If you’re in a dry, hot environment and evaporate water in a swamp cooler, you lose about 2.3MJ/l, from which you can skim maybe ~10% with a thermocouple. If you’re charging a Dacia Spring consuming 156Wh/km, you’d have to evaporate ~30 liters of water to drive 100km.

en.wikipedia.org/wiki/Enthalpy_of_vaporization#Ot…
en.wikipedia.org/wiki/Thermoelectric_generator#Ef…
ev-database.org/…/energy-consumption-electric-car

But then, what if you bought solar panels and a wind turbine instead of thermocouples and water?