One of the most important measurements you’ll need to make when planning your DIY wind turbine is wind speed and direction. Knowing where the wind blows best and at what speeds will be important factors for determining what size and type wind turbine will be best for your location and what kind of power your turbine will produce. There are companies around who can come and do a really professional site assessment, but for small machines, this could end up costing as much as the turbine itself!

The easiest way to measure wind speed is with an Anemometer. Big word. Tricky to say. If you want to measure wind speed in your area yourself, Amazon sells a bunch of them, quite cheaply. Best thing to do is measure wind over your site for a number of weeks or months to get an idea of the overall picture. So, investing in your own anemometer is probably a wise move.

Below are some of the more decent units available from Amazon.

Modelled Data
Another way of determining wind speed is to use modelled data. There are a number of sites that will provide this data for free, but there are problems with this method. Usually, you enter your zipcode or postcode and the site provides average data for your region. If you think about this for a minute it will become obvious that this information needs to be taken with a grain of salt.

Here’s a list of factors you need to take into account when you’re thinking about wind turbine placement and information recieved via modelled data:

* Take account of nearby trees and buildings
* A site at the bottom of a valley or hollow will have a lower wind speed than the average, so adjust the average wind speed down
* A site on top of a hill or knoll will have a higher wind speed than the average, so adjust the average wind speed up
* The modelling does not include the effect of sea breezes, so for coastal sites add 0.5 – 1 m/s to the wind speed
* For flat open countryside the model returns a more accurate result
* For complicated terrain the model is less accurate.

Modelled Data Sites
In the US
Wind Powering America
In the UK
The Carbon Trust