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- Nov 04, 2017 -

Photovoltaic Effect

Assemblies of solar cells form solar panels. The    raw material in solar cell- silicon in its purest form makesa an ideal neutral platform for the transmission of electrons. Silicon also has some atomic-level properties which make it even more attractive for the./ creation of solar panels. Solar panels receive sunlight and actively convert that energy into electricity. The solar cells have a large area p-n junction diode which convert the energy from sunlight into usable electrical energy. The basic principle behind the procedure is Photovoltaic Effect, photo = light, voltaic = electricity ie. conversion of sunlight into electrical energy

Electricity Production Process

Most of the panels contain a top protective layer, two silicon layers with collecting circuitry attached to the top layer, and a polymer backing layer. When photons strike the surface of the solar panel, the energy that is generated from it allows electrons to be released, and electric fields in the solar cells pull these free electrons. PV cells also have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the cell, one can draw that current off to use externally. The electrons thus collected by electrical contacts on the surface of the top layer are then routed through an external circuit, thus generating electricity.

How Efficient is Electricity Production from Solar Energy

The total electrical output of the solar panel is directly proportional to the quality & quantity of solar cells in it ie. the higher the number of solar cells & the better the quality of solar cells used, the better is the output from the solar panel. Other factors that affect the output of solar panels are weather conditions, obstructions to direct sunlight, and the angle and position at which it is installed. Solar panels function the best under direct sunlight. This can be achieved by using dynamic mounts that follow the position of the sun in the sky and adjust the solar panel accordingly, to get the maximum amount of direct exposure to the sun as possible.

Challenges in Electricity Production

Normally, the solar cell absorbs only about 15% of the sunlight’s energy. Firstly, Electromagnetic radiation is not monochromatic ie. it is made up of a range of different wavelengths, and therefore various energy levels. Hence, some of the photons do not have enough energy while others  have too much energy. So, some of it would just pass without getting utilized & for the others, the extra energy is lost.

Secondly, the electrons  flow from one side of the cell to the other through an external circuit. So the bottom layer is covered with a metal allowing good conduction, but if  the topmost layer is also covered, then all the current might be lost because the photons will not be able to get through the opaque conductor. If contacts are put only at the sides of the solar cell, then the electrons have to travel an extremely long distance to reach the contacts.

Thirdly, the silicon that goes in making a solar cell is a semiconductor – not as good as a metal for transporting current. Its internal resistance is fairly high, and high resistance means high losses. To minimize these losses,the cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface.

Solar Panels despite being mostly a commodity comes in a wide variety of types,technology,prices,size and colors.

Size of Solar Panels

Solar Panels come in all sorts of sizes, colors and power. Solar Panels of 20-40 Watts are typically used for applications like a Solar Lamp,Lantern and products using small amounts of power. For Putting Solar Panels on the Roof for Generation of Electricity, sizes vary from 150 Watts to 300 Watts.

Type and Color of Solar Panels

Application of solar street lights, all in one solar street lights.