| Hi!
I had some spare time last weekend and raised my solar air heater up again
for some more testing.
So I put it up and it looked like this.
This photo is taken last time so it is not facing directly in to the sun.
My new calculations are listed below:
Tinlet = 80.6 ºF
Toutlet = 161.6 ºF or 131 ºF (I used two different blowers)
Vair = 24.3671 ft³ or 63.5663 ft³
Dair = 0.075 lb/ft^3 at sea level and 60F, but the air density decreases as it is heated, so for normal collector temperatures, 0.065 lb/ft^3 is pretty good.
Cair is 0.24 BTU/lb-F
This fitted in Gary's formula (www.builtitsolar.com) looks like this
Qout = (Vair)(Dair)(Toutlet - Tinlet)(Cair)
Qout = 24.37 * 0.065 *(161.6ºF - 80.6ºF) * 0.24 gives me 30.8 BTU/min or 1847 BTU/hr.
This gives me about 540 watts (using two solar powered computer blowers)
And the second one is calculated with 230V/40W ductblower
Qout = 63.57 * 0.065 * (131ºF - 80.6ºF) * 0.24 gives me 49.98 BTU/min or 2998.8 BTU/hr.
This is about 880 watts.
My collector area is 34.5 ft².
So the efficiency of my collector with these figures comes out like this:
Solar In = (300 BTU/ft² - hr) (34.5 ft²) = 10350 BTU/hr
Efficiency = (Heat out)(Solar in) = (1847 BTU/hr)(10350 BTU/hr) = 0.178 (17.8%)
or
Efficiency = (Heat out)(Solar in) = (2999 BTU/hr)(10350 BTU/hr) = 0.289 (28.9%)
Not as good as i hoped for but still it makes nice amount of heat.
I left my heater up to make the global warming come true and left to help
a neighbour at his building project. It was a nice, warm, calm sunny day...
What I did find when I came back?
There was one small breeze and my collector was lying face down on the ground!
One of the small solar chargers crasher under it. (Sorry G)
The top layer of glazing was cracked many places.
What the heck was I thinking about leaving the collector up untied unsecured?
I felt quite bad and I needed something else to do for a while so we went for
a little boat trip on the lake.
Next morning my mind was settled and all seemed OK again.
I can get new glazing from work for reasonable price.
And now few selected pictures of how I made this one.
Inner layer is 2mm polycarbonate sheet and outer is/was 3mm acryl sheet.
Two layers for better winter performance. 340 beercans.
20 pipes. 17 cans in one pipe.
Insulation is somekind of acoustic insulation. It's only 30mm thick but I
hope it will be enough.
This have been a fun project for me (plenty of beer drinking).
And like my girlfriend always says:
"I need to help my boyfriend with his hobbies!"
Best regards Jaskiainen |
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