This paper analyzes the impact of the snail trail phenomena on photovoltaic (PV) module performances and energy production. Several tests (visual inspection, maximum power determination, dielectric withstand, wet leakage current, and electroluminescence test) were carried out on 31 PV modules located in a PV plant in Italy. The electroluminescence test highlighted the strong correlation between the appearance of snail trails and presence of damaged cells in PV modules. The daily energy produced by four PV modules affected by snail trails ranged between 68% and 88% of the energy produced by a damage free commercial PV module over the same period.

The impact of wind turbines and photovoltaic systems on network operation and power quality (harmonics, and voltage fluctuations) is very important. The capability of the power system to absorb this perturbation is dependent on the fault level at the point of common coupling. The paper deals with power quality case studies conducted on existing renewable resources-based systems. Voltage fluctuations determined by a 0.65 MVA wind turbine are analyzed. The impact of photovoltaic systems on steady state voltage variations and current harmonics is investigated. The correlation between the generated power and the main power quality indices is highlighted.

The current economic crisis, combined with growing citizen expectations, is placing increasing pressure on European cities to provide better and more efficient infrastructures and services, often for less cost. This trend has contributed to the growing popularity and use of the term `Smart City' [1]. The Smart City, represent a new way of thinking about urban space by shaping a model that integrates Green Energy Sources and Systems (GESSs), energy efficiency, sustainable mobility, protection of the environment and economic sustainability, that represent the goals for future developments. Smart cities are made by a high level of Information and Communication Technology-ICT- structures able to transmit energy, information flows multidirectional and connect a different sector that include mobility, energy, social, economy. Into Smart Cities transport systems are sustainable, smart grids are enhanced to ensure greater integration capabilities of production plants from renewable sources, public lighting is efficient, the buildings are equipped with sensors and devices aimed at rationalizing consumption energy and create greater awareness on the part of citizens, with the aim of improving the quality of life of people through a new governance of public administration capable of managing this innovation and cultural change. However, while wishing the transformation of cities in smart systems, have not defined models infrastructure, that allow different subsets to communicate and interact, in order to make the concrete realization of a smart city. The objective of this paper is to discuss a model of Smart City with a multi-agent systems and Internet of things, that provides intelligence to a city, as basic infrastructure for a definition of a model repeatable and exportable, so as advocated by the European Community, that is allocating considerable funds (Horizon 2020) for the creation of Smart City.