An innovative variable flow control strategy and system performance analysis of a solar collector field

Abstract

The dynamic changes in the environmental variables and the fluctuation characteristics of the thermal storage temperature have notable influences on the efficiency of solar collector fields. In addition, the optimal flow rate of solar collector fields varies under different combinations of variables and depends primarily on the collector scale and connection form. On this basis, it is imperative to carefully and comprehensively determine and adjust the optimal operating flow rate, considering the specific characteristics of the employed solar collector field under diverse variable combinations. To address this, this study proposes and develops a variable flow control strategy for solar collector fields based on maximizing net income. The presented strategy adjusts the operation flow according to environmental variables and the thermal storage tank temperature. The control principle of the proposed strategy and the corresponding method of obtaining the optimal flow are described. Based on this principle, the optimal flow optimization model is established, and the polynomial function of the optimal flow value is obtained by regression. Using the developed model, several conventional control methods are defined and simulated, and an analysis is performed to compare the collector’s performance under different scenarios. The results indicated that the variable flow control strategy proposed in this study can significantly improve the economic feasibility of solar collector fields. A 100 m2 series–parallel flat-plate solar collector field is considered as an example, and the proposed variable flow control strategy is implemented. As a result, a notable increase in the net income is reported compared to other conventional operation strategies, ranging from 6.70 % to 14.04 % in three different regions, namely Lhasa, Yinchuan, and Xi’an.