# Photovoltaic Roundabouts for Enhancement of Self-Sufficiency and Resiliency
###### Abstract
In particular, the CE classes mentioned in Table 1, i.e., illuminance classes (E) in conflict areas (C), are intended for motor vehicle drivers and other road users in conflict areas such as shopping streets, road intersections of some complexity, roundabouts, queuing areas, etc. Figure 1: Photometric illustration of perimeter and central illumination design. CE classes can also be applied to areas used by pedestrians and cyclists, e.g., underpasses. The average illuminance (E\({}_{i}\)) and the overall uniformity of the illuminance (U\({}_{o}\)) are to be calculated and measured in accordance with EN 13201-3 and EN 13201-4 [20,21]. Italy uses a translated and slightly modified version of EN Part 1, UNI 11248 Illuminazione Stradale-2012 (Roadway Illumination), as the regulation for lighting roundabouts. This document does not differ from EN with respect to roundabout lighting. Parts 2, 3 and 4 of EN are used as the standard for lighting. In 2006, the Ministry of Infrastructure and Transport established the guidelines for lighting roundabouts. Rural roundabouts with split-level maneuvers or grades must be illuminated. If a roundabout does not belong to either of these categories, the decision whether or not to illuminate it is the responsibility of the local road authorities. In this context, there are many benefits that the road administration can gain from a photovoltaic (PV) system beyond the immediate financial and environmental benefits. The use of solar energy allows for a significant degree of energy independence and independence from utilities and power outages. The latter two aspects are critical for lighting roundabouts in the event of a power outage. On the other hand, electricity consumption for public lighting in Italy was about 6000 GWh in 2017, with a per capita consumption of 100 kWh, twice the European average of 51 kWh. In 2017, spending on public lighting in Italy amounted to 1.7 billion (1.7 \(\times\) 10\({}^{9}\)) euros, and per capita spending was 28.7 euros, well above the average of the main European countries (16.8 euros). The renewal of public lighting in terms of reduced and efficient consumption of electrical energy is therefore an important priority for all public administrations. On the other hand, many European countries are making efforts to develop solar energy as the main energy source for electricity generation in order to reach the environmental target imposed by the European Community, according to which 32% of the gross final consumption in 2030 should be covered by renewable energy sources [22]. Specifically for Italy, the PNIEC (the Integrated National Energy and Climate Plan) proposes an overall target of 30%. For the sectoral level, the target RES (Renewable Energy Sources) is set at 55.4% of gross electricity consumption, estimated at 337.3 TWh, corresponding to a production of 187 TWh from RES. To achieve these results, there is a large increase in installed RES capacity, especially photovoltaic (PV), which will reach 60 GWh of installed PV by 2030 [23]. Based on the previous considerations, there are many experiences with street lighting where PV systems are installed in each pole. This is one of the areas where off-grid PV energy systems are used, and in the last decade, interest in these systems has increased due to recent developments in both LED and PV technology [24]. The studies on the use of roundabouts for PV system installation are very limited in the literature. The most relevant study deals with the use of a PV system equipped with a vertical tracking system, called RAST (RoundAbout Solar Tracking) [25]. In this study, only the operating principle of the vertical tracking system is described, without establishing a relationship between the PV system sizing and the local electricity demand. The proper integration of distributed renewable generators can benefit the whole energy system, and the use of energy close to the production site helps to achieve this goal.