## 5 Conclusions  
The influence of hot water setting temperature on the operation and the performance of SASCHCS was analyzed in detail based on the data of the entire cooling period in subtropical Guangzhou. The corresponding conclusions are summarized as follows:  
1. Despite the fact that the COP of the absorption subsystem went up slightly with the increased hot water temperature, the excessive improvement of the collector setting temperature was harmful for the energy saving, since the serious reduction of heat transfer caused by the low flow rate notably decreased the amount of collector useful heat. It was derived that the daily cooling output of the absorption subsystem based on August data dropped by 11.6% as the collector set point temperature went up from 80 \({}^{\circ}\)C to 105 \({}^{\circ}\)C.
2. Although the enhanced temperature of generator hot water lowered the amount of solar heat, the appropriate rise of generator set point temperature was favorable for the solar cooling owing to the remarkable growth of COP in absorption subsystems, i.e., the daily cooling capacity of the absorption subsystem based on August data enhanced by 13.6% if the setting temperature of the generator grew from 60 \({}^{\circ}\)C to 75 \({}^{\circ}\)C.
3. The collector set point temperature should be 8-10 \({}^{\circ}\)C above the generator one in terms of the tradeoff of collector useful heat and absorption subsystem COP. In particular, the above-mentioned relationship is independent from the meteorological data.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\(\mathbf{T_{g,i,set}}\) (\({}^{\circ}\)C)} & \multicolumn{6}{c}{**Optimal Collector Outlet Set Temperature (\({}^{\circ}\)C)**} \\ \cline{2-7}  & **Apr** & **May** & **Jun** & **Jul** & **Aug** & **Sept** & **Oct** \\ \hline
65 & 75 & 75 & 75 & 75 & 75 & 75 & 75 \\
75 & - & 83 & 83 & 83 & 83 & 84 & 83 \\
85 & - & 94 & 94 & 94 & 94 & 95 & 94 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Optimal \(T_{c,opt}\) for different \(T_{g,i,set}\).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \(\mathbf{Q_{ete}}\) (kWh) & \(\mathbf{Q_{e,as}}\) (kWh) & \(\mathbf{E_{save}}\) (kWh) & \(\mathbf{\eta_{etc}}\) & \(\mathbf{COp_{as}}\) & \(\mathbf{COp_{cs}}\) \\ \hline
73310.7 & 30854.7 & 8841.3 & 0.39 & 0.63 & 4.86 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Annual performance of SASCHCS in the optimal case.  
It was demonstrated that a 71.6 \({}^{\circ}\)C collector setting temperature with a 64.5 \({}^{\circ}\)C generator one was optimal for the annual operation by the global optimization. The corresponding peak annual specific energy saving of SASCHCS was 32.75 kWh/m\({}^{2}\). In addition, the annual collector efficiencies, the COP of absorption and compression subsystems, were 0.39, 0.63, and 4.86, respectively, in the optimal case.  
[PERSON] contributes to data analysis and writing. [PERSON] contributes to conceptualization and methodology. [PERSON] contributes to formal analysis. [PERSON] contributes to the validation. All authors have read and agreed to the published version of the manuscript.  
This work is supported by: (1) Natural Science Foundation of Guangdong Province under the contract No. 2018A030313310, (2) Guangzhou Municipal Science and Technology Project under the contract No. 201904010218, (3) State Key Laboratory of Compressor Technology under the contract No. SKL-YSJ201806, (4) Key Laboratory of Efficient and Clean Energy Utilization of Guangdong Higher Education Institutes under the contract No. KLB10004.  
The authors declare no conflicts of interest.