While pumping trying waterwheel generator

[fivewin]

Every day I am pumping water (solar powered) 2 hours+ like in the pict during the day. It is normally not drawing from the battery during peakhours. Im wondering if i make a (small) waterwheel i can produce some extra electricity in the 2 hours pumping, for example to charge another 12volt battery.

Is it worth?

[citabria]

I think the perpetual motion machine has been proven a MYTH. I suppose a pelton wheeled turbine located below the free falling water would not add to any friction losses to the pipe line supply while filling the tank. But generally speaking any mechanical turbine is going to have its own efficiency losses. Would it be more efficient to electrically couple the photovoltaic system to a battery charger and simply charge the accessories that way?

You probably need to work out some math on paper before proceeding. Good luck.

[J.P.M.]

In theory, yes. As a practical matter, and for a lot of reasons having mostly to do with the size of the flow and, because of that, the large portion of the produced power that would be dissipated by friction, no.


I suppose you could always increase the head by a lot, but there's only so much free potential energy and that's limited by height of available head.

Also, if flowrate is a consideration, a simple water wheel type generator for example, will reduce the flowrate. Other schemes will have the same reduction of flow limitations. I'd consider a smaller pump and/or a bigger holding tank and save the electricity before it gets partially used. that'll reduce the need to recover some of it.

[fivewin]

Thanks for all replies. I was indeed thinking of a small waterwheel below the falling water. I think there is then no loss whatsoever so i thought i perhaps can produce some extra electricity.

The solar system i use is a small system enough for pumping during peak hours and enough to charge a agm battery which i use in the evening for some leds & gadgets.

After reading all your replies it is indeed not worth. For the costs of making a wheel + buying a brushless or stepper i can better add a solar panel (50Wp for example)

[bcroe]

Seems to me, just lowering your fill pipe to the bottom of the tank would reduce the pumping
energy, giving you back all that energy and any inefficiency of the pump system as well.
Bruce Roe

[J.P.M.]

Thanks for all replies. I was indeed thinking of a small waterwheel below the falling water. I think there is then no loss whatsoever so i thought i perhaps can produce some extra electricity.

The solar system i use is a small system enough for pumping during peak hours and enough to charge a agm battery which i use in the evening for some leds & gadgets.

After reading all your replies it is indeed not worth. For the costs of making a wheel + buying a brushless or stepper i can better add a solar panel (50Wp for example)

Why it will work, in theory anyway, is because you will be converting what was the sum of the water's potential energy of elevation, and the kinetic energy of the flowing water at the higher elevation to a lower energy state at a lower elevation and probably a lower (but not zero) velocity, converting some of the energy differential at the two sates to electricity.

You could also pump the water to a higher elevation and, giving it more "head", or height, get more energy out of it on the way down. That however would be a counterproductive waste as you would use up more power getting the water to the added height than you'd gain on the way down. Mean old Mr. Entropy and the 2d law of Thermodynamics will get you on that one.

Don't raise/pump the water any higher than necessary for the application.

[fivewin]

Bruce Roe & JPM thanks. Ive learned again ...