The unequal distribution of radiant heat from the sun on the surface of the Earth produces variations in heat contents of the air mass with corresponding variations in its density. These variations cause air movement, which is modified by the Earth's rotation, inclination, uneven distribution of land and ocean masses, and geographic abnormalities. This flow of air is called wind. The wind can be used in many passive ways. The rate at which heat is removed is proportional to the velocity of the air.
Combustion air is required for fire.
Fire is easily adjusted by controlling fresh air intake. Pumping water by windmills was familiar to rural Americans early in this century. About three-fourths of the Earth's surface is water. The natural cycle of water evaporation and precipitation created by the sun is a force needed to sustain life on Earth. Many forms of energy can be realized from this movement of water in its natural cycle.