# A Sustainable Polygeneration System for a Residential Building
## 2 Materials and Methods
### System Model  
The configurations have been modeled in TRNSYSv18, using its types whenever possible. There are two unusual situations in this regard: The first is that the regression models available for the HP and SEAC types have been used to adapt the capacities required in the installation with variable load performances. The second is that there is  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Service** & **A** & **B** & **C** & **D** \\ \hline Electricity & & & PV + PVT + TEG & \\ Heating and DHW & & PVT + (AE) + SP + ST + BB + BP + HWDT & \\ Cooling (CWT+) & HP & HP & SEAC & SEAC \\ Freshwater (FWT+) & MED & RO & RO & MED \\ \hline \hline \end{tabular}
\end{table}
Table 4: Configurations analyzed in the polygeneration scheme.  
Figure 3: The general layout of the polygeneration schemes to serve the building demands.  
no specific type for this technology in the case of desalination. Consequently, complex models were first developed in the EES software for RO and MED. However, given the slowness of calculation observed when integrating both software, a simplified version of each technology has been incorporated into the TRNSYS scheme through a new DHW demand and its return or additional electricity consumption but with fixed performance parameters (see the next table). In the case of TEGs, a simple EES model was carried out and then immersed in the PVTs and the BB types as other equations to estimate the power generation.  
The following Table 5 summarizes the essential information of the components included in the analyzed configurations. If no parameter number is given, it will depend on the end design of each composition (Var.). Auxiliary types for integrating variables and graphical representation have not been included for simplicity.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Component** & **Type** & **Parameter** & **Value** & **Unit** \\ \hline Weather & 15–6 & Slope surface & 37 & \({}^{\circ}\) \\ \hline Tap water & 14-a & Temperature & Var. & \({}^{\circ}\)C \\ \hline  & & Module area & 1.93 & m\({}^{2}\) \\ PV & 103-b & I\({}_{\text{sc}}\) at RC & 9.38 & A \\  & & V\({}_{\text{oc}}\) at RC & 46.2 & V \\ \hline  & & Module area & 1.63 & m\({}^{2}\) \\ PVT & 50-a & Cell efficiency & 16 & \% \\  & & Collector & 92 & \% \\  & & absorptance & 89 & \% \\  & & Cover transmittance & & \\ \hline Aerotherm (AE) & 5-g & Cooling airflow & 285,600 & kg/h \\ \hline TEG & – & ZT & 0.72 & \\ \hline Inverter & 48-a & Efficiency & 95 & \% \\ \hline Solar loop pipes & 31 & Overall loss & 0.3 & W/m\({}^{2}\)\(\cdot\)K \\ \hline Solar controller & 113 & Cooling setpoint & 90 & \({}^{\circ}\)C \\ \hline Solar pump (SP) & 3b & Power & Var. & W \\  & & Flowrate & Var. & L/h \\ \hline  & & Capacity & Var. & m\({}^{3}\) \\ Solar tank (ST) & 156 & Number of nodes & 10 & - \\  & & Overall loss & 0.35 & W/m\({}^{2}\)\(\cdot\)K \\  & & coefficient & & \\ \hline Demands (5.txt files) & 9-c & Periodicity & Var. & h \\ \hline Hot water demands tank (HWDT) & 534 & Capacity & Var. & m\({}^{3}\) \\  & & Number of ports & Var. & - \\  & & Overall loss & 0.35 & W/m\({}^{2}\)\(\cdot\)K \\ \hline Biomass boiler (BB) & 122 & Output power & Var. & kW\({}_{\text{th}}\) \\  & & Efficiency & 80 & \% \\  & & Minimum load & 5 & \% \\ \hline Boiler pump (BP) & 3b & Power & Var. & W \\  & & Flowrate & 50\(\cdot\)ApVT(m\({}^{2}\)) & L/h \\ \hline \hline \end{tabular}
\end{table}
Table 5: Summary of main components of the TRNSYS installation.  
The simulation was performed for the entire annual period in the four configurations and three locations, with a time step of 5 min. Several key performance indicators (KPI) have been used from the annual results with TRNSYS to evaluate the best alternative comprehensively. They will be presented next.