This is meant for mechanical closed system for hydroponics. Two wheels connected by same shaft so the wheel going down lifts the water back with the other interconnected wheel to a slight incline. I suppose the torque created by falling water should be higher and so there's should be a difference in wheel's cups volume or radius. A high reservoir also could be used to be replenished by gravity ballast lifting pulleys once a while. Any suggestions on feasibility?

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    $\begingroup$ Aka perpetual motion. $\endgroup$
    – Solar Mike
    Mar 26, 2023 at 12:51
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    $\begingroup$ Perpetuum mobiles should be off-topic … $\endgroup$
    – MS-SPO
    Mar 26, 2023 at 13:09
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    $\begingroup$ how do you intend to power this? $\endgroup$
    – jsotola
    Mar 27, 2023 at 5:50
  • $\begingroup$ Gravitation is a way of "free" available energy and horizontal axis wind turbines already use gravity forces when the blades go down increasing rotation. And so In this case there's a balance of upward and downward torque as it happens in vertical axis savonious wind turbines (which can be fixed by covering half turbine) so for the water wheel to work in some period of time, the flow rate is important besides wheel diameter and filled cup volume, and probably the design of cup shape and catch and release mechanism is important too $\endgroup$ Mar 27, 2023 at 12:13

1 Answer 1


The device you are describing is called a pressure exchanger. They are common on high pressure reverse osmosis systems and use positive displacement pump/turbine instead of wheels. The efficiency is not 100%, (no perpetual motion) so additional input is required; such as pumping additional water to keep the system going.

I would not recommend it for your application because the cost for such a system is high and the energy recovery at the low pressure would be very low.

  • $\begingroup$ What you have described is also an integrated process system's energy recovery device that people here smears as "perpetual energy" fanatism. While the project I have exposed here is a sort of gravitational energy recovery system similar to funiculars, the pressure exchanger you have cited seems a compressed fluid energy recovery system. $\endgroup$ Apr 3, 2023 at 19:53

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