Wind can be converted into energy by a wind turbine, which typically consists of a wheel with large blades connected to a series of gears. As wind causes the blades of the turbine to spin the turbine collects mechanical/kinetic energy, which can either perform mechanical processes or be converted into electrical/potential energy. Some mechanical processes that make use of wind turbines are pumping water and grinding grain. To store electricity the turbine must be connected to a generator, which converts the mechanical energy from the blades into stored electrical energy. Typically, wind speeds of 7–10 mph are needed to generate energy using a wind turbine. The orientation of a wind turbine can be controlled by a computer to optimize the amount of energy it collects.
Photovoltaic cells, or solar cells, work by containing materials such as mono- or polycrystaline silicon, cadmium telluride, or copper indium selenide whose electrons are easily excited by photons from the sun, creating electricity.