Author Topic: pelton pipe?  (Read 4536 times)

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greenkarson

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pelton pipe?
« on: April 04, 2010, 06:45:40 AM »
the first winter with my aquair turbine surprised me.  It took me by surprise plugging away under the ice. It acuatualy worked a little better the ice froze over the top of the dam forcing the water through the covert. I expected the covert to eventualy freeze being that it is just under the surface but i guess there must have been too much current. here is a youtube link to it from last fall http://www.youtube.com/watch?v=-wNF2anLxjI

Anyways now that its working im bored again. So here come the questions again.

My property has two creeks the big one you see in the video and a small one that runs 90 degrees into it its much smaller mayber 6 inches deep and 2 feet across. basically the big creek in the video runs paralel to the road but about 400 feet from it and about 150 to 200 feet lower then the road. so the small creek runs underneith the road through a covert where it drops out of falls about 8 feet then runs the rest of the way down the hill to the main creek. on the way down the hill it passes my battery shed from the aquair turbine.  

  So heres my plan make a hoper under covert under the road. but id like to only use 1.25" back poly pipe because its cheep and easy to run down the hill with minimal visual impact. And because im in canada i was thinking that if i ran the pipe a couple of feet off the ground it may be able to run a little longer into the cold with the back pipe collecting a little heat. I know 1.25" is a little small but Im only hopping for around a 100watts.  im thinking a little pelton setup near my battery shed so this would give me about 50 feet of head over 150 feet of lenght. To be honest not sure how to calculate flow in pipe but it would be as much as can be gravity feed through a 1.25 pipe.

 any suggestions what to use for the generator its self. Ive been wanting to try winding one my self after reading about them on here for the last year or so.


any input you guys have would be apreciated


thanks karson  


heres some links to a woodfired hot tub i built last summer someone might find usefull and my hydro ram(by the way most useful thing i ever built)

http://www.youtube.com/watch?v=Z0iECQiLk5w

http://www.youtube.com/watch?v=qGXLrmaadIA

http://www.youtube.com/watch?v=XkcPnkZ_BxU

« Last Edit: April 04, 2010, 06:45:40 AM by (unknown) »

bob g

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Re: pelton pipe?
« Reply #1 on: April 04, 2010, 08:51:53 AM »
as long as the water is moving it won't freeze in your pipe, if you gate it off

and stop the flow for any reason and it is very cold, you will be done till spring thaw.


so it should work, just don't stop the water flow in the pipe


bob g

« Last Edit: April 04, 2010, 08:51:53 AM by bob g »
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greenkarson

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Re: pelton pipe?
« Reply #2 on: April 04, 2010, 09:33:39 AM »
sorry everbody i feel like a moron. Just read my own post and relized i type back instead of black ever time.  I guess its true can't be good looking and smart.


By the way if your reading this and havent made a donation to this board for the wonderful job they do. I encourage You to do so.  If you don't think its worth it try to find this kind of info at your local book store. You will be back.


thanks karson

« Last Edit: April 04, 2010, 09:33:39 AM by greenkarson »

ghurd

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Re: pelton pipe?
« Reply #3 on: April 05, 2010, 11:53:00 AM »
I am following this out of curiosity, and hope someone will have something more relevant.


I don't think you can get much power out of a 150' of 1.25" black pipe, even with a 50' head.

Consider 2" pipe?  It is more than 2.5X larger, will have a lot less head loss from the flowing water, and doesn't cost much more.


Best example I can quickly find:

Using 25 gallons / minute,

Head loss in 2" pipe is 1.28.

And 3" pipe is only 2.25X larger than 2" pipe,

But head loss for 3" pipe with the same flow is only 0.18, or less than 1/7th the losses.

Moving from 3" pipe to 4" pipe (1.7X larger) reduces the losses from 0.18 to 0.04.

Meaning a small change in pipe diameter makes a large difference in losses, and moving from 2" pipe to 1.25" pipe could be quite considerable.

Also meaning if the flow in a given pipe dia is doubled, the losses increase 3.6X.

Together that's a good argument for 2" pipe.

That came from here, chart at the bottom,

http://www.exmork.com/how-to-measure-water-head.htm


I figure to get 100W, it needs about 17.5 gallons per minute of flow.


Gosh.  If you can only get 50W out of it, thats still over a KWH a day!

And I am jealous.

G-

« Last Edit: April 05, 2010, 11:53:00 AM by ghurd »
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Ungrounded Lightning Rod

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Re: pelton pipe?
« Reply #4 on: April 05, 2010, 01:13:23 PM »
Black will help it warm in the daytime.  But it will also help it cool at night.  Not what you're after (unless you're hoping that it will thaw from sunlight if it ever happens to freeze up).


Supporting it in the air lets the cold air circulate around it and pull heat from it.


Putting it underground, even a little, insulates it.  (Especially if it's above the water table.)


Ideally you'd put it below the frost line (assuming you're not in a permafrost area where the freezing is BELOW the frost line).  Then it probably wouldn't freeze unless you fed it slush and let it clog.  But given the insulating properties of plastic pipe, keeping the freezing winds from circulating around it, feeding it with water warm enough to flow, and letting it run all the time will probably keep it running all winter.


Tap the water as low as practical.


The reason water runs under ice is that it has a maximum density at about 4C (a tad over 39F).  So when it's freezing cold the warmer water sinks and the temperature of standing water tends to rise with depth until it reaches that critical temperature.  (Meanwhile, turbulence is friction and turns the energy of the moving/falling water in a stream into heat, making up for losses.  Tap the running water and you get something where you have to pull out a bunch of heat before it even begins to crystallize, followed by a LOT MORE to get it to slush and ice up.  If your run isn't enormously long and surrounded by something like moving cold air it won't lose enough heat to stiffen up on you.  So just insulate it and keep it moving.

« Last Edit: April 05, 2010, 01:13:23 PM by Ungrounded Lightning Rod »

Ungrounded Lightning Rod

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Re: pelton pipe?
« Reply #5 on: April 05, 2010, 01:24:58 PM »
corollary:  Add a bypass valve at your turbine so, if you have to shut it down for tweaking, you can keep the water flowing in the main run.
« Last Edit: April 05, 2010, 01:24:58 PM by Ungrounded Lightning Rod »

ghurd

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Re: pelton pipe?
« Reply #6 on: April 05, 2010, 01:38:28 PM »
Completely theoretical.

In borderline temps, if it does manage to slush up or exhibit icing on the pipe walls, the flow losses will be increased,

which is heat in the slush,

so it could be a bit self-regulating if insulated?

G-

« Last Edit: April 05, 2010, 01:38:28 PM by ghurd »
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hydrosun

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Re: pelton pipe?
« Reply #7 on: April 06, 2010, 01:49:02 PM »
A creek 6 inches deep and 2 feet across must be running hundreds of gpm. If it is 150 to 200 feet above the main creek it could deliver a lot more power. If I'm reading this correctly you would need 400 feet of pipe to get this much head. So if you can use the power I'd put in a larger (4 inch?) pipe that can move up to 200 gpm without losing too much head. That would produce enough power to run a house including heating.  If you can't use the power then go ahead and put in the smaller pipe to be able to play with it. The 1 1/4 pipe can handle about 10 gpm at 50 feet head for about 50 watts. Much more than that will require a larger pipe. I find that 4 inch gasketed sewer pipe is lower cost than 2 inch poly pipe but needs to be buried or protected more than poly.

The simplest generator for the lower output would be a brushed dc motor. The trick to efficiency is getting the correct rpms. At 50 feet head a 4 inch pelton would run at about 1400 rpm.   At 120 feet head it would run at about 2000 rpm. So a motor rated at the voltage you want at these rpms would work at a high efficiency. Nice thing about designing for hydro is they have a constant rpm unlike wind.

Chris
« Last Edit: April 06, 2010, 01:49:02 PM by hydrosun »

ghurd

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Re: pelton pipe?
« Reply #8 on: April 06, 2010, 02:34:20 PM »
(I was hoping you'd show up for this one)


"this would give me about 50 feet of head over 150 feet of length"


I figure it is not flowing very fast, or Karson would want more than 100W.

G-

« Last Edit: April 06, 2010, 02:34:20 PM by ghurd »
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hydrosun

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Re: pelton pipe?
« Reply #9 on: April 07, 2010, 08:58:32 AM »
I was under the impression that he started with how much power he thought he could produce, ended the pipe where it was close to the battery and picked a pipe size because it was easy to use. So with that setup he can produce 50 watts. If he wants more power he has the option to go to a larger pipe, go farther down the hill and use more of the water.  If he measures how much water is in that stream and how much head he can use I could calculate the maximum power he could produce. It's up to him to decide.

chris
« Last Edit: April 07, 2010, 08:58:32 AM by hydrosun »

Ungrounded Lightning Rod

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Re: pelton pipe?
« Reply #10 on: April 08, 2010, 02:07:10 PM »
So if you can use the power I'd put in a larger (4 inch?) pipe that can move up to 200 gpm without losing too much head. That would produce enough power to run a house including heating.  If you can't use the power then go ahead and put in the smaller pipe to be able to play with it.


Also:  If the cost isn't prohibitive you can go with the larger pipe even if you don't use its full potential flow at first (or don't have enough flow available to run it full bore).  You can restrict it as much as appropriate near the turbine (such as by using few and/or small jets) to limit the flow to what you need and/or keep the pipe full of water for maximum head.


The size reduction at the end limits the flow without reducing the pressure, while the smaller the long run is the greater the pressure drop in it from a given flow.  So you gain pressure/effective head with a larger pipe and a reducer compared with running the smaller pipe the whole way.

« Last Edit: April 08, 2010, 02:07:10 PM by Ungrounded Lightning Rod »

greenkarson

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Re: pelton pipe?
« Reply #11 on: April 11, 2010, 08:50:21 PM »
Thanks for all the info. Gives me lots to think about im going to keep an eye on the creek flow for a couple of months before i start anything.
With a DC motor for a generator do i look for a 12v dc motor or a higher voltage? And how should the rpm rating on the motor compare with the rpms of of my turbine?
 thanks karson