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re: piping to collectors
8 oct 2000
bert menkveld wrote:
>i'm putting up a couple of 4x8ft collectors in my back yard, about 40 ft
>or so from the house (for domestic hot water)...
so you might collect 0.5x1000btu/dayx64ft^2 = 32k btu of heat at 50%
efficiency on an average december day, enough for 22 minutes of 110 f
3 gpm showers, heating water from 50 f...
>i'm wondering what kind of pipe or tubing i could use to bury in the ground,
>and how to insulate it. the system will use a glycol solution, so freezing
>won't be an issue...
you might look at swan's pm5875 160 f 100 psi 5/8" reinforced garden hose,
$23.95 for 50' from grainger as stock #1p609 or $34.95 for 75' as #2p098.
>i've looked at some pvc tubing that comes in 50ft rolls for not too much
>money. it's rated up to 82c at 100psi, and i found some place on the web
>that says it will take up to 100c (presumably at lower pressure). will this
>kind of tubing work?
sounds like it would, but why would you need more than 5 psi with glycol?
>for insulation, i was thinking of getting some "sytofoam sm" (the blue
>stuff), and effectively building an insulating "box" with two compartments
>for the two piping runs. is this a crazy idea?
well, 2" (r10) styrofoam all round would make the heat loss something like
40'(140f-40f)1ft^2/r10 = 4k btu/h with 140 f water and 40 f soil, 24k btu
over 6 hours. you might lose 3/4 of the solar heat to the piping...
can this be a batch/draindown process, with intermittent flow and no glycol,
and a single hose that slopes down to the house? you might pump 55 gallons
of 50 f water out to the collectors over 10 minutes at dawn, then let it
thermosyphon to 50+32kbtu/(55x8) = 123 f by afternoon, then let it run back
to the house over 10 minutes at sunset.
can this a pressurized system, with no heat exchanger? the hose would only
hold 5 pounds of water...
nick
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