Jon, your Peltier device with a COP of 0.5 is way less efficient that a standard refrigeration system which has a COP of around 3.
So your 12V 7A device (84W) only puts out 42W of cooling power versus the a compressor drawing the same power would give you 252W of cooling power. That's about 0.07 tons of refrigeration or the ability to make 143 lb of ice in an hour. No idea whether that's enough cooling for a typical truck cab. (My math may be a little off, as I haven't been in the business for over 5 years - a little rusty.
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Also no idea how much power a typical 12V compressor draws. Looks like Jason's setup draws 82 amps total, but that's at 115V.A little rusty on observation as well, I guess. I mistook that 115A alternator for 120V.
