gondolas, turbine nacelles, engine nacelles
The nacelle is the housing for those units of a wind power station which have to be placed on top of the tower. The nacelle is mounted rotary onto the tower.
The nacelle (/nəˈsɛl/ nə-SELL) is a housing, separate from the fuselage, that holds engines, fuel, or equipment on an aircraft. In some cases—for instance in the typical "Farman" type "pusher" aircraft, or the World War II-era P-38 Lightning—an aircraft's cockpit may also be housed in a nacelle, which essentially fills the function of a conventional fuselage. The covering is typically aerodynamically shaped.
Source: Wikipedia - Nacelle