Wind turbines are lovely machines to look at as their blades spin and they turn in response to the wind. Though they might seem simple, a wind turbine is a complex machine and installing one requires careful thought and planning. While many folks in the Blue Ridge Mountains feel like they live in a pretty windy place, the reality is that there are very few locations in this region where a wind turbine can be installed and generate electricity in a cost effective manner. However, if your property has a good wind resource then a wind turbine may be the most effective way to generate a lot of electricity cheaply. So read on and we will look at some of the things you need to know to end up with a quality installation.
Fact #1: Turbines need a steady turbulence free wind. To operate efficiently, a turbine needs to be placed in an area well away from obstructions such as buildings, trees or topographical irregularities like hillsides. There is a reason why all those big wind farms are installed in the Midwest and Texas…. It’s flat. In our mountainous area, some ideal locations would be clear ridge tops or long open valleys. A conservative rule of thumb when siting a turbine is: “the bottom of the turbine blades need to be 35 feet above the nearest obstruction within 500 feet” If you really think about that, this is not so easy to accomplish in an area of rolling hillsides and forests. A tall tower (>35’) may be required to place the turbine above the zone of turbulence but a tall tower will increase the installation cost. Perhaps you have the ideal site on the back corner of your farm but that location might be a thousand feet from where you need the electricity. It is costly to trench and bury wire. Obstructions make the wind turbulent and turbulence makes the wind speed vary. And while you cannot see the turbulence, turbulent winds severely increase the stress and strain on the moving parts of a turbine. (more on this later) Yes, you can install a turbine in a location that does not meet the 35/500 rule, but you need to know that the performance will suffer.
Fact #2: Turbines need minimum wind speeds to generate electricity. All turbines have what is referred to as a “cut in speed” which is the minimum wind velocity needed for it to produce electricity. This speed is typically 8 mph and that is a fair bit of wind. There are just not that many places in these mountains that have constant winds above 8 mph year round. It is important to understand that just because the blades are turning, that does not mean the turbine is producing electricity you can use.
Fact #3: The relationship of power to wind speed is cubic. As the wind speed increases, the power triples. Most manufacturers rate their turbines in terms of instantaneous power output, typically measured at about 25 to 30mph. A turbine rated at 2000 watts in a 25 mph wind will generate about 300 watts in a 12 mph wind and probably less than 50 watts at its rated cut in speed. Now you can see why Facts #1 & 2 are so important. As you can see, when wind speed drops off, so does the power output. And sustained energy (power over time) output is what you are really looking for.
Fact #4: Power vs. Energy: Power is measured in Kilowatts (KW) Energy is measured in Kilowatt Hours (KWH). When you burn a 100 watt light bulb for 10 hours you have consumed a KWH. That 2KW wind turbine referred to above will make 2KWH in an hour ONLY if the wind blows steadily at 25mph the whole hour. When the wind speed varies between 10 and 25 mph because of gusting or due to turbulence, the energy output will drop. When you consider which wind turbine to buy, you should always look at the Monthly Energy Production and NOT the Power Output.
Fact #5: Wind Turbines are NOT maintenance free. A wind turbine is a moving piece of equipment continuously subjected to variable & extreme weather conditions. Heat and cold, rain, ice, dirt, dust and hard gusting winds combine to make a turbines job of producing electricity very demanding. And all of that is located on a very tall tower that you either have to lower to the ground or have a specialized equipment to get to. Moving parts will wear out eventually and a quality wind turbine will be built of robust materials that are designed to take a beating. Typically, an inexpensive and lightweight machine will produce a less power and need a lot more maintenance.
Having second thoughts about a wind turbine? Don’t despair, Floyd County has some good wind resource locations but they are not everywhere. In the right location they can be effective power generators but if you are not one of the “lucky” ones, then a Photovoltaic (PV) installation may work better for your needs. If you can’t install a turbine or PV system, there are many ways to reduce your energy consumption and lower your electric bill. Just look at the back issue archive of Floyd Magazine for other articles on how to save energy.
The author, David Zachow is a Master Electrician who lives in Floyd County. His company Direct Connect Solar & Electric installs renewable energy systems that generate electricity for homes and businesses.
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This story was published in Floyd Magazine Fall/Winter 2010 ~Senior Editor Dee Wallace