Sunday, November 20, 2011

Flow of River Hydro -- Using Only Stream Velocity to Drive a Turbine

I get email questions from people who live on a stream and would like to use the stream to make electricity.
If the stream has some elevation drop over the property and the flow is decent most of the year, then the answer is that if you can meet the legal requirements, its possible to make electricity, and that it can be quite cost effective.

Quite a nice underflow water wheel.

But, if the stream has no elevation drop, and you just want to make use of the velocity of the stream water to make electricity, then its more challenging.  I've added a new section that goes into what's involved in generating electricity only from the water velocity.  It covers how to estimate the amount of power your stream might generate, provides a bit of design information, and it lists all of the home scale example projects I could find that seemed like they might actually work.  Its a place to get started on your quest for free no pollution energy from your stream.

One of the reasons getting power from your stream is difficult is that while its clear that there is energy in that flowing water, it not nearly as dense as the energy you can extract from water dropping through an elevation difference.  This plot shows you roughly how much power you can get from 1 sqft of flow area at various stream velocities.

Just a glance will tell you that if you have a 2 mph 6 inch deep stream, your power generation possibilities are pretty limited.  But, if you have a deep 5 mph stream, there is some worthwhile power there.

I found a few commercial and few homemade examples of flow of river turbines and water wheels -- the link below provides pointers to all the ones I could find.  If you know of others please let me know.

The new section on Flow-Of-River hydro installtions...

The micro-hyro page for info on more conventional hydro...



  1. Go ahead and build the wheel and just see if it works then stash it. Believe me, when the SHTF, there will be no inspectors around to tell you you can't run it.

  2. i think there should be more of these then sub stations and power plants i think this be cheaper then the substations and power plants

  3. Sounds and looks interesting. How does one calculate water velocity? Also what size motor would one need to generate 3 to say 5 KVA for a a farm?

  4. Hi,
    This page has more detail:

    Normally you would measure water velocity by dropping something that floats and does not have much mass into the stream and timing how long it takes to traverse a measured distance. Dividing the distance traveled by the time gives velocity.



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