Study on the hysteresis characteristic of solar thermal storage system

Abstract

The thermal storage efficiency is one of the important indicators for evaluating the operation of solar thermal storage system. Affected by the thermal inertia of the system, the analysis of the relationship between the thermal storage efficiency and solar radiation, which is inadequate at the smaller time scale. This paper measured the operation of a flat plate solar collector system, studied the hysteresis characteristics of the system’s collector efficiency changes with solar radiation, took a numerical solution method for the actual lag time of the system and finally obtained the actual influence rule of solar radiation on the collection efficiency per minute. The results show that the solar collector’s efficiency change lags behind the solar radiation by 27 min; combined the lag time, the relationship between the modified thermal storage efficiency and solar radiation also were analysed; initially the modified storage efficiency per minute increases with the solar radiation, then gradually decrease after reach a certain value, due to the overall system temperature is higher and the system temperature rise is smaller when the solar radiation is large enough; the varying curve conforms to quadratic function. It provides theoretical support and practical reference for contrasting and evaluating the thermal storage efficiency changes with solar radiation in a smaller time scale.