Hydro turbine system

[Ronmar]

Well if you are estimating 20-25 GPM, if you can get all the turbine exhaust into one flow, it should fill a 5 gallon bucket in 12-20 seconds.  That should be easilly captureable with a stopwatch...

[mbryner]

Thanks for the encouragement guys, but lots of frustration today.   I spent all afternoon up at the intake pond/weir trying to seal up the leaks, but to no avail.       

First, I placed some heavy plastic drum-sized trash bags over all the gravel and rocks that make up the dam.  Then  I shoveled lots of clayish dirt over the plastic.  Still lots of water seeping through the dam somewhere and coming out next to the screen.   Of course the water gets really cloudy so I can't see much afterwards.

Now there's about 5-10 gpm going over the coanda screen.     If I could save all that water I might be able to make about 300 watts but when I open up only a single 1/4" nozzle down at the turbine the head drops to about 30 psi and was still falling when I turned it off (maybe 60 watts, but I would have had to go down to the house to look).   The creek flow has  dropped because it hasn't been raining much in the past week and it's still pretty early in the wet season.

If any of you have great ideas for plugging up a leaky dam/weir I'm all ears. 

Marcus

[Ronmar]

Do you have a source of sand, or a screen to sift the rocks out of your soil? Make sandbags with smaller wastebasket sized plastic bags. You could start by placing these into all the low spots/ depressions.  You could of course cover the bottom with these in an overlapping fashion, but even a small basin will require a large number of sandbags.  In this case the goal is to smooth out the bottom as much as possible. 

Once all the depressions and holes are filled with bags, pull in a sheet of real heavy plastic, pulling from the weir side upstream towards the water filling the basin.  Once the basin is covered, work the edge of the plastic in under the water entering the basin and allow the water to flow over the top of the plastic. It is a good idea to roll the plastic a little on that leading edge so you have a little extra to play with on that end. As the water flows over the top of the sheet, it will sink down as the water leaks out of the basin under the sheet. You need to assist this process so the plastic dosn't hang up around the edges and fills in all the way to the bottom.  You also need to pretty quickly get the downstream end of the sheet fit into the weir to  give the water someplace to exit and to keep it from tearing out someplace undesireable. You want that leading edge to be as high as possible and still allow the inflow to pass over it, that is why a little extra is desireable when the sheet starts to settle to the bottom.  The goal here is to get the sheet in under the inflow so all the flow is forced over the top of the sheet.  Of course you need to make sure the plastic guides all the water out over the weir and down across your filter.  The sandbags smoothing out the bottom help prevent the plastic sheet being pulled down into holes where it will get stretched too far and break/rip...

Once the basin plastic is in place, another rectangle of plastic in the ditch above the basin to help consolidate the flow so it is definitely forced onto the basin plastic is a good idea.  If the water entering the basin passes over a ledge, this will make it easier to get the basin plastic in and under the flow...
I lined a running irrigation ditch on my property with rectangles starting at the bottom and working my way upstream this way, allowing a few feet of overlap on each sheet.

Good Luck... 

[sailawayrb]

Marcus, what you really need long-term is to build a proper capture pond.  It doesn't really matter if you use medium rock or cinder blocks for the walls, but it should have a proper footing that should be a couple feet below the creek bed and the entire structure should be cemented together for both strength and water tightness.  It should look J shaped to allow flood water to bypass to one side during flood condition without overstressing the structure.  Place an appropriate sized pipe (perhaps 4" diameter) at the base and lead it downhill but a little off the normal creek bed to where you should locate your coanda screen.  This capture pond doesn't need to be very large, only large enough to reliably capture the flow rate your want...figure a CF volume of about 10-20 times your GPM   I recognize you can't build this now, but that's what you should be thinking about for next summer if you are stuck on the coanda screen approach.  For now I would try to create something similar with just rocks.  It would have to be higher than the permanent one and you would be relying on silt or weighted plastic sheet to make it somewhat water tight.  This will be a challenge to accomplish now.

Bob B.

[sailawayrb]

Marcus, if you are willing to lose the coanda screen approach, I would suggest using a stand pipe approach.  Place perhaps a 12" diameter stand pipe placed perhaps 5-10 feet lower in elevation than from where you will feed it with perhaps 3" diameter poly...i.e., a larger size than your existing 2" diameter poly going to the turbine to ensure that the stand pipe will always remain full and that this approach will NOT be flow rate limiting.  Put a fish screen on the other end of the 3" diameter poly...not so much to keep out fish as to keep out large debris and just place this end in deepest section of your existing stream bed.  Please keep in mind that the top of the stand pipe MUST 1-2 feet higher than the surface of water from which you are feeding it as it will fill and stay full of water at this level!

You will want the 3" diameter poly to enter the stand pipe about 1-2 feet above ground level of the stand pipe.  You will want to extract the water from stand pipe about 1-2 feet above the 3" diameter poly using your 2" diameter poly .  Doing this will ensure that you won't feed any small debris into the turbine.  You should also install a drain out fitting at the base of the stand pipe...perhaps 1-2" diameter.  You will remove the plug from this fitting when necessary to clean out the debris from the bottom of the stand pipe.  You may also want to drill a 1/4-1/2" diameter hole in the plug to allow continuous clean out if you can afford to waste this flow rate.

I recommend that you take the time to do a flow rate analysis for your setup prior to building it to ensure that the flow rate into your stand pipe will be greater than the flow rate out of the stand pipe!  You can accomplish this using this calculator and 140 for the friction coefficient:

http://www.borstengineeringconstruction.com/Pipe_Capacity_Calculator__Hazen-Williams_.html

I attached a photo of an 8" diameter stand pipe setup used to feed a hydraulic ram pump.  Your should dig a good sized hole, fill it with concrete, and place perhaps 2-3 feet of the lower section of the stand pipe into the concrete.  The concrete keeps what will be a heavy water-filled stand pipe secure/stable and keeps the base from leaking. I prefer to use SS tube for stand pipes to ensure long life and because thinner walled tubes are easier to work with to create proper fitting holes...i.e., one can flatten the areas of the tube where the fittings will be located.  However SS can get pricy and standard steel or plastic pipe may be used too...but you will need thicker gasket material for the fittings to keep them from leaking.  You will need to close the valve near your turbine to allow all the piping and the stand pipe to completely fill with water before starting operation.

BTW, if anyone is interested in hydraulic ram pumps and calculating their performance, we created what is most likely the best performance calculator available:

http://www.borstengineeringconstruction.com/Hydraulic_Ram_Pump_Perfomance_Calculator.html

There is also a wealth of info about hydraulic ram pumps in the Calculator Instructions on the Calculator tab of our website.

Bob B.

[XYZER]

Marcus,
Lots of good suggestions.....whatever you do think of a plan and give it your best shot this summer. I can tell you from hard learned experience you cannot get greedy with Mother Nature and think you will win. I learned from beaver dams that when they get a big spring runoff the excess water needs someplace safe to go. Grass is good rock is better, dirt will float away. Beaver dams don't lets the excess energy focus on one spillway, the whole dam is a spillway.
 
If the water flow recedes it then can be focused at your usage but when there is an excess it needs a safe place to flow. I would do as mentioned with sand bags (bags of cement?). Pull all of the rock away with your backhoe to a solid base and build a level dam with sandbags with a low spot to feed your needs when the flow is reduced. Use all of your rock to hide and support the sand bags (bags of cement?) and a nice rock spillway focusing the excess back into the normal creek channel. I suppose there are many ways to get the water to your hydro but you need your control point to be able to survive a heavy runoff. I fought this levy crossing for years at our off grid ranch and learned some things from the beaver. I also learned that this mild mannered creek became a raging bull in the spring for 1-2 weeks. The longer it rages the more of a chance of damage.

The heavy rocks on the downhill side are situated a bit higher than the uphill side. This reduces the water velocity behind it to keep my gravel from disappearing downstream. It is wide to allow for the excess and gets wider as the flow increases. That about all I know.......Good Luck!

[mbryner]

Thanks for the ideas.   Bob B., I love the standpipe idea.   Never saw that before and it's not to difficult to implement either.

Keep in mind I can't get the backhoe up there anymore -- too slippery and too steep.   I tried 2 days ago; it just made big ruts and spun all 4 tires.   Anything mechanized will have to wait until next summer.   

The coanda screen wasn't cheap and it works great, so I'm not ready to give up on it.   You guys are all correct: come summertime, it will be a big project.   The overall plan will be to haul a bunch of concrete up there with the tractor and line the whole collecting pond with concrete, and maybe even some thoroseal grout on top of that.   Until then, I'll have to come up with a temporary fix.   

Tomorrow I'll drive down to the hardware store and get a big sheet of heavy plastic and do something like Ronmar suggested.   The only problem is that there are a lot of bigger rocks on the bottom.   The pond is about 10' diameter (if that) and if I get a 20' square piece of plastic that may cover it.

If that doesn't work, I'm thinking about shoving some wire mesh around a piece of perforated drain pipe, and putting that contraption over the 2" poly pipe.   Then shove the whole thing underwater in the deepest section 2-3' deep and let it siphon.

Marcus

[LowGear]

Another neat project.

I sidewalk superintend an impromptu creek damming every year.  This is done to divert the creek while a sediment pond is hoed out.  "We" use sand bags filled with what ever is handy and lay 10 mil plastic over this lining of bags - bag protection.  Then "we" bag and rock the sides of the small pond.

The water pulls that I've seen are almost upstream from where the water enters the pond.  The debris must make it around the pond and then into the out pipe.  Most everything washes on down the main outflow leaving fairly clean water for the fish ladders and irrigation.

I'm surprised your turbine isn't complaining about the grit and other crap you're asking it to eat while generating electricity?

Casey

[sailawayrb]

Marcus, et al.,

We had a couple folks contact us about designing an intake for keeping small debris and sediment out of their hydroelectric turbines to reduce turbine blade erosion.  As you know, we also always prefer fish to end up on our BBQ and not in our turbines too.  Anyhow, we designed what we call a Fish Screen By-Pass Tank and we also created software to assist DIYers in designing/constructing it.  By all accounts, this design works extremely well.  I have requested the Oregon Fish & Wildlife Department to assess the design for perhaps broader application.  Please be sure to read the instructions before designing and constructing it.

http://www.borstengineeringconstruction.com/Fish_Screen_By-Pass_Tank_Design_Calculator.html

Bob B.

[mbryner]

Casey,

Sorry, I didn't see your most recent post until now.   Actually, with the coanda screen in place there's practically no debris or grit flowing through the turbine.

Bob,

The coanda screen is adequate for now.   If I had known about the stand-pipe concept before buying the coanda screen I probably would have tried it.   This summer I'll just line the weir with a layer of concrete and everything should be fine next year.   Currently, I probably would have enough flow to generate at least 300 watts, but we haven't had a lot of rain in the past few months.   Bad omen for early summer fire season but good for solar panels today.

Marcus