ASK THE EXPERTS: Wind Power for Charging Batteries

Beginner
Books (and Home Power articles!) can help you clarify the variables of implementing effective wind power systems.

I have a few questions regarding charging batteries with a wind-electric system. First, does the direction the turbine is spinning affect how the battery is charged (will switching directions charge or draw on the battery)? A turbine I’m considering only spins in one direction, but I have seen others that will spin in either direction.

Second, can the turbine be in series with other devices? Or does it need to be run directly to the battery and have the power diverted from there?

Third, what specs does a car-mounted wind turbine need in order to keep the battery charged?

Jacob Johnson • via e-mail

There are some wind turbines on the market that spin clockwise, and others that spin counterclockwise. If you’re buying a turbine, this is of no concern. If you’re building your own, work with existing plans to match the blades to the alternator.

There are systems in which wind turbines power loads directly, though they are uncommon. Appropriate loads for this configuration might include water pumps and heating elements. These systems run at variable voltage (dependent on the rotational speed), so they work only with certain loads. There are also wind turbines that tie directly into the utility grid, either via an inverter or via an induction generator. Battery-based systems—either on-grid or off—use the turbine to charge the battery, and the loads run off the battery.

If a battery is 12 volt, the turbine that charges it needs to be 12 V nominal, or be stepped down to that voltage via electronics. Beyond that, the battery capacity and the energy (kWh) load, plus the site’s average wind speed, will determine the size of wind turbine needed. A load analysis and site analysis are critical to turbine and battery sizing.

Using a wind turbine on a vehicle is a losing proposition. A vehicle is powered by fuel, and its body is designed to reduce wind resistance. Putting a wind turbine on it adds wind resistance, requiring more fuel to overcome that resistance. Any electricity generated will be less than the additional fuel used to overcome this resistance.

For a deeper understanding of wind electricity, see the many articles at homepower.com, and a variety of books on the subject, including Paul Gipe’s Wind Energy for the Rest of Us.

Ian Woofenden • Home Power senior editor and author of Wind Power for Dummies

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