A: What do we mean by photovoltaics? The word itself helps to explain how photovoltaic (PV)
or solar electric technologies work. First used in about 1890, the word has two parts: photo, a
stem derived from the Greek phos, which means light and volt, a measurement unit named for
Alessandro Volta (1745-1827), a pioneer in the study of electricity. So, photovoltaics could
literally be translated as light-electricity. And that's just what photovoltaic materials and
devices do; they convert light energy to electricity, as Edmond Becquerel and others discovered
in the 18th Century.
A: When certain semiconducting materials, such as certain kinds of silicon, are exposed to
sunlight, they release small amounts of electricity. This process is known as the photoelectric
effect. The photoelectric effect refers to the emission, or ejection, of electrons from the surface
of a metal in response to light. It is the basic physical process in which a solar electric or
photovoltaic (PV) cell converts sunlight to electricity.
Sunlight is made up of photons, or particles of solar energy. Photons contain various amounts
of energy, corresponding to the different wavelengths of the solar spectrum. When photons
strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the
absorbed photons generate electricity. When this happens, the energy of the photon is
transferred to an electron in an atom of the PV cell (which is actually a semiconductor).
With its newfound energy, the electron escapes from its normal position in an atom of the
semiconductor material and becomes part of the current in an electrical circuit. By leaving its
position, the electron causes a hole to form. Special electrical properties of the PV cell—a builtin
electric field—provide the voltage needed to drive the current through an external load (such
as a light bulb).
A: A PV system is made up of different components. These include PV modules (groups of PV
cells), which are commonly called PV panels; one or more batteries; a charge regulator or
controller for a stand-alone system; an inverter for a utility-grid-connected system and when
alternating current (ac) rather than direct current (dc) is required; wiring; and mounting
hardware or a framework.
A: A PV system that is designed, installed, and maintained well will operate for more than 20
years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts
and can last more than 30 years. The best way to ensure and extend the life and effectiveness
of your PV system is by having it installed and maintained properly. Experience has shown that
most problems occur because of poor or sloppy system installation.
A: PV can be used to power your entire home's electrical systems, including lights, cooling
systems, and appliances. PV systems today can be blended easily into both traditional and
nontraditional homes. The most common practice is to mount modules onto a south-facing
roof or wall. For an additional aesthetic appeal, some modules resemble traditional roof
A: PV systems can be blended into virtually every conceivable structure for commercial
buildings. You will find PV being used outdoors for security lighting as well as in structures that
serve as covers for parking lots and bus shelters, generating power at the same time.
A: A photovoltaic (PV) system needs unobstructed access to the sun's rays for most or all of the
day. Shading on the system can significantly reduce energy output. Climate is not really a
concern, because PV systems are relatively unaffected by severe weather. In fact, some PV
modules actually work better in colder weather. Most PV modules are angled to catch the sun's
rays, so any snow that collects on them usually melts quickly. There is enough sunlight to make
solar energy systems useful and effective nearly everywhere.
A: The size of solar system you need depends on several factors such as how much electricity or
hot water or space heat you use, how, the size of your roof, and how much you're willing to
invest. Also, do you want the system to supply your complete energy usage or to supplant a
portion of your higher cost energy usage?
A: People decide to buy solar energy systems for a variety of reasons. For example, some
individuals buy solar products to preserve the Earth's finite fossil-fuel resources and to reduce
air pollution. Others would rather spend their money on an energy-producing improvement to
their property than send their money to a utility. Some people like the security of reducing the
amount of electricity they buy from their utility, because it makes them less vulnerable to
future increases in the price of electricity.
If it's designed correctly, a solar system might be able to provide power during a utility power
outage, thereby adding power reliability to your home. Finally, some individuals live in areas
where the cost of extending power lines to their home is more expensive than buying a solar