## 2 Overview of the Proposed System  
The high costs of electricity produced from the sun highlight the importance of optimizing system operation, energy production and reliability. As a result, it is essential to analyze data and outputs of a photovoltaic (PV) plant in order to enable the elaboration of detailed and precise evaluation of the system performance and, in particular, of the effective energy production with respect to the plant's potential. As previously stated, monitoring systems currently available on the market are generally based on data coming out from the inverter, which is a fundamental component of the plant and allows direct current to be transformed into alternating current and, therefore, into current entering the electrical grid. Generally, PV plants have an inverter every ten or fifty solar panels. The main parameters available are usually: instant power, frequency, voltage, electric current, environment temperature, inverter temperature, _etc._  
Each plant has a nominal power value depending on its characteristics (dimension, technologies, _etc._), but also on the climatic conditions, particularly sun irradiation. Measurements from the inverter allow us to calculate the average power produced in a given time interval: day, week, year, _etc._; However, although relevant, average power is not sufficient to detect whether the plant production is the effective optimum one or if some plant components (one or more solar cells) are affected by failures. In fact, average power significantly depends on some other parameters such as atmospheric pressure, wind speed and sun incident radiation. As an example, a full sunny day with dirty panels or a cloudy day with perfect clean panels could produce the same quantity of energy. In the last years, significant developments have taken place in some technologies which can be usefully applied to the management of a PV plant, namely:  
* Sensors and wireless sensor networks. * Micro-inverters and electronic on-board of each panel. These technologies allow users to implement new and powerful monitoring systems capable of optimizing the efficiency of each panel as well as that of the whole plant, while detecting faults or critical events. Several works can be found in literature related to remote monitoring of solar power plants [20, 21, 22, 23], but not many go as far as trying to determine the performance of single panels [24]. The conceived system aims to overcome the limitations indicated above by designing a WSN to monitor the efficiency of a photovoltaic plant and optimize the energy production. Through this network real-time monitoring of some relevant parameters, such as electrical characteristics, critical parameters of the plant, sun irradiation or meteorological and ambient parameters for each panel, is carried out. Monitoring and analysis of these parameters will make the system suitable to carry out relevant services as described:  
* Complete reports about production cycles supporting a set of tools to plan the activity (_i.e._, maintenance) and the energy production. * Surveillance system based on sensors, thus improving the security of the plant. * Automatic signaling alerts to let operators know about failures or intrusions through different communication strategies: audio alerts, SMS, _etc._* Real-time monitoring of the effective energy power produced by each solar panel and, obviously, by the entire plant, according to the sun radiation and meteorological conditions. * Measuring solar radiation in real time to optimize the exposition of panels with respect to sun irradiation. * Estimating, through historical data stored by the system and weather forecast day per day, the production of energy. * Specific and real-time maintenance through the individualization of eventual breakdown in short time. In short, a solar power plant equipped with the system described in this paper can optimize energy production based on the surrounding ambient state.