Félix Sorribes-Palmer

Accurate and simple mathematical models are usually required to assess the performances of photovoltaic devices. In particular, it is common practice to use explicit models to evaluate the current–voltage (I–V) performance curves, mainly based on simple analytical expressions that enable the parameters determination with a little computational effort. Six different explicit photovoltaic models (i.e., explicit I–V equations) by different authors (Akbaba & Alattawi; El-Tayyan; Karmalkar & Haneefa; Das/Saetre et al.; Das; and Pindado & Cubas) are analyzed and compared. This comparison is carried out by fitting these models to eight I–V curves for different technologies, including Si, Si polycrystalline, Ga–As, and plastic solar cells. The accuracy of each model depends on the photovoltaic technology to which it is applied. The best fit to each I–V curve studied is normally obtained with a different model, with an average deviation under 2% in terms of short-circuit current (normalized RMSE). In general, the model proposed by Karmalkar & Haneefa shows the highest level of accuracy, and is a good fit for all I–V curves studied.

Electronic components in spaceships are subjected to vibration loads during the ascent phase of the launcher. It is important to verify by tests and analysis that all parts can survive in the most severe load cases. The purpose of this paper is to present the methodology and results of the application of the Steinberg’s fatigue model to estimate the life of electronic components of the EPT-HET instrument for the Solar Orbiter space mission. A Nastran finite element model (FEM) of the EPT-HET instrument was created and used for the structural analysis. The methodology is based on the use of the FEM of the entire instrument to calculate the relative displacement RDSD and RMS values of the PCBs from random vibration analysis. These values are used to estimate the fatigue life of the most susceptible electronic components with the Steinberg’s fatigue damage equation and the Miner’s cumulative fatigue index. The estimations are calculated for two different configurations of the instrument and three different inputs in order to support the redesign process. Finally, these analytical results are contrasted with the inspections and the functional tests made after the vibration tests, concluding that this methodology can adequately predict the fatigue damage or survival of the electronic components.

This work proposes a new analytical model to extract the 1-Diode/2-Resistor solar cell/panel equivalent circuit parameters. The methodology is based on a reduced amount of experimentally measured information: short-circuit current, the slope of the I-V curve at that point, the open-circuit voltage, and the current and voltage levels, together with the slope of the I-V curve at the instantaneous operation point. This procedure is specially designed to analyze the performance of autonomous photovoltaic systems, which are most of the primary sources for spacecraft power. Results show good agreement with experimental data. Furthermore, this methodology allows for fast and accurate I-V curve maximum power point (MPP) identification.