Yer talking milliamps out of the furnace thermocouples.
Just been playing with what I had on hand, iron, copper, constantan wire, yup, those give out microvolts, best output I could get was 1.1 millivolts with one stuck in flame. I guess those furnace and boiler type ones have multiple junctions in. Gunna go dig for one I've got in a box of junk somewhere and see if that is more like 2 or 300 millivolts...
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice