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

Comments (3)

stevenlanders's picture

There are some wind turbines spinning clockwise, but what are the characteristic features for the placement? As of the date when it was suggested at Student Associations Conference 2016.
Steven - Wind Power Group visit our site and contribute.

mberdan's picture

It should be noted, that most wind systems are powered by 3-phase generators. so direction does not mater. On smaller systems 1-5kw they also use 3-phase generators so for either Vertical or Horizontal
it is the design of the blades that propel the direction. with Low voltage generators, the performance for storage is greater on Vertical systems than horizontal. Storing energy to batteries is the most efficient method then gird tie. From Storage you can then invert to other applications, such as electric cars, or what ever source is needed. This makes more sense. this way it does not matter the type of battery or the voltage , such as 12,24,48 volt systems. the wind power is controlled from a charge controller to the batteries, similar to that of solar systems. The advantage of a small
wind system is that, you have the possible out come of producing energy 24 hours a day and are only effected by wind conditions. where as solar is limited by daylight hours and over cast weather conditions.
Together they offer the optimal solution for energy, either grid tied or storage capacity.

Ian Woofenden's picture
Vertical-axis wind generators have not made a place in the market, and have been over-advertised by their promoters. The performance is not equal to horizontal-axis machines. I can't see any difference between the two in relation to battery storage. Grid-tie in most situations is considerably more efficient to the customer than batteries, since under net metering laws, a kilowatt-hour tossed back at the grid is credited in full for later use. Batteries at best are in the 80-85% efficient range, while net metering is 100% efficient to the end user. And with grid-tie, exactly when the energy is made is not important -- it's possible to make most of your energy with sunshine during the summer and use up the surplus credit over the darker months. Hybrid systems (wind and sun) are not particularly valuable in most on-grid situations, and it's often better to invest more heavily in the stronger technology for the site. Off-grid, hybrids are very important and useful. I live where sun and wind are excellent complements, and only need to turn my backup generator on a handful of times a year. Storage issues are primarily a utility concern if you are grid-tied, unless you have a strong need or desire for backup. In most U.S. states, batteryless grid-tie is still a great deal, and avoids the trouble and cost of batteries. Where utilities make it difficult to grid-tie, or where backup is a strong value, battery-based grid tie can be the best of both worlds.
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