No abstract

Only few manufactures provide the wide set of graphical data that are necessary to use high performance predictive tools for PV systems. On the other hand, reliable graphical data require accurate laboratory measurements that increase manufacturing costs. For this reason PV system designers have to choose between the use of cheap PV modules, lacking in technical data, and the reliable energy predictions that are possible only if the current–voltage characteristics are provided by the PV module manufacturers.\ud This paper describes the procedure to evaluate the parameters of a one-diode equivalent circuit able to accurately epresent the electrical behaviour of a PV panel by means of the minimum set of technical data that are usually provided by all manufacturers. To reach the purpose some correlations based on the survey of more than one hundred PV module characteristics were defined to make up for the lack of technical\ud information. The computer routines used to evaluate the values of the model parameters are listed; the routines are written in BASIC and can be easily implemented, even like VBA macros in Microsoft Excel.\ud The capability of the new model to calculate the current–voltage characteristics was tested by comparing the results with data measured by four different manufacturers. The results of the application of the new model confirm the reliability of the proposed procedure. The differences between the calculated and the measured data are always less than the data tolerance usually declared by the manufacturers

Nowadays the achievement of a comfortable environment in aircraft cabins is a factor of paramount importance in air travel business competition; on the other hand, the need of reducing the propulsion fuel cost has driven the airline companies to adopt air handling systems that may reduce the levels of thermal comfort and air quality inside the cabins of commercial airliners. With the aim of contributing to a better knowledge of this matter, this paper reports the results of an experimental study upon the indoor air quality aboard commercial aircrafts for 14 domestic flights less than 1 h and half long. The parameters monitored were temperature, relative humidity and carbon dioxide concentration; the measurements were performed during the whole flight from the takeoff to the landing. The relative humidity inside the cabin was also calculated using the rates of outside air and the carbon dioxide as a ventilation tracer; the theoretical results were compared with the measured data. The relationship between relative humidity and carbon dioxide concentration during fights was highlighted in order to define the environmental conditions that may provide acceptable levels of both the air quality and hygrometric comfort to the crew and passengers. The results of calculations confirmed the possibility of improving the hygrometric conditions in aircraft cabins without the need of using humidification systems.

No abstract

The assessment of PV energy in an urban context is extremely complex because many factors have to be considered. Moreover, when the purpose is calculating the realistic amount of the electricity demand of a city that can be covered by the photovoltaic generation, it is necessary to estimate the number of photovoltaic systems whose installation is economically advantageous. Such a topic requires an economic analysis, which is affected by the number of energy and economic parameters involved and the values assigned to them to perform calculations. Some parameters are perfectly known and unvarying, like the paid incentives. Adversely, some parameters, like the efficiency degradation of photovoltaic panels, can only be supposed. Other parameters require some information that is specifically related to each particular photovoltaic system.\ud With the aim of estimating the influence of the manifold energy and economic parameters that characterize how photovoltaic penetration develops in urban areas, a specific study was conducted for a city in the south of Italy. A sensitivity analysis was carried out in order to verify parameters have an irrelevant influence and what are the parameters whose definition can be a crucial element of the energy and economic analysis of photovoltaic systems because dramatically impact on the results. The presented study represents a valuable help for photovoltaic systems designers and energy decision-makers because it permits to evaluate the impact of the deviations of the main parameters on the profitability of photovoltaic systems and the role played by them in the effectiveness of the energy policies implemented to achieve the required shares of electricity demand coverage

No abstract

No abstract

Models for photovoltaic (PV) cells and panels, based on the diode equivalent circuit, have been widely used because they are effective tools for system design. Many authors have presented simplified one-diode models whose three or four parameters are calculated using the data extracted from the datasheets issued by PV panel manufactures and adopting some simplifying hypotheses and numerical solving techniques. Sometimes it may be difficult to make a choice among so many models. To help researchers and designers working in the area of photovoltaic systems in selecting the model that is fit for purpose, a criterion for rating both the usability and accuracy of simplified one-diode models is proposed in this paper. The paper minutely describes the adopted hypotheses, analytical procedures and operative steps to calculate the parameters of the most famous simplified one-diode equivalent circuits. To test the achievable accuracy of the models, a comparison between the characteristics of some commercial PV modules issued by PV panel manufacturers and the calculated current-voltage (I-V) curves, at constant solar irradiance and/or cell temperature, is carried out. The study shows that, even if different usability ratings and accuracies are observed, the simplified one-diode models can be considered very effective tools.