Contribution to the optimization of the autonomous photovoltaic solar systems with hybrid storage for loads with peak power with constraints of volume and loss of power supply probability

Abstract

The storage of energy is a fundamental aspect in the performance and the lifespan of the autonomous photovoltaic solar systems. The batteries with lead-acid are the most widespread technology of storage, because of their great availability, their low cost and their weak maintenance. They are generally failing because of certain defects such as: the stratification, sulphating, short-circuits, oxidation…These various defects strongly affect the lifespan of the batteries and thus the lifetime cost of the solar system. The appearance of these defects is for most of the time related to a non-optimal dimensioning of the system which does not take into account the starting peak power of certain electrical appliance. Indeed, the taking into account of these peak powers generate an oversizing of the batteries, consequently of the photovoltaic field and thus a very significant investment. To answer these problems, we proposed in this work a method of optimization of the autonomous solar systems by integrating ultracapacitors to meet the requirement in peak power. A program of optimization was developed in Matlab for this purpose, simulations were also done under Simulink to explore the advantages of the integration of ultracapacitors in the element of storage of an autonomous PV system with various profiles of load. The program of optimization has a step of time able to collect the fluctuations of the load and profiles of solar radiation and generates the best orientation according to the site so that the photovoltaic panel generates the maximum annual power. The program also makes it possible to determine the financial economy carried out by exploiting the Hybrid System of Storage with ultracapacitors and proposes various combinations of panels, batteries and ultracapacitors compared to LVD limit fixed with the lifetime cost and the LPSP corresponding. The management system of energy for the complete system was studied with imposed constraint the full charge of ultracapacitors between the peak powers.