photovoltaic systems أنظمة الطاقة الشمسية: Solar energy PV systems

الجمعة، 26 فبراير 2016

Solar energy PV systems

Nowadays, solar energy has become one of the best options for replacement of the present conventional fuel consuming power generators. Due to the availability of solar radiation in most part of the world and in particular in equatorial regions, development and implementation of this technology has received a lot of attention and momentum by energy industries and it is expected that with the growing rate of the global energy consumption, solar energy will be the best viable choice. Currently, solar energy is utilized for such applications as producing of energy, water heating, water purification, etc. with each having their own technology. This article briefly narrates some aspects of PV systems, their power efficiency, and components.

Basics and applications

Of most important applications of solar energy is the production of electricity. This can be achieved either through solar collectors that generate electricity by using solar powered sterling engines or by water vapor rotating turbines, or by PV panels that are now commonly used in even home applications as well as large-scale institutional grid-connected solar PV (Photovoltaic) systems using such constructions as the roofs of Buildings, car parks, etc. There is a lot of debate over the cost-effectiveness of each of these methods and even hybrid systems have been developed for better solar power efficiency; however, due to fast progress in photovoltaic systems as well as increase in power efficiency of solar panel, the development and implementation of PV panels have now become an indispensable part of every power company.

PV systems and terminology

PV systems convert solar radiation into electricity. The average direct solar radiation is about 1367 W/m2 and PV systems are designed for efficient conversion of this power into electricity.

The main component in a PV system is the solar panel composed of PV cells. The smallest components of a solar PV system are PV cells. They are made up of semiconducting materials such as arsenide, silicon, gallium, copper indium diselenide and other compounds capable of turning s
unlight into electricity. An efficient commercial PV cell can turn above 23% of the solar radiation into electrical power. Arranging of PV cells together forms a PV module. Several modules together form a solar array, and finally several arrays form a solar panel. The modular nature of PV cells make it flexible for use in a wide variety of power applications from milliwatt systems such as mobiles and hand calculators to large PV solar generators in central stations with several megawatt electric energy production that can be fed to the central state grid.

Classification of PV systems

PV systems can be grouped into two categories: grid-connected systems and off-grid systems

Off-grid systems: They are used in locations where it is not possible to connect them to the mains utility grid. This includes remote villages and urban areas that do not have access to the grid utility. These systems need to have a storage system like a battery bank to provide electricity at nights when there is no sunlight. Some other applications of off-grid systems include telecommunication systems and traffic signs.

Grid-connected PV systems: these systems as their name imply are solar systems connected to the mains utility grid feeding the excess power of the consumer’s solar power into the state grid. Grid-connected systems are usually employed either in decentralized grid-connected PV systems such as rooftop mounted PV panels and generators or centralized grid-connected applications where the power output is much higher ranging from several KWs to several MWs.

With the advent of smart grids in which it is possible to feed the excess energy back into the main utility grid thereby reducing the cost of electricity for consumers, a new era has been opened for a cost-effective solution using solar energy.