What is a Photon?

A photon is a type of elementary particle that forms the basic unit of electromagnetic radiation, which includes radio waves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Photons have no mass, no electric charge, and travel at the speed of light. Unlike some particles, like protons and neutrons, they are not thought to be made up of smaller components. They belong to a class of particles that are responsible for the fundamental forces of nature, and carry the electromagnetic force. According to the theory of quantum electrodynamics, the way electrically charged particles behave toward one another can be described in terms of photons.



What Are Electrons?

Electrons are extremely tiny particles which carry a negative charge, and which create electricity when they flow through a conductor. They are one of the most basic components of a solar cell, and the entire process of converting sunlight into electricity is based on their activity. Sunlight transfers its energy to the electrons in the atoms of the solar cell, and they become part of an electrical current. It is this direct current (see "DC - direct current") that can then be stored (see "Batteries") or converted into alternating current (see "AC - alternating current"), and used to power electrical appliances and equipment.



Conductor, Semi conductor and Solar Cells

A Conductor is literally anything which will allow the flow of, or "conduct", electricity. Substances like rubber will not conduct electricity and are used as insulators. Materials like copper wiring offer almost no resistance to electrical current and make excellent electrical conductors. Semi conductor materials are used to make computer chips and solar cells.


Semi Conductors
Semi conductors are made from a variety of different types of silicon: single-crystalline, polycrystalline or non-crystalline (amorphous or thin film). The silicone partially insulates electrical current, and conducts only a limited amount of electricity.


Solar Cells
Solar Cells (also knows as "PV cells" or "photovoltaic cells") are the basic unit of any solar electric system. They can be made from many different types of semi conductor materials, but the most commonly used in the conventionally designed solar panels that people are used to seeing are crystalline silicon-based. The PV cell converts sunlight into electricity during a process that causes the electrons in the semi conductor material to create an electric field. Since each solar cell is quite small and generates only 1 or 2 volts of electricity, a solar panel (or PV module) contains dozens (or tens of dozens) of solar cells that are connected together.


In response to the shortage of silicon and its increasing cost, other materials (for example, cadmium indium gallium selenide, also known as CIGS) have been used in the last 10 years. But since these materials are also expensive, innovation has led to manufacturing processes that use less of the materials in order to bring prices down. As a result," thin film" solar cells have been developed and products are now being manufactured that rival the electricity production of the larger and heavier conventional solar panels made with silicon-based solar cells. (See "Thin Film Photovoltaics (TFPV)")





Solar Panel Advances

Thin Film Photovoltaics (TFPV)
The newest frontier is solar cells belongs to the "thin film" category and is dye-based. It uses materials that are much less expensive than silicon-based or other thin-film solar cell technologies. Research and development is currently underway in several countries around the globe to produce dye-sensitized solar cells that convert sunlight into electricity as efficiently as the solar cells which are currently available in the consumer marketplace. Once this efficiency is reached, this new generation of cheaper and smaller solar cells will be able to be incorporated into to be consumer products such as windows and exterior paints.


Thin Film Shingles
Thin film shingles are a type of solar panel that can be integrated into existing composition or tile roofing systems. They are the same size as a roofing shingle and eliminate the need for a separate solar array and racking system. For this reason, they are a good choice for tract or custom housing developments which have strict design guidelines prohibiting large solar array installations on the roof or on the ground. As long as the roof faces the sun for enough hours during the day to produce electricity, they can be successfully used in areas of high density housing. Thin film technology has advanced far enough that it can produce electricity even in geographical areas which experience a lot of cloudy or foggy weather.


Thin Film Laminates
Thin film laminates encapsulate solar cells into a flexible, lightweight polymer product that allows light transmission but is resistant to ultra violet rays so that it does not break down like many plastics under long term exposure to direct sunlight. It is manufactured in rolls (like rolled roofing material) and can be easily applied to the types of flat roofs that are commonly used in commercial buildings. Unlike conventional solar array mounting systems which require anchors, the thin film laminates are made with self-adhesive backing that does not require penetrating the roof with screws or bolts.


Thin Film Windows and Walls
Semi transparent photovoltaic panels that can be used as a substitute for glass in windows, walls and skylights is already being commercially manufactured and used successfully. The technology is formally known as Building Integrated Photovoltaics (or BIPV) and currently it's most effective application is when used on large scale surfaces such as business, government and educational campus offices and classrooms.

Whether building solar panels or a complete solar energy system, you will find the information here very useful and don't forget to check out the Electricity Basics page for comprehensive information on electricity.