Potential for installing photovoltaic systems on vertical and horizontal building surfaces in urban areas

• We estimate potential PV location on buildings by a street block scale.
• We analyze PV electrical energy when shaded and unshaded in summer and winter.
• The efficiency of PV on vertical facades is compared with that on rooftops.

This study analyzes the PV potential on rooftops and vertical facades in the research area of West Central District of Tainan City, a rich insolation area in Taiwan. By using the energy calculating software EnergyPlus and the grid-based computational fluid dynamics (CFD) software Windperfect, the electrical energy generated by PV modules on vertical walls from eight directions in both shading-covered areas and non-shading-covered areas was simulated and calculated. Three databases – the database of the electrical energy generated by building facades, of spatial information, and of shadow coverage – are established to estimate the potential electrical energy. The covered-shading condition was simulated by sunshine trajectory method, and the insolation potential of building surface was evaluated by analyzing the accumulating insolation hours and the spatial location data. It was observed that shading affects vertical facades more significantly. The average electricity generation of per unit area on rooftops demonstrates that the electrical energy in summer is twice as much as that in winter. Although the electrical energy generated by that of per unit area on vertical facades is higher in winter, it is only 1.1 times greater than that in summer. If the amount of electrical energy generated is taken into consideration, the installation area for the southwest walls should be 1.5 times larger than that of the rooftops so that the same amount of electrical energy can be generated. When considering the installation of PV panels in the research area of this study and other geographically similar locations, the priority should be the rooftops, followed by southeast-, southwest-, and south-facing vertical facades.