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Wind resource assessment is something of a dark art. It’s not taught in schools, you can’t study it in university: it’s handed down from one professional to their trainee bit by bit. In fairness, that’s mainly because the growth of the wind industry is still a fairly recent phenomenon and it takes a bit of time for schools and universities to catch up.

Still, it does mean that when people are asked to comment on a met mast planning application on some prospective wind farm site, they don’t really know much about why it is needed, what benefit it brings to the developer, or what it is attempting to measure. What will it look like? How much space will it take up?

I’m going to begin by thinking about the wind. Chances are that the wind is considerably more challenging and complex than you realise, unless you are an atmospheric scientist or an expert in fluid dynamics. In fact, the wind is a constantly-changing phenomenon, interacting with itself and with the ground in interesting and difficult-to-predict ways.*

An example I particularly like which illustrates this is a pedestrian walking through a town centre with an umbrella on a windy day. Town centres are full of right angles, rarely found in nature, which redirect gusts of wind in strange directions, sometimes providing shelter and at others channeling a powerful blast. Such a pedestrian would find that they need to keep changing the position of the umbrella as they walk, to avoid it being blown inside-out.

On a bigger scale, that happens with even relatively simple landscapes. Hills force the wind upwards and around, making for more wind at the top of the hill than the bottom. Buildings block the wind, diverting it around themselves and creating a turbulent wake behind themselves. Forestry provides a very challenging environment for the wind, resulting in shelter within the trees and turbulence above them. The ground itself slows the wind, so that as you move away from the ground it gets windier.

We are small fry to the wind. It covers the whole landscape, and our tiny area is relatively small. We experience only a tiny fraction of it at a time (unless we’re carrying an umbrella…) Buildings, bridges, lorries and wind turbines are far larger and more likely to feel its devastating effects.

Considering all this, it’s perhaps not surprising that there is a dark art to measuring the wind. Deciding where to make the measurements, working out how the wind will vary across the landscape, establishing the best positions for turbines, and providing a confident estimate of how windy the site can be expected to be over the next ten or twenty years are all genuine challenges faced by wind farm developers. It plays a crucial role in establishing whether the money spent on building the wind farm can be recouped, and how long it might take. This in turn helps to convince investors to provide loans, and insurance companies to provide insurance.

It’s an art, and a science, yes. But there’s no need for it to be a dark art. I’ll share some of it with you over the next few months.

* In this case I’m simply talking about the wind as we experience it near the ground. There are large scale atmospheric winds higher up, but these are not really of much interest or use to the wind industry at present, save perhaps as a potential future resource. (Back)

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