How can I heat a 8ft x 4ft x 2ft cold frame using solar power?

Question

The cold frame is connected to the house and contains cacti, which need to be kept at about 6C. I am struggling to keep the cacti in suitable conditions and may lose them in a hard freeze.

Answer 1

Put the cold frame below ground level (grade) with the glass or window top is facing south. Preferably on the south side of a building for protection from the north wind. Also, unobstructed path from east to west to receive maximum sunshine as it passes over head throughout the day. This should supply sufficient solar heat during daylight hours in the hardest of freezes. Before sunset cover glass top with what ever you have. Blanket, tarp, cardboard, even hay or straw, to hold the heat in for the night. Make a dry run with no plants inside first and check temp. with a thermometer. A cheap large round garden store type and leave it in the cold frame for quick reference any time. My bet is you'll need to worry more about over heating your plant than getting a freeze on them. In that case you simply prop open the top a bit until tun temp. is OK! Good luck.

Answer 2

That is what a "cold frame" is . It is not a green house. It gets it's heat from the sun. So the cacti need to be removed and brought indoor. and/or do not water them during this time. Guaranteed freeze. The deserts get mighty cold during the night(below freezing) and these plants survive there naturally.

Answer 3

You will probably get enough solar to heat it ok during the day, assuming you have good open southern exposure, but at night you will lose the heat real fast. Putting another layer of poly either inside or outside will help slow down that heat loss. Pile leaves or straw around the frame but not so much you block the sun. Put jugs of water inside the frame, these will absorb heat during the day and release it slowly at night.
You might consider some heat-tape with a thermostat to handle the coldest times...maybe wrap it around the pots.

Answer 4

Solar power won't work. There isn't enough at this time of the year. However, putting lots of blankets over the frame at night will help a lot.

If I really had to power it by solar, I'd have a heat collector and then circulate the heated water in underground pipes so the ground stores the heat. At night the solar shuts down and the heat is released. You still need the insulation.

Answer 5

Don't worry about it. I have seen cacti growing next to a shed, unprotected. in Northern Wi. My friend didn't know what else to do with them. So He just put them outside. They have adapted very well!!

Answer 6

Homemade Solar Power Videos : http://SolarPower.siopu.com/?ZUf