Before anyone builds a wind farm, someone has to find out how much wind there really is. Maps and computer models are a useful start, but lenders and planners usually want measurements taken on the actual site, at heights close to where the turbine blades will turn. This page explains the kit used to do that, in general terms. KBB2 Wind Notes is independent and does not sell, recommend or represent any equipment maker.
The meteorological mast
The classic tool is a tall, slim lattice or tubular tower called a meteorological (met) mast. It is held up by guy wires and fitted with instruments at several heights. Measuring at more than one height shows how quickly wind speed increases as you go up, which helps estimate conditions at the hub height of a modern turbine.
What is mounted on it
- Anemometers measure wind speed. The familiar cup anemometer spins faster as the wind blows harder; ultrasonic types measure how sound travels between sensors.
- Wind vanes record direction, which matters for laying out turbines so they do not sit in each other's wake.
- Temperature, pressure and humidity sensors help work out air density, because denser air carries more energy at the same speed.
- A data logger collects readings at short intervals, stores them and usually sends them on by mobile network or satellite.
- Power supply, often a small solar panel and battery, keeps everything running at remote sites.
Remote sensing
Some campaigns use ground-based devices that measure wind higher up without a tall mast. LiDAR uses laser light and SoDAR uses sound pulses reflected by the air. They can be moved more easily and reach greater heights, but they are often used alongside a mast so the results can be checked against a trusted reference.
Why measurement takes time
Wind changes from hour to hour, season to season and year to year. A short campaign can be badly misleading if it happens to catch an unusually calm or stormy period. Measured data are therefore often compared with long-term records from nearby weather stations or modelled datasets to judge whether the measured period was typical.
Keeping the data honest
Good practice includes calibrating sensors before they go up, inspecting them regularly, checking for icing, bird damage or loose fittings, and documenting every change. Gaps and faulty readings are flagged rather than silently filled. Independent reviewers often examine the data before money is committed, because a small error in average wind speed can make a large difference to expected output.
Where it fits in a project
Measurement is one of the earliest steps in the journey described on our Projects Explained page. To understand what the numbers mean, read Wind Basics, How a Wind Turbine Works and How to Read a Wind Map. If you live in Cape Town, the Cape Doctor is a fine reminder of how much local wind can vary.