Representative cycle for heat pump energy flexibility evaluations - A comparative simulation study of existing day selection procedures to a new consecutive day procedure

Heat pumps allow to decarbonise the heating sector and to provide energy flexibility services. Hence, flexible heat pump control strategies are being developed. When testing these strategies, hardware-in-the-loop experiments using representative test cycles allow to evaluate the real heat pump behaviour. While several works investigated the representative cycle composition for retrieving the yearly energy performance, it is unclear if they can still be used for energy flexibility analysis. This paper investigates the performance of the three mainly used representative day selection procedures available in literature in presence of seven heat pump control strategies. A new approach, in which only consecutive days are used, was also evaluated. Two hydraulic configurations, i.e. with and without an energy storage between heat pump and building, and three climatic zones spread over the European Union were used in order to reach a general conclusion. Simulation results showed that approaches using consecutive days or approaches which select days based on their energy consumption can be used for the energy flexibility analysis. Though, only approaches with consecutive days were able to closely follow the operative room temperature profiles when compared to a full winter simulation due to the avoidance of abrupt temperature variations between the different days.