[water_wheel_chaz (OP)]

Hello,
I live in an old Welsh Mill with a water wheel. Up until about 5 years ago the wheel turned without any problems and I was interested in using it to generate my own electricty, however, I was told by the local water company that if I was to use the wheel for this purpose I would have to pay an extraction fee of £1000 a year as the water leaves the ground for approx: 3 seconds, the wheel is an over shot variety, the water is fed from above instead of below. I decided to leave the idea for the time being although I was told by the local electricity supplier that I could sell any unused electricty back to the national grid it still would not cover the extraction fee. The water supply that was feeding the wheel is no longer available due to new land ownership where the water passes through but there is a stream about 100 feet down hill from the wheel, what I would like to attempt to do is find some way to use a pump that works from the stream itself and does not require fossile fuels to run it but instead uses the pressure of the water to pump enough water up to the wheel. This may not have anything whatsoever to do with science but I just thought I'd ask so any ideas or links to ideas would be appreciated.

Cheers,

Chaz

[another_someone]

It is a perfectly valid science/engineering question to pose.

If you are going to pump some of the water up 100ft (OK, it is not 100ft up, but 100ft along a gradient - the important matter is how much is the actual increase in height by which you want to take the water), then you will only be able to achieve this for a small fraction of the water.  The water that does the work to raise the rest of the water can only fall.

For instance, assuming you had 100% efficiency (which in practice will never happen) then if you wish to raise 1 gallon of water by 10ft, and you have a drop of only 5ft from which to extract the energy to do this with, then you will need to have 2 gallons of water dropping 5ft in order to raise 1 gallon of water by 10ft.

The reality is that you are likely to lose the vast majority of your energy to various inefficiencies in the system, so you will have to use considerably more than 2 gallons dropping 5ft to get 1 gallon to be raised by 10ft - but I cannot say what the actual efficiency you can expect is going to be.

[eric l]

The problem you face is to a smaller scale the problem the engineers of Louis XIV had to deal with for feeding the fountains in the gardens of the Versailles palace. 
They built the famous "Machine de Marly" for that.

• http://world.std.com/~hmfh/machine1.htm
• http://world.std.com/~hmfh/mpics.htm

(there are of course dozens of links in French)
It was not very efficient, and it was so noisy that they were not allowed to make it run between sunset and sunrise, but it was used for over a century !

[water_wheel_chaz (OP)]

Thanks for your replies and for the links. I can see it is going to take quite a bit of working out. The wheel is 3 foot wide and 15 foot in diameter and made from cast iron with wooden buckets. It turns fairly easily on phosphor bronze bearings. First off I put down 300 feet of 6 inch pipe to bring the water to it but had to reduce the amount to 3 inches by putting a plastic flower pot in the end of the pipe with a 3 inch hole cut in it. So, 3 inches of water travelling through a 6 inch pipe was plenty enough when I could bring the water from the original source but now there is the problem of bringing it up hill over 100 feet and then up to the height of where the water originally fed the wheel which is about ten feet high....I can see this taking a while  [] []

[Bored chemist]

http://en.wikipedia.org/wiki/Hydraulic_ram

[water_wheel_chaz (OP)]

That looks like the solution to my problem, many thanks!