Was considering Wind - Now considering Hydro

[Tapsnap]

Hi, I'm very new to all this so please forgive my dumb questions. I bought the "Homebrew Wind power"  book and read it. Very interesting but realistically, looking at my site, I think the amount of power I could generate would not be worth it. I'm now looking at the stream that runs through my property. It runs about 150 yards across my property and it's about 200 feet from my house.  On average, it's about 10 feet across and about 7" deep. It drops about 5 feet from one side of the yard to the other. The pictures show it just as the snow is beginning to melt. In a week or two this will be a blasting torrent that will wash away a truck. I have also seen this river dry up completely twice in the summer over the 10 years I have lived here, but mostly it kind of looks like the photos. I was looking at the site a few minutes ago and really the biggest drop occurs over about 75 yards. It might not be worth the extra digging, penstock and wire to cover the full length of my property. It drops about 4 feet within this range
Can anyone tel,l just by looking at this site, if it would be possible to draw 1KW or more from it, at least the way is is flowing right now. Can anyone give me links to posts that calculate the flow and penstock diameter I would need to run? Any other advise?

[hydrosun]

Quick answer is to check out the low head ESD turbines at microhydro.com  It uses about 1000gpm and at 4 feet head would put out about 400 watts.  Just looking at the picture it seems you have at least 1000gpm flowing right now. You need to measure the flow to see for sure. An estimate can be calculated with speed and cross section. Throw a stick in and time how long it takes to move a measured distance. An average cross section will show how many square feet. If 10 feet wide and 7 inches deep would be 5 square feet. How wide is the concrete bridge? in the picture.  So multiply by feet per minute will give cubic feet per minute. Multiply that by 500 to get gpm.  You would need 2500 gpm to produce the 1 kw. That  is if you can get a setup as efficient as the ESD. You could use multiple ESD turbines to take advantage of changing flow rates.
In this case a pipe large enough to carry that volume of water would be pretty expensive.  Can you do a 2 foot high weir and level channel Concrete? to gain the 4 feet head and then into a short flume over to a suitable turbine?
Flood events have to be considered to place everything so it won't wash away.  So a turbine placed high with a exit tube to gain all of the drop and still be above flood water would be best. An overshot wheel would be in danger in that situation. A poster on this site who builds wooden water wheels mentioned he was considering making propeller based turbines. I hope he chimes in on this hydro site.
Chris

[keithturtle]

Considering the fact that water flows more steadily than the wind blows, you could get power output all the time, whilst the wind turbine will produce its rated output a small percentage of the time.

I'm to the point of building the stator for my Piggott mill, but I am also developing the stream site as I can.  I figure 300 watts produced 24/7/365 will far exceed the 1 kW windmill, given my lame wind resource.

Your capitalization might be higher with the water project, but the output will be non-stop; you can also employ axial-flux-dynamo principles if you wish.

Use the calulator here  http://www.energyalternatives.ca/content/Categories/MicroHydroInfo.asp  to determine your site's potential; looks like you have at least 5 CFS flow, and that should translate to ~600 watts potential over a 4' drop.  If that is so, do the math and make your choice.

Turtle, still at it

[Tapsnap]

Thanks for your help. I went out there again today and the depth of the river is already significantly greater. It's now about 12" and flowing faster. It still has nothing like the power it will when the snow and ice really begin to melt. Hydrosun, I wasn't sure where you got "multiply by 500 " to get gallons from cubic feet. So I multiplied by 7.48 which is the figure I found elsewhere on the web as a conversion of cubic feet per gallon. Today, it works out that I have approximately 7,330 gallons per minute. By summer of course, it will probably drop to about 250. How do you calculate the power per foot of head? BTW, the bridge is just over 8' from one side to the other. The river is actually wider than it appears as it is cutting under the ice.

[hydrosun]

The 500gallons/minute  number comes from rounding for cubic feet per second. So you are right a cubic foot contain 7.48 gallons times 60 seconds to get close to 500 gallons a minute. When calculating in my head I tend to round all the number, because I know the input numbers are just estimates too. I was tired last night when writing so I made some mistakes in talking about gpm  and feet per second. The outcome was correct, just the labeling was wrong.  The power per foot of head was what I remembered from the ESD turbine putting out 1000 watts at 10 feet head.  That comes out to a 50% efficiency. Now that I think about it it wouldn't be linear because the water flowing through would be lower with lower head. You'll need to check the microhydropower.com web site to get the right number for your head.  I just checked and at four feet head it would use 625 gpm and produce 250 watts.
 The hard part of your system is getting all that water to the point it can fall into the top of a turbine. Any canal, flume or pipe would have to be as large as your stream is now. Actually bigger so the same volume will flow with a lower slope so you don't use up the head.  You will have to choose the flow rate you will divert into a canal before you can calculate how big it will need to be.  You will need to determine how much of the year at each level of flow rate to see how much return for investing in harvesting the higher amounts.  If you can live with 250 watts you could design around 625 gpm and one turbine that would work most of the year until summer. a 12 inch pipe would lose little pressure in 75 yards  A second turbine would work for a shorter time and require a 15 inch  pipe. More turbines or one larger one would need even bigger pipes or open canals.
When calculating the average cross section you also have take into account the rocks sticking up. They also slow the flow so your average speed may be suspect. So use round numbers and adjust lower to get closer to accuracy.   The cross section times flow rate is only accurate with a smooth bottom.  A more accurate way to measure flow rate is with a calibrated weir method but your flow varies so much I'm not sure if you would gain anything by knowing exactly how much water is flowing. You really need to know how much of the year the  flow is greater than the amount you want to use. Using multiple turbines would allow you to vary the amount or water you could use as it is available.  The simplest design would be a 4 foot dam with fish ladders and short flumes to individual turbines. I've no idea if that is possible in your case.  Because of the low head and high volume nothing will be cheap and easy.
Chris

[Tapsnap]

Hmm, I think it would be wise for me to study my site for a few months before committing to a plan of action. Most of what I am telling you regarding the flow over the year is from memory. I think it would be good to actually measure the flow through spring to summer at regular intervals. Hydrosun, from what you are telling me , this could be extremely expensive. I also don't want to take all the water from the river and dramatically change the ecosystem. We have trout, crayfish, otters, ducks, and herons - and that's just the wildlife I've seen along this 150 yard stretch. I think I should weigh the pros and cons of any system before building anything. Thanks for your advice.

[keithturtle]

Check with your local EPA or conservancy officials.  In some places it is illegal to block or redirect the flow of a stream.  Remember that to some folks, fish and animals are more important than people, even if you own the land that the stream runs through.  I suppose everyone has their perspectives.

The last time I hugged a tree was when I lost my balance, just before I laid a screaming chain saw to its base

Turtle

[Tapsnap]

My thought now, is, I might put in a large pipe that collects water only when the river is high - when the water level is above 8" or so. The river often brakes over the banks and our yard gets flooded 3 of 4 times a year. As a means of preventing the flooding and generating electricity at the same time, I could install a large run-off pipe further down the stream where the flooding occurs with a turbine to generate some power. Maybe some kind of banki turbine setup.  It would only run at certain times of the year but it would kill two birds with one stone and at the same time, kill less wildlife!

[Tapsnap]

So, it's a few days later and the snow is beginning to melt and we had some rain last night.







Further down the river has broken its banks

[Tapsnap]

I'm looking around the hardware stores at piping and this caught my eye. This is double walled culvert pipe. It's relatively smooth on the inside. It's about $170 for 20' @ 12". Can these things be sealed up tight to hold pressure, or should I be looking at something else? What kind of fittings are available to reduce the diameter?

[hydrosun]

Culvert pipe might be useful for carrying water at one level along a contour and then connected to pvc pipe to go downhill.  The joints aren't meant to hold pressure and I'm not aware of reducing valves.  That's not to say that you couldn't find a way to caulk the joints to hold up to the pressure of 4 feet head and then switch to pvc to reduce the diameter.  You could try one joint and block the end and fill with one end 4 feet higher to see if it is possible.  You might have to mechanically hold the pipes from separating under pressure.  You are talking about 2 psi , with a 12 inch pipe that would be over 200 pounds of pressure.  You might want to see what the cost would be for a 12 inch pvc pipe that can be glued for comparison.  I've used 4 and 6 inch pvc sewer pipe for hydros for years.
Chris

[Tapsnap]

After further investigation I found this site. http://www.ads-pipe.com/en/product.asp?page=Low_Head_Irrigation

[wpowokal]

Fantastic flow of water, and snow (I have never seen snow in person) but please read the size limits on pics, I am not quite sure how the board police have bypassed you but I have quite fast download and they are still loading.

I like your stream, not sure if snow appeals to me, far too cold for my joints, but I will have my own streams next month in the oldest rain forrest in the world, so am interested in your progress.

allan