HOW SOLAR WORKS

There are a variety of solar PV technologies available for your home or business. Read below to learn more.

SOLAR PV

Solar electric systems, otherwise known as photovoltaic (PV) systems, convert sunlight into electricity. Solar cells, the basic building blocks of a PV system, consist of semiconductor materials. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the "photoelectric effect." These free electrons then travel into a circuit built into the solar cell to form electrical current.

Multiple solar cells are included in solar modules, which are wired together into an array that will generate electricity for your home. Only sunlight of certain wavelengths will work efficiently to create electricity. PV systems can still produce electricity on cloudy days, but not as much as on a sunny day. For more about the basics of PV, visit the Department of Energy, NREL, EIA, and Solar Technologies Program websites for more solar energy resources. 

Most PV systems today connect to the local utility system so the consumer can still receive electricity from the grid to power their home at night. Net Metering allows the consumer to send any excess electricity generated during the day from the consumer's solar system back out to the grid in exchange for credits. Using the free electricity from your solar system will lower your electric bills and decrease your carbon footprint.

TECHNOLOGY

PV panels produce DC electricity, which is converted into AC power by an inverter. Generally there is only one inverter for an entire array of panels, but some systems have a newer technology called micro-inverters where each solar panel feeds into a small inverter. Micro-inverters are more efficient, although they can also be more expensive. A similar new technology is ‘DC optimizers’, which provide similar efficiencies and panel-level monitoring but are connected to a central inverter. Appropriate technologies vary depending on the application, and you should consult with a certified solar installer to decide what is right for your needs.

SOLAR CELLS

The performance of a solar cell is measured in terms of its efficiency at converting sunlight into electricity. There are a variety of solar cell materials available, which vary in conversion efficiency.

SEMICONDUCTOR MATERIALS

A solar cell consists of semiconductor materials. Silicon remains the most popular material for solar cells, including these types:

* Monocrystalline or single crystal silicon
* Multicrystalline silicon
* Polycrystalline silicon
* Amorphous silicon

The absorption coefficient of a material indicates how far light with a specific wavelength (or energy) can penetrate the material before being absorbed. A small absorption coefficient means that light is not readily absorbed by the material. Again, the absorption coefficient of a solar cell depends on two factors: the material making up the cell, and the wavelength or energy of the light being absorbed.

THIN FILM

Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Thin film technology has made it possible for solar cells to now double as these materials:

* Rooftop or solar shingles
* Roof tiles
* Building facades
* Glazing for skylights or atria.

Thin-film rooftop or solar shingles, made with various non-crystalline materials, are just now starting to enter the residential market. The following are benefits of these solar shingles:

* Attractive integration into homes
* Dual purpose: serves as both roofing material and electricity generator
* Durability

Commercially-available solar shingles generally have lower efficiencies and greater expense compared with the standard small solar electric system.

For more information on solar PV technologies, visit the Department of Energy, NREL, EIA, and Solar Technologies Program websites.