7. The UK Wind Speed Database Program
For the UK, there is a national wind speed database available from the Department of Energy and Climate Change that gives estimates of wind speeds at heights above the ground of 10, 20 and 45 metres. It is based on the Ordnance Survey grid system and gives speed estimates at grid points 1 kilometre apart. However, it is not a very convenient means of accessing wind speed data and a program is available from our download page that is far more flexible to use. This program gives much better access to the database by being able to scroll your position to anywhere within the UK. It also gives an interpolated wind speed for any height above the ground up to 80 metres. The position input can be either an Ordance Survey grid position or latitude and longitude. There is a nominal charge of £5 for this program to help with the maintenance of this site and to develop the programs further.The option to input a postcode is not yet available because of licencing difficulties with the Royal Mail. A postcode converter to either an Ordnance Survey grid reference or latitude and longitude is available at http://www.nearby.org.uk/coord.cgi.
The figure below is a screen capture of the program display for a location near to the Bears Down windfarm in Cornwall. At each position, it shows the easting and northing of the location and displays by a small blue circle the position both on a small scale map showing the Ordance Survey grid and also on a larger topographical map. For the topographical map, there is the option to zoom in on the point so its position can be seen more clearly. A topographical map is used because it demonstrates the general link between topography and wind speed as you scroll around a location.
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It is important to stress that the calculations on which the database is constructed makes use of the large scale geographical topography of the area but not the detailed topography - particularly the man-made contribution to the topography. In particular, it is difficult to get reliable estimates of wind speeds in urban areas because there is such variability in wind speed depending on the local building layout. However, urban sites are rarely suitable for wind power in any case.
It is interesting to note a comparison between the wind speeds obtained from the database and the measured wind speeds from Meteorological Office weather stations. The figure below is obtained from the report Small-scale wind energy Technical Report. July 2008. (UK Met Office Report). It shows that there is tendency for the database to underestimate wind speeds in the range from 5 to 10 knots (i.e. 2 to 5 metres/second) but possibly to overestimate them above this speed range. However, the scatter in the results is such that not too much emphasis should be put on this comparison.
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As a final example of a screen capture of the program, the figure below shows the database windspeed results for a location in Cumbria called Great Dun Fell at an elevation of 857 metres. It can be seen that the speed profile is nearly uniform because of the rapid acceleration of the flow over the top of this fell - see the discussion on the previous web page 6. In this example, the latitude and longitude was used for the position input which is shown by the blue dot on the zoomed-in map.
The picture below shows the top of Great Dun Fell with a radar station on the top. It would be a very good site for a wind turbine too!
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