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Thermoelectric Generator With No Moving Parts
Savage-Rabbit writes "These guys have produced a working prototype of a thermoelectric generator. The thing uses extremely cold and hot liquids to achieve a heat transfer through a semiconducting material. This produces a voltage in the semiconductor who can produce up to 50-100 Watts which is actually enough for this thing to have practical uses. This generator could for example be useful in the chemical industry where many production processes generate a lot of excess heat that normally is simply lost. With a thermoelectric generator some of that lost energy could be recovered."
This is just a Peltier device in reverse. Instead of using a forced flow of electrons to drive heat from a cold surface to a warmer one, it is using the flow of heat from a warm surface, through the Peltier element, to a colder surface to drive electrons, generating current.
You got it right - they only use 50/4000 = about 1% efficient....for the heat they actually remove from the system
Also realize that they only made use of a small portion of the temperature drop. Assuming they had a cold sink of infinite (relatively) mass, they should get a temperature drop of approx 65 C, assuming a typical icelandic 10 C temperature. So take that ratio as well and they made use of only about 0.4% of the maximum Carnot efficiency.
However, carnot efficiency is capped as well - you can never get all the heat in the water - so then multiply by the carnot efficiency found from 75 C and 10C, which is 0.19. So now we're down to an absolute efficiency of about 0.06%. Not too good...
To get the absolute efficiency the easy way, take 50g/s of water, and multiply by the temperature of the hot source, and also by the heat capacity of the material. Then divide the actual power by that.
-Looking for a job as a materials chemist or multivariat