Small Dam & Micro-Hydro Building

[RE]

What about splitting off the posts from the other thread to merge into this one?

I'll respond on the technical issues later.

RE

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[Eddie]

What about splitting off the posts from the other thread to merge into this one?

I'll respond on the technical issues later.

RE

I'm fine with splitting the thread, but I'm no good at actually doing it.

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[RE]

What about splitting off the posts from the other thread to merge into this one?

I'll respond on the technical issues later.

RE

I'm fine with splitting the thread, but I'm no good at actually doing it.

Oh, no issues. I'll do it.  It's not the easiest task on SMF, sorta like extracting wisdom teeth but without the blood. lol.  Takes some practice.

Just please nobody post to this thread until I am done and give the Thumbs up.

RE

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[RE]

OK, split, merged and retitled.  You are now safe to post to this thread.  lol.

Sorry it took so long.  I hadda reboot because the laptop was hanging up, and then the sub-thread wen back quite far, 6 pages deep!  Fortunately, no other topics were discussed in between, so I was able to do a bulk transfer.  Otherwise, it would have been a nightmare.

RE

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[RE]

Good points.

I expect the water diversion issue will be a non issue at some point, we'll have a seriously dry late summer and fall that will dry the creek to a trickle that won't interfere much.

I think it's better to build a dam that's low and strong and bulletproof that it is to get fancy and install a gate, which really won't do much in full flood anyway. It isn't unusual to have full size live trees get washed out of the banks of my creek and swept away in a flood. I've seen it. No gate will hold up to that.

The dams I've seen that last are just long, low, straight check-dams.

I wish I could estimate the flow through there right now. I'd like to know, but the turbine people talk about filling up buckets, which is not going to work. When you don't have a lot of head, flow becomes crucially important for power generation.

A few points.

1- A long, low dam will not provide enough pressure to efficiently run turbines.  You need either decent depth or fast flow rate, or both.  A long low check dam is not going to do this job.

2-  The main purpose of the gate is not to release a lot of water at times of high water, that is the job of the spillway.  The job of the gate is to release water at times of low water/drought, so it makes its way downstream.  So it doesn't need to be very big.If you are building the dam out of concrete, you just set the gate in at the lowest point under the dam.  It's not vulnerable to trees or other debris floating down in a flood, because it is at the bottom of the dam.

Easier alternative to this is just to run a pipe under the dam with a valve you can open and close, but it will need to be kept clear of sediment at both ends so it doesn't block up.  You would want to use a fairly large diameter sewer pipe for this purpose.  6-12" or so I would estimate.

3-  I have another Rube Goldberg solution I am working on, but it will take a day or two to get some schematics done and research the type of hardware to use.  I won't let on to what this is until I have it reasonably bulletproof and can't get hammered from the first post.  LOL.

RE

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[Eddie]

2-  The main purpose of the gate is not to release a lot of water at times of high water, that is the job of the spillway.  The job of the gate is to release water at times of low water/drought, so it makes its way downstream.  So it doesn't need to be very big.If you are building the dam out of concrete, you just set the gate in at the lowest point under the dam.  It's not vulnerable to trees or other debris floating down in a flood, because it is at the bottom of the dam.

A pipe is usually how it's done around here, I consider it fairly superfluous though, for a four foot dam that is probably going to be holding less water than my backyard pool in town.


2-  The main purpose of the gate is not to release a lot of water at times of high water, that is the job of the spillway.  The job of the gate is to release water at times of low water/drought, so it makes its way downstream.  So it doesn't need to be very big.If you are building the dam out of concrete, you just set the gate in at the lowest point under the dam.  It's not vulnerable to trees or other debris floating down in a flood, because it is at the bottom of the dam.

A tall dam creates all kinds of problems and complexity that I have no desire to deal with, so that isn't going to be in the cards.  The viability for generating electricity comes down to flow rates. I doubt they are easily measurable for this site, but maybe I can figure out how to do it. The performance of the turbines can be computed easily if you have the head height and the flow rate. Low head turbines require high flow to generate much power. It might not be enough to even make it practical. Have to see about that. I'm pretty sure it would take several turbines too, for this particular site. Expense is a factor.

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[RE]

The performance of the turbines can be computed easily if you have the head height and the flow rate. Low head turbines require high flow to generate much power. It might not be enough to even make it practical. Have to see about that. I'm pretty sure it would take several turbines too, for this particular site. Expense is a factor.

No worries.  I got it figured out for around a 3-4' high dam and the turbine system too.  Get a knot meter and drop it in the water at its current fastest running location.  Let me know how fast the water is moving.

RE

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[RE]

Did you ever see The Flight of the Phoenix?

You are playing the Jimmy Stewart Role.  I am playing the Hardy Kruger role. lol.

<a href="http://www.youtube.com/v/1PrhC_l7RPo" target="_blank" class="new_win">http://www.youtube.com/v/1PrhC_l7RPo</a>

RE

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[Farmer McGregor]

I am ready to be hammered with the usual Diner Negative Waves on this.  --RE

Brace yourself, RE, here it comes: You make a lot of really valid points.
That said, I have a few comments to add... 

Good points.

I expect the water diversion issue will be a non issue at some point, we'll have a seriously dry late summer and fall that will dry the creek to a trickle that won't interfere much.

I think it's better to build a dam that's low and strong and bulletproof that it is to get fancy and install a gate, which really won't do much in full flood anyway. It isn't unusual to have full size live trees get washed out of the banks of my creek and swept away in a flood. I've seen it. No gate will hold up to that.

The dams I've seen that last are just long, low, straight check-dams.
Except that...  Don't you need a formed concrete flow channel thru the dam in which to install your turbine system?  That channel, if its depth extends to the bottom of the creek's flow line (presumably you want to utilize the flow at the lowest possible elevation in order to maximize head pressure), can serve as the 'drain-the-whole-reservoir' outlet if needed for maintenance or restoration work.  It needs a gate of some sort so that you could close off flow in case of trouble with the turbines.  All it takes is a pair of vertical grooves formed into the concrete (better if lined with iron because its very straight and provides a better seal surface than concrete) into which you can drop a flat panel like a sheet of plywood to close off the flow.  Irrigation headgates are done this way, usually with a permanent operating mechanism (not necessary in your case?) that allows the gate to be held at a precise level to meter the flow through it.  I use these on my ditches (slots formed in concrete that I can shove a board into).

I wish I could estimate the flow through there right now. I'd like to know, but the turbine people talk about filling up buckets, which is not going to work. When you don't have a lot of head, flow becomes crucially important for power generation.

A few points.

1- A long, low dam will not provide enough pressure to efficiently run turbines.  You need either decent depth or fast flow rate, or both.  A long low check dam is not going to do this job.
Unless some portion of the dam is a well constructed reinforced concrete channel that extends to the bottom of the flow line, and is gated on the upstream side to control flow through it (any excess flow goes over the spillway).  That flow channel houses the turbine system, and serves as a full-release valve for draining the reservoir.  The rest of the dam can be the long, low, massive earthen check dam variety, which if properly constructed could withstand the once-in-a-blue-moon overtopping event.  Of course, a section of this needs to be a spillway that can withstand constant overflow.  The overall height of the dam cannot exceed that of the surrounding terrain or you'll invite all kinds of trouble in a high water situation.

2-  The main purpose of the gate is not to release a lot of water at times of high water, that is the job of the spillway.  The job of the gate is to release water at times of low water/drought, so it makes its way downstream.  So it doesn't need to be very big. If you are building the dam out of concrete, you just set the gate in at the lowest point under the dam.  It's not vulnerable to trees or other debris floating down in a flood, because it is at the bottom of the dam.

Easier alternative to this is just to run a pipe under the dam with a valve you can open and close, but it will need to be kept clear of sediment at both ends so it doesn't block up.  You would want to use a fairly large diameter sewer pipe for this purpose.  6-12" or so I would estimate.
Definitely not a big fan here, as these can have a problem with clogging from sedimentation unless they are regularly flushed.  Also they are a construction hassle, requiring special care to prevent them from becoming a leakage pathway.  Eddie's dam is too shallow to bother with such.

3-  I have another Rube Goldberg solution I am working on, but it will take a day or two to get some schematics done and research the type of hardware to use.  I won't let on to what this is until I have it reasonably bulletproof and can't get hammered from the first post.  LOL.
Bring it, Rube.
RE

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[RE]

I am ready to be hammered with the usual Diner Negative Waves on this.  --RE

Brace yourself, RE, here it comes: You make a lot of really valid points.

Eddie is in trouble now. Getting ganged up on by the Farmer and the Model Man Physics teacher, stuck in the middle of that is not a good place to be. lol.

Like I said though in #3, I think I got the model for this worked out so it can be done small first, then scaled up.  I should have it ready either later today or tomorrow.

RE

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[Eddie]

You must not have read the stuff I posted about the low flow turbines I was looking at. They sit at water level and use a drop pipe. It's a completely different design from a typical microhydro turbine. No Pelton wheel.  This renders most of Gregs' last comment moot, I think.

http://www.powerspout.com/low-head/

Here is how you direct the water.

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[RE]

You must not have read the stuff I posted about the low flow turbines I was looking at. They sit at water level and use a drop pipe. It's a completely different design from a typical microhydro turbine. No Pelton wheel.  This renders most of Gregs' last comment moot, I think.

http://www.powerspout.com/low-head/

Here is how you direct the water.

This won't generate as much juice as my plan.  A low flow turbine is going to have a low output of electricity, by definition.  We can do much better than this, and with off-the-shelf components at a reasonable price.

RE

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[Eddie]

No, this site is tailor made for these low flow turbines, if the flow is adequate.

Conventional turbines won't work. Not enough head. End of story.

I spent a lot of time looking at numbers before I ever started this thread. Do some more homework.

Here's another view of one working. They are cheaper than conventional turbines, not more expensive. The problem is that it takes multiple units to get a lot of power.

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[Farmer McGregor]

You must not have read the stuff I posted about the low flow turbines I was looking at. They sit at water level and use a drop pipe. It's a completely different design from a typical microhydro turbine. No Pelton wheel.  This renders most of Gregs' last comment moot, I think.

You are correct, I hadn't caught that.
What I remembered (somewhat incorrectly, as it turns out) was this:


My recollection of it was as a flume through the middle of a dam, not as a flume apart from the dam fed by a pipe.
This does change everything.  All you need is a modified portion of the spillway to direct some flow to your turbine(s) which could actually be somewhat remote from the dam itself.

Cool stuff.  Sorry I wasted our time.

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[RE]

One of the marvelous things about electric motors is they work both ways.  If you put electricity in, the motor turns.  The other way, if you turn the motor, electricity comes out.

This principle is used by many DIY people,for instance 12V Electric drills are used with bicycle cranks to spit out a small amount of electricity.  It's enough to power up your cell phone, or trickle charge a batt so after say 10 hours of pedaling you might run your laptop for an hour or two.  How much juice you can produce depends on how much mechanical force is applied, and how big the motor is.  A Homo Saps legs just are not all that powerful, a drill motor is small, so not much juice comes out.  Even less hand cranking.

<a href="http://www.youtube.com/v/iviAtyXGu_U" target="_blank" class="new_win">http://www.youtube.com/v/iviAtyXGu_U</a>

It's tiring too!  But if you can use another form of mechanical energy to turn the crank, not tiring.

Sailors though took this idea a step further, using Trolling Motors to generate electricity for their boats.  When under sail with a good wind and doing say 10 knots, you drop the trolling motor in the water behind the boat,and the prop starts turning because of the water passing through it.  This adds drag to the boat and slows it down a tad, but not by much in a good wind.  A trolling motor is much bigger than an electric drill motor, so it generates a good deal more juice.  Now you are starting to talk about enough electricity to power stuff like refrigerators.

<a href="http://www.youtube.com/v/G_OJPHhk3kk" target="_blank" class="new_win">http://www.youtube.com/v/G_OJPHhk3kk</a>

Now, apply this same principle to a dammed up stream.  Instead of the motor prop moving through the water pushed by the sail, the water passes by motor prop on it's way downstream.  So if you can get the water moving fast enough with enough pressure, it's going to turn the prop and will keep generating electricity as long as the stream is running good.  The more pressure that you get, the bigger the prop you can use and the bigger the motor. But you start small and work your way up on this.

So, how do you design this with your small dam?  To start with a little one, you'll need a 12V electric drill, a small prop for a model boat, and a small kid size dam you can build in an hour or two of recreation time.  You'll need some metal rod and small gearing to go with this, to transfer the mechanical energy up out of the water to the drill motor, which has to be kept out of the water, obviously.

The next level up is to build a bigger dam, with slots to drop in your trolling motors.  Now you have no little gears to buy, the trolling motor is already constructed with them, plus it already has a prop on it.  So now all you need is a way to drop your trolling motors into the dam structure so the props are down under the flowing water while the motors are on top of the dam.

Here is a basic schematic on how to do this:

Details Dam Turbines

Dam Turbines

Now, in terms of total Dam/Berm structure, actually only a small part of it needs to be the concrete section that houses the trolling motors.  To either side of it you just berm up with a front end loader and dump truck.  Sand, gravel, dirt, clay, the usual suspects there.  A 12' section of reinforced concrete wall between berms on either side and well anchored should be long enough to drop 4 trolling motors onto.  Ideally, drive Rebar into the bedrock and into the berms before pouring the concrete.  Rent a Jackhammer if the creek bed is real rocky for this.  The berms will not be an issue, you lay the rebar in there you dump the dirt onto it.  You will of course have corrosion issues if this is steel rebar and not basalt rebar, but it still should last quite long.  Coating it with Polyurethane will help to keep corrosion low for quite some time if using steel rebar.  Gate the concrete tubing allowing water to flow past the propellers for control.

The real advantage to this is that if you are expecting real high water, you can easily pull the motors off the dam.  Just disengage the propellers, then lift out the motors.  Hopefully the dam and the berms withstand being overtopped.  Even if they are, it shouldn't be too much worse downstream than it otherwise would have been. You do have to take into account how much water you actually back up, and that depends on the terrain grade. Even a 4' Dam can back up a LOT of water if the grade is not too steep, much more than a swimming pool.  It goes all the way back upriver to the high point of the dam, and can spread out.  When the dam fails, it all goes downstream in one big burp.  This scenario would be unlikely though with a combination Berm-Dam arrangement.

OK, hammer away at the Model Man. 

RE

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