Collecting energy from 70-80 Celsius degree heat heat
Thermoelectric generators (TEG) or peltier or seebeck devices.

Aliexpress lists lots of these. I see that some are now listed as optimised for generation, rather than cooling.

You need heat to flow through it, and a temperature difference across it, so it needs a heatsink that is cooled by the room air (maybe colder at floor?)

The good news - cheap and capable of making heaps of current if you can keep the cold side cold.

Alternatives: Ali has little inline water powered generators that power shower leds/thermostats etc.