Backyard Aquaponics
A place to discuss aquaponics

I've been looking into thermal mass storage options recently, and came across pressurized anhydrous ammonia.

Has anyone tried storing pressurized anhydrous ammonia as a thermal mass storage device?

At 50 psi it would have a vaporization temperature of 50 degF (10C). If the sun could keep it above 50 during the day, it would have to release 527 Btu/lb to condense. That's 147,000 Btus per 50 gallon barrel, which is a huge amount of energy - like a large furnace output.

I very much doubt anyone would consider ammonia as a phase change mass storage substance. The amounts in the older refrigerators was very small, in larger amounts it can be very dangerous.
There are many other suitable and cheaper options available.

The heat is released when you are compressing it, in order to turn it into a liquid, so you will end up with a much smaller volume of liquid NH3, but you have to remove the heat from the gas to somewhere else to store it, as it wont form a liquid while it is hot.

Now what? You have your liquid Ammonia, when you want to put it back into your barrel it is going to get very cold- that's why it is used as an industrial refigerant- not for thermal storage.

There are a number of materials that can be used for phase change thermal storage, around the solid-liquid phase change, and they are much easier to handle than toxic Ammonia.

Then there is water, which has a very high specific heat- it is ideal for moderating temperatures, and is non-toxic and inexpensive. For a somewhat higher temperature than 10C there are a number of waxes that are ideal for phase change thermal storage, paraffin, beeswax, palm wax, etc, around 50-60C, easy for evacuated tube solar, even in winter sun.

Hey guys,

My idea was to leave it in the barrel all the time, not to compress it like refrigeration. That would be a bit safer. The daytime sun would gasify and superheat it, while at night it would start to liquify if temperatures got cold. With a vaporization temperature of 50, it would release that heat when condensing and hopefully keep the greenhouse above 32.

I realize it's horribly toxic, but I also see it every time I visit refrigerated warehouses. They store hundreds of gallons in rated tanks. There's a whole infrastructure behind it.

I think the fact that it's a gas/liquid phase change rather than solid/liquid means there's about 5x the heat storage capacity available. Plus the fact that it condenses at 50 degF makes it just about perfect (other than that it would kill you to breathe it).

Gunagulla, can you point me to another substance that phase changes at 50? Preferably from liquid/gas. I know pariffin does solid/liquid around 80, though you could dope it to lower that.

http://pcmproducts.net/

liquid-gas is a bit harder to find, but there are no doubt some organic solvents with a suitable BP, but right now I cant lay my hands on my old copy of SI Chemical Data ... but again you run into the toxicity problem.