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re: heating solarium with sun
21 oct 1998
wrote:
>i bought a house this may with a 10ft x 18ft solarium with a hot tub in it.
>the sunroom has a south western exposure and has double glass widow panes.
with lots of black widow spiders inside? :-)
>i want to be able to capture energy from the sun during the day
>to help heat this room. does anyone have any ideas?
well, you could
1. fill up the room with thermal mass, eg lots of 55 gallon water drums,
a concrete floor, lots of bricks and so on, as the passive solar industry
council concrete and brickmakers recommend. this would store solar heat
during the day, and lose lots of heat through the glazing all night. the
day and night temperatures would be about the same, coolish on average
december days, and cold at night and on cloudy days, or
2. put some sort of thermal shutters or shades inside the windows, and
manually operate them twice a day. (how much would these cost, and where
you would buy them, and what would their r-value be, including the air
leaks through tiny cracks around the edges?), or
3. avoid thermal mass in the sunroom itself, and stand up 18 drums in
a 3x6 array about 4' deep x 12' long x 3' tall, with a 3" layer of
styrofoam insulation all round and the hot tub sitting on top:
70 f house |
18' |
------------------r15---------------------------------|
| | |
r d d d d d d r r
1 hot hot r15 1 2
5 d d d d d d 5 6' |
| tub tub | | 10'
| d d d d d d | 80 f day |
|-----r15-----------------------------| 50 f night |
|------------3'x12' glazing-----------| | (use
| | courier
| reflective surface | font...)
---------------------------------------r2------------------
southwest
this solar closet might have an $60 3'x 12' single layer of polycarbonate
glazing over its south insulated side, with a reflective surface to the
south of that, a layer of dark window screen in a 3" insulation-glazing
gap, and a couple of $60 36 watt 560 cfm grainger 4c688 149 f fans with a
$6 120 f thermostat in a glazed box to circulate solar-warmed air between
the heater and drums during the day.
where i live, in december, it might collect about 34k btu (10 kwh) of heat
on an average day, when the sunroom is 80 f. with 120 f water, the south
wall would lose about 6h(120f-80f)36ft^2/r1 = 8.6k btu during the day and
18h(120f-50f)36ft^2/r15 = 3k btu at night. the east wall would lose
6h(120f-80f)18ft^2/r15 = 0.3k (day) and 18h(120f-50f)18ft^2/r15 = 1.5k
(night), the top would lose 6h(120f-80f)72ft^2/r15 = 1.1k btu (day) and
18h(120f-50f)72ft^2/r15 = 6k btu (night), and the bottom might lose
24h(120f-60f)72ft^2/r25 = 4.1k/day. the north and west walls would lose
24h(120f-70f)54ft^2/r15 = 4.3k, which leaves 5.1k btu (1.5 kwh) per day
for heating the tub. hmmm. not much. let's make the top 6" thick so we
have 8.7k btu/day for the tub, and enough room to put some fin-tube pipe
in the top or plumb together a couple of drums to heat the tub with its
pump and a little more plumbing and a solenoid valve. and we could use
another fan and thermostat to heat the room when the tub is in use.
nick
nicholson l. pine system design and consulting
pine associates, ltd. (610) 489-0545
821 collegeville road fax: (610) 489-7057
collegeville, pa 19426 email: nick@ece.vill.edyou
computer simulation and modeling. high performance, low cost, solar heating
and cogeneration system design. bsee, msee. senior member, ieee. registered
us patent agent. web site: http://www.ece.vill.edu/~nick
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