The difference between COP and Efficiency is not as hard as we think, the COP and Efficiency both are the level of performance that is used to estimate (or calculate) the performance of the cycles, systems, and devices.
If you observe carefully, in the Carnot Cycle we measured the performance of the cycle in terms of efficiency, and when it comes to the Reversed Carnot Cycle, we are using the term called COP. Why so? Let us try to read the difference between COP and Efficiency.
Difference Between COP And Efficiency:
The Carnot Cycle is the heat engine cycle that absorbs the heat from the source and rejects it to the sink. In the time between absorption and rejection of little heat, the major amount of heat will be converted into the work that can be called net work done.
So, the performance of the heat engine depends upon the net work done by the system. So, the amount of heat converted into the required work and rejected to the sink in the Carnot cycle is the performance of the cycle that measured in terms of Efficiency.
The efficiency of the system is measured in terms of Percentages like 50%, 60%, etc. The cycles that absorb the heat from the source and rejects the heat to the sinks will be calculated in terms of Efficiency.
Coming to the Reversed Carnot Cycle, the heat will be absorbed from the sink (or space in practical application) and rejected it to the heat source (or surroundings) to keep the system cool. So Reversed Carnot Cycle is ideal for the refrigeration system which is quite opposite to the Carnot Cycle.
The performance of the refrigeration system or Reversed Carnot Cycle is dependent upon the amount of heat absorbed from the system and rejected to the sink. We can say that the work is done on the system instead of work is done by the system.
We can say that the Reversed Carnot Cycle performance is depends upon the work done on the system and not work done by the system. So, the Reversed Carnot Cycle performance is measured in terms of Coefficient of Performance.
The Coefficient of performance COP will be a maximum of 1 and do not exceed more than that for every cycle, system, and device. The cycles that the performance calculated in terms of COP are Refrigeration Cycles, Air Conditioning Cycles.