What is exergy? Why some joules travel first class

One kilowatt-hour of electricity can run a motor. One kilowatt-hour of lukewarm heat might struggle to run a convincing argument. Both contain the same energy, but not the same ability to do useful work. Meet exergy, thermodynamics' brutally honest exchange rate, and discover why heat pumps, power plants, and factories should stop treating every joule like a first-class passenger.




