Apparatus for harnessing energy from wind comprises upper and lower continuous-loop trackways defining a continuous loop path and a series of connected, movable wind foils. Each wind foil has a leading edge mast engaging and guided by the upper and lower trackways. Each wind foil is movable between first and second orientations when moving along first and second portions of the path. A second example comprises a support structure having upper and lower closed loop trackways having inner and outer trackway rails and defining a closed loop path which guides a series of connected trolleys. Each trolley has a roller mounted to a roller support. The roller is guided by the rails of the upper and lower trackways. Sail assemblies each have a mast and a sail extending from the mast, with the upper and lower ends of the mast mounted to and supported by upper and lower trolleys.