Conventional wind turbines had a horizantal axis. They would be replaced by more advanced turbines.
Windmills had been around since Roman times, but the first practical windmill was was built in AD 500 in Persia. The axis was vertical and the sails were horizontal. The windmill was set inside stone walls that funneled wind through a gap. Around the year 1400, as many peasants were moving into the towns, millers started using windmills to grind wheat into flour. The Europeans improved the design by mounting the sails vertically on a tower. This allowed the wind to strike every sail at once. Windmills became more common as a result. In 1850, the agricultural windpump was invented. A tail fan was used to keep the main fan facing the wind. They would continue to be used into the 21st century along with wind turbines.
Tech Level: 8-10
Conventional horizontal axis wind turbines were invented in the 1890s. They consisted of a shaft that turned an electric generator. The shaft normally contained three blades. In the late 20th century, these blades were pointed into the wind by motors that were controlled by a computer. The blades were stiff to prevent them from braking. A wind sensor was used to measure wind speed. A servo motor turned the turbine. All turbines had to be protected at high wind speeds. For this, the blades were feathered, and the brakes came on. Wind power became common in the early 21st century. By then, other turbines were being considered like a vertical axis turbine.