Hi Chris,
As for pipe freeze, there is a good chance that the problem is caused by frazil ice. Frazil ice forms in "supercooled" water, or open water with no ice cover at very low temperatures. If the pond above your intake has open water and is not ice-covered, maybe this is the problem. You may want to consider looking at the condition of the stream upstream of the intake, and if you could "induce" the formation of a cover with an ice boom. Here in Alaska, frazil is the main cause of problems in winter for hydroelectric plants. You may want to ask the engineers over at Yukon Energy (http://www.yukonenergy.ca) about what they do. The Yukon Territory gets 90% of its electricity from hydro, despite averages of -20 C in the winter, so somehow they pull it off. -Brian Yanity Quoting Carlos Bonifetti <[EMAIL PROTECTED]>: > > > Dear Chris: > > As penstock is of relative low diameter (4") and some long, at > -20 �C must > freeze if the water velocity is low and as you can see. I think > that your > isolation pipe idea is good. > > Our experience with low temperatures was with 36 kW, 48 m gross > head MHP > Plant "El Chenke", sited at Rio Cisnes Farm in chilean Patagonia, > near > Argentina border. The penstock is PVC 355 mm diameter, 285 m > length, but > buried 800 mm depth into the stony soil. Some days in winter > temperature is > as low as -17�C, the pipe never freeze, but forebay become > completly freeze > and flow of water stop, so the penstock must be drained and > turbine shut > down waiting for ambient temperature increase. > > Regards, > > Carlos E. Bonifetti > Concepcion, Chile > > > ----- Original Message ----- > From: "Hoppy" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Tuesday, February 01, 2005 11:34 AM > Subject: [microhydro] Freezing penstock > > > > > > > > Dear Group, > > > > Has anyone had experience running micro hydro systems in > freezing (-20C) > > conditions? > > > > I have a 4 inch (100mm) penstock pipe that froze solid. It's > 440 feet long > > but only 30 feet head. Because of the rocky landscape, I was > unable to > > bury about 200 feet of it. > > > > The local "experts" consensus was that the flowing water would > not freeze > > in the pipe - but of course it did. It's possible that the > intake somehow > > got partially blocked and I can see how this reduced flow could > layer ice > > and eventually block the pipe. > > > > However, assuming the water flow is full and continuous, would > the pipe > > always freeze? > > > > Can anyone suggest some solutions? Wrap the pipe in insulation? > > > > How large a penstock diameter would you need so that the > flowing water > > wouldn't freeze? > > > > Any help would be much appreciated. > > > > Many thanks, > > > > Chris Hopkins, > > Quebec, Canada > > > > > > [Non-text portions of this message have been removed] > > > > > > > > > > > > > > > > Does your company feature in the microhydro business directory > at > > http://microhydropower.net/directory ? 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