Wind turbine location and sizes are really important for a successful wind project. It’s no secret that wind turbines work best when exposed to the strongest winds. Windier sites produce much more energy (and therefore income) compared to less windy sites. This is why wind developers always want to locate wind turbines on the tops of hills in upland areas, or want to use the tallest towers – so if you want to maximise the commercial viability of a community wind project you will need to locate the turbine(s) in the most exposed location.
There may be good aesthetic reasons for locating a wind turbine in a less-exposed spot if it means the wind turbine(s) is less-visble from key viewpoints, which may help with obtaining planning consent.
The ‘size’ of a wind turbine is made up of two key elements: the hub-height and the rotor diameter. From a technical perspective, high hub-heights are preferred because this exposes the turbine to higher average wind speeds, and larger rotors are preferred because they capture more wind. There are a couple of reasons for opting for shorter towers/smaller rotors – one is technical, to avoid microwave transmission links or aviation radar interference, and the other is aesthetic and is an attempt to reduce visual impact. You can’t do much about the technical reasons, and from an aesthetic perspective we would generally argue that a large wind turbine is by definition large, so it is best to avoid compromising its performance with a shorter tower/smaller rotor, because it will still be visible regardless.
The number of wind turbines depends on how large the site is. The wind turbines themselves need to be around ‘5 rotor diameters’ apart so that they don’t affect each other with turbulence. For a 500 kW wind turbine this means 250 metres apart, and for a 2.5 MW wind turbine it is 410 metres. You can see from this that you need a lot of available land to host several wind turbines, but provided you have a site with the space, the land between the wind turbines can still be used for farming etc. with effectively zero impact from the wind turbine.
Also bear in mind the ‘constraints’ that apply to all sites that limit where you can locate wind turbines. Typical constraints are:
- Noise/visual amenity buffers from inhabited buildings
- Bridleways, railways, woodland and hedges, watercourses, ponds…
It’s surprising just how much of a large landholding is eliminated once these basic constraints are applied – see the example below. These graphics come from our ‘Constraints Map Stage 1 (CM1)’ service where the initial checks are made to work out the developable area on a site. In this example it is only the yellow shaded areas that are available for development!
While on the subject of constraints maps, once the developable area has been determined the next step is the ‘Constraints Map Stage 2 (CM2)’ which checks the developable areas for aviation, communications, landscape & ecology and heritage constraints and results in a further series of constraints map so you can decide which areas are best to focus on for development.
Before any of these constraints maps need purchasing you can narrow down your search for the perfect site using our free ‘Wind site self-assement tool which will take you through a number of the basic checks to:
- Estimate your wind speed
- Check proximity of nearby properties
- Check site access and approach roads
- Grid connection
The tool even emails you a pdf summary report at the end for your records and distribution after a couple of days. Just by using the tool a non-wind industry person would quickly learn the kind of things you need to look out for in a good wind site, which will make your time spent searching more productive anyway.
Want to install a wind turbine?
If you are in the UK then take our Wind Site Self-Assessment - Step 1 of our modular Windpower Feasibility Study. It takes about 20 minutes to work through the basic checks to see if your site might be suitable, including:
- Estimating wind speed
- Checking proximity of nearby properties
- Checking site access and approach roads
- Investigating connection with the grid