How can one convert Mechanical energy into Electrical energy efficently?

Question

We have all seen those "shake flashlights" and the "Hand crank radios."

If I want to build a motor to generate electrical energy, how would I do that. Maybe there is some science store that sells a kit.


Also, assume you have this motor, which when you exert mechanical energy, converts it into electrical, how would you store the said converted energy.

Thank You!

Assuming one has a rechargeable Lithium ion battery, how would you hook it up to a motor to charge it?

Answer 1

The force of falling water through a turbine or water wheel that drives a generator is the most productive and uses the force of gravity along with the weight of water to power civilization. Tidal generators operate on a similiar principle of capturing water behind dams at high tide and releasing it at low tide through turbine generators.
Not very portable though.
Any means of converting constant natural forces like gravity, tides or geothermal heat through mechanical means into electrical energy will be the most efficient. Or something you do daily anyway like walking up or down stairs could be converted into electrical energy and stored in batteries. I've even heard of ideas of shoes with generators built in to the soles and heels to power cell phones or lap-tops when walking. Or ramps for parking your car at night that slowly sink down overnight, geared to a generator and hooked up to batteries.
The two items you mention are very viable for portable power and can be coupled with storage batteries....lithium-ion having the most density for electrical energy storage. The hand-cranked radio relies on a spring to store energy when you wind it up and releases this energy over time to power a dynamo or generator. Poor countries use this form of power for radios in rural areas.
http://www.sciplus.com/ is a good site for kits and ideas as is Radio Shack.

Answer 2

Well, storage is the first thing you look at. What are you trying to do? Keep the memory alive on a powered-down computer? Use a capacitor. Store energy to use when you are no longer charging a circuit for high power applications? Use a battery. Store energy for use when demand is low? Pump water back up to a higher location.

But simply, converting energy from mechanical to electrical involves magnetic fields. Somehow, you have to cut a magnetic field to create current flow in a secondary. That is where you need to start your search. It can be rotary (most common) or translational, like in the flashlight (least efficient).

This should get you started. But the answer is not easy to find, or energy supplies would not be in such short supply.

Answer 3

A motor does just that by passing a coil or loop of wire through a magnetic field--the result is an electical current! Why don'y you apply this principle to your exercise machine! Now you might ask where you could get a magnet to give you a magnetic field, but if you pass an electric current through a coil of wire, you'll get an electromagnetic field! Isn't physics great? Hence, you could convert mechanical to electrical energy to get the current for the magnetic field you'd need to convert your mechanical energy to electrical energy! In any event, it will be the mechanical energy which powers your device...it is indeed a most interesting project! Good luck!

Answer 4

So you want to build a generator.

My personal choice is a 3 phase permanent magnet brushless design using NIB magnets. But there are many other options out there.

Most motors when driven will generate electricity, some more efficiently than others.

Do a search for "homebuilt windmills" for a great deal of information.

For energy storage, deep cycle SLA (Sealed Lead Acid) batteries are among the cheapest, though they are heavy. With them, it is important not to let them fall below ~20-25% charge, and not to charge or discharge them at faster than 20% of thier capacity per hour, preferably slower. And there some other caveats that you should research.

Answer 5

To generate electrical energy, you require a generator and not a motor. A generator converts mechanical energy into electrical energy, while a motor does the opposite. You have AC and DC generators to produce AC and DC electricity. Click on http://www.amasci.com/amateur/coilgen.html to build an ultra-simple AC generator to light a tiny incandescent light bulb.
There is no way you can store electric energy.

Answer 6

Here is an example:
http://www.stirling-tech.com/stirling/cogenera.htm

Another simple example is a bicycle dynamo that can generate enough electricity to light a small bulb. The wire from the dynamo can be configured to attached to a rechargeable battery that should go through a voltage regulator to limit overcharging with a light indicator etc.

Answer 7

Buy cells.

Answer 8

BY FILLING A SIMPLE FORM....!!!