sentences:  In some countries such as Germany, the wind power installations are required by law to make full use of the prevailing weather conditions and always produce the maximum possible amount of electric energy.Firstly it has to be stated that the wind is a completely flexible energy source per se, since the head of the wind turbine can be rotated, thereby stopping to turn and to produce electric energy.However, this flexibility is taken away by the prevailing environmental and energy laws in order to maximize the share of renewable energy in the production portfolio to the fullest extent possible.