###### Abstract
It has been pointed out by [PERSON] [13] that the constant-flow control strategies are appropriate for the low-grade solar thermal facility. Accordingly, the decision of collector flow rate is one of the critical issues regarding the SASCHCS, due to the heat input temperature of solar heat ranging from 60 \({}^{\circ}\)C to 90 \({}^{\circ}\)C. It was found that the heat convection coefficient of collectors goes up by 45.5% as the collector flow rate rises by 66.7% [14]. Hence, a higher collector flow rate is favorable for the thermal efficiency of collectors [15]. It was revealed that the solar thermal gain could be increased by 112.5% and the auxiliary energy consumption could be reduced by 75% as the collector flow rate grows from 100 kg/h to 500 kg/h [16]. Furthermore, the required collector area and storage tank volume come down by 3% and 16.7%, respectively, when the collector flow rate grows by 42.9% [17]. In addition to the collector flow rate, it was obtained that the higher hot water flow rate of generators is beneficial for the cooling output of solar absorption chillers, i.e., the monthly cooling output increases by 13% as the flow rate goes up by four times [18]. Although solar cooling performance benefits from higher generator flow rates, the rapid consumption leads to the drop-off of heat quality. This means that an excessive generator flow rate is disadvantageous for operation of solar absorption cooling systems without auxiliary heat sources. Consequently, there is an optimal collector flow rate that maximizes the solar fraction [19]. It was derived that the optimal specific flow rate approaches to 30 kg/(h m\({}^{2}\)) for solar single effect absorption chillers [4]. Similarly, the aforementioned optimal value maximizes the thermal efficiency of collectors as well [15]. Additionally, [PERSON] [20] performed a global optimization for flow rates of the collector and generator by the genetic algorithm. Subsequently, [PERSON] [21] pointed out that the appropriate ratio of the generator flow rate to the collector one is 1.15. In the open literature, absorption cooling systems with auxiliary heat source are mainly investigated, and the effect of hot water flow rate on system performance is discussed. However, the corresponding operation guidelines are not fully appropriate for the SASCHCS, since its absorption subsystem is exclusively driven by solar energy. Given that there is a high temperature difference between the collector outlet and generator inlet in an absorption cooling system with an auxiliary heat source, its performance is relatively independent on the hot water flow rates of its collector or generator. Thus, the relationship of hot water flow rate in collectors/generators and performance of absorption subsystem/collectors are relatively weak. As for SASCHCS, the interaction effects between the collector and generator temperatures are more pronounced, so the operation characteristics of its collectors and absorption chiller are sensitive to the hot water flow rate. Thus, we attempt to study the relationship between the SASCHCS performance and hot water flow rate, and propose the decision guideline. In this work, a typical office building in subtropical Guangzhou and the local climate are considered for a case study. The daily operating processes of this system are simulated and compared under different hot water flow rate conditions. The optimal hot water flow rate of the collector and generator is obtained by genetic algorithm. The novelty of this paper is to explain the effect mechanism of hot water flow rate and present the corresponding decision criterion of SASCHCS. This paper is helpful for the improvement of system operation performance.