I have found an easy way to use a water wheel to make energy and need to know??

Question

I need to figure out what size the real water wheel needs to be b4 I build the full size model, but I do not know how to figure this out.

I was told during a tour once that a relatively small amout of water was able to produce enough power to run an entire mill because of the distance of the drop and so if there is a way to figure such things out I would like to know what it is.

Thank you in advance.

Answer 1

This is not an exact science because there are many unknowns when converting the energy of water into another form, but lets start from the basics:

If you were able to convert the energy in water at 100% effciency, what you are converting, is the potential energy in the water due to its elevation, so at most the energy you have is:

P.E. = mass x gravity x height

Now energy / time = power, and we can incorporate this though the mass term, since this is the mass of the water...

1000 cc = 1 liter = 1 kg
gravity is a constant and = 9.8 m/s^2 or about 10 m/s^2

so if you have 1kg/sec of water falling 1 meter your maximum power out is:

P = 1 kg /s x 10 m /s^2 x 1 m = 10 N-m /s = 10 Watts
(Note N=Newton, unit = kg-m/s^2)

so you can scale that up based on your actual flow and height. But now you have to consider losses, because your water wheel will be no where near 100% efficient - If you can make it 10% efficient you may be lucky. Consider the following:

1 - What percentage of falling water's energy will your wheel actually be able to convert to rotation of the wheel
2 - What losses to have have due to friction and air resistance (note if you drop water from a high height, the air will slow it down if it is just flying freely.. it must be in a tube and flow continuosly).
3 - Your generator will also have losses converting the rotational motion to electric.

But #1 is probably your biggest and thus the design of your wheel's hydrodynamic qualities will be the most important.

Answer 2

The link below has lots of information about designing and building a water power generating system.

Good luck in getting off the grid!

Answer 3

The most energy you can get out of water a water wheel is the potential energy of the water.

E=mgh
mass*gravitational constant*height of the water