ABSTRACT
Wind energy is an indirect form of solar energy in contrast to the direct solar energy described in previous chapters. Solar irradiation causes temperature differences on Earth and these are the origin of winds. The wind itself can be used by technical systems. Wind can reach much higher power densities than solar irradiance: 10 kW/m2 during a violent storm and over 25 kW/m2 during a hurricane, compared with the maximum terrestrial solar irradiance of about 1 kW/m2. However, a gentle breeze of 5 m/s (18 km/h, 11.2 mph) has a power density of only 0.075 kW/m2.
