Thanks Bryan. Your comments will be useful for me also. Carlos --------------------- ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[email protected]> Cc: <[EMAIL PROTECTED]> Sent: Wednesday, February 02, 2005 4:34 AM Subject: Re: [microhydro] Freezing penstock
> > > 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 ? If not, please register >> free of >> > charge and be exposed to the microhydro community world wide! >> > >> > NOTE: The advertisements in this email are added by Yahoogroups >> who >> > provides us with free email group services. The >> microhydro-group does not >> > endorse products or support the advertisements in any way. >> > >> > More information on micro hydropower at >> http://microhydropower.net >> > >> > To unsubscribe: send empty message to >> > [EMAIL PROTECTED] >> > Yahoo! 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