How does the dispersal of energy (increase in entropy) affect the usefulness of that energy for performing work?

Answer

Dispersed, high-entropy energy has very little potential for work.

Energy quality decreases as it spreads out; concentrated, low-entropy energy (like a lump of coal) has high potential for work, whereas widely dispersed, high-entropy energy (waste heat) has very little.

How does the dispersal of energy (increase in entropy) affect the usefulness of that energy for performing work?
ThermodynamicsLawsystementropy