Do you have a good wind site?
Wind powered battery charging systems can be cost effective if the average wind speed is nine miles per hour (mph) or more at the location of the wind generator. If you are using wind in combination with photovoltaic power, it may be cost effective if you have good wind only during part of the year. The power available from the wind is proportional to the cube of the wind speed. When the wind speed doubles, the power delivered is eight times as great. Most wind generators are designed to deliver maximum power at a wind speed of 30 mph. At 15 mph, they will deliver about 1/8 their rated power. A wind generator should be mounted at least 20 feet higher than any obstruction within 300 feet to avoid turbulence.

Wiring
It is important to avoid excessive loss of power from voltage drop in wire from the wind generator to the batteries. It is not necessary to use a wire size that minimizes voltage drop for maximum generator output. It will be more economical to choose a wire size that gives a 2% voltage drop at the average generator output for your site. The Air403 has two wire DC output. Use the wire loss chart at the back of this catalog to decide on wire size. The Whisper wind generators have 3-phase AC output that is rectified to DC at the control box. Wire size can be smaller on these machines. Use a wire designed to carry 1/2 the rated current of the generator you are using, but remember, three conductors are required. If wire size required is too costly, compare the price of a whisper HVLV machine, which has a 240 VAC output that is stepped down to battery charging voltage. This results in significantly smaller wire size, which will usually more than offset the extra cost of this machine.

Measuring Wind Speed
You can use one of the measuring devices in this section to determine wind speed. The NRG Wind Totalizer acts like an odometer in a car, giving you the total wind passage over time. Average wind speed is calculated by the user by dividing the miles of wind passage by the number of hours the machine has been running. This unit can be installed and checked weekly or monthly. If you are patient, you can measure for a year or two and get a good idea of your potential power availability. The Dwyer and Kestrel wind speed indicators are both like a speedometer, displaying wind speed at the time you are looking at it, but it does not record any information for future reference. The Dwyer and NRG can be mounted on a tower to give you an idea of wind speed where the generator will be located. If you measure wind speed at ground level, you can expect about 1.5 times the wind speed 30 feet up, which equates to about three times the power. At 120 feet above the ground, wind speed will be twice what is measured at ground level and power output will be more than twice the output at 30 feet. If you do not have a wind gauge, you can get a rough idea of wind speed from the table below.

Towers
We do not recommend mounting wind generators on roofs. Though it is possible with wind generators of 500 watts or less output, it will be noisy. Larger wind generators could cause severe damage to the building. Freestanding towers, guyed towers or guyed poles may be used with wind generators. Wind generators can be mounted on freestanding towers designed for antennas. They require a large, engineered concrete base for support, but since they do not require guy wires, they can be installed in the smallest space. Guyed steel truss towers, also designed for antenna mounting are less costly, but require a large area for guy wire placement. A tilt-up pole tower is the most economical and the easiest to install. Wiring and mounting of the wind generator are done before the tower is erected. No climbing is necessary. The four or five inch steel tubing can be bought locally to save freight.