A linear alternator is a generator that produces alternating current (AC) using linear motion, and may not be as common as the rotary alternator that generates AC using rotary motion. Most of the time, it is simpler and more practical to translate linear motion into rotary motion. For instance, a hydroelectric power plant harnesses energy in the potential energy of stored water. This energy delivers power seen as a vector pointing downward, so it can drive a linear device, but it is a lot easier to convert the power into rotational energy using a turbine. For other purposes, using a linear device is also more practical.
Electrical generators, including the linear alternator, generally make use of electromagnetic induction, which makes use of the principle that a wire that is moved so that it cuts through magnetic lines of force will have current generated in it. Electrical energy is generated on a massive scale using electromagnetic induction. The linear motor, the counterpart of the linear alternator, makes use of a shaft that can move back and forth partly in and partly out of its housing. The resulting motion is similar to the movement available in air-driven or pneumatic actuators and in fluid-driven or hydraulic actuators. Electric linear motors are applied in relatively low-force requirements, such as in dispensing food products in vending machines.
This principle may be applied to the common shake rechargeable flashlight. The light-emitting diode (LED) in this flashlight consumes little power, so the rechargeable flashlight is practical to use because a few shakes could extend the flashlight “on time" significantly. Linear alternators are seen as a possible technical growth area due to the many applications that can be expected. For instance, if any footwear is requires electrical generating capability, it could use a linear alternator with small displacements in the sole. The idea is that the compression action of stepping and the release of weight can be harnessed to generate electricity for personal gadgets.
New uses are continually found for linear alternators and linear motors. The current and future breakthroughs in increasing the magnetic field densities in permanent magnets are one factor. Another factor is the potential of smaller machinery under nanotechnology. There may be new applications that will surface due to advantages in cost and easier manufacturing. For instance, harnessing small-scale mechanical energy on a large scale could lead to welcome changes in the way people live.