Windmills and waterwheels used the motion of wind (windmills) or water (water wheels) to turn an axle, the energy of which was transferred to run a mechanism of some sort. American Midwestern farms traditionally had a windmill to pump water from a well. Windmills and water wheels were also adapted by millers to grind wheat or other seeds to produce flour.

Occasionally one finds these "natural energy harvesters" used for the milling process of ore produced by mines. Forges and black smithies sometimes used wind or especially water power to run their equipment.