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I How much power would this system generate from waves?

  1. Apr 10, 2017 #1
    I'm looking for some back-of-the-envelope calculations on an idea.

    Say there is a buoyant mass floating on the water. It is connected to a system which, when waves move the mass up and down, it pulls a string which turns a wheel of an electromagnetic generator (assume there is a mechanism which allows only pulling in one direction to spin the wheel). Assuming the wave height and frequency is known, and the mass of the object, how can the output power be calculated?

    I think the output power of the generator should be the torque multiplied by the angular speed, but I'm not sure if this is correct or how to complete the process.

    Also, how would the generator's efficiency affect the mathematics?
  2. jcsd
  3. Apr 10, 2017 #2


    Staff: Mentor


    Yes that's right torque times speed. You have to correct for efficiency, and for the fact that the string stops moving twice each wave, but the principle is correct.

    But you are far from the first person to think of this. There are hundreds or maybe thousands of trials and pilot projects already. https://en.wikipedia.org/wiki/Wave_power

    Keep thinking though. Maybe next time you will be first.
  4. Apr 10, 2017 #3
    I didn't think I was the first, I'm just looking for the correct equations which would give me a better idea of how the system works
  5. Apr 10, 2017 #4
    Using Buoyancy - how is this not just Mass, volume displaced and Vertical displacement.

    So as you displace a volume of water, that much force is applied to "lift" it.

    Relevant company = OPT

    The energy available is significant, but IMO the technical challenges make this fools errand for generic energy generation. eg -Remote buoy energy generation - OK. Bt look at the stats - this is 10KG system for 100W continuous load)
  6. Apr 10, 2017 #5


    User Avatar

    Staff: Mentor

    Right; weight of water displaced times distance times frequency of half cycles.

    ...and being generous, maybe multiply by 75% for efficiency.
  7. Apr 10, 2017 #6
    My point being discussing the torque and generator is just a mechanical system added to a basic linear force.

    Note the dynamic rage of the energy in an ocean wave is > 100:1 . The systems need instantaneous conversion of about this ratio. Want a 1KW converter, you need to handle 100KW to 0KW over single wave cycle.
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