In the spirit of using less energy, and also because I'm lazy, I've been considering trying to chill my wort without running water or electrical input. I usually boil my wort up high on a table so my 1.5 year old son can't reach it. I just installed a weldless shutoff valve on my brew pot, and have considered freezing an immersion chiller or a small finned tube radiator in a bucket of water. On brew day, I'd just route the discharge from the kettle valve thru the wort chiller and into my fermenter. It would also mean I could add my hop back in between the kettle valve and cooler, and have almost instant cool down after the hop back addition.
If the chiller was in a block of ice, I believe the surface of that copper coil would remain very close to freezing. As soon as a little bit of hot wort went thru the coil, there would be a thin layer of 32 degree water around the coil. This layer of water would slowly increase in size, but with the huge heat sink of ice around it, would remain close to freezing.
I guess my questions are: has anyone ever done this? and if so, is 25 or 50 feet of copper tube frozen inside a block of ice a sufficient length to cool wort down to 80 degrees or so based on the relatively slow volume of water that goes thru the chiller because of gravity? It would only be a single pass thru the chiller.
I've already tested the flow principles of this, and there is enough head from the height of the brewpot to flow through all of my devices. I guess I need to test it with real boiling water and a real frozen ice block...
Oh, and I know that the energy used to freeze the block is probably more than a pump would consume