Essay On Photovoltaic Technology

I. General
1. Introduction
For recent years, the reduction of using fossil fuel resources to produce energy, thereby reducing the emission of CO2 in the environment has been a great interest of many countries all over the world. In this situation, moving from centralized power to decentralized power seems to be a promising solution to face the increase of electricity demand and to avoid negative effects on our ecosystem. The photovoltaic technology is one of the most common renewable energy generations and is well developed and improved throughout the years. Because it is sustainable, eco-friendly together with the abundance of the solar energy, the photovoltaic technology expand gradually and has diverse applications in both domestic and commercial levels. There are many categories of photovoltaic system. In remote area, a stand-alone photovoltaic system has gained the popularity, this kind of system is usually hybrid, which means a system with

When a cell is connected to an electrical load, a chemical reaction occurs between the electrodes of the cell. Consequently, a flow of electrons runs through the cell to the load. The process of the cell releasing its stored energy into useful electrical energy is call discharging. Most PV system use storage devices, the most common being rechargeable batteries. They are also called secondary batteries, in contrast to primary batteries, which are not rechargeable.
In primary cells, the chemical processes that occur during discharging cannot be reversed by applying an external electrical current. Whereas, in secondary cells, the chemical processes of discharging can be reversed by applying an external electrical current. This procedure is called charging. The charging process has to be carried out with some care, especially to prevent damage from overheating or overcharging and deeply