Solar cells convert solar energy into electricity. The process begins when light hits your roof's solar panels with photons (particles of sunlight). The solar panel converts those photons into electrons of direct current ("DC") electricity. The electrons flow out of the solar panel and into an inverter and other electrical safety devices. The inverter converts "DC" power (commonly used in batteries) into alternating current or "AC" power. AC power is the kind of electricity your home appliances use when plugged into the wall outlet. Any power generated by the PV system not used by you is exported to the utility grid.
Solar cells are small, square-shaped panel semiconductors made from silicon and other conductive materials, manufactured in thin film layers. When sunlight strikes a solar cell, chemical reactions release electrons, generating electric current. Solar cells are also called photovoltaic cells or "PV cells" and can be found on many small appliances such as calculators.
Solar Photovoltaic (PV) System Components
Components of a PV system include:
- PV modules (groups of PV cells) also known as PV panels
- Charge regulator or controller for a stand-alone system
- Inverter to covert solar power from direct current (DC) to the alternating current (AC) of the utility grid-connected system
- Mounting hardware or a framework
- Optional features:
- Batteries for energy storage
- Solar tracking system
Other Solar Technologies
- Concentrating solar power (CSP) systems concentrate the sun's energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
- Solar water heating systems contain a solar collector that faces the sun and either heats water directly or heats a "working fluid" that, in turn, is used to heat water. For more information on installing a solar water heating system, please see the California Solar Initiative (CSI).
- Transpired solar collectors, or "solar walls," use solar energy to preheat ventilation air for a building.
The California Department of Forestry and Fire Protection - Office of the State Fire Marshal (CAL FIRE-OSFM), local fire departments, and the solar photovoltaic industry have developed a guideline for installations to increase public safety for all structures equipped with solar photovoltaic systems.
The guideline was developed with safety as the principal objective. The solar photovoltaic industry has been presented with certain limitations in roof installations due to firefighting suppression techniques. The guideline provides the solar photovoltaic industry and local building and safety agencies with information that will aid in the safe design and installation of solar photovoltaic systems.
Solar contractors should always contact their local fire department to determine if the installation of PV systems is acceptable to the fire department and meets local code requirements.
For more information on solar fire safety, please see the following 2-part video by Capt. Matt Paiss, of the San Jose, CA Fire Department. These videos offer further understanding of how solar electric systems work and tips on how to stay safe.