Poly Barrels H2O mass heat storage and freezing

Anyone know how much freezing Poly barrels can handle? Will I have to drain them? or can I just let them freeze when I am done heating the greenhouse for the winter? TIA, Julie

Julie,
First I have no real experience with barrels, so grain of salt.
I freeze smaller containers all the time. I leave an MT head space and an open lid. So that when the ice expands during freezing, it fills the MT space.
I would think that barrels would do the same thing?
I don't know how long a frozen barrel would take to thaw out in the spring, when you are ready to use it for thermal storage, might slow you down.
Are you set up to drain the barrels easily?

One good thing about freezing water is that it does an effective job of buffering temperatures. Water freezing actually releases energy to the environment, keeping the surroundings a tiny bit warmer. Conversely ice melting takes in lots of energy, delaying the warming of the surroundings.

You may be able to use that to help keep a chill off at certain times of year.

As Miles said, leave an empty expansion space at the top of each barrel, and leave the lid loose for air to escape.

I was wondering about the energy use in spring...but we do start getting good sun in Feb. And our days get long pretty fast.Plus I don't mind running the RMH extra to get things going. I will leave room for expansion, but I have had open buckets burst on me when they froze.(trying to make ice blocks for winter ice fort thanks for your ideas!

What about adding salt to them so that they don't freeze so easily?

where are you located?
are you trying to keep the barrels from freezing, or just dont want them to get ruined if they do freeze?

if you do not want them to freeze, you could add some more glazing to help capture more heat.


also, for what its worth, i have had a pair of 55g poly rain barrels freeze solid while they were full, with no issues. it has gotten down to ~-20*f here.

I've had them freeze quite a few times without damage. You wouldn't want to fill them 100%. Maybe 95%?
Depending on the greenhouse and outside temps they might not freeze.