This article briefly describes the key points on wind turbines and how to measure wind speeds on a site when looking to install a small wind turbine.

When thinking of installing a small wind turbine at your home or farm, there are a few things to consider. The most important three and I consider them main rules are:

• Location
• Height
• Diameter of the wind turbine blades

Location: We need to watch out for any possible obstacles that may interfere on the wind turbine performance. If there is a lot of turbulences on the wind turbine path, its performance will be compromised

Height: This is simple, the taller the wind turbine tower the better. The higher, the fewer obstacles

Diameter: This is simple too, the wider the diameter the more wind energy the wind turbine will capture and the more time it will spend spinning. However this may profe risky on high speed wind areas like North of Scotland.

With these three rules in mind, we can look for the “perfect” site to install a wind turbine but before that, it is highly advisable to log some wind speeds for a period of time to ensure the site is as good as it looks. For this you will need a wind logger.

You will need to log the following:

• Average and maximum wind speeds in periods of 1 minute. For large wind turbines 10 minutes is ok, but for small scale ones, 1 minute recordings will give you a much more accurate picture.
• Wind direction, you will need to know from where the wind comes most of the time and at what wind speeds.
• Professionals record at different heights most of the time, as this gives them a much better picture of turbulence, wind shear, etc. Also by recording at different heights you are able to conclude that a site may not be very good at 10 meters but much better at 15 meters. If you record at just one height you may possibly be missing out on some important information, and this information could possibly give you more options when it comes to planning permission etc..
• Standard deviation can also give a good view of how turbulent or gusty the wind is. This can be very helpful, and definitely worth showing to the wind turbine manufacturer you may be thinking of buying from.
• Long data storage, you will need more than a few months of data to make sure you take the right decision when investing in a wind turbine. Extrapolating from a local weather station or airport is ok but can be a bit risky too.
• When you have all your wind data ready what do you do with it?
• Find your average wind speed, that already will give you some idea of how much energy is available on your site
• You will need to calculate the number of hours that the wind speed has been blowing at different wind speeds
• The number of hours per wind speed can then be multiplied by the power curve of any wind turbine manufacturer and give you the total energy output for the amount of hours logged.
• Most of the professional wind loggers can do this (ie: LeWL wind logger) but it is advisable to consult the installer or even the wind turbine manufacturer to confirm how much energy you should expect per year with the data you provide them.

In summary, knowing the number of hours of wind incidence is very useful to provide realistic energy

estimations.