters must shut down when there is a power outage. This prevents the power from small wind turbines entering the grid and potentially shocking personnel repairing the grid.
The diversion mode of a wind power charge controller senses when the batteries are fully charged, or when a grid tie inverter shuts down. When either of these things happens, the power is diverted to a dump load.
A good rule of thumb is to not have a charging source greater than 80% of the diversion load controller’s current handling ability. For example, if a 40 amp diversion charge controller is being used, do not place a charging source capable of putting out more than 32 amps (80% of 40 amps) on the load controller’s circuit.
The dump loads used for home wind generators are devises that dissipate the excess current as heat, while keeping the small wind turbines loaded. They can be wound resistors, hot water heating elements, or DC heaters.
The dump load must be sized to the home wind generators they are used with. They need to be large enough to absorb and dissipate all of the energy the small wind turbines will produce.
The wattage of the loads must be at least as large as the wattage of the home wind generators being used. Also, the voltage must match the diversion voltage of the charge controller. If the diversion voltage is less than that of the dump load devise, the rated wattage of the load devise won’t be dissipated.
Depending on the size of home wind generators used, more than one dump load devise can be used. For example, if the home wind generators output is 1000 watts; four 250 watt dump loads can be wired in parallel (4x250watts=1000 watts).
The selection of home wind generators, as well as the components to use them, is growing rapidly. Coupling small wind turbines, with solar power, and good energy conservation practices, is enabling the consumers to have a greater impact on their energy costs, as well as preserving the environment for future generations.
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Note: All prices in US Dollars