PHOTOVOLTAICS - How it works
Photovoltaic (PV) systems produce electricity when exposed to sunlight. Sunlight is composed of particles of energy called photons. When sunlight strikes a PV material, photons will either pass through, be reflected, or be absorbed. If the photon is absorbed, its energy will be transferred to an electron in an atom of the PV material. With its new found energy, the electron is able to escape from its normal position in orbit around that atom. In this way, the electron can become part of, and augment, the current in an electrical circuit. This "photovoltaic effect" is the basic physical process through which sunlight is converted into electricity. The primary building block of a PV system is the PV cell. A typical PV cell is about 3 X 3-in. and very thin. By itself, a single PV cell produces only a small amount of electricity. Fortunately, we can easily increase the total power in a PV system by connecting several cells to form larger units called modules. Modules, in turn, can be connected to form even larger units know as arrays, which can be interconnected to produce more power, and so on. In this way, we can build a PV system to meet almost any power need, no matter how small or great.
Types of Solar Cells:
All commercially viable PV products are made using one of two groups of technologies; Crystalline Silicon or Thin Film materials.
CRYSTALLINE SILICON
Traditional crystalline silicon is by far the most common solar cell material for commercial applications because:
It has been in use for more than 50 years, and its manufacturing processes are well known. Those processes are now largely in the public domain.
The raw material used, silicon, is very abundant (it's the second most abundant element in the Earth's crust - second only to oxygen)
Forms of Crystalline Silicon PV
There are two basic forms of crystalline silicon PV; Single-crystalline silicon and Poly-crystalline silicon.
Crystalline Silicon Points:
• Higher efficiency
• Durable – Ideal for permanent installations
• Little maintenance required
• Designed to withstand rigorous weather conditions
THIN-FILM
Thin-Film Forms
The principal thin-film technologies is Amorphous Silicon (a-Si)
Amorphous Silicon Points:
• Lightweight, portable, shade tolerant
• For entry to solar or hands on solar
• Generally used for the chassis battery
• Best for smaller output temporary set ups, areas that do nonot receive predictable sun conditions
