# Modeling Photovoltaic Potential for Bus Shelters on a City-Scale: A Case Study in Lisbon
## 4 Concluding Remarks  
The purpose of this study was to analyze the potential of structures in the public space for low-carbon innovative technological solutions while contributing to meeting local sustainable energy targets. The renovation of bus shelters with solar-based applications is presented as a case study. Bus stops' large protective panels provide ideal spaces for the application of solar cells. For low energy consumption applications, the bus shelter may not consume much energy, and so the excess energy could be fed into the electricity grid, if such a connection is economically viable. Shelters can also house a variety of amenities for travelers that can improve satisfaction with wait times, improve safety perceptions and provide valuable system utilization information. Outside of buses, bus stops are the most visible representation of the public transport system. Two situations favored the choice of these structures. On the one hand, bus shelters are spread across the urban area and serve thousands of passengers every day. Consequently, their renovation has a great impact on the quality of the public space around them. On the other hand, good bus shelters are an essential part of the public transport system. Their modernization through the provision of  
Figure 12: Solar bus shelter locations according to the PV applications and tourist (**a**) and commuter (**b**) preferences. innovative services is a way of improving the users' perception of public transport, thus promoting sustainable and smart mobility. The bus shelters were assessed in terms of local electricity production capabilities and local electricity demand potential. The methodology used, as input data, a Very-High-Resolution image and a detailed Digital Surface Model. All the shelters were evaluated in a GIS environment, based on geographical, technical and social criteria. The result was the determination of the city's potential to implement solar bus shelters. Using Lisbon as a case study, the results show that 612 shelters out of 1132 (54%) receive the required solar radiation to install PV panels. These results are in line with those presented by [15]. We also investigated which PV-based applications could be installed in these solar bus shelters, according to their PV-generation capacity. Four typified applications were analyzed, from lower-energy-demanding applications (such as remote small-scale sensors or small-scale info displays) to higher-energy-demanding ones (such as refrigerated vending machines). While every shelter would be suitable for remote small-scale sensors, all the other applications were only possible in fewer shelters, and the top-level applications were only possible in those shelters with higher dimensions, usually present at interface stations. The possibility of having lighting was also tested, and the results indicate that all the PV shelters would be suitable for up to 7 W/m\({}^{2}\) LED lamps but only 40% would be suitable for 10 W LED lamps. Higher-energy-consumption LED lamps would not be possible to install. Future studies shall verify these results obtained from geographic modeling against measured data. The results are presented in planning scenarios. These show where and what PV-based applications can be implemented and serve as a demonstration of the usefulness of the proposed methodology to planners and energy advisers. Such knowledge about the city's potential for PV-based applications can be used to improve urban development plans, to integrate solar energy into new regulations or to support and orient incentive policy design towards the use of more efficient sites or neighborhoods within the city. The planning scenarios were based on target audiences--tourists and daily commuters. Since no data about the average daily boarding or passenger transfer activity were available, proximity analysis was used as a proxy to characterize the local electricity demand. For this analysis, we applied buffer distances around each bus stop to identify the areas of influence.