# Simulation of a Solar-Assisted Air-Conditioning System Applied to a Remote School
## 3 Methodology  
The TRNSYS software was used to carry out the operational simulation of the solar thermal cooling system. This program allows analyzing the system in a semi-dynamic way, having the advantage of working with typical meteorological databases (TMY) in the region, studying the system under more realistic operating conditions. By using modules programmed with validated mathematical models of various equipment, such as pumps, motors, heat exchangers, storage tanks, solar collectors, power cycles, and refrigeration, among many others, TRNSYS becomes an ideal software for the simulation of this type of process. The validated mathematical models used in the simulator modules can be reviewed in Reference [37]. Table 1 shows the characteristics of the cooling system equipment installed in the Puertecitos school, which were used as input parameters in the developed simulator, and Table 2 presents the description of the components within TRNSYS. \begin{table}
\begin{tabular}{l c} \hline \hline \multicolumn{2}{c}{**Solar Collector**} \\ \hline Brand/model & Suntask/SHC24 \\ \hline Collector type & Evacuated tube with parabolic reflector \\ \hline Number of tubes & 24 \\ \hline Aperture area & 4.41 m\({}^{2}\) \\ \hline Optical efficiency (a\({}_{0}\)) & 0.668 \\ \hline First order efficiency coefficient (a\({}_{1}\)) & 1.496 W/m\({}^{2}\) K \\ \hline Second order efficiency coefficient (a\({}_{2}\)) & 0.005 W/m\({}^{2}\) K\({}^{2}\) \\ \hline Fluid & Water \\ \hline Mass flow & 0.02 kg/sec m\({}^{2}\) \\ \hline Number in series & 5 \\ \hline Number of loops & 5 \\ \hline \multicolumn{2}{c}{**Thermal Energy Storage Tank**} \\ \hline Volume & 12 m\({}^{3}\) \\ \hline Height & 2.5 m \\ \hline Material & Fiberglass \\ \hline Insulation thickness & 0.025 m \\ \hline Loss coefficient & 1.4 W/m\({}^{2}\) K \\ \hline Fluid & Water \\ \hline \hline \end{tabular}
\end{table} 
Table 1: System characteristics. In order to carry out the analysis of the system with the aforementioned software, the following considerations were taken into account:  
* Steady state;
* 15-min simulation intervals;
* Maximum thermal load of 8.5 kW per classroom at 12:00 p.m.;
* Pressure drops and heat losses in the equipment were not considered, only the heat transferred to the environment by the TEST losses was considered;
* On/off control by temperature difference in the solar field (\(T_{sf,out}-T_{sf,in}>0\));
* Only fresh water was used in the cooling water circuit;
* System operation with solar energy only. \begin{table}
\begin{tabular}{l c} \hline \hline
**Absorption Chiller** \\ \hline Model & Lucy New Energy/RXZ-35 \\ \hline Refrigerant & Water–lithium bromide \\ \hline Cooling capacity & 35 kW \\ \hline COP & 0.7 \\ \hline Hot water nominal temperature & 90 °C \\ \hline Hot water nominal flow rate & 8.3 m\({}^{3}\)/h \\ \hline Chilled water nominal inlet temperature & 15 °C \\ \hline Chilled water nominal flow rate & 6 m\({}^{3}\)/h \\ \hline Cooling water nominal temperature & 30 °C \\ \hline Cooling water nominal flow rate & 15 m\({}^{3}\)/h \\ \hline Power consumption & 0.3 kW \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._