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_maxis greater than 1, and is higher when the temperature difference is smaller.
- In this case, it's actually the inverse: