Living Off The Grid
In West Branch Michigan
Wind
Introduction
Humans have been using wind power for over a thousand years to grind grain, pump water, or to move ships. It was not until the the end of the 19th century that electrical energy was being produced by wind energy. The value of using a wind turbine over a photovoltaic array is that the wind turbine will continue to work even when the sun goes down. And if it is installed in a windy area, the turnine will generate power as long as the wind is blowing.
There are all sizes of wind turbines available. Large industrial turbines generate megawatts of power and are usually owned and operated by large utilities companies. However there is a growing market for small wind turbines for residentual use. These units generate between 38 kWh/mo @ 12 mph - over 500 kWh/mo @ 12 mph. Small wind turbines are now used to produce electricity for a variety of applications including utility-connected homes and businesses, remote homes, water pumping, telecommunication systems, off-shore platform lighting, and more.
One wind turbine manufacturer, Southwest WindPower ,manufactures various sizes of wind turbines for residential use. Below is a table showing power generated by each product at various wind speeds.
Wind (MPH) 7 8 9 10 11 12 13 14 15 16 Air X 4 8 12 18 24 30 37 43 48 53 Whisper 100 25 37 53 71 91 114 138 162 187 212 Whisper 200 47 73 103 136 171 206 241 274 306 335 Whisper 500 124 192 274 266 464 567 670 771 868 958
As the table shows, the higher the wind speed the greater amount of power that can be generated. For these turbines to generate power the wind speed should be at least 7mph for them to generate their minimum amount of power. You can find your average relative wind speed at Average wind speed from the National Climatic Data Center.
Once you've determined that you have enough wind speed to generate power you need to locate a site where to install your tower to hold your wind generator. There are two basic requirements for a good wind generator site: relatively high average wind speed, and relatively low wind turbulence. The higher the average wind speed, the more power your wind turbine will produce. The lower the turbulence, the lower the stress your turbine will have to endure and the longer it will last. Lower turbulence also usually results in more power.
The power available in the wind goes up with the cube of the wind speed. This means that a comparatively small increase in average wind speed can make a dramatic difference in power production. The power available at a site with a 9 mph (4 m.s-1) average speed is over 40% more than that at a site with an 8 mph (3.6 m.s-1) average. Also, wind speed increases with the height of the tower. Higher towers will generate more power than lower towers and the benefit of a higher tower is the reduction of turbulence encounter due to nearby trees and buildings.
Another issue you need to keep in mind is the voltage loss encountered with long runs of wire from your wind turbine and your battery storage. For a 12 volt system the following table describes the wire gage needed versus the length of run of the wire.
Wire Length ft 0-75 76-120 121-190 191-300 301-385 386-488 Wire Length m 0-23 24-37 38-58 56-91 92-117 118-149 Wire AWG Gage #6 #4 #2 #1 #0 #00
My System
I decided to use a 12v wind turbine that would generate 50watts @ 12mph. I found an open area where I could erect a 40 foot guy-wire tower. I used screw-in anchors to attach the guy wires to the earth. I wired the system to my batteries using #00 AWG gage wire because I didn't want to lose too much energy from wire loss. Because of the system I purchased I could directly hook up the wind turbine to my batteries because the turbine has a charge controller built into the housing unit. This charge controller will ensure that my batteries will not overcharge. Also, the turbine is mounted on a pivoting head that pivots the blades when the wind speed reaches a speed where damage to the system could result from over speeding. As the blades rotate back a breaking system is engaged to slow the blades down.
Links
Below are some links where I did my research on Wind Turbines.
- Southwest Windpower
- Manufacture of wind power systems for home and business.
- AE Wind Turbines
- News and Information about Wind Generator Technologies.