# Photovoltaic Roundabouts for Enhancement of Self-Sufficiency and Resiliency
## 3 Results and Discussion  
Table 3 shows the available areas within the center islands of the roundabouts included in the analysis. In the case of the mini roundabouts, it is useful to refer to configurations with a diameter of 20 m or more. In fact, below this size, the available surfaces offer an area of less than 5 m\({}^{2}\), which is not suitable for the installation of photovoltaic systems. Table 4 presents the values of the performances that can be achieved by the installation of photovoltaic modules, related to the two options considered: monocrystalline silicon and polycrystalline silicon. With reference to the roundabouts identified on the basis of the diameter values that represent the size thresholds of each of the categories defined by [PERSON] 19 April 2006 (with the exception of configurations with a diameter of less than 20 m), Table 5 shows the values of electricity productivity differentiated by the types of photovoltaic modules and in relation to the geographical areas into which the Italian territory is normally divided. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Type of Roundabout**} & **Inscribed Circle Diameter** & \multirow{2}{*}{**Available Area [m\({}^{2}\)]**} \\  & **[m]** & \\ \hline Mini roundabout & 14 & Negligible \\ Mini roundabout & 15 & Negligible \\ Mini roundabout & 20 & 7.07 \\ Mini roundabout/Compact & 25 & 27.34 \\ roundabout & 30 & 116.90 \\ Compact roundabout & 35 & 274.65 \\ Compact roundabout/ & 40 & 483.05 \\ Conventional roundabout & 45 & 855.30 \\ Conventional roundabout & 50 & 1134.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Areas available for the installation of the RAPS. The calculation of the energy demand for the self-sufficient lighting of the roundabouts (E\({}_{\text{L}}\)) was carried out with the DIALux software through a series of simulations of system configurations characterized by the use of different types of lamps on the market, from the classic lamps to newer applications such as the LED lamps. The results presented in Tables 6 and 7 refer to the minimum (E\({}_{\text{Lmin}}\)) and maximum (E\({}_{\text{Lmax}}\)) consumption required to meet the lighting requirements in the case of the six system configurations considered. In all cases, the system solutions with the lowest consumption (expressed in kWh/year) were those where the luminaire was equipped with a LED lamp. It is well known that the LED lamps (Light Emitting Diode) represent, to date, the best technology on the market to meet the requirements of public lighting systems in general and specifically for use in road roundabouts. Street lighting systems equipped with LED lamps not only have a significantly lower consumption than the classic discharge lamps, but also numerous other advantages, such as a very long life (greater than or equal to 100,000 h), high luminous efficiency, high color rendering index, low maintenance, flexible installation, easy maintenance, long durability of materials and components, and easy replacement of elements. These advantages mean significant benefits, both in terms of maintenance, thanks to the long operating time and installation flexibility, and in terms of energy consumption, thanks to the remarkable luminous efficacy and high color rendering index. The energy consumption required to light the simulated roundabouts was then compared with the energy generated by photovoltaic systems that could be installed on the center islands of the roundabouts. Figure 3 shows examples of the diagrams of the configurations that require the most energy consumption. These are roundabouts illuminated high mast poles and where the legs are equipped with an artificial lighting system on both sides for a length of 100 m. The diagrams refer to the three configurations with monocrystalline silicon modules (geographical areas: northern, central and southern Italy) and to the three configurations with polycrystalline silicon modules (geographical areas: northern, central and southern Italy).