# Assessment of Energy Use and Photovoltaic Energy Potential in Saudi Arabian Governmental Schools
## 4 Results and Discussions
### PV Systems Analysis
#### 4.3.2 Zero-Bill Scenario  
Based on the findings for the zero-energy scenario, it can be concluded that a grid-connected PV system is especially beneficial for government schools; in general, using it helps reduce the service provider's peak demand and supply surplus energy to the grid. These systems achieved nearly zero bills for schools 1 and 2 for the lifespan of the grid-connected PV system by using the roof only. However, school 3 did not reach the study target due to high consumption and a lack of suitable space on the roof, but it can be used on the roof of the car park to increase the number of PV modules. As shown in the economic indicators, these resulted in a SPBP between 10.58 and 13.64 years if the undiscounted condition was considered and between 20.24 and 39.14 years if the discounted condition was considered. This indicator shows that the systems are not economically feasible, even though the LCOE ranging between $0.0194 and 0.0223 per kWh was obtained, as shown in Table 6.  
To achieve the nearly zero-bill scenario, Figures 4-6 show the electricity consumption curve and the electricity produced by the PV systems with the economic indicators of the three schools throughout the systems' lifetime. It is seen that the three systems exhibit comparable trend behavior. Given that electricity must occasionally be drawn from the grid, the figures show that the systems generate more than is required each year to offset the price differential between electricity generated and exported to the grid and electricity  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **School 1** & **School 2** & **School 3** \\ \hline Annual load (kWh/year) & 84,402 & 277,259 & 164,603 \\ \hline Available roof area (m\({}^{2}\)) & 1646 & 3532 & 1391 \\ \hline Maximum number of PV modules on the roof & 351 & 782 & 290 \\ \hline Installed modules number & 116 & 374 & 222 \\ \hline PV Peak power (kW) & 63.8 & 205.7 & 122.1 \\ \hline \multirow{2}{*}{SPBP (year)} & Undiscounted & 7.69 & 7.56 \\ \cline{2-4}  & Discounted & 11.75 & 11.46 & 11.46 \\ \hline LCOE (\$/kWh) & 0.0229 & 0.0252 & 0.0249 \\ \hline Annual yield factor (kWh/kW\({}_{\text{P}}\)) & 1950 & 1994 & 1994 \\ \hline Capacity factor (\%) & 22.26 & 22.33 & 22.33 \\ \hline Performance ratio (\%) & 86.81 & 88.84 & 88.84 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Available roof area, maximum number of PV modules, installed modules number, and economic parameters of the investigated schools for zero energy.  
imported from the grid. As the load increases and the effect of the degradation factor of PV modules increases over time, the gap between the amount of energy generated by the PV system and the amount of consumed energy narrows. According to Figures 4 and 5, the loss is constrained during the first five years of the system's existence, which limits the gap between the price of power and its benefits. After that, the loss rises, and the economic return falls until the bills are almost zero.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **School 1** & **School 2** & **School 3** \\ \hline Load (kWh/year) & 84,402 & 277,259 & 164,603 \\ \hline Maximum number of PV modules on the roof & 351 & 782 & 290 \\ \hline Installed modules number & 166 & 622 & 436 \\ \hline PV Peak power (kW) & 91.3 & 342.1 & 239.8 \\ \hline \multirow{2}{*}{SPBP (year)} & Undiscounted & 10.58 & 11.85 & 13.64 \\ \cline{2-4}  & Discounted & 20.24 & 25.93 & 39.14 \\ \hline LCOE (\$/kWh) & 0.0223 & 0.0184 & 0.0194 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Technical and economic parameters of the investigated schools for zero bill.  
Figure 3: Generated electricity from PV and consumed energy along the project life cycle for zero-energy scenario for the three schools.  
Figure 4: Energy and costs along the project life cycle for school 1.  
Figure 5: Energy and costs along the project life cycle for school 2.