Photovoltaics
Photovoltaics (PV) literally means "light-electricity," and is the process of converting sunlight into electricity. The term "photo" comes from the Greek word "phos" or light, and "volt" was derived from Volta (1745-1827), a pioneer in the study of electricity.
For more information on how to get started with solar, click here.
How does it work?
When some materials are exposed to sunlight, they release small amounts of electricity giving off what is known as the "photovoltaic effect."
Sunlight is composed of photons, or particles of solar energy that contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, the energy of the photon is transferred to an electron in a cell's atom. The cell is made of a semiconductor material.
With its newfound energy, the electron escapes from its normal position on the atom and becomes part of the current in an electrical circuit. When this happens, the electron creates a "hole." Special electrical properties of the PV cell, specifically a built-in electric field, provide voltage that drives the current through an external load, such as a light bulb, a hairdryer or a television set.
For more information about the science behind PV,
visit the National Center for Photovoltaics.
The components of PV systems
Photovoltaic modules are the basic building blocks of solar electric power systems.
PV modules can be made from several different materials, which vary in cost and conversion efficiency. Modules are combined to create panels. Panels are combined to form arrays. Solar electric power systems may also have batteries, charge controllers, and inverters, which convert the direct current generated by PV system into an alternating current, the type of electricity sold by utilities and required to run most appliances and electronic devices.
Types of Solar Modules
There are two major categories of solar modules, Crystalline and Thin Films. There are a couple types of each and each has its positive and negative factors.
| Crystalline |
Thin Films |
 |
 |
Types of Crystalline panels
Single Crystalline (15%)
Multi-Crystalline (14%)
(% of sunlight converted to electricity)
|
Types of Thin Film panels
Amorphous Silicon (5-7%)
Copper Indium Diselenide (10%)
Cadmium Telluride (7%)
(% of sunlight converted to electricity)
|
Positive factors
Efficient
Requires less space
Long track record |
Positive factors
Less expensive
Very versatile
More shade tolerant
Less temperature sensitive |
Negative factors
Costly
Limited applications
Shade intolerant
Temperature sensitive
|
Negative factors
Shorter track record
Lower efficiency
Requires more space
|
PV systems in use today...
Did you know that PV is part of our daily lives? San Diego's highway call boxes and the I-15 FasTraktm signs are PV powered, and many wrist watches and small calculators are too.
If you own a home or business in a remote region of the county, photovoltaics can provide affordable electricity to your residence, water pumps and communications equipment. If you are buying a new home in San Diego, you can get one with a built-in PV system, like the Shea Homes in Scripps Ranch.
For existing San Diego homes and businesses that buy their power from SDG&E, PV is a viable and increasingly attractive method of generating power. Why? PV Systems are now more efficient than ever, and rising electric rates, incentive programs and environmental concerns have compelled many San Diegans to think seriously about buying PV Systems. |
