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High flow Low Head Solution Desired

 
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Hi everyone! We purchased a distressed property in Montana that contains some of the infrastructure  of a previously functioning hydro system. It was an old 12 volt system from the mid-90’s.  I’d like very much redesign this system and make it functional again.

Here’s what I have to work with, and it is challenging: A high flow year around creek, with a diversion channel dumping into a 2’ diameter buried corrugated pipe running approximately 900’ with only 2.7’ of drop/head. The pipe is continuously full. My calculations (I’m not 100% sure of my math) indicate that is over 8000gpm and at 100% efficiency, should generate over 2kw continuously.  I cannot find an off the shelf resource that would fit my site and would like expert, or at least well reasoned opinion, on my math for what is possible. Also can anyone out there guide me to good resources for suppliers of low head solutions and advice?
 
pollinator
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I was going to suggest an archimedes screw turbine, see renewables first website.  But it looks like you need at least 1m to have a reasonable system, so I'm not sure if it would scale down further.
You may need to be more creative.  I haven't searched the Permies forum itself though, so someone here may already have installed a small scheme like yours.  What sort of turbine was there perviously?
 
pioneer
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Try a pelton wheel.  You can buy one or make it,  The voltage is dependent on what you want.  The higher the voltage, the further the current will travel with smaller % losses.  Just remember that ultra low voltage (usually DC) and low voltage (usually AC) wires are different in that ultra low voltage has more wires of a smaller diameter but more in a bundle so it is thicker.  Depending on the distance, you can use a ground negative system where only the positive (or active) wire is run and you use ground spikes for the negative (or neutral) run.
 
Rocket Scientist
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I have just the opposite.  A high head low flow system.
I use a one nozzle permanent magnet pelton with  a stainless wheel from Harris hydro,
here is a link http://harrishydro.biz/
A 4 nozzle arrangement would be ideal with the volume of water you have.

I have a very old system @12 vt  
I highly recommend 24   volt or even 48 volt.
Your whole system from hydro to solar panels should be higher voltage.


EDIT)  Where in Montana is your property?   Sanders county perhaps?
DSCN0805.JPG
[Thumbnail for DSCN0805.JPG]
 
Russ Daniel
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Nancy Reading wrote:I was going to suggest an archimedes screw turbine, see renewables first website.  But it looks like you need at least 1m to have a reasonable system, so I'm not sure if it would scale down further.
You may need to be more creative.  I haven't searched the Permies forum itself though, so someone here may already have installed a small scheme like yours.  What sort of turbine was there perviously?



I wish that I knew the answer to that. The entire system, except for the inlet and underground pipe, has been vandalized and stolen. The fact that the surviving charge controller and battery bank is 12 volt tells me that perhaps they had not figured it out either.
 
Russ Daniel
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Paul Fookes wrote:Try a pelton wheel.  You can buy one or make it,  The voltage is dependent on what you want.  The higher the voltage, the further the current will travel with smaller % losses.  Just remember that ultra low voltage (usually DC) and low voltage (usually AC) wires are different in that ultra low voltage has more wires of a smaller diameter but more in a bundle so it is thicker.  Depending on the distance, you can use a ground negative system where only the positive (or active) wire is run and you use ground spikes for the negative (or neutral) run.



Good advice, except there is zero probability of a peloton wheel working with only a 2.7’ drop. Thanks for your reply though.
 
thomas rubino
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Hey Russ;
Not sure what question you are referring to.
System voltage?    In the 1990's 12 volt was what we all used.
My system went in in 1996 and its 12 volt to this day.
Nothing wrong with 12 volt if your expectations are low.

Sounds like you have an inlet and 900' of  2' dia. pipe .  Culvert I assume?
That alone is thousands of dollars worth of material and labor, already in place!
The battery's you found are probably not very viable anymore. (I could be wrong)
The charge control is of course 12 volt and probably outdated.

 
pollinator
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Wow, Russ. You have an incredible resource at your fingertips. I am green with envy. The head may not be impressive, but that much water is a great deal of mass, and in motion it represents a great deal of energy, though the corrugated pipe will steal a percentage. I find it hard to believe that the right nozzle and pelton wheel would fail to produce useful torque. Keep in mind that torque can be used to directly power mechanical equipment as well as for electrical generation.
 
Paul Fookes
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Russ Daniel wrote:

Paul Fookes wrote:Try a pelton wheel.  You can buy one or make it,  The voltage is dependent on what you want.  The higher the voltage, the further the current will travel with smaller % losses.  Just remember that ultra low voltage (usually DC) and low voltage (usually AC) wires are different in that ultra low voltage has more wires of a smaller diameter but more in a bundle so it is thicker.  Depending on the distance, you can use a ground negative system where only the positive (or active) wire is run and you use ground spikes for the negative (or neutral) run.



Good advice, except there is zero probability of a peloton wheel working with only a 2.7’ drop. Thanks for your reply though.



Have a look at this site in the US: https://windturbineusa.com/hydro.html The pelton wheel can be home constructed or bought.  It only needs water flow to make the wheel turn.  There are high pressure systems using jets to turn the wheel, but you will need continuous flow low pressure system.  To manage your voltages, have an inverter close to the system and bring AC from the inverter into your house.  I am assuming that you use 110V AC.  The best batteries for storage (from my experience) are tubular lead.  They are sealed and can be placed vertical or on their sides to save space.  48 Volt DC is fast becoming standard which provided good voltage to get power to the inverter.  Your inverter needs to be twice the size of what you measure because of the need to cater for induction starting rather than soft start motors.

Because we have has solar since 1986, and are totally off the grid, we have learned many lessons and made lots of mistakes.
Best wished with your endeavour
Paul

Edit: Russ, this is not a bad post to get the basics if you don't already have the knowledge. https://www.instructables.com/DIY-Off-Grid-Solar-System-V20/  Just swap the solar cells with hydro-generator.  Happy to chat further via purple moosages if you want.  I am not an electrician so can only speak from experience.  We have now converted to Victron because it is very easy to use and they have good support (I do not get anything from this endorsement and paid to buy the components from a third party) I can monitor our system on the phone no matter where we are because of the Web connectivity.  You will need to also comply with your country codes for electrical supply.
 
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A pelton wheel is an impulse turbine, which by design calls for a high velocity jet of water. With less than 3 feet of head, it would barely spin. Pelton wheels are probably the most commonly available off-the-shelf designs, because they meet the design criteria that is most likely for a micro-hydro setup: low flow and high head.

Your site has the opposite - low head but massive flow! Seriously, even if it is half as much water as you estimate, it is still an incredible resource. The bad news is that it is so large that you are probably not going to find a plug and play solution. What you ideally would have is a reaction turbine, which would be submerged in the water flow - look up a Kaplan turbine to get an idea. You will notice that the pictures that come up tend to be massive... You might also look at a cross-flow turbine (which is what I use). You could try and build something, but it would likely be a pretty challenging project.

What does the outflow look like? You say the pipe buried, so does it just come out of the ground right at the stream bank? If it were me, I think I would start with something very simple. I would think about building some sort of simple tail-race, and just putting a little undershot or breastshot water wheel in there. It would not be the most efficient, perhaps, but it would be super cheap compared to the other options. Even a wooden wheel turning a permanent magnet motor with some v-belts would work.

How far is the site from where your batteries would be? 12v is terrible from a transmission standpoint, so unless the pipe is like tens of feet from the house, you will probably want to up the voltage. This is not hard to do, and there are inexpensive controllers that will let you input up to 100 volts and step it down to whatever your battery voltage is.
 
Paul Fookes
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I agree with Carl.  You will need to increase the velocity of the water flow.  This may be achieved by introducing a restricter at the outflow end and adding a conical piece to the inflow end.  With the increased pressure there could be enough pressure. I am not sure of the fluid dynamics.  There are Pelton style wheels that have reducers on the outflow to create a nozzle  so increase pressure.  These wheels are often made using Pelton cups and bicycle wheels The alternatives are a floating water wheel or a vortex flow, both of which have good information on the net.  To increase the height slightly/ intake pressure, can you create a partial weir?
 
Carl Nystrom
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The changes you suggest would not change the pressure. Pressure is created by head; about 0.4 psi per foot. A long pipe like this would also add drag, which reduces the pressure further. Reducing the end of a pressurized pipe would increase the velocity of the jet, which is what you would want for an impulse turbine.

I am not an expert, but I do not think a pelton wheel will work at all in this application. It would have to have comically large spoons, and what you would basically have is a horizontal waterwheel.

 
Russ Daniel
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Carl Nystrom wrote:A pelton wheel is an impulse turbine, which by design calls for a high velocity jet of water. With less than 3 feet of head, it would barely spin. Pelton wheels are probably the most commonly available off-the-shelf designs, because they meet the design criteria that is most likely for a micro-hydro setup: low flow and high head.

Your site has the opposite - low head but massive flow! Seriously, even if it is half as much water as you estimate, it is still an incredible resource. The bad news is that it is so large that you are probably not going to find a plug and play solution. What you ideally would have is a reaction turbine, which would be submerged in the water flow - look up a Kaplan turbine to get an idea. You will notice that the pictures that come up tend to be massive... You might also look at a cross-flow turbine (which is what I use). You could try and build something, but it would likely be a pretty challenging project.

What does the outflow look like? You say the pipe buried, so does it just come out of the ground right at the stream bank? If it were me, I think I would start with something very simple. I would think about building some sort of simple tail-race, and just putting a little undershot or breastshot water wheel in there. It would not be the most efficient, perhaps, but it would be super cheap compared to the other options. Even a wooden wheel turning a permanent magnet motor with some v-belts would work.

How far is the site from where your batteries would be? 12v is terrible from a transmission standpoint, so unless the pipe is like tens of feet from the house, you will probably want to up the voltage. This is not hard to do, and there are inexpensive controllers that will let you input up to 100 volts and step it down to whatever your battery voltage is.



Carl, every measurement and subsequent bit of math that I’ve been able to scratch out of this, indicates somewhere between 3 & 4 kw of potential.
I don’t understand enough about fluid dynamics to calculate or frankly estimate what I’d lose through the pipe, but if I’m able to de
n and implement a breast shot waterwheel, I believe I’ll be able to squeeze 1.5kw out of my stream. If I meet the right engineer, I believe I may possibly be able to achieve a little more, maybe up to 2kw. That, in conjunction with a few decent solar panels, a moderate Ann JJ mm battery bank, a charge controller and inverter.. and
I hope we’ll be golden! My next challenges will be design wheel.
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