On the parameters of performance of combined refrigeration and power plants

•Literature shows several parameters of performance defined in different ways.•Some parameters are critically analyzed in order to indicate the most proper one.•The indicated parameter is the primary energy ratio and it is formally analyzed.•The coherence and robustness of the primary energy ratio is proven.•The use of the primary energy ratio is recommended as universal parameter.

Combined Refrigeration and Power (CRP) plants generate power and refrigerate a thermal load simultaneously from the same fuel. The overall efficiency is a parameter based on the first law generally used to quantify the fuel saving, in the sense that a plant that has greater overall efficiency saves more fuel than others to generate the same useful energy. However, the literature shows that the overall efficiency and other parameters of performance are defined in several different ways. This heterogeneity is not desirable when considering a coherent and universally accepted parameter of performance based on the first law. In this work, some parameters found in the literature are critically analyzed in order to indicate the most proper one. The indicated parameter is then formally analyzed in order to verify its mathematical consistency. The primary energy rate is considered the most well-suited parameter based on the first law to characterize the performance of a CRP plant.