Can free heat be turned into usable energy?

Question

I know heat from steam and whatnot can be changed to electricity, but is it possible to change the heat from the atmosphere to electricity?

Answer 1

Yes, but only if you have a hot sink (a place from which you can extract heat), and a cold sink (a place into which you can dump heat).

The greater the difference in temperature between the hot and cold sinks, the more efficient the engine will be.

The problem with the atmosphere is that while it may contain some heat, there is no convenient nearby region to conduct heat to that's colder than the atmosphere.

Geothermal power works by using the interior of the Earth as the hot sink, and the surface of the Earth as the cold sink.

Answer 2

The direct answer is yes.
But the set up will be elaborate with small electrical yield.

To generate electricity directly from heat, you will need to harness the Seebeck Effect. The simplest way to do so is to use a Peltier Junction in reverse.
(You can check out how Peltier junction/plate look like in ebay).

If electricity is run through a Peltier junction, one plate will end up becoming warmer, and the other plate will end up cooler (Peltier Effect).
And in reverse, if heat is applied on one plate, and the other plate is cooled, electricity will flow (Seebeck Effect). The greater the difference between the two plates, the higher the electricity generated.

In your case, the heating of one late will be minimal since you are relying on atmospheric heat, thus you will need to cool the other plate vigorously (creating large temperature difference) to see any significant electric flow.

Another option is to use reflective parabolic bowl to focus the heat from sunlight onto your Peltier junction.

Either way, the answer is Yes, you can generate electricity, but it won't be practical and economical.

Answer 3

In general, no. A French engineer named Sidi Carnot came up with the basic rules for heat engines; you can get work from heat only if you have two reservoirs at different temperatures. The more different the temperature is, the more work you can get. But without that second reservoir, you can get nothing. Carnot's observations wound up becoming the laws of thermodynamics.