What effects wind velocity?
Obviously this varies with the daily weather but it is possible to measure the average wind speed at a location and indeed this has been done as shown here on the national wind speed map. This is the average wind speed measured at a height of 10m in a location free from any obstructions. The two caveats here are height and obstructions. Height The average house is 6-8m in height and wind speed is increases with height. This would mean between 15-30% less power just due to the lower mounting height of the turbine. Obstructions The average turbine will either be mounted on the roof or side of the house. These will act as obstructions to any wind flow – as will neighbouring buildings, trees, hills etc. This means the air speed measured in the national database is likely to be very different to that on the roof of a house in a built up area. Location, location, location! The average wind velocity itself isn’t enough information to work out the power available anyway. You need to know how i
