I was just looking at the back of one of the little window ACs and it sure has a lot of exposed heated area..
Around 15x11 inches..
What if, you were to make a flat plate heat exchanger?
A 15x11 metal-to-metal direct-contact heat exchanger and mount it on the surface of the hot coil?
Load up the Hot coil and the 'Heat Collector' plate with thermal conductive epoxy and bolt them together.
Add insulation, re-route the fan power leads to a circulator pump and you are cookin!!
Or maybe if you can make the Collectors thin enough, put one on each side.
When it gets too cold in the basement, the AC thermostat will turn it off..
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