## 3 Analyzing Systems Improvement Programs
### Efficient Use of Solar Energy Resources  
China possesses a vast territory and abundant solar energy resources. The solar energy resources on Earth are generally expressed in terms of the total annual irradiation (J/(m\({}^{2}\)-a)) and the annual sunshine duration (h). The solar radiation energy received by the land surface of China is about 5.0 \(\times\) 10\({}^{19}\) kJ. More than two-thirds of the country experiences annual sunshine hours exceeding 2200 h, and the total radiation amount is higher than 5.86 \(\times\) 10\({}^{6}\) kJ/(m\({}^{2}\)-a) [22]. Figure 5 illustrates the monthly distribution of total solar radiation in the Yichun area. According to the Assessment Method for Solar Energy Resource classification method GB/T37526-2019 [23], global horizontal irradiance (GHR) is divided into four levels: most abundant (A), very abundant (B), abundant (C), and general (D), as shown in Table 4.  
The total annual horizontal irradiance of the area where the substation is located is 4118.1 MJ/m\({}^{2}\), which belongs to class C, indicating an area rich in solar energy resources. It \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multicolumn{2}{c}{**GHR**} & \multirow{2}{*}{**Grade Symbol**} \\ \cline{2-3}  & **(MJ/m\({}^{2}\))** & & **(kWh/m\({}^{2}\))** & \\ \hline Most abundant & GHR \(\geq\) 6300 & GHR \(\geq\) 1750 & A \\ Very abundant & 5040 \(\leq\) GHR \(<\) 6300 & 1400 \(\leq\) GHR \(<\) 1750 & B \\ Abundant & 3780 \(\leq\) GHR \(<\) 5040 & 1050 \(\leq\) GHR \(<\) 1400 & C \\ General & GHR \(<\) 3780 & GHR \(<\) 1050 & D \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Classification and regional distribution of total solar radiation in China. Figure 5: Monthly distribution of total solar radiation in the Yichun area. can be considered to use solar power generation to provide electricity for the HVAC system on the site to achieve a zero-energy consumption building. To simulate the building's solar irradiance and other parameters, the Building Photovoltaic Software (BPV2024) in GBWARE2024 is used. By setting the project location and constructing the building model, the solar resource data can be reasonably analyzed, and the best tilt angle and installation position can be calculated, along with the power generation of the photovoltaic panels. As shown in Figure 6, the substation unit is modeled. The calculation of a building's photovoltaic system's power generation should consider the solar energy resources of the location, the design of the photovoltaic system, the arrangement of the photovoltaic array, and environmental conditions. To obtain the power generation value of a photovoltaic system, one should refer to the \"Design Code for Photovoltaic Power Station\" GB 50797 [24] and other relevant standards. The formula for calculating power generation (\(E_{p}\)) is as follows:  
\[E_{p}=\frac{H_{A}}{E_{S}}\cdot P\cdot K_{t} \tag{6}\]  
where \(H_{A}\) is the total solar irradiance of the horizontal plane (kWh/m\({}^{2}\)), \(E_{S}\) is the irradiance (constant) under standard conditions (1 kW/m\({}^{2}\)), \(P\) is the installed capacity (kWp), and \(K_{t}\) is the comprehensive efficiency coefficient. The latter is affected by various parameters, including inverter efficiency, collector line loss coefficient, photovoltaic module surface pollution coefficient, and correction coefficient. The specific parameters are given in Table 5.