[ryanmarsh]

I wonder how efficient water is for storing and transferring energy as opposed to something like a lead acid battery.

Ice takes a lot of energy to freeze. That means your freezer is going to be really inefficient for a long period of time once the power kicks back on. Also, any other food you put in the freezer is a thermal mass as well. It might be the last to thaw but it could also be the last to freeze if you deplete the "battery" and have to start the process over.

I'm surprised he didn't invest in further insulating the freezer. Deep freezes are not well insulated and waste more cold than your typical cheap foam beer cooler.

[mikepurvis]

I feel like preserving ice over long periods of time has become a bit of a lost art, but before mechanical refrigeration, ice was sent extreme distances by ship and rail and stored for months at a time, see: https://en.wikipedia.org/wiki/Ice_trade

[ryanmarsh]

I've read up on this quite a bit. It was incredibly inefficient and worked mostly in cooler northern latitudes.

At southern or tropical latitudes often 90% of the product would melt before it made it to market. Insulation was primitive (saw dust).

[ghostly_s]

You need to throw out your fossil-economy preconceptions. Efficiency is irrelevant when you're running off direct solar energy. Sure, you could drop the price of a complete unit if it can run on a smaller panel, but the significant variable is not energy efficiency, its resilience to intermittent insolation.

[ryanmarsh]

It takes up space in the boat, it requires labor to extract the ice. If you're buying 10 times the boat and 10 times the labor the price is going to have to support it.

This is why Tudor ended up in debtors prison before he got the business model right.

[vanderZwan]

> Ice takes a lot of energy to freeze.

Well, yes, but that means it also takes a the same amount of energy to thaw. That's the whole idea: large heat capacity to create a temperature buffer.

[soulofmischief]

Not the same amount of energy. There is heat and kinetic by-product from the compressor.

[vanderZwan]

Sure, there is overhead. But it is not immediately obvious whether or not GP was referring to those particular energy inefficiencies, or the relatively large heat capacity of water.

It is also not immediately obvious whether the losses when freezing ice would be less efficient than energy losses due to the heat produced by charging up a battery, and the leaking of charge. If you take all energy loss into account, the questions of efficiency can have counter-intuitive results[0].

[0] https://www.lowtechmagazine.com/2014/06/thermal-efficiency-c...

[ingenieroariel]

I live 10 degrees north of the equator.

A lot of times during the really hot midday all I can think of is making ice and letting it melt during the night so it can cool the side of the bed.

If the freezer is next to your bedroom then the bad insulation becomes a good thing because you may save on air conditioning.

[ghostly_s]

I'm not clear if you're describing this project or a conventional freezer, but freezers/fridges are counter-productive to air conditioning because they vent the evacuated heat into the surrounding environment (your home). This is still operating on the same principle, and no matter how poorly-insulated as long as the R-value of the freezer is greater than 0 it's not going to be helping you cool your space.

I've often wondered if there's not meaningful efficiency to be gained in piping the coolant to remote coils outdoors like we do for A/Cs (with a control system to vent the heat indoors when heating is desired, or even use atmospheric cooling instead of the compressor when the outside temp is low enough).

[ryanmarsh]

Like a "swamp cooler". The problem is the melting happens in transit. By the time it gets to you there's very little ice and it is thus very expensive. Too expensive to leave by your bed side at night next to a fan to cool you... unless you were wealthy.