Conference Year



Conversion factor, Energy saving, Performance evaluation method


Due to the growing concern about energy savings in recent years the Japan Industrial Standards Committee (JISC) revised the performance rating of industrial air conditioning systems in October, 2006. The coefficient of performance (COP), the conventional factor, does not consider the actual operation of air conditioning systems corresponding to seasonal temperature changes. Instead it is evaluated under constant temperature conditions. In actual operation, the capacity and power consumption of cooling and heating varies according to outside air temperatures. As a result, the annual performance factor (APF) was adopted as the new criteria to evaluate energy savings performance. Under this method, model cases were designed in order to conduct proper evaluations that are approximately equal to real operation. Factors were estimated by calculations of annual total energy consumption and thermal building load. As the efficiency characteristics of the APF and COP are respectively indicated, calculation of conversion factors became necessary in order to compare their energy saving capabilities. In this study, the energy consumption and its characteristics of the APF and COP machines were calculated using the annual operating data of electric driven heat pumps (EHP) under equivalent load conditions. Effective efficiency was defined as a parameter to estimate conversion factors as follows: Effective efficiency = Annual generated heat amount / Annual energy consumption Using these conversion factors, the performance of machines can be easily compared when evaluation standards change. Furthermore, this approach can also be applied to gas engine driven heat pumps (GHP).