Get hold of a 55-gallon drum and paint the outside FLAT black. Then position in the greenhouse and fill with water. The idea is that the black paint will absorb solar heat and heat the water during the day and then release the heat slowly at night.

I intend to try this, but haven't yet.

Sue

Assuming you can increase the water temperature by 20 degrees, that is still very little BTUs.

The thing to consider is the following:

After a night's cold temperature, the tank of water gets very cold, the next day the sun is not out, then the tank of cold water will take away heat that's in the greeen house.

My point: water tank is a good idea, but design your system carefully.

dcarch

Beautiful stuff to use behind the greenhouse:
1. In the day time, they bounce sun light into the greenhouse (sunlight = 200+BTUs per SF).
2. Best insulation in the night time.

Also, have the floor in the GH as dark as possible to serve as geothermol source.

dcarch

I thought the heated water might do the trick, but with the gloomy clouds lately, I'm starting to think I will need more heat. I have been trying to find a SOLAR way to heat the GH. I personally have a problem with paying to heat a GH when there has to be a better way for our environment and the checkbook.

I have looked into using the water heater sticks :) URL below. I was thinking this might use the least electricity. Does anyone have any other suggestions I could try? There has to be some great Solar ideal out there I haven't stumbled across yet.

To get heating and cooling via geothermal you have to plan ahead and size the system appropriately however, and I have no clue yet how to do that. But then heating and cooling costs go to fans to move the air instead of $$ for fuel and such.

Just a thought.

I have wondered about solar heating using an underground tank. Heat water using the well known roof-type solar water heater system. Circulate it with a small 120 V pond pump. When you need heat, you would recirculate the warm water through a non-pressurized radiator with a small pond pump and with a fan behind the radiator.

Dan

"A solar-powered pump is inexpensive"
Solar cell generates not much power. Depending on many hydrostatic factors, I think a water pump about at least 100 watts will be needed, A 100 watt solar panel is very expensive with other electrical and electronic to go with it. When you need it the most when the sun is not out, you don’t have the power to operate the pump.

" I also see the high-end method of taking the hot air at the top of the GH and putting it underground to heat the soil. "
Not easy to make this practical at all.

Geothermal, where there is no hot spring type of underground heat source, I believe is a concept works best with a heat pump system to extract the small amount of BTUs in the soil.

"I also use dark-colored water in containers to absorb solar radiation to help things along."
Water does not have a lot of heat storage capacity (One BTU per lb per degree F) unless it goes thru phase change (144 BTU/lb of ice). Whatever heat it gives up in the cold nights, it will take away in the day time in your greenhouse.

dcarch

BTW, the temps inside are measured just a few inches above the ground - it always feels much warmer at my waist or head.

Mike

A number of different solar pumps exist for such an application already, and pipe under, say, an 8x12 GH, you are only running maybe 3-6 gal of water around at any one time - not much weight at all. Not a problem.

My coldframe setup - necessarily vague as I want to patent - is indeed a sealed and insulated reservoir and I WANT to lose heat to the soil, as that is the point.

I also use water to store and release heat to the GH (the point) at night. There is much precedent for such a setup, which was expanded to many GHs in earnest in the 1970s. Not perfect, but it helps.

My next big project (family hasn't approved) will be a GH with something like a trombe wall like polcat did. There is much precedent for this as well.

Returning to the OP, a drum heated however - drop an element in there and plug in and heat for maybe 10.00/month and then run 1/2" poly under the floor and run water thru there and your soil will be warm enough at ground level in the winter to grow greens. Pump, barrel, pipe, mesh for protecting pipe and time should be 150.00 tops.

Dan

Get an electric generator and run it inside a greenhouse. Making sure that exhaust is completely safe to outside thru a heat exchanger. You get free heat when you supply power to the your home.

dcarch

Dan