The 1-diode/2-resistors electric circuit equivalent to a photovoltaic system is analyzed. The equations at particular points of the I–V curve are studied considering the maximum number of terms. The maximum power point as a boundary condition is given special attention. A new analytical method is developed based on a reduced amount of information, consisting in the normal manufacturer data. Results indicate that this new method is faster than numerical methods and has similar (or better) accuracy than other existing methods, numerical or analytical

Due to the high dependence of photovoltaic energy efficiency on environmental conditions (temperature, irradiation...), it is quite important to perform some analysis focusing on the characteristics of photovoltaic devices in order to optimize energy production, even for small-scale users. The use of equivalent circuits is the preferred option to analyze solar cells/panels performance. However, the aforementioned small-scale users rarely have the equipment or expertise to perform large testing/calculation campaigns, the only information available for them being the manufacturer datasheet. The solution to this problem is the development of new and simple methods to define equivalent circuits able to reproduce the behavior of the panel for any working condition, from a very small amount of information. In the present work a direct and completely explicit method to extract solar cell parameters from the manufacturer datasheet is presented and tested. This method is based on analytical formulation which includes the use of the Lambert W-function to turn the series resistor equation explicit. The presented method is used to analyze commercial solar panel performance (i.e., the current-voltage–I-V–curve) at different levels of irradiation and temperature. The analysis performed is based only on the information included in the manufacturer’s datasheet.

New explicit mathematical expression is used to describe the behavior of a photovoltaic device (solar cell/panel), that is, its I-V curve, based on the characteristic points normally included in the manufacturers’ datasheets. This expression consists of two simple equations, one for voltage levels lower than the voltage at the maximum power point, V < Vmp, and the other one for voltage levels above this point, V > Vmp. The first equation is defined with two of the three characteristic points (short circuit and maximum power points), whereas the second one is defined with the current and voltage levels at maximum power point, the open circuit voltage, and a constant that can be adjusted based on: 1) the best fitting to the data within the bracket [Vmp, Voc], or 2) one point within this bracket, or 3) the slope of the I-V curve at the open circuit point, or 4) an estimation of that slope. Results of the solar cell/panel behavior analysis obtained with the proposed methodology, are similar to the ones obtained with the well-known 1-diode/2-resistor equivalent circuit model, in terms of accuracy

The results of several research campaigns investigating cup anemometer performance carried out since 2008 at the IDR/UPM Institute are included in the present paper. Several analysis of large series of calibrations were done by studying the effect of the rotor’s geometry, climatic conditions during calibration, and anemometers’ ageing. More specific testing campaigns were done regarding the cup anemometer rotor aerodynamics, and the anemometer signals. The effect of the rotor’s geometry on the cup anemometer transfer function has been investigated experimentally and analytically. The analysis of the anemometer’s output signal as a way of monitoring the anemometer status is revealed as a promising procedure for detecting anomalies.