High-power thermoelectric generator utilises thermal difference of only 5°C
The Carnot efficiency of a heat engine is 1 - T_low/T_high. When operating between 305K and 300K (room temperature(ish)), for example, this is 1 - 300/305, or about 1.6%. In other words, the absolute most amount of energy a device operating over a 5 K temperature difference at room temperature is pretty dismal. Just because their band gap (for lack of a better term) is small does not make this device "useful."<p>For all stories about heat engines running between smaller temperature differences, the <i>smaller</i> the temperature difference, the <i>less</i> excited you should be. For example, I have a device that reaches the Carnot efficiency across temperature gaps of 0K! HINT: It's a rock. Or a paper clip. Or a wet tissue. Or...