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Problems with Preexisting Hydro | 16 comments (16 topical, editorial)

Re: Problems with Preexisting Hydro (3.00 / 0) (#15)
by 74VDC on Wed Aug 27th, 2008 at 12:31:09 PM MST
(User Info)

I'm stumped..and I'm probably going to ask more questions and present more problems than solutions...but:

My calculations suggest that you should be expecting much, much more power than you
indicate.

(head in feet) x (flow in gals. per sec.) x (efficiency of turbine) / 11.8 = kw

420 (feet) x 2 (gals. per sec.) x .8 (pelton efficiency) / 11.8 = 56.9492 kw

Assuming a generator efficiency of around 30% that would equate to 17 kw.

Assuming additional losses like penstock frictional losses, poor nozzle aiming, the slightly damaged runner, parasitic losses (field current), I could see this number reduced by as much as half.

Still...I'm thinking around 9kw. Part of me says this cannot be right, but then 420 feet of head...WOW...and 120 gpm.

My numbers must be wrong...they probably are, but these meager outputs you describe gotta be way off. This is definitely NOT a electrical line loss issue if my power calculations are even close to being right.
I can give you exact calculations for line loss and all of the electrical side stuff. I need to know how to calculate the hydro side correctly if I'm wrong before anything else.

BTW...I never did understand why everyone wants to use auto alternators...give up way too much for the convenience of being easy to obtain etc.

Re: Problems with Preexisting Hydro (3.00 / 0) (#16)
by 74VDC on Thu Aug 28th, 2008 at 02:04:38 AM MST
(User Info)

OOOPS!
Just reread the initial post and I see it was 40' head and a 420 foot long penstock....ok, now that certainly makes a difference.
Still I'm coming up with 5.42 kW.
So after generator losses I get 1.63 kW.
The 420 feet of penstock friction, runner damage, possible slight nozzle misalignment (I know this is critical)and other deducting factors would account for some loss for sure. Your measured current at generated voltage is barely breaking 100W.
The batteries may pull down the voltage depending on their state of charge, but while doing so, current will increase. I like to get things simple and unmistakable for testing things like this. I'd get several 5 0hm wire wound ceramic resistors along with several other smaller higher value resistors and putting them in various connections of series/parrallel begin making measurements for optimal power. I would do this because I have all this stuff.
I live in Maryland and we have net metering, so I'd never consider charging batteries, but instead grid tying. You will lose so much power with batteries it isn't even funny. Far, far more than a grid tie inverter.
I still cannot imagine expecting only 240W with 120 gpm and 40' of head. I also have a hard time beleiving so much drop on your xmission line, particularily with DC, but 630' is a long, long way at 15v. I'll crunch the numbers later when I can look of the circular mil area of 2/0 and specific resistance of Al, although I think it's 17.7 and soft drawn Cu is around 10.4 I think.
I do not fully understand your set-up or what you're exact goals are.
You seem to be set on DC, so why then did you spend $600 on triplex...were you wanting the possibility of future 3 phase?
If you really think you have line loss issues parallel the old #8 AWG conductors alongside the 2/0's...just for temporary test purposes...I'm thinking you're gonna see little difference. If it turns out that it helps...get some al/cu connectors, Penatrox and leave it. It would not be code approved, but unless you grid-tie your not subject to the NEC, besides, there are numerous paralleling provisions in the NEC for instances such as these. You could have saved a bundle of cash by utilizing the #8's and paralleling to begin with. You're voltage is low, but so is your current.
I'd find a good 30VDC PM genny like another poster suggested....like fast!

[ Parent ]

Problems with Preexisting Hydro | 16 comments (16 topical, 0 editorial)

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