re: solar air home heating
26 jan 2002
edwin earl ross wrote:
>i am considering building an active solar home heating system as follows:
>...air collector to be built with clear corrugated polycarb over plywood
>painted black. home depot now has the polycarb at very reasonable prices.
you might also check out flat replex polycarbonate, about $300 for
a 49"x50'x0.020" roll including ups from rimol greenhouse systems
(877) rimol-gh. making a mesh absorber with a layer of dark window
screen might raise the efficiency and lower the cost/btu.
>2. the hot air would heat a collection of 3 liter pop bottles stored in a
>super-insulated vault (under my deck).
you might not need superinsulation in texas. for efficient "charging,"
you might make the bottle surface at least 10x the collector glazing area,
and use a fan that can move 25 cfm per square foot of glazing (home depot
was selling 56" 110w 9744 cfm ceiling fans for $19.97 last week :-), and
leave enough space between the bottles so the vault air velocity (cfm/ft^2)
is less than 400 linear feet per minute. you may need a one-way plastic
film damper to keep the warm air from escaping from the vault into the
collector at night.
or put the glazed vault behind a north window inside the house and beam
the sun into the vault with heliostats, as anthony suggests. you could
blow room air through the vault with a small fan and thermostat, or use
a motorized damper or automatic foundation vent. a 4'x8'x2' box might hold
576 2-liter bottles, storing 576x4.4(130-80) = 127k btu at 130 f with
a min 80 f usable temp. or make a 4'x8' hydronic target and put a $400
1500 gallon tank in the basement to store 600k btu. the target could also
be a radiator at night. you could fold up a black grill surface and fold
down a 45 degree reflector for daytime solar barbeques.
>2. can anyone recommend a thermal control system that will turn the
>collector fan on when collector temperature is higher than vault
grainger sells differential thermostats for about $100.
>i live in central texas, where the mean temperatures in january are
>60f/37f mean 49f and record low 0f.
maybe you don't need heat.