2.4kW Skystream wind turbine from Southwest Windpower
Wind energy has been used for thousands of years to pump water, mill grains, and move ships across lakes and seas. Windmills became a fairly standard fixture on farms across rural America during the 20th century. Eventually, the windmill was used to generate electricity, and ultimately gave birth to more modern wind turbines in the 1980's. Since then, dramatic advances in the efficiency of wind power production have created tremendous opportunity for use in residential and commercial applications.
The United States initially took a lead in the development of wind turbines, but the wind power industry in Europe established much higher gains in terms of the percentage of power provided by wind. According to the 2008 World Wind Energy Report, the US has reclaimed its position to boast the largest installed windpower capacity (25,170 megawatts), but the energy produced from wind represents only about 1.3% of our total consumption. This remains tiny in comparison to Denmark, with 19%, Spain and Portugal with 11% each, and Germany and Ireland with 7% each. In the US, it is estimated that three states alone, Texas, Kansas and North Dakota, have enough wind power potential to supply the entire country's current demand.
While the wind may come and go, it is by and large very predictable and reliable. The American Wind Energy Association provides wind maps that show general trends. Another source, FirstLook, provides more detail readings for specific areas. You can select a point on the map to get an estimate of the average wind speeds for that area.
To get reasonably good power production, you should have a minimum of 10 mph average winds, though 12 mph winds produce a substantial increase in power production. Within a given area, a flatter topography with fewer obstructions (like a river valley) posess higher winds than hilly or forested lands. The Griggs-Putnam Index can be used to look for prevailing winds by observing deformities in vegetation. In windier areas, you'll see an imbalance in the growth of tree branches, with a greater proportion of branches leaning downwind.
Another consideration is turbulence. Obstructions that redirect the wind flow will create a spinning effect, which adversely affects the performance of the wind turbine. With this in mind, a rule of thumb is to mount the turbine on a tower 20 feet higher than any obstruction within 250 feet. The picture below illustrates wind flow, turbulence, and how different tower heights fit into the flow.
It's important to minimize turbulence when selecting a site
The Skystream 3.7 wind turbine (pictured above) is a very popular turbine due to its all-inclusive design. The unit is intended to be used as a grid-tied solution - supplementing existing electric power from the local utility. The inverter, which converts DC power to the AC power that most appliances use, is housed in the turbine itself so the output is easily streamed into the existing electrical system. The turbine has a power* rating of 2.4KW, which means it is capable of producing 2.4kW of power at its peak performance, with 29 mph winds. In typical 12 mph winds, the system will produce roughly a third of the average home's electric needs. The installed price, without financial incentives, starts at about $15,000. Read about sample Skystream installations>>
For smaller off-grid applications, such as in cabins, trailers and boats, a battery-based system is ideal. The Air-X wind turbine is a 400W turbine, designed to charge one or more batteries to run lights and other DC-based appliances. The battery power can also be converted to AC using an inverter. This turbine will produce 38kWh per month with sustained winds of 12 mph. The installed price without incentives starts at about $2,500. Read about sample Air-X installations>>
In urban settings where the built environment results in increased turbulence, vertical-axis wind turbines can be more effective. Traditional wind turbines spin on a horizontal axis, parallel to the ground. Vertical axis turbines, on the other hand, spin around the tower itself, and are less susceptible to turbulence. The Mariah Windspire is a 1.2kW wind turbine that can be easily incorporated into a residential or commercial setting. The turbine produces approximately 166kWh of power per month in 12 mph winds. The installed price before incentives are applied starts at $10,000. Read about sample Windspire installations>>
Wind is a rich, clean, abundant source of energy, and if you are blessed with sufficient resources to benefit from this gift, please be sure to consider the worthwhile investment. In the past, people have been quick to curse the wind, but now many are smiling upon their newfound fortune!
