Monthly Archives: November 2012

Read the Basics Here: This Is How Solar PV Works

Solar PV generates electricity in a somewhat similar way as batteries do, albeit much more intelligently: in PV, neither any components wear out nor is there any poisonous substance involved (like acid in batteries, which also wears out through use). While also degrading as there is no Perpetuum Mobile in our environment, solar cells do last a lot longer than those “state-of-the-Arch” technologies called batteries. PV cells can produce energy for 35+ years before really “sucked-out”.

Over 90% of solar cells consist of silicon, a semiconductor material derived from sand. Semiconductors are materials whose electrical conductivity increases under light or heat.

For building solar cells, the silicon is doped (other chemical elements are added to it), either creating an electron surplus (n-conductive layer) or an electron shortage (p-conductive layer). That way, the doped areas become charged, and if two differently doped semiconductor areas convene, a so-called space charge region is created at the boundary layer (p-n junction), meaning there is a difference in electrical potential across the boundary.

This is what makes them somewhat related to batteries which use acid and two different metals to create the same effect for a limited time — until the battery becomes dis-charched or “empty”.

In order to achieve the desired effect in solar cells, the initial silicon material is normally p-doped lightly and a thin surface layer heavily n-doped. This creates the space charge region required for separating the charge carriers, known as electrons (negative charge) and holes (positive charge).
Different than batteries, solar cells do not need any added substances (like acid) in order to work, but the entire process is induced by just exposing them to sunlight (or even just daylight, i e it also works on an overcast day).

When the energy from the sun hits the semiconductor material, photons transfer their energy to the material, and electrons and holes achieve a higher energy state. This allows them to move. The negatively charged electrons move to the positively charged area, and the positively charged holes move to the negatively charged area. This process repeats, and the net flow of charge across the boundary is the electricity generated by that cell. To generate usable amounts of electricity, cells are arranged into modules, which are in turn arranged into your PV array.

The front is a metallic grid, enabling the sunlight to penetrate into silicon between the contacts. Solar cells are also coated with an anti-reflection coating, serving to protect the cell and to reduce energy losses resulting from reflection. From this layer solar cells receive their blueish-black visual appearance.

The basic output is then converted to usable voltages and currents in accordance with specifications needed using rectifiers, inverters or micro inverters, and similar electrical equipment.