A flexible design scheme for a direct expansion solar-assisted heat pump system is presented. Based on the flexible theory for the virtual operating point of the basis design

which was stored in the flexible space

all of the operating points within the flexible space could achieve almost the same heat transfer effect. The weights of the environmental factors for the system’s coefficient of performance (COP) were obtained in a simulation and verified in an experiment

including the irradiation intensity (52.2%)

temperature (34.7%)

and wind speed (13.1%). A total of 25 sets of systems were simulated under typical weather conditions. The purpose was to verify the operating points that fell in the flexible space based on the weights for the optimal combination of virtual operating points obtained. The values of the irradiation intensity (It)

ambient temperature (T0)

and wind velocity (uw) were 559.97 W/m2

21.6 ℃

and 2.89 m/s respectively. The simulation results showed that the variance in the system’s COP was 0.156，which was superior to the traditional static design result.