Archive:000/Carnot's theorem

(see Wikipedia page for more detail)

General formula:

efficiency_max = (t_hot - t_cold) / t_hot

This describes how much usable work (physics energy) you can obtain from a difference of temperatures t_hot and t_cold. The temperatures must be measured in kelvin (or any other units that are relative to absolute zero). efficiency_max is a theoretical maximum energy efficiency, not quite obtainable in real life.

This applies...

• to any power plants that use a fuel to boil water to make steam to drive a turbine to generate electricity.
  • This includes coal, natural gas, biomass and nuclear power.
• in reverse, to heat pumps and air conditioning.
  • In this case, it's actually the inverse: efficiency_max = t_hot / (t_hot - t_cold). In this case, efficiency_max is greater than 1, and is higher when the temperature difference is smaller.