self-cleaning intake designs

[Rabrsniver]

My microhydro setup, though small, provides us a decent amount of power (in the winter).

However, I am not always there to babysit the intake to remove the debris, and the abundance of alder leaves can be quite a problem.

My flow is usually not strong enough to use a coanda screen setup, and I'm very stingy about "wasting" any potential power the water can provide.

Does anyone have another way to screen debris that doesn't require frequent cleaning?

I know this is one of the major problems with hydro, but I was hoping someone out there had come up with a new idea or two.

John

[jimovonz]

Here is a posting I did showing one of the hydro intakes I have made using 6" PVC pipe and some stainless mesh. This intake has performed without fail since installation over three years ago and has weathered a number of significant floods. It wastes very little water (only a drop or two if a particularly large chunk of debree temporarily blocks the chute) In the pics it appears to be spilling quite a lot of water but this is only because at the time I had shut down the turbine and no water was flowing, causing water to spill from the top.

http://www.fieldlines.com/story/2007/6/11/34653/1661

[harley1782000]

Could you make a bigger imput, Like a wide mouth funnel on the imput pipe.  Then put your screen around that, or make something that would brush over the screen every hour or so.

Jim

[ghurd]

I thought something like that too.

Maybe a "C" over the pipe, that rotates back and forth every 15 or 30 minutes?

Not as simple as jimovonz's, but more work. :-)

G-

[robl]

John

I have a very small set up as well. As first built, the intake had to be cleaned about every two days in the fall. Now it goes several weeks before needing any attention. I use a 6" by 4 foot PVC pipe capped on the end. It has several hundred 1/2" holes drilled all over it. The dam spillway is not in the middle, but at one end. A diagonal screen (1/2" hardware cloth secured over a pressure-treated wood frame) diverts almost all the debris to the spillway. What does get into the forebay is flushed out about once a week through a 4" drain set in the bottom of the dam. The system does not need to be shut down for this, but suction does keep some leaves stuck over the holes otherwise and have to be manually swept off and sent towards the 4" drain.

You can see a highly compressed video of the prescreen version here:

http://www.youtube.com/watch?v=_xn1cz3F4Q0#GU5U2spHI_4

Note the accumulation of debris in the little whirlpool on the other side of the spillway. That problem is now resolved.

Hope this helps.

Rob