Re: Constructing collectors for a solar hot water system
nicks...@ece.villanova.edu
>When I decided to put a flat plate collector system on my house-
>http://www.solarfacts.net/articles/diy/diy_solar_hot_water_heater_-_doug_kalmer.html
>I called plumbers and roofers in the nearest large city, just by looking in
>the yellow pages. Second call founda plumber who had a stack of 3'x13'
>aluminum boxed, copper plumbed collectors, guarenteed not to leak, for $100.
For the whole stack? :-)
>That was over 16 years ago, and it`s still working fine on my roof.
Nice...
>I would call as suggested above, and if that proves fruitless, try putting
>wanted ads in local papers and online. Failing that, and wanting to build
>collectors, consider doing what these manufacturers did- use fin tube as
>the plumbing in the collectors, the same as used in baseboard radiation.
I've never seen a commercial collector with baseboard fin-tube inside.
It's fairly expensive and doesn't collect well at low temp diffs.
>Just paint with flat black high heat, or selective surface coatings.
Ideally, we'd want a small amount of fin-tube inside a large air heater, so
the fin color wouldn't matter much. David Delaney suggested something like
this with passive auto radiators and a vertical poly film airflow separator.
Jeff <dont_...@all.uk> wrote:
>I've looked at a lot of flashing and absolutely everything I saw was
>.01" to .011". Where do you find .018"?
Lowes and Home Depot. With 2'x50'x0.018" rolls of Amerimax 69124 brown/white
coil for $78 and 10'x1/2" copper pipes for $10.85 and 3/4" pipes for $17.62
and 3/4"x3/4"x1/2" copper Ts for $2.34, the materials for a 10'x10' bare
collector with 18 10'x6.4" fins would be about $78+$17.64+18($10.85+2x$2.34)
= $375. Screwing it into 3 4'x8' sheets of 1/2" OSB into 3 4'x8'x1" foil-
polyiso boards onto a south wall might add $60.
A draindown version might look like this, viewed in a fixed font:
10'
in -->-------------------------------------------
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | | <-- 18 vertical
| | | | | | | | | | | | | | | 10' fins
| | | | | | | |4'x8'| | | | | | 4'
57.6"| | a| | | | | | | | | | | | |
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
| | | |..|..|..|..|..|..|..|..|..|..|..|
| | | | | | | | | | | | | | |
|..|..|..| | | | | | | | | | | | 10'
| | | | | | | | | | | | | | |
| | | | | | | |4'x8'| | | | | | 4'
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
57.6"| | a| | | | | | | | | | | | |
| | | |..|..|..|..|..|..|..|..|..|..|..|
| | | . | | | | . | | | | | |
| | | . | | b| | . | | |b | | | 19.2"
| | | . | | | | . | | | | | |
| | | . | | | | . | | | | | |
-----------------------------------------|
2' 4' 4' |
out --<-------------------------------------------
Cutting diagram:
19.2" 19.2" 57.6"
--------------------------------
| . . |
| . . a | 2'
| . . |
4' | b . b .....................|
| . . |
| . . a | 2'
| . . |
| . . |
--------------------------------
8'
This might be inside a 12'x12' frame on a south wall covered by 3 $84 4'x12'
sheets of U0.58 Thermaglas Plus twinwall polycarbonate with 80% transmission.
In 250 Btu/h-ft^2 sun and 34 F outdoor air on an average December day in Phila,
140 F fins with lots of water flow would gain 0.8x250x100ft^2 = 20K Btu/h with
144-100 = 44 ft^2 of parasite heating and no heat loss to 140 F frame air, so
back insulation is useless. If we simultaneously collect frame air to warm
the house and lower the frame air temp and raise the overall solar collection
efficiency, back insulation can raise the water collection efficiency.
Nick
nicks...@ece.villanova.edu
>
> 10'
>in -->-------------------------------------------
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | | <-- 18 vertical
> | | | | | | | | | | | | | | | 10' fins
> | | | | | | | |4'x8'| | | | | | 4'
> 57.6"| | a| | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | | | | | | | | | | | | |
> |..|..|..| | | | | | | | | | | | 10'
> | | | | | | | | | | | | | | |
> | | | | | | | |4'x8'| | | | | | 4'
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> 57.6"| | a| | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | . | | | | . | | | | | |
> | | | . | | b| | . | | |b | | | 19.2"
> | | | . | | | | . | | | | | |
> | | | . | | | | . | | | | | |
> -----------------------------------------|
> 2' 4' 4' |
>out --<-------------------------------------------
Oops. This might drain better:
>in -->-------------------------------------------
> |
> -----------------------------------------
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | | <-- 18 vertical
> | | | | | | | | | | | | | | | 10' fins
> | | | | | | | |4'x8'| | | | | | 4'
> 57.6"| | a| | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | | | | | | | | | | | | |
> |..|..|..| | | | | | | | | | | | 10'
> | | | | | | | | | | | | | | |
> | | | | | | | |4'x8'| | | | | | 4'
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> 57.6"| | a| | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | . | | | | . | | | | | |
> | | | . | | b| | . | | |b | | | 19.2"
> | | | . | | | | . | | | | | |
> | | | . | | | | . | | | | | |
>out --<-------------------------------------------
Or this, with some pipe squeezes (how deep?) on the left to equalize flow:
>in -->-------------------------------------------
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | | <-- 18 vertical
> | | | | | | | | | | | | | | | 10' fins
> | | | | | | | |4'x8'| | | | | | 4'
> 57.6"| | a| | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | | | | | | | | | | | | |
> |..|..|..| | | | | | | | | | | | 10'
> | | | | | | | | | | | | | | |
> | | | | | | | |4'x8'| | | | | | 4'
> | | | | | | | | | | | | | | |
> | | | | | | | | | | | | | | |
> 57.6"| | a| | | | | | | | | | | | |
> | | | |..|..|..|..|..|..|..|..|..|..|..|
> | | | . | | | | . | | | | | |
> | | | . | | b| | . | | |b | | | 19.2"
> | | | . | | | | . | | | | | |
> | | | . | | | | . | | | | | |
>out --<-------------------------------------------
Nick