Available wind resources as a function of yearly average wind velocity and different typical terrains are indicated in the diagram below.
The resources refer to the power present in the wind at level 50 m. Be aware that wind turbine efficiency is typical 20-30%.
Example - Available Wind Resource
The available wind power resource at a sheltered location with average wind velocity 5 m/s is approximately 140 W/m2 from the diagram above. The available energy output per square meter from a wind turbine with efficiency 25% and a operation time 8000 hour a year can be calculated like