Can we recover more energy ?

Discussion in 'General Science & Technology' started by ajanta, Aug 14, 2016.

  1. ajanta Registered Senior Member

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    Car engine efficiency is about 30-40%. Over 60% energy transformed into heat. Thermoelectric generator(20-25% efficiency) can recover some energy from heat into electric energy. But can we recover more energy from heat + TEG of heat engine ?
     
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  3. exchemist Valued Senior Member

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    Your diagram seems to show an engine plus a heat recovery turbine plus a thermoelectric generator.Which is fair enough, I'm sure you can get a bit more out by these supplementary devices. (When I worked with big powergen diesels, a heat recovery turbine was sometimes used, downstream of the turbochargers, to extract a bit more energy.) The limit will be Carnot cycle efficiency, which is determined by the temperature of the initial combustion, "Tc" and the temperature of the environment into which the waste heat is ultimately rejected, "Te". Carnot efficiency, η = (Tc -Te)/Tc (both temperatures in Kelvin, i.e. absolute units of temperature).

    From this relation you can see that 100% efficiency would require either combustion at infinitely high temperature, or rejection of waste heat at a temperature of absolute zero, neither of which is of course attainable in practice.
     
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