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Designing a Hydro Generator for my Farm

  1. Jun 6, 2009 #1
    Over the past few years I have like many of you become interested in renewable energy.

    Over the past few months we have gotten a lot of rain.

    We also have a small creek in our pasture and it begins with 2-12 inch field tiles. The end (beginning i guess) has been filling with silt over the past 20 years and has now reached the top of the retaining wall so we need to build a new one a few feet taller.

    I am thinking why we are down there working it may be a perfect opportunity to set up a small hydro generator.

    I can weld and build basically anything ( I am a home builder) and my brother is a commercial electrician so I think we have the know how. I am just looking for some engineering and design help/suggestions.

    OK so while I was down there the other day the 2-12 inch tile were running at what seemed to be full capacity. Maybe 60% full I would think that would be about 1 gal per sec per tile. If anyone has any opinions on that I am guestimating.

    It is probably running 20%-30% higher than avg right now. Water weighs about 8 lbs per gallon. So .... I think i can reasonably get to 10 lbs a second avg. And it falls about 1 ft initially out of the tile. We have nice concrete walls on 3 sides and a concrete floor for about 10 ft.

    I will be adding a illustration soon.

    OK I have done some more research and found I have 2-12 inch tile and they can flow 2 cubic ft per sec each. I think avg is probably 1/4 of that. appx 60 lbs per cubic ft. So avg work done is 30lbs drops 1 ft per sec on avg.

    30 x 60sec = 1800 lbs 1 ft per minute

    550 ft lbs a min = 1 hp

    So i have a little over 3 hp

    750 watts per hp x 3 = 2250 watts

    2250 x 24 hrs a day= 54kWh

    Any comments on these assumptions would be great.

    Last edited: Jun 6, 2009
  2. jcsd
  3. Jun 6, 2009 #2


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    Staff: Mentor

    You're so close to having figured it out yourself (maybe you have, but you put ??? in there...). Power is in foot-lb/min and you have information in units of feet, lb, and min. Put them together!

    If I'm understanding you correctly, you only have a 1 foot drop to work with? anyway, potential energy is simply weight times height and power is flow rate times height. So if you have 60 lb/min dropping 1 foot, you have 60 ft-lb/min of energy at your disposal. That is about 1/10th hp, or 70 watts.

    1 ft of drop seems awfully small, but if that's what it is, ok. Flow rate is pretty easy to find, though, if your water source is coherent: find yourself a 5 gal bucket, direct the water flow into it and measure how long it takes to fill it.
  4. Jun 6, 2009 #3
    So 2 minutes of research made me redo my assumptions.

    As far as the 1 ft of work that is about how far the tile are from the concrete floor. maybe 18 inches but its under water so its hard to see and remember from yesterday.

    I did edit my first post so if you could reread it with the new assumptions and let me know what you think so far
  5. Jun 6, 2009 #4


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    Gold Member

    Amateur hour again... I don't really know anything about the subject. I am wondering, however, if you could dig the receiving basin a couple of feet deeper to gain more gravitational assistance from the falling water.
  6. Jun 6, 2009 #5

    Are you calling me an amateur? I know I am. But I am trying to learn and I find this site very helpful. Should I just keep my comments to myself or.......

    If you were talking about yourself being an amateur I enjoy all points of view.

    I have found a micro hydro calculator and I according to it 100 kWh a month are possible in the wetter months. Also since I am at the beginning of the creek I have a perfect opportunity to harness this energy for a very low initial cost.

    So far I am imagining a 6 ft radius water wheel a pulley and shaft up to dry land. At that point I could have a mounting plate for 3 generators (or one big one) They could be connected and disconnected very easily.

    100 kWh is about the entire farm monthly use. So maybe just a 2-3 year return on investment.
  7. Jun 7, 2009 #6


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    Staff: Mentor

  8. Jun 7, 2009 #7
    Thank you I had not thought about wiki

    I went to the creek again this morning. I was expecting some rain according to the radar but nothing and I am trying to decide how tall to make the new dam for overflow water.

    The tiles though where in fact still flowing I would say 80% max. So I think it will be easy to take another piece of 12 in tile and build a small model in the garage and then simply side it in to place once completed.

    I will keep you updated.
  9. Jun 7, 2009 #8


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    Gold Member

    That is indeed the case; I hoped that you would understand that. :smile:
  10. Jun 7, 2009 #9
    I feel pretty intelligent when I talk to friends and peers but I get a bit intimidated on when I put some ideas out there for others to see.

    In reference to the generator I have found there is a small dam about 100 yards doinw the creek. I can lower the water by removing it. This will get me to about 3 ft of head.

    Also I have found water wheels are not easily adapted to electric generation so I am looking at a kaplan style turbine.
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