Isn't the freezing temp of vodka too low? I've kept vodka in the freezer, and it never actually freezes. In order to get the benefit described during a power outage, you need something that will be frozen at normal freezer temps, but will melt before the food starts thawing.

The latent heat of alcohol is also only about 1/3 that of water per unit mass, so not a very dense way of storing energy, even if you were to freeze it.

Adding salt to water reduces the latent heat density too (pure water is hard to beat there), but not as much as adding alcohol does.