Wind energy has conquered many startup problems and has attained in a new, more mature phase. The annual market volume increases by 20-30% per year, making significant contributions to the national electricity supply in some countries (DK, DE, ES). Wind turbines have increased in size, achieved compliance with severe grid connection requirements and have cautiously gone offshore. The cost of wind-generated electricity approaches the cost of fossil -fuel-generated electricity. With this success, new challenges arise: the integration of wind energy into the electricity supply system, the step from wind turbines into (offshore) wind power plants, the associated extreme reliability requirements and the prospect of a continued cost decrease. The chapter presents the state of the art, and discusses perspectives on these issues.
