## 4 Discussion
### Influence of PV Surface Increase  
The solar roof surface considered for all the simulations above is 1.44 m\({}^{2}\). Car manufacturers may increase this surface in the future if they prefer to use the solar roofs only  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**System Efficiency** & **Locality** & **PV Energy (kWh)** & **Evolution** \\ \hline \multirow{2}{*}{93\%} & Paris & 102 & 0\% \\  & Malaga & 212 & 0\% \\ \hline \multirow{2}{*}{80\%} & Paris & 77 & \(-\)25\% \\  & Malaga & 170 & \(-\)20\% \\ \hline \multirow{2}{*}{70\%} & Paris & 56 & \(-\)45\% \\  & Malaga & 135 & \(-\)36\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: Influence of lower system efficiency on useful PV energy, 30% shading; directly charging HV battery and battery never fully charged.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Shading Losses** & \multicolumn{3}{c}{**Variable between Months**} & **30\%** & **Evolution** \\ \hline \multirow{2}{*}{PV useful energy per year (kWh)} & Min & 92 & 85 & 8\% \\  & Max & 129 & 126 & 2\% \\ \hline \multirow{2}{*}{Mileage covered by VIPV per year (km)} & Min & 588 & 543 & 8\% \\  & Max & 822 & 805 & 2\% \\ \hline \multirow{2}{*}{kg CO\({}_{2}\)-eq} & Min & \(-\)78 & \(-\)79 & 1 \\  & Max & 0 & \(-\)2 & 2 \\ \hline \multirow{2}{*}{Mileage covered by VIPV (km/day)} & Min & 0 & 0 & 0\% \\  & Max & 6.2 & 5.7 & 9\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Simulation results with variable shading between months compared to constant shading of 30% in Paris.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Shading Losses** & \multicolumn{3}{c}{**26\% Driving/52\% Parking**} & **49\%** & **Evolution** \\ \hline \multirow{2}{*}{Charge via 12 V battery} & Paris & 73 & 74 & \(-\)1\% \\  & Malaga & 139 & 142 & \(-\)2\% \\ \hline \multirow{2}{*}{Charge via 48 V battery} & Paris & 74 & 76 & \(-\)3\% \\  & Malaga & 142 & 145 & \(-\)2\% \\ \hline \multirow{2}{*}{Direct charge in the main battery} & Paris & 51 & 52 & \(-\)2\% \\  & Malaga & 119 & 123 & \(-\)3\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Simulation results with different shading between driving and parking compared to constant shading of 49% in Paris and Malaga, energy in kWh.  
on sedans with a bigger roof instead of all passenger cars. This subsection will discuss the effect a solar roof surface increase to 2 m\({}^{2}\). [PERSON] et al. consider this second value in the reference [7] as a solar roof surface for passenger cars. The consumption per km is not modified since the one considered is an average between smaller and larger cars. The surface of the roof, moreover, is not necessarily correlated with vehicle's weight and consumption. Only the surface is changed, and all the other parameters are fixed to distinguish the effect of the increase in the surface and, hence, of peak power.  
Table 7 summarizes the results of the simulation with both solar roof surfaces in such conditions. It shows that such an increase in the surface induces 39% higher peak power. Regarding the yearly PV useful energy and the distance covered by the VIPV, it leads to a 31% increase in the max values and 47% of the min values. For the best month, the increase in the surface leads to a 33% increase in the max value and 39% increase in the min value.  
With a 2 m\({}^{2}\) solar roof, for the best case in Europe (Malaga, 30% shading, architecture of energy transfer through a 48 V battery and without losses due to a full battery), the driver obtains 2078 km per year at midlife of the vehicle, which represents 17% of the driven distance during a year. The auto-generated distance for the best month is \(\sim\)21 km in this case; in addition, the driver has almost 42% of the daily distance (\(\sim\)50 km).