MadSci Network: Engineering

Re: How can i build a water or wind powered generator?

Date: Thu Mar 9 17:58:38 2006
Posted By: Madhu Siddalingaiah, Physicist, author, consultant
Area of science: Engineering
ID: 1141011426.Eg

Hi Erin,

That's a great question!

You could try and build a generator using magnets and a coils of wire, but
it probably won't generate a lot of power. In order to make a good
generator, you need good magnetic flux coupling, which can be done with
commonly available materials, but it's a fair amount of work.

There's a much simpler solution: use a motor in reverse. Motors and
generators are very similar. Motors convert electrical energy into
mechanical energy and generators do the reverse. Because of this duality,
their construction is very similar. Of course, many of the design
parameters are different, but the principles are the same. Here is some
information on motors and generators:

So how do you do it? Get a hold of a permanent magnet DC motor and drive
the shaft using wind or water. Electric power will be available at the motor
terminals. You can find DC motors in toys, discarded consumer electronics
such as tape players, VCRs and so on. You can purchase higher quality
motors from online distributors, but I'm sure you can find plenty of motors
if you look around. The Mabuchi motor company manufactures most of the
motors used in toys and consumer electronics. You can find engineering data
on these motors here:

Driving the motor shaft will take a little creativity, but you should be
able to come up with something that works. If you want to use wind power,
find a propellor from a toy plane and attach it to the motor shaft. You can
come up with something similar for a water drive. I would start with wind
drive, it's not as messy. You can use a hair drier to drive your propellor
and use flowing tap water for water drive.

If you get the motor shaft turning fast enough, you should be able to power
a small light bulb from a common flash light. You can try small single
bulbs from discarded Christmas tree lights. What would happen if you
connect the motor terminals to the terminals of another motor? You can try
some simple experiments, such as observing the drag on the motor shaft if
you connect a light bulb or short circuit the terminals. You can measure
the output voltage using a voltmeter to see how the voltage changes with
shaft speed. If you can get the engineering data for a specific motor, you
can calculate the expected output voltage and current given the shaft
rotational speed.

This can be a fun project because you can see how a power station works.
Power stations are bigger and more efficient, but the principles are the
same. Good luck!

Madhu - blog

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