Reply to a non-scientist who asked, at a public discussion on energy, why the thermodynamic efficiency of a standard power plant is so low (35-45%)


Hi, Pat,
    35% is low, for the very oldest coal-fired or nuclear plants; new coal-fired plants hit 45%.  There are fundamental thermodynamic limitations to efficiency of a heat engine.  The limit discovered by Sadi Carnot about 150 years ago is firm: the maximum efficiency for a heat engine operating between a high temperature T2 and a low temperature T1 is (T2-T1)/T2.   All temperatures are absolute (Kelvin, or, if you're stuck in US units, Reaumur).  A few points:

So, in short, higher efficiencies in central power generation, or even medium-scale power generation, are a ways off in time.  Many, many people are working to advance this, but the technology is not there yet.  We can't stop pushing hard for this.