On Sun, 16 Feb 2003 16:40:37 -0500, Trace Curry
wrote:

What's the best method for using water to store heat to be released
during the night to keep a cold frame from going below freezing?

I was thinking a bunch of those black balloons that you often see at
people's 40th birthday party - filled with water of course.

Any better ideas?

I got one of those Gro-quick heating cables, but it doesn't seem to be
doing much as far as heat production, maybe because it's only 15
degrees?

I have some plans for a great cold frame, not that it's rocket science
or anything. If anybody is interested it's just a PDF file - email me
and I'll send it to you.

Thanks,
Trace

Zone 5/Ohio

The cables are intended to warm the soil rather than the air. My
experience (though in a much warmer climate) has been that I needed to
insulate the area heated by the soil cable. I was heating a
3'x6'x6"deep "tray" of sand and peat on which my flats of sown seeds
were placed. It was elevated and so needed insulation on the bottom
and sides.

I keep 8-10 large (26"H x 26"Dia) faux terra cotta pots (plastic) full
of water in my cool/cold greenhouse. They are open on top but covered
with plastic or old greenhouse roofing (Tuffak). Half of them are
filled from runoff from the roof of the greenhouse, the others from a
hose. I use the water in the winter to water seedlings as it is
warmer than the tap water from the hose and contains less chlorine.

Since you have power, there is another "Rube Goldberg" setup that I
have used but never perfected. It consists of an aquarium heater
(900W as I recall), a 10 Gallon insulated metal container (because
the aquarium heater will melt plastic if it touches it), a small
aquarium circulating pump and some copper tubing. The tubing was run
under my seedlings, and the heater (it is controlled by a built-in
thermostat) kept the water at a set point. I think that it can work,
but in my experience the thermostat should be in the soil near the
roots/seeds and the flow should be balanced such that the heat of the
water is not largely dissapated at the "front end".