Black colored water tanks in the middle of the greenhouse or an elevated rectangular ditch running along the perimeter of the greenhouse serves as a very good equilizer or stabilizer of temperature. During the day it absorbs heat, and during the night, it releases heat. Water has a high capacity for heat and would be ideal to use. This would minimize the difference between your high and low temperature. You can place koi, bass, carps, catfish on these water structures, or perhaps water plants as well.

Anyone using big water structures? I have seen documentaries of its use in the discovery channel.

The question I have is:

Would it be better to have a clear top over these containers or one the same color as the container itself?

I can picture a black (or blue) plastic drum with a clear top, allowing the sun to reach the water inside and be absorbed by the dark material on the inside as well.

Does this make sense?

I've only seen dark lids or tops. The heat collection will occur through the (dark) walls of the barrels or containers, sunlight doesn't have to reach or penetrate the water. Incidentially, often the "north" half or shaded side of the barrel or container is painted white to reflect light into the rest of the gh or growing area.

Joencolo has been in my greenhous many times, and has seen my black and white 55-gallon barrel benches. I have twelve benches pluse various raised beds, which are used for planting in the ground. Of the twelve benches, eight of the benches are made with black plastic 55-gallon barrels filled with water. Each bench is comprised of seven water filled 55-gallon drums placed in a row, that are black on the south side which faces the sun, and painted white on the north side to reflect light around the greenhouse. A gallon of water weighs 8-lbs., so a 55-gallon drum contains 440-lbs. of water, or a total of 3,080-lb. of water per bench. In total there is 24,640 -lbs. of water in the 8 benches. Also The outside walls are lined with black plastic 55-gallon drums which also act as a long bench. The outside rim is made up of an additional 40 drums. In total the greenhouse "benches" are made up of 96 X 55-gallon drums, which contain 5,280 gallons of water, which is equal to 42,240-lbs. of water. This gives a lot of free heat. By defination, one BTU is the amount of heat required to raise one pound of water one degree F. Or, when one pound of water loses one degree of heat, it gives off one BTU. Therefore in my greenhouse every time my water barrels drop one degree in temperature during the night, I gain 42,240 BTU's of heat. At this time of year when the sun is nearly at it lowest level in the southern sky, the average water temperature in the barrels at dusk is 74F. In the morning the average water temperature is 66F +or -. This is an average drop of eight degrees during the night X 42,240-lbs. of water = 337,920 BTU's of free heat per night. Or 10,376,600 BTU's of free heat per month during the winter. months During the summer the water storage works in reverse and helps cool the greenhouse. All this is free heat, plus it give me the use of 8 two foot wide, 15-ft long, 4-ft. high benches to set my plant on. I'll take some pictures and put it on this forum in a couple days. - Millet

The Botanic Gardens in Cheyenne, Wyoming has a greenhouse and arboretum. The greenhouse/atrium is heated pretty much by passive solar and heat retained/released from contained water. Same principal that Millet uses and spoke of. Dark barrels with the shaded side painted white. In talking to the folks in Cheyenne, they seldom use the backup heat source, 'tho it sometimes gets kinda cool in there. Visit their website,
http://www.botanic.org/

Wow, that's one heck of an explanation! I would love to see pics of these benches Millet. Do you ever have any problems with algae or mold growing inside these drums? Do you have to flush them out and change the water every so often?

There you have it folks! Millet has expressed them in the US English units. I am currently running an energy balance model in SI units in an LCA project and would have explained it that way.

Ironically, when you look at the various greenhouse kits for sale, or even in building any greenhouses for that matter, NONE OF THEM have emphasized in detail the importance of massive amounts of water to conserve energy and stabilize your greenhouse temperature. The energy involved is all free, with minor investments for the containers or water structure.

They'd rather have you invest in airconditioning and heating, so that they'll get more money if you buy these items for your greenhouses. You couldmagine the savings in oil imports, and greenhouse gas emissions.

Follow the tips of Millet and most other practical greenhouse owners, it will be good for your wallet, your plants and the environment.

Chops, no I never get alge build up inside the barrels, because they are made of heavy black plastic, and sunlight cannot penitrate the barrel. Alge cannot grow with out sunlight. The barrels were free, they came from my business after we used up the products that came in them. Actually they are cheaper then free. We have to pay $8.00 per barrel to have them hauled off. One other point. Because the barrels absorb heat during the day from the sun, plants that love heat such as pineapples, guavas, palms ect. do very well setting on top of the warm drums. Also they good for some germinating seeds. Lastly my cat ust loves to sleep on top of them during the cold Colorado winters. - Millet

Great! thanks for the post. Makes me wish I had room for a greenhouse. Maybe I'll convert my garage one day.

egads, I'm only now seeing all these discussions about bulk water storage and utilization. (I've been sick). Once again, I am amazed at the vision and knowledge in this forum.

I have a "screenhouse" for my outdoor hydroponic system. Also have three barrels. Will be tweaking my screenhouse hydro system to use solar heating for the barrel this Winter. Given the raw simplicity and yet prevalent influence of thermal heating from black water barrels, it seems a "hydronic" soil warming method (distinct from hydroponic) should look hard at solar heating like this as the first step, with or without an aquarium heater and copper pipes. Thank you, JoeReal.

Here is some research I did for friends awhile back, listing some bulk water containers in the context of emergency readiness. I trust nothing of governmental assistance in emergencies, particularly water. Another benefit of your recommendation, JoeReal, is that one does not have to ponder that question. I have drunk (repeatedly) from black water barrels, and taken readings. The water remains good tasting, but I'd be scared in a bad way if such barrels ever held toxic substances in previous uses. Thanks. http://members.cox.net/v-francis/WatrStor.htm -Vince

There are ways to actively manage at least a portion of your thermal mass. A fellow in Australia I know from another forum uses a computer controlled system of pumps to run his water through black tubing when he wants to gain or store heat. The same tank of water can also be sent through swamp coolers.

Thanks for the explanation on the thermal mass properties of your water barrels, Millet. I knew this, but hadn't really thought about it in the context of my own greenhouse. This will be helpful when I get the larger one finished this coming weekend. More buckets!

.....Alan.

Casa, Glycerine and or dyes. - Millet