Answer: Each process has an energy type that can be either "purchased", "useful" or "other" energy. Purchased energy generally represents all of the outside energy you had to supply to the cycle. Useful energy represent the net balance of the cycle, in other words, the sum of energies produced and consumed. The efficiency of the cycle is defined as the ratio of "useful" energy to "purchased" energy. In a steam power plant, the "purchased" energy is the energy supplied to the boiler, and the "useful" energy is the difference between the energy produced by the turbine and the energy consumed by the pump to pressurize the water. "other" energy is the heat released in the condenser. In a compression refrigeration cycle, "purchased" energy is the energy consumed by the compressor, "useful" energy is the refrigeration effect (heat extracted by the evaporator) and "other" energy is the heat to be evacuated in the desuperheater and the condenser.