What Is a Linear Alternator?

Geisha A. Legazpi

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.

Alternators charge a vehicle's battery and supply its electrical system with power.
Alternators charge a vehicle's battery and supply its electrical system with power.

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.

An automobile engine's alternator essentially serves as an electric generator.
An automobile engine's alternator essentially serves as an electric generator.

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.

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Discussion Comments


Linear generation is now developed for use in existing alternating current thought and therefore limited to a hundred year old theory of manipulating a found power source in a previously unknown technological environment.

Why not develop a linear generator that produces electrical current in a "non violent," "less heat producing" electricity. The green movement and solar mentality brings us to a world of self production of personal, commercial, and even industrial energy needs. Did Edison or Tesla spend there time working with what they had found, and therefore overlook a better way? Rotation generation was as obvious as the stone wheel, but could it have been done better? Can it be done better now? -- Stan T.


I am working on a new generator. It uses eight free-floating pistons made from a powerful magnetic substance launched back and forth through their eight coil packs using a microprocessor controlled system which I can't talk much about at the moment. I haven't patented the system yet.

A small scale test yielded output rivaling portable work generators, and at a much smaller, more portable size while requiring a slightly less fuel. I will be finished with the design by the end of December, and I'll then post the finished generator online. Look out for the Blox Linear Generator.


Any ideas about companies which might be selling linear alternators? I am at that point in my research but all companies I found so far are still developing. Any information will be of great help.


@miriam98 - I think you’re right. I do think the application of the lights on kids’ running shoes would be a decent application. These lights are not meant for illumination, just for effect.

So the power output of the LEDs would be sufficient in that case. A linear generator on the bottom of the shoe would be the ticket. It saves money too.

It’s bad enough they make us spend hundreds of dollars on these fad sneakers; to make us pay for batteries too just adds insult to injury.


I understand the principle of the linear electric generator, but I think in consumer applications it has been a little lacking in performance.

Take the shake rechargeable flashlight which is mentioned in the article as an example. With flashlights you want enough light output to shine on whatever surface you’re looking at.

While I appreciate the energy efficiency of the LED light, I personally find its power output to far less than my regular flashlight. Another beef I have with the shake rechargeable flashlight is that you get tired after awhile shaking it.

Yes, it works, but how many shakes does it take and how long does each “charge” last? I suppose with a mini key ring flashlight it might be okay, but not for a regular flashlight I need in an emergency. That’s my opinion anyway.

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