ABSTRACT
Horizontal axis wind turbines (HAWTs) are the main type of wind turbine for wind farms, with around 600 gigawatts installed by the end of 2018. A wind turbine with one blade will save on material but a counterweight is needed for dynamic balance. For HAWTs with rotors on the same axis, the wind speed behind the first rotor is reduced by 2/3, so the amount of energy passing through a second rotor placed close to the first rotor is reduced by a significant factor. The Messerschmitt-Bolkow-Blohm Monopteros and FLAIR designs were single-bladed wind turbines built in Germany. Riva Calzoni built the following single-bladed wind turbines: M5, M7, M30, and M33. Wecs-Tech built a number of sailwing units for wind farms in Texas and California. The wind farm near Dalhart, Texas originally had a few vertical axis wind turbines, however, they later changed to the horizontal axis sailwing.
