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Is my garden windy enough for a wind turbine?

Posted by Alex Barrett on 20 June 2016 at 10:05 am

Generating energy from a wind turbine seems like a great way to save on your energy bills. But how windy does your area need to be in order for a turbine to be viable? How do you measure wind speed and which are the windiest parts of the UK?

We have a long history of using wind turbines to power our machinery. Windmills originated in medieval times and revolutionised the amount of work it took to grind grain and do manual labour. Now we can generate electricity from a turbine and use it to do all manner of tasks. Unfortunately wind can be an intermittent source of power, even in a windy country like the UK. Not all sites are suitable for a turbine.

All wind turbines have a “cut in” wind speed. Below this the turbine might turn, but it won’t generate enough electricity to register. This is usually around 3-4 m/s, so you need to have average wind speeds of more than 5 metres per second for it to be worth your while to install a turbine [1, 2]. So, you have to plan carefully when deciding where to install one [3, 4].

It is recommended that anyone considering installing a wind turbine first gets an anemometer. This is a sensor that measures wind speeds. You should run it for several months and work out what the average wind speeds are at different times of year. You can then see whether a turbine is likely to pay off. Wind speeds increase with height, so if you can mount a turbine on a mast or tower then you will find it to be more effective. Hand held anemometers are available from around £10.

There are several online tools that use meteorological measurements to work out what the average wind speeds in your area are. These are good for getting a general idea, but unless you live right next to a weather station then there will be some estimation involved. Weather stations are quite spread out, and so measurements have to be interpolated between them. This means that the measurements at adjacent stations are used to estimate the wind speeds in between.

We found a nice calculator at Aeolus Power [4] which uses data from the Department of Energy and Climate Change. This has a point spacing of one kilometre, so should provide an estimate close to where you live. However local variations in topography, the position of buildings and a range of other factors can alter wind speed on the small scale. Urban areas generally have lower wind speeds than the countryside due to the proximity of large buildings. So while it is fun to see what the reported averages are for your postcode it is no substitute for making your own measurements.

It turns out that the YouGen offices aren’t in a very windy location, we’d have to build a turbine at 45 metres height in order to get 5.9 m/s winds.

So which are the windiest parts of the UK? Unsurprisingly the highlands and coastal regions are windier than the lowland and inland regions. The South East of England is much less windy than the West of England and Scotland. The Met Office have a nice map that summarises wind speeds across the UK. They report that the record for highest wind speed was 150.3 knots, around 278.4 km/hour on the summit of Cairngorm in 1986 [6]. Although that might be a slightly inaccessible site for a wind turbine!

References

  1. The Energy Saving Trust
  1. Wind Power Program
  2. University of Nottingham (Links to pdf)
  3. Aeolus Power Wind Energy: Wind Speed Calculator
  4. Which? Magazine
  5. The Met office

Image Credit TechnoSpin via Flickr

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Comments

2 comments - read them below or add one

Sandra Hayes

Sandra Hayes from Comment left on: 9 August 2016 at 9:17 am

Dear Pte22324057

To answer your questions in turn:

1.        The average wind speed should ideally be measured over a whole year if not longer, as there can be a lot of variation in wind speed from year to year and month to month.  If you go to http://www.rensmart.com/Weather/BERR you can find the NOABL Wind Map.  From this you can find the average wind speed across each 1km square of the country. Like the Aeolus Power Wind Energy calculator referred to above this is a good starting point and should be checked before investing in an anemometer or other data.  A good general guide to small and medium scale wind has been produced by Renewable UK and can be found at http://www.renewableuk.com/page/smallmediumwind

 

2.     Vibration and potentially noise from roof mounted wind turbines can be an issue for domestic dwellings, particularly at night when the occupants wish to sleep.  The other issue about roof mounted turbines is the amount of turbulence caused by the wind buffering against the side of the building which causes turbulence.  Ideally want you want is a smooth flow of air from the direction of at least the prevailing wind.  For this reason, the rule of thumb is not to place a wind turbine within 10 hub heights of the nearest obstruction, whether these be trees or buildings.  More detailed guidance is given to MCS accredited installers (which you should always use) to be found at http://www.microgenerationcertification.org/mcs-standards/installer-standards/small-and-micro-wind-turbines

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Pte22324057

Pte22324057Comment left on: 1 July 2016 at 9:23 pm

1. What is the "average" wind speed of any area? Is it taken over the whole year or just a part of a year?

 If a house has already got solar panels, the owner will only be nterested in the months when there is little sun, and plenty of wind. 

2. Wind turbines generally require mounting on towers away from the buildings they serve. The reason for this is usually said to be that if a tower were to take advantage of the apex height of a house, vibration would destroy the fabric over time. But is this necessarly so? Vibration can be isolated or dempened, as happens elsewehere (mtorway bridges for example.) 

A house with an apex height of 8.5 metres would only need  a turbine mounted on a further 10 metres to get useful air.

 

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