## 4 Active Systems
### Electricity Production from Renewable Energy Sources  
Once the potential for energy savings in the Stadium has been exhausted, the following step is the investigation for any possible electricity production from the exploitation of the locally available R.E.S. potential. In such cases, the most feasible and favorable technology is the photovoltaic panels. In the specific application, a PV station is proposed to be installed in the western roof of the main Stadium's stands, which has been removed due to corrosion and the strong blowing winds (only the bearing structure has remained). In this way, the new PV station, apart from the obvious task of electricity production, will also act as a new roof, saving a considerable monetary amount for its restoration.  
The PV station will be integrated in the local electrical grid under \"net-metering\" mode. This implies that the electricity consumption in the Stadium will be compensated with the production from the PV station on annual basis. The annual electricity procurement charge will be performed versus the net annual electricity consumption, derived by this annual compensation.  
The siting of the PV panels is presented in Figure 16a. The photovoltaic panels are laid on the roof's surface, hence their inclination angle versus the horizontal plane and their orientation are configured by the inclination and orientation of the roof's surface (3\({}^{\circ}\) with western orientation). The total available space on the installation roof is 5585 m\({}^{2}\). To maximize the total installed power, a PV panel of 300 Wp nominal power is selected. With the presented siting, the achieved total installed PV power is 645.30 kWp.  
The calculation of the annual electricity production time series is based on the available data of the incident solar radiation, the wind velocity and the ambient temperature, presented in Section 2.2. The calculation of the annual electricity production is a simple, straightforward process, thoroughly described in [61]. The final (after losses) electricity production annual time series is presented in Figure 16b. The total annual electricity production from the photovoltaic station is calculated at 932,711 kWh, with a corresponding primary energy of 2,704,862 kWh. The annual, final (after losses) capacity factor is calculated at 16.50%.  
Figure 16: (**a**) Siting of the photovoltaic station on the main stadium’s western roof and (**b**) electricity production annual time series from the proposed PV plant.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & \multicolumn{2}{c}{**Annual Electricity**} & \multicolumn{2}{c}{**Annual Primary**} & & & \\  & \multicolumn{2}{c}{**Consumption**} & \multicolumn{2}{c}{**Energy Consumption**} & & & & \\
**Lighting Area** & \multicolumn{2}{c}{**(kWh)**} & & & & & & \\ \cline{2-7}  & **Existing** & **Proposed** & **Existing** & **Proposed** & **Electticity** & **Primary** & **Percentage** \\  & **State** & **State** & **State** & **State** & **(kWh)** & **Energy (kWh)** & **(\%)** \\ \hline Indoor spaces & 433,232 & 164,958 & 1,256,374 & 478,379 & 268,274 & 777,995 & 61.92 \\ Outdoor surrounding spaces & 123,494 & 75,027 & 358,134 & 217,577 & 48,468 & 140,557 & 39.25 \\ Main stadium-daily usage & 65,494 & 38,770 & 189,932 & 112,434 & 26,723 & 77,498 & 40.80 \\ Main stadium-sports events & 35,343 & 30,459 & 102,495 & 88,330