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United States Department of Agriculture

Agricultural Research Service

Title: Battery Charging with a Small Downwind Horizontal-Axis Wind Turbine

item Vick, Brian
item Neal, Byron
item Clark, Ray
item Holeman, Adam - WTAMU-AEI

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 2, 2003
Publication Date: May 19, 2003
Citation: V26. Vick, B.D., Neal, B., Clark, R.N., Holman, A. Battery Charging With a Small Downwind Horizontal-Axis Wind Turbine. CD-ROM. WindPower 2003 Conference Proceedings. 2003.

Interpretive Summary: For remote locations (like cabins, farmhouses, etc.) where utility electricity is not available, wind-electric systems are frequently the most economic way of generating electrical power for windy locations. Many of these wind systems require fairly high winds (averaging 15 to 20 mph) to be able to meet the electrical load demand at these remote locations. In 2001 a 11.5 ft diameter wind turbine on a 64 ft tall guyed pipe tower was installed at the USDA-ARS laboratory located near Bushland, TX (elevation = 3800 ft). This wind turbine has been used to charge batteries and power DC electrical loads via a 48 volt controller. This wind turbine reached its peak efficiency at a wind speed of 12 mph while most wind turbines reach peak efficiency at approximately 18 mph. This wind-electric system at an elevation of 3800 ft would produce 96 kWh of usable DC energy per month assuming an average wind speed of only 10 mph. Assuming sea level, standard day conditions and an average wind speed of 10 mph, this system is estimated to produce 108 kWh of usable DC energy per month. The controller for this battery charging system was shown to prevent the batteries from being over charged. However, it was discovered that a manual switch between the controller and the batteries needed to be installed to keep the controller from draining the batteries if the wind turbine was down for a long length of time ¿ time period depends on Amp-hour capacity of batteries. It was also necessary to install a relay between the batteries and the electrical load to keep from discharging the batteries excessively. These improvements to prevent excessive discharging should make this wind-electric battery charging system more desirable for consumers.

Technical Abstract: Testing was initiated in Jan 2002 on a small wind turbine designed for battery charging which used a uniquely designed furling system. This downwind horizontal-axis wind turbine furls by the tail lifting the rotor and alternator from a blade rotor horizontal-axis position to a blade rotor vertical-axis position (e.g. similar to a helicopter) at moderately high wind speeds. For Bushland, TX elevation -- 1159 m (3800 ft), the wind turbine began furling at a 13.5 m/s wind speed and would be fully furled for wind speeds above 20 m/s. This 3.5-m diameter wind turbine had a cut-in wind speed of 3 m/s and power peaked at 830 Watts (corrected to sea level, standard day conditions) at a wind speed of 13.5 m/s. For a Rayleigh wind distribution with a mean wind speed of 4.5 m/s, this wind turbine generated 4.1 kWh/day (AC power) or 3.2 kWh/day (DC power) at Bushland, TX.

Last Modified: 4/19/2014
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