My son, who was involved with electric power generation in Ireland said there were problems with the efficiency of wind generated power. The primary problem was with the placement of wind turbines with respect to the primary wind direction. The propellers downstream of (behind) the first row of wind turbines were being subjected to turbulence produced by the blades of the upstream propellers. It was found that the third and fourth row wind turbines were hardly turning at all due to the confusing wind patterns. Hopefully this phenomenon has been resolved and the downstream wind turbines are now placed in cleaner airflow. This reminds me of the WW-II aircraft where turbulence from the propellers would cause the rudder and stabilizers to do crazy things, like causing the aircraft to flip on its back...not good. LOL.
