Using 55 Gallon Drums

I am building a passive solar greenhouse and going to use 55 gallon drums for passive heat storage.  Does anyone use them as a heat storage and does it work?

Any mass will work if the structure is sized appropriately for the conditions. Theres plenty of numbers available on sites like Engineers Toolbox when figuring how quickly heat flows through a system.

I'm sold on the idea for the greenhouse build I'm working on! Much easier to pump some water into a drum (and drain it out in the future) than it is to deal with moving and stacking stone or concrete. Cheaper too, especially since you can get second hand drums for cheap or free. I would most definitely go with a drum that's black already, rather than painting one.

Hi Douglas; Welcome to Permies!
Were you hoping to extend your growing season with water barrels?
They work well all summer long to take the chill off.

However , be forewarned they work completely backwards, when you ask them to work in the spring or fall.
That same water mass that holds heat, also will go cold and steal heat... Will take all day on a sunny spring day for them to absorb heat.That heat "might " be enough to keep your plants warm.
On a cloudy day they stay cool and steal heat! Plants go cold., nothing thrives, if they survive at all.
They also take up a huge area...
That same area "could" have a rocket mass heater!  Nice long warm mass to set your starts on.  Will definitely extend your season right into winter if you wish.

Come check out the RMH forum here at Permies.  We even have a section on rmh's in greenhouses.
I keep a plastic greenhouse warm all winter in northern Montana with a RMH.  No fire all night long...  no creosote ever, clean ash out once a year...Less than 5 cords of wood to do this.
Even if you do not desire one in your greenhouse, it is just good information to have in your head.
You never know... you might want one in the future in your home.

thomas rubino wrote:Hi Douglas; Welcome to Permies!

However , be forewarned they work completely backwards, when you ask them to work in the spring or fall.
That same water mass that holds heat, also will go cold and steal heat... Will take all day on a sunny spring day for them to absorb heat.That heat "might " be enough to keep your plants warm.
On a cloudy day they stay cool and steal heat! Plants go cold., nothing thrives, if they survive at all.
They also take up a huge area...
That same area "could" have a rocket mass heater!  Nice long warm mass to set your starts on.  Will definitely extend your season right into winter if you wish.

You've brought up an interesting notion I'd not thought of: thermal mass heated entirely by passive solar can be entirely thwarted by clouds even into the next sunny day. So adding thermal mass in a free-standing greenhouse is only a good idea if you are in a reliably sunny climate or have some auxiliary heat planned (like a RMH.)

On an attached greenhouse I think thermal mass remains viable because you can bum heat from the home on the cloudy days to get by, and hopefully still get net gain on energy on sunny days when you can use the greenhouse to heat the home.

thomas rubino wrote:Hi Douglas; Welcome to Permies!
Were you hoping to extend your growing season with water barrels?
They work well all summer long to take the chill off.

However , be forewarned they work completely backwards, when you ask them to work in the spring or fall.
That same water mass that holds heat, also will go cold and steal heat... Will take all day on a sunny spring day for them to absorb heat.That heat "might " be enough to keep your plants warm.
On a cloudy day they stay cool and steal heat! Plants go cold., nothing thrives, if they survive at all.
They also take up a huge area...
That same area "could" have a rocket mass heater!  Nice long warm mass to set your starts on.  Will definitely extend your season right into winter if you wish.

Come check out the RMH forum here at Permies.  We even have a section on rmh's in greenhouses.
I keep a plastic greenhouse warm all winter in northern Montana with a RMH.  No fire all night long...  no creosote ever, clean ash out once a year...Less than 5 cords of wood to do this.
Even if you do not desire one in your greenhouse, it is just good information to have in your head.
You never know... you might want one in the future in your home.

I agree with Thomas, I live in mid Mo. and I have a large high tunnel I got through a grant trough the NRC it is 30 x 72 ft and I gave up trying to heat it in the winter, its just too big. On a good sunny day it takes all day to warm the barrel slightly so without a good heat source and a lot of barrels its just not going to work well. It has taught me what I can grow in the winter with no heat and the ground inside rarely freezes at least not for long. Lots of cold crops like spinach, kale and cilantro will do fine with no heat. When and if I build another one its going to be small, insulated on the north side and 2 layers of plastic and most likely set down in the ground a few feet and have a rocket mass heater. I am building another homestead  three hours away so I have a lot of big plans and I am wanting to document it on my youtube channel (Little Beaver Creek Homestead). My hopes are that I can help others find cheaper ways to do things and become more self sufficient, and I have a lot of ideas like how can I keep a green house cooler in the summer to grow cool crops in the summer. If i could pull cool air from a small cave I have or underground tubbing it may work.
Anyway think small and insulated for a winter greenhouse then your heat source would be easier to do. Have a good one, hope this helps and good luck.

I saw something somewhere and 55 gal drums were painted black, filled with water and used as thermal mass with great success in a greenhouse. adding a solar water heater panel and small circulating pump could help keep the heat up.

bruce Fine wrote:I saw something somewhere and 55 gal drums were painted black, filled with water and used as thermal mass with great success in a greenhouse. adding a solar water heater panel and small circulating pump could help keep the heat up.

 Bruce I'm just speaking from my experience. Here in the midwest I have seen weeks with no sun and my drum was painted black. I'm no expert and may have been able to do something to get it to work better but I think its safe to say your not going to successfully heat a greenhouse where I live anyway, with barrels full of water. What I will say is it will help keep it warmer longer if you can have a heat source. Your solar water heater may work in some climates but if you have a lot of cold and no sun you get little heat. One big factor is how well your greenhouse is insulated too, an underground greenhouse may do pretty well even here with just solar. My thoughts are as Thomas said, a rocket mass heater. They use little wood as compared to a wood stove, you can heat up a lot of mass well into the night or on a cold day with just sticks you clean up out of your yard or a few busted up pallets. You could even set your warm loving potted plants on the thermal mass.
 Oh, you could set up a thermal syphon with a rocket stove or something but it will take you all day to get you barrel hot, I know this one from experience too. And if you have more than one barrel you have a job on your hands.
 I hope this helps, just my two cents.

Thanks for your inputs.   I will look in to rocket mass heater.  

 My wife and I grow a bit for the farmers market and the rest for us. We start seeds in a basement bedroom and transfer them to the greenhouse in early spring. We have been doing this for 4 years now. Our small greenhouse is attached to the east side of our house with a 2nd floor deck over it. I have 4 black 55 gallon barrels on the south side and 4 on the east side, all full of water and all right near the plastic walls. There is also a 2 foot diameter concrete column painted black in the SE corner of the greenhouse. I made my growing tables directly over the barrels so any stored heat would keep the plants warm at night. This took away some growing area but if I had put the barrels on the far side of the greenhouse they would have gotten almost no sun. I only get east and south sun entering the greenhouse and Michigan winters are "very" cloudy. The barrels freeze solid every winter and take a long time to heat up in the spring, however I've noticed that when we are ready for the greenhouse, the greenhouse is definitely warmer than the outside temps (especially at night). Even if the greenhouse is not super warm, it still evens out the temps a lot.
 IF you use water barrels, be sure to loosen or remove covers to let the water expand as it freezes. I forgot to do this and the top and bottom of the barrels expanded about 3 inches. Then you have to wait till they thaw in spring, drain them and straighten them, re-install and re-fill. Pain in the ass...............
 I could have probably installed a RMH instead of the barrels, but the barrels were free, fast, easy and need zero fuel and zero input and I don't have room for both.
 Hope this helps...............

Thanks for the info Kirk.  That is what I am looking for.