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Does a dam count as head
By peter nap, Section Hydro Posted on Tue Oct 09, 2007 at 11:49:56 PM MST
I have a total of 4 springs that come together in a ravine

The first two come together and flow east.
The the second and stronger two flow south for 500 yards between tow high hills and then connect with the first two.
Piping them separately would be impossible but I thought about damming them where they all come together. The problem there is that I'm losing head. I think I can get about 15 feet from the proposed dam site.
The flow from the dam would be about 30 GPM.
If I dam these and back water up say 4 feet deep, will it give me enough head?

Does a dam count as head | 6 comments (6 topical)

Re: Does a dam count as head (3.00 / 0) (#1)
by richhagen on Tue Oct 09, 2007 at 07:35:22 PM MST

Certainly you can do something with it. How much power are you hoping to generate?

See: http://www.otherpower.com/otherpower_hydro.html
and: http://www.otherpower.com/scotthydro1.html

Note that they only have about 3 feet of head, Your dam height of 4 feet should give you 4 feet of head. They might have had a bit more flow rate though. Rich
'A Joule saved is a Joule made'

Re: Does a dam count as head (3.00 / 0) (#2)
by Countryboy on Tue Oct 09, 2007 at 08:29:34 PM MST

Head is the distance the water will drop. It doesn't matter if the water is dropping over the edge of a dam, or if it is dropping as it runs through a pipe. The only way you would lose head by building a dam is if you could have piped water from a higher distance.

4 feet of head and 30 gallons a minute will give you roughly 12 watts. I don't know how much power you are expecting, so you will have to decide if you have enough head and flow.

Re: Does a dam count as head (3.00 / 0) (#3)
by peter nap on Wed Oct 10, 2007 at 04:03:33 AM MST

The four feet is just the dam. If I start piping there I can get another 10 feet further down the line (100 feet further)\

As far as power needs, what I can get is what I can get. 12 watts 24/7 would be great with solar and wind making up the rest of whatI need.

[ Parent ]

Re: Does a dam count as head (3.00 / 0) (#4)
by finnsawyer on Wed Oct 10, 2007 at 09:05:31 AM MST

You should rent a transit level and determine the actual potential head you could get from various possible sites for the dam. It's really hard to accurately eyeball changes in elevation. You might, in fact, be better off just damming the two stronger streams farther back.
GeoM

Re: Does a dam count as head (3.00 / 0) (#5)
by finnsawyer on Wed Oct 10, 2007 at 09:31:49 AM MST

I thought I'd add a little to this. Obviously, as you work upstream along the two stronger streams you are adding head relative to the bottom of the dam and the generator site, but you may also have the option of building a deeper pond and higher dam for the same cost. In general a deeper pond is preferable as you would have less weed problems than with the shallower pond. At four feet the pond could fill with weeds choking the water intake. At 12 feet depth you should have little or no weed problem. At least that would be the case around here. The first pond I built was 12 feet deep and the cattails only grow around the edge. I built a small pond (about 100 foot in diameter) behind my current house. At best its about eight feet deep and the cattails are trying to take over. We had a drought this summer and the cattails were following the water as it dried up. Now we've had a lot of rain and the pond is filling up, tending to drown the cattails. I hope it does.

When I built the first pond (400 foot by 200 foot triangle) with the twelve foot depth I placed a 4 inch pipe in a barrel of rocks that passed through the bottom of the dam (you need to weld a plate around the pipe). Weeds have never blocked it. It does need to be flushed occasionally by opening the valve (every spring).
GeoM
[ Parent ]

Re: Does a dam count as head (3.00 / 0) (#6)
by picmacmillan on Fri Oct 12, 2007 at 10:52:53 AM MST

hi peter ...i have seen some cool turbines using very little head ..theres a fellow on here named burkesfallsman....he has a beauty and it runs off a beaver dam very good unit i think he told me he gets a kilowatt a day out of very little head..take care,...pickster

http://www.frecklefarmloghomes.com

Does a dam count as head | 6 comments (6 topical)

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