I understand that one of the concerns with generating power from a water tower, allowing the falling water to turn a generator, is that if the water wasn't coming from a natural source, thus having to be pumped back up, that you would use more electricity to power the water pump than you generated. Is that correct? I'm just a dumb old country boy that has absolutely no book learning on physics, so I understand none of the math involved in calculating if this would work or not.

My idea is to weld a skeleton framed tower, 4 feet x 4 feet x 24 feet tall. Then at intervals install 4 feet x 4 feet x 1 foot deep reservoirs. There would be multiple outlets for water on each side of the resevoirs with nipples to direct the flow to each flow's water wheel, for which I would build using bicycle rims, which would be geared to a small generator, but also to do away with the concern of not generating enough electricity to pump water back up could the water pump not be ran by being gear driven from the spinning water wheels.

Is this possible?

  • 1
    $\begingroup$ Using two reservoirs for water and pumping water back up to the higher one is a valid technique and uses nighttime electricity when demand is low. See electricmountain.co.uk/Dinorwig-Power-Station as one example. The electricity companies use this for "power matching" against rapid demand surges... $\endgroup$ – user207455 Jul 7 '19 at 21:21
  • $\begingroup$ @SolarMike That's storage, not generation though, right? $\endgroup$ – JMac Jul 7 '19 at 23:07
  • $\begingroup$ @JMac they can go from ready to full power in about 6 seconds so not storage... generation ie fast response to changing drmand. Did you click on the link? $\endgroup$ – user207455 Jul 8 '19 at 3:56
  • $\begingroup$ @SolarMike I had skimmed it, just wanted to clarify that they weren't collecting mountain water or something that I missed. OP asked about generation, that's why I wanted to try to clear up the difference a bit. $\endgroup$ – JMac Jul 8 '19 at 14:12
  • $\begingroup$ Actually it would be multiple reservoirs. The first would sit on top of the 24 foot tall steel frame. I could have maybe as many as 12 reservoirs. Each reservoir would have mulutple water outlet on each side with nipples directing water to each outlets individual 10 speed sized bicycle rim turned into a water wheel. The wheels would then in turn be belted or chained to it's own individual small generator. My idea could run 16 wheels per level, and if there were 12 levels that would be a total of 192 small generators, like car generators, creating electricity. $\endgroup$ – Bill Jul 9 '19 at 17:48

Your invention sounds like a perpetual motion machine: using the fall of water from a tower to both generate electricity and pump the water back up to the tank again. Using the falling water to generate electricity and then pumping the water back up is done commercially, but more power is needed to pump the water back to the top than is generated by it falling down. The technique is used when there is a surge in demand and more power is needed instantly, but it is not a perpetual motion machine. Cheap, off peak power is used to pump water back up to the top when demand is low. Perpetual motion machines don't obey the 1st Law of Thermodynamics, which means they don't produce as much energy as is needed to operate them, so your falling water won't be able to pump itself back up again. Perpetual motion machines never work, because they have to obey the laws of physics. Your proposed tower should be able to generate electricity, but you will either have to pump it back up manually, get a wind turbine to do it, or find some other way. Your device sounds unnecessarily complicated.

  • $\begingroup$ Michael, my system would be 24 feet tall with the first reservoir sitting on top. I think I could put reservoirs every 2 feet, so I would have approximately 12 reservoirs. Each reservoir would have 4 outlets on each side, so 16 per reservoir x 12 reservoirs is 192. Each outlet would supply water to it's individual water wheel which would in turn a belt which would turn a car generators. It would be 192 generators from top to bottom. I once saw a guy that was running his entire home with car geneartors....3 of them I think. I would probably have a lot of excess electricity. $\endgroup$ – Bill Jul 9 '19 at 17:52
  • $\begingroup$ One more thing. The site is own my wife's family land and my dad told me yesterday that up the hill from my build site is where my wife's forefathers had their pig pen, and that he remembers their being a seeping spring that supplied the pigs with water. If I can dig that spring out I can dig a trench to supply water to a small fish pond near the house. If that were the case the water tower wouldn't be necessary as I could simply mount my water wheels to spin from the force of the running water. I've been looking at cost of steel, and that tower will cost me a lot to construct. $\endgroup$ – Bill Jul 9 '19 at 18:04
  • $\begingroup$ Well,you could try it. If it works it would cause a sensation, Be sure to let Stack exchange know if it works as you expect,and send us some photographs of it. $\endgroup$ – Michael Walsby Jul 9 '19 at 18:05
  • $\begingroup$ If you have a spring on high ground and can take energy from it as it flows to low ground,that would be a completely different proposition, You could augment it with a wind generator just in case the water supply fails. $\endgroup$ – Michael Walsby Jul 9 '19 at 18:09
  • $\begingroup$ If it works I will post here, however i failed to mention that the "house" I spoke of is a future house, so it will still be a few years before we move back to the area and make that house, and hopefully a working version of my idea, a reality. $\endgroup$ – Bill Jul 10 '19 at 19:58

but also to do away with the concern of not generating enough electricity to pump water back up could the water pump not be ran by being gear driven from the spinning water wheels.

The electricity from the generator could not be enough to supply enough power to the pump to get all the water back up. The absolute maximum amount of energy in the water that your generators could theoretically extract is just the potential energy they gain from being pumped to that height.

The absolute minimum amount of energy theoretically required to pump the water up to that height will be the same as the absolute theoretical maximum that the generators can extract.

The problem: No pump or generator can even achieve those theoretical efficiencies. The generator will generate less than the maximum theoretical power from the waters potential energy.

The pump will require more power input than it is able to add to the waters potential energy.

At best if you had a 100% efficient generator, pump, and setup, the system could run itself indefinitely with no external energy input, but that is not physically achievable due to effects such as friction. This is sometimes called perpetual motion of the third kind.

  • $\begingroup$ Downvoter care to explain here, or was it just random? $\endgroup$ – JMac Jul 8 '19 at 1:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.