...

[Neko-chan]

...

 

[sunsaver]

Solar electric power for heating is not practical. Electrical heat is very inefficient. A small space heater is 1500 watts. Thats 15 times $400 per 100 watt solar panel. A better idea for solar heat is called thermal mass. This could be a large stone or concrete mass that is painted black to absorb heat from the sun during the day, and release it at night. Five gallon buckets filled with water or oil and spray painted black would work. One option is kerosene lanterns mounted firmly in a bed of sand or gravel on the floor, and the plants elevated near the ceiling of the green house. Silver tarps are pulled over the roof each night to stop radiant cooling. Care must be taken to prevent small animals from knocking over the kerosene lanterns. This is the technique that i intend to use for an avocado tree. Hope this gives you some ideas. Chat with ya later!

 

[Marianne]

I know exactly what you're talking about as a neighbor behind us has one.

This would be in your house somewhere, right? Or were you planning on putting it in an outdoor building somewhere? What kind of low temperatures are you dealing with?

 

[valmom]

Someday I want to build a greenhouse with a thermal mass heated by a rocket stove! OK, probably more involved than you are wanting, but that would be the gold standard for me!
http://www.youtube.com/watch?v=qtFvdMk3eLM&feature=relmfu

 

[Marianne]

Yes! I'd love one, too!

 

[sunsaver]

Problem here is that temps fluctuate so wildly in winter. It can be 60*F one day and be 17*F that night. Careful monitoring or automatic vents with thermostats are in order. These type of things can be found at Farm Tek.

 

[MorelCabin]

Well here is an idea...not solar though, but cheap to set up and cheap to run. Put a hundred watt lightbulb inside a large ceramic flower pot on the bottom shelf, it will keep it well above freezing at night and you can turn it off during the day if it is warm enough.

 

[~gd]

I have a question. I want to get some tomatoes and peppers and other plants started early this year, but the book suggests I need a heated greenhouse to keep them.

Well, I have a "mini" greenhouse (essentially a shelf rack with several shelves and some wheels on the bottom, with a zip up plastic cover thing enclosing it).

I was wondering if it was possible to create a solar powered heat coil or something that I could slip in the bottom most shelf to keep the whole unit warmer.

If that's practical and a good idea, I want to know how to build such a unit, what I need for it etcetc.

Any thoughts?

The plants you mentioned will not take off until the weather is warm. Around here they are usually started from seed in flats in a glass house or a cold frame which also depends on the sun for heat. They allow sun in for heat and then trap it. It is a classic example and green house gases and/or the greenhouse effect is named for the effect. To be blunt I think your answers so far have been by gaget people who are making a simple answer complex. I suggest you read up on greenhouses and cold frames to see if they will work in your climate. The rig you mentioned is the one I use for tropical plants and the plastic cover is to hold in humidity not heat.

 

[sunsaver]

Cold frames are fine for early spring, but the question was how to over-winter plants. For colder climates, some sort of night time heating from a "gadget" is required. I over wintered all my pepper plants in my living room, near the wood-burning stove. It has a thermal mass under it, so that the room never gets below freezing.

 

[Neko-chan]

...