Sizing of off-grid PV systems with Python

Abstract

It is a fact that solar energy generation is becoming more available and affordable every year. At the same time social awareness of the traditional energy system and its negative impact on the planet is changing the mentality of the people towards renewable ways of energy supply. Now, a pending task in all this process of global energy transformation is to give the people the chance to size their own renewable systems in a trustworthy way and as easy as possible, but above all free of charge. That is why a module written Python is presented in this paper. It allows the user to size their own PV system in a relatively easy way. This module is initially focused on off-grid (stand-alone) PV systems, but it can be upgraded to size off-grid solar-wind hybrid systems as well. The sizing is based on the reliability of the system to supply the energy demand. One way to quantify this is by a parameter known as the Loss-of-Load Probability (LLP), defined as the ratio between the estimated energy deficit and the energy demand over the total operation time of the installation. The module makes use of well stablished models for crystalline silicon solar cells, leadacid battery cells and other elements in a typical PV system. Apart from that, all the information required to perform the sizing is available online. It is worth mentioning that solar radiation information based on satellite images is becoming increasingly available and is improving on ground coverage and resolution.