It sure is tempting to think of heat as just energy. I mean it is. Of course. But the kind of device you're talking about is like Maxwell's Daemon. The article

It sure is tempting to think of heat as just energy. I mean it is. Of course. But the kind of device you're talking about is like Maxwell's Daemon. The article is talking about a step towards making an inexpensive thermocouple. These require temperature differentials, not just heat. And you don't want to be drawing power from the temperature differential in your house ;)