Before building a wind turbine for your back yard it's probably a good idea to know if it's going to operate more than it's not (or at all for that matter). Let me explain, if it's not windy enough then obviously your turbine is not going to turn but also if it is too windy your turbine could thrash its self apart or burn the generator out. Neither of these outcomes are good. There are other reasons for doing this too which I'll come back to at the end. You may have lived where you live for ages and think you know it's fine but do you really know? I mean really know? Do you have enough wind - that might sound like a bit of a personal question but there's no “bad gas" here (sorry, couldn't resist a “fart gag"). There are many ways to find out for sure but I'll just cover a couple here.
You can go out and buy an air-flow meter or anemometer and take measurements over a period of time in your exact proposed location for your turbine (or you could take measurements all over your property to build up a “wind map"). There are also kits and plans available to build your own anemometer, an interesting and fun project in its own right but I want to focus on a free method of getting a good idea of wind levels in your area and show you a short-cut for data gathering.
Since you're here reading this then you must have at least a passing acquaintance with the world wild web and it is your friend here. You can search for specialist web pages like berr. gov.uk (this one's for the UK but there are sites for most countries) where you enter your grid reference and it'll tell you the wind speed but more usually your usual weather site is perfectly adequate. I use the BBC site and the Weather Channel site for the UK, in the USA you can also use the Weather Channel weather.com or something like USA Today's site. For other countries you'll probably already know where you can get weather forecasts. Open up a spread sheet (openoffice.org will supply you with a free one if you don't already have one) and create a spread sheet with a date column and wind speed columns as are appropriate and available from your forecast. You may be able to get an average for the day or min. and max. values or if it's only a basic forecast that gives one value for the day then use that. If the site you have chosen only gives instant data then choose a time of day to take your measurements and use the same time every day (within reason). Spend a year building up your data and you'll have an excellent yearly graph to work everything out from and you can update it for ever more in case last year was a freak in some way. If, however, you don't want to mess around for a whole year before getting to the fun bit of making your wind turbine and of course reaping the savings it'll bring you can get hold of historical data. This is great, you may be able to get hundreds of years of data for free online. In the USA you can get a PDF for 1930 to 1996 and find your nearest town that's included.
www.ncdc. noaa. gov/documentlibrary/pdf/wind1996. pdf is the URL you'll want to plug into FireFox or which ever browser you use. Historical data can be tricky to find for other countries but some time spent with Google should find the info you require. The only draw back to this is that your exact location will be different from any online resource due to geographical contours, nearby buildings and trees etc. The only true way is with an anemometer as per the top of this article but I believe for amateur purposes this data will probably suffice coupled with a bit of common sense in looking around for these features and working out where the windiest position is.
Perhaps not entirely scientific but as I said probably sufficient for our needs. As above, highly local issues like buildings and trees will have an impact as will “social" issues - your neighbours might not like a turbine on the edge of your property right next to one of their bedroom windows, turbines do generate a bit of noise as well as electricity, you have to be aware of these potential issues.
Now you know if you have enough wind for a turbine you'll need to get some quality information and plans to build your turbine. Follow that link and you'll also find solar information if you found you don't have enough wind!