Discussion on the uniformity between efficiency of solar collector and power curve

The instantaneous efficiency equation of the solar collector could be expressed in different ways that depends on different presentation of collector area.As a result,the thermal performance of the solar collector could not be reflected actually,meanwhile,the users are usually misguided.In or-der to solve the problem,in this paper,another expression for reflecting the thermal performance of the solar collector is proposed and is verified by testing the thermal performance of the vacuum glass tube solar collectors and the U-tubular vacuum tube CPC solar collectors.According to the test data,the Least Squares Fitting for the instantaneous efficiency and energy equation of collector are calcu-lated.The calculation results show that energy equation and energy curve of each collector are unique.The influence factors of energy equation are just the gross solar irradiance and the differential temper-ature of the inlet temperature and the ambient temperature,there is no any influence from the collec-tor area.Therefore,it is proposed that the power equation and the power curve should be adopted in interrelated standards to reflect the thermal performance of solar collector accurately.