The most important decision in buying a residential wind turbine is determining if you have enough wind! Unfortunately nature hasn't made determining your average wind speed at the site of your wind turbine that easy. With Solar PV, calculating your annual solar energy output and solar PV payback is easy with all the tools that are on the web. As long as you don't have any trees or buildings shading your roof, you can use the calculator to get a pretty accurate estimate of how well solar PV or solar thermal panels will perform on your roof. But finding reliable wind speed data is much trickier!
This case was highlighted on our post on the Honeywell wind turbine where Karen asked in the comments: "I live in Western NC just North of Asheville. How can I find my wind stats?" Which reminded me that it is very hard for homeowners to decide if a wind turbine will work in their location. Many of the resources out there showing wind speed data are like this one from the American Wind Energy Association (AWEA); which are nice to look at for a general idea, but not very helpful for people like yourself, who may want to place a wind turbine in your back yard. Or they are like this wind speed map from the Department of Energy which shows wind data at a height of 80-meters; which is perfect for wind developers but not for home-sweet-home.
But have no fear, because Mapawatt is here to point you in the right direction! Building off the success of our Temperature History post (currently number 1 on Google for that obscure topic) I thought about using Weather Underground's great collection of data to see if I could find wind speed data for my location. The steps to finding wind speed data close to your location are as follows:
- Go to www.wunderground.com/history
- Put in your location and keep the date as today's date
- Click on the custom tab for the date range
- Choose a date range that is one year ago from today and today's date (you have to choose less than or equal to a year's worth of data) and scroll down until you see the wind speed data.
The annual wind speed data from Weather Underground shows the average wind speed and the average Gust Wind. The NOAA defines Wind Gust as: "...the maximum 3-second wind speed forecast to occur within a 2-minute interval at a height of 10 meters. Wind gust forecasts are valid at the top of the indicated hour."
So this data is helpful, but unfortunately it's not perfect. Unlike the sun which shines straight down and is easy to predict ("Is there a tree in the way?") wind blows from the side and is affected by the landscape, trees, buildings, other houses, etc. The only real way to predict how a wind turbine will perform at your house is to buy an anemometer. Because wind can be so fickle, you can't just rely on a computer program to predict if a wind turbine is going to be a good investment. You should really do the measurement yourself, or have a reputable dealer help you do it.
Another thing to remember with wind-speed is that the "average wind speed" can be misleading when it comes to determining how much power a wind turbine will produce. As I said in our post on the Anemometer:
You see, wind speed is so important because it is cubed in the equation above (P = .5 • ρ • A • V³; where P = power and V= wind speed). If you double your wind speed you don’t double your power output, you increase it by a cubic factor! For instance, increasing wind speed from 4 mph to 8 mph is not double the power output, but increases it 8 times (8³/4³=512/64=8)!
For another example, look at this dummy data below. Pretend we are looking at the windspeed in two different locations over 3 hours to determine an average wind speed so we can predict the power output of a turbine we want to install:
As you can see, in both hypothetical locations the average wind speed over 3 hours is the same (5), but the average power in location 2 is more than twice the average power in location 1! Therefore average wind speed will give you a generic idea of how a wind turbine may perform, but you also need a location where the wind blows at a high rate of speed for considerable amounts of time. A gusty location may just be better than a constant breeze!
In summary, use the online tool from Weather Underground above to get a good idea if your city might be a good candidate for a wind turbine, but that wont provide everything you need. Talk to others in your area who have a wind turbine (this will be easier once our online community is launched later this year) or speak with reputable wind dealers. If anyone tries to sell you a wind turbine without doing detailed analysis first kick them to the curb!