Posted by Scott on December 13, 2003, 2:49 am
I've been enjoying reading your posts and I've been trying to learn a
little bit about this stuff. Here is why. My wife wants a heated
greenhouse. The problem is we live in Indiana. In the winter, it can
get down to -10 at times. UGhh.
With normal space heaters/etc.. it would cost a fortune to do this and
to be honest I would feel a little bad wasting all that energy to keep
some plants warm.
So, I came up with an idea to minimize the energy usage. I've seen
solar panels used before to heat water for pools. So, I have this crazy
idea to pump water through the solar panels and then through a copper
pipe maze in the floor and then back to the panels. The floor would be
made up of pea gravel so it would be a kind of hot water/steam system.
Haven't really figured out what to do at night though. :(
What do you think, carzy? any advice or websites with further info
would be appreciated. also, can you recommend any sources for these
type of products?
Posted by firstname.lastname@example.org on December 13, 2003, 3:26 am
I bet nick can tell you how to do a bubble wall that will work.
Posted by nicksanspam on December 13, 2003, 11:36 am
Two plastic film covers with a trough at the bottom with a 10% detergent
solution and a 2" pipe full of holes and a shop vac blower that fills
the space between the plastic films with bubbles with 1000X the solution
volume at night, with an insect screen in an air return at the top that
pushes on a microswitch to turn off the vac when bubbles appear at the
air return. The vac would run for a few seconds each hour to make more
bubbles, as they collapse over time...
NREL says 510 Btu/ft^2 falls on the ground and 770 fall on a south wall on
an average 30.9 F December day with an average max of 38.5 in Indianapolis.
You might just keep them from freezing at night and on cloudy days.
Carzy. Foam insulation is better. A 16'x24' greenhouse with 800 ft^2
of R20 foamed surface would have a thermal conductance G = 40 Btu/h-F.
If it's 70 F on an average December day and 40 F after 5 cloudy 30.9 F
days, it needs RC = -5x24/ln((40-30.9)/(70-30.9)) = 82 hours = C/G, so
C = 82x40 = 3293 Btu/F, eg 7 dark plastic water drums under benches
near the south wall.
Posted by Sonideft on December 13, 2003, 11:35 pm
The option that you mentioned at the beginning about running tubes through
the floor is also a very good one. If you make the floor with about 4" of
concrete and heat it with warm water, the thermal mass of the concrete
should be enough to get you through the night. This is the same principle we
use for Space Heating of homes with Solar Panels.
Stephen Cumminger, P.Eng, MBA, MCPM
Posted by Scott on December 15, 2003, 4:16 am
are there any sites out there that have more info on building such