Harnessing kinetic energy from impact of rain water

  1. I read in a science magazine that you would be able to generate more energy by collecting a mass of water and tipping it through a turbine than from generating energy from the impact of that mass of water as individual raindrops. Now this may simply be to do with the technology we have that can't collect enough useful energy from the impact of rainwater as opposed to turbines

    But what confused about this is that that mass of water as rain has fallen from a great height where it has reached terminal velocity and so should have much more kinetic energy than merely being tipped from a small height.

    I should mention that I do not have or am doing a degree in physics so I apologise if I'm being dumb, but was just very curious.
     
  2. jcsd
  3. sophiecentaur

    sophiecentaur 14,114
    Science Advisor
    Gold Member

    If you are actually hoping to make use of the kinetic energy of the rain as it falls onto a receiver of some kind, you should consider just how little actual energy is involved. Raindrops reach a terminal velocity of no more than 10m/s for the largest drops ( mostly, we're talking 1 or 2 m/s) and the actual mass of rain falling in a shower could be only a few grammes on a paddle wheel or equivalent.
    I think there would be much more energy available from the wind in most locations. The clue is that (ifaik) there are no serious installations for harvesting 'rain energy' and people have really tried most things where there is a chance of success.

    The terminal velocity of large, massive objects is high (say 50 m/s) but there are very few of these around (just as well).
     
  4. A.T.

    A.T. 6,276
    Science Advisor
    Gold Member

    Compare the surface area of the biggest turbine we can build, with the surface area that collects water into a reservoir from a dam. Even if rain would have more energy per liter, it is so much simpler to collect huge amounts with less energy density and put them through a smaller, simpler to build turbine.
     
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