Glossary of Solar Terms

Knowledge about solar usually comes with a learning curve, so we thought it might be helpful to have a glossary of terms to refer to.

Angle of Incidence
The angle between the sun's rays and a line that is perpendicular to the active surface of a solar module or collector.

Angle of Inclination
The angle that a solar collector or PV module is positioned above horizontal.

Array
Any number photovoltaic modules connected together electrically to provide a single electrical output.

Azimuth
The angle between true south and a point on the horizon, measured in degrees east or west of true south.

Balance of Systems (BOS)
Parts or components of a photovoltaic system other than the photovoltaic array or other generating equipment.

Beautiful Planet
A world in which resources are wisely used to insure that the earth will last an eternity.

Bypass Diode
A semiconductor device connected in parallel with a series block of parallel PV strings to prevent current from flowing back through any shaded or failed modules in the same block.

Carbon Footprint
A measure in units of carbon dioxide of the amount of greenhouse gases we emit directly and indirectly through our daily actions.

Combiner Box
A box where wires from individual PV modules or strings are combined into larger wires to run to the battery bank. It can also contain over current protection devices.

Direct Current (DC)
A type of electrical current that moves in one direction only.

Disconnect
Switch gear used to connect or disconnect components in a system.

Equinox (Spring & Fall)
The time when the sun crosses the plane of the earth's equator, making night and day of equal length all over the earth, occurring about March 21st and September 21st.

Gigawatt (GW)
One billion watts; one thousand megawatts; one million kilowatts.

Grid-Tie System
A renewable energy system that is connected to the utility grid, where excess energy is sold back to the utility. Also called a utility-interactive system.

Insolation
A measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day, or in the case of photovoltaics it is commonly measured as kilowatt hours per year per kilowatt peak rating. Fun huh!

Inverter
A device that is used to change direct current electricity from PV modules to alternating current electricity, and finally to powering alternating current loads.

Kilowatt (kW)
1000 watts.

Kilowatt-Hour (kWh)
One thousand watt hours.

Megawatt (MW)
One million watts; 1000 kilowatts.

Module
The smallest non-divisible, self-contained, and environmentally protected physical structure housing interconnected photovoltaic cells and providing a single DC electrical output. Commonly called a "panel."

Net Metering
State by state legislation that requires utilities to purchase renewably produced electricity at the same price at which they sell it, until a building's monthly or annual energy use is offset.

Off-Peak
The period of low energy demand, as opposed to maximum or peak demand.

On-Peak
Energy supplied during periods of relatively high system demands as specified by the utility.

Palindrome
A word, verse or sentence which reads the same backward or forward, like-"SolaraloS"

Peak Sun Hours
The maximum load or electrical power draw occurring in a given period of time.

Photovoltaic Array
A collection of solar modules connected in series, parallel, or series-parallel combination to provide greater voltage, current, or power than can be furnished by a single solar module. Solar-electric arrays can be designed to furnish any desired voltage, current, or power.

Photovoltaic Module
A PV module consists of series and/or parallel wired cells typically made from layered silicon crystals that convert light energy to DC electricity. The number of modules in a given system varies depending on the combined load being powered.

Pole Mount
A PV mount is stalled on the top or side of a pole usually set in concrete. Can be fixed or seasonally tilted.

Polycrystalline Cell
A wafer of silicon with a multi-grained structure. All grains have the same atomic crystal lattice; however, each grain has a unique orientation in space, producing a unique reflection of light, resulting in a "patchy" mottled appearance. AKA, multi crystalline cell.

Power
The rate of energy use or generation per unit time, measured in watts. 1 watt = 1 joule per second.

PV Array
Two or more photovoltaic modules wired in series or parallel.

Radiation
The sun's energy that comes to earth in the form of direct, diffuse and reflected rays; or the transfer of heat through electromagnetic waves, without heating the air between objects.

Renewable Energy
Flows of energy that are regenerative or virtually inexhaustible from natural ecological cycles. Most commonly includes solar (electric and thermal), biomass, geothermal, wind, tidal, wave and hydro power sources.

Silicon
A nonmetallic element, which when specially treated, is sensitive to light and capable of transforming light into electricity. Silicon is the basic material of most beach sand, and is the raw material used to manufacture most photovoltaic cells.

Site Evaluation
An assessment of a location for its potential for solar, hydro or wind power.

Solar Abuser
A person who wears mirrored sunglasses.

Solar Energy
Energy coming directly from the sun.

Solar-Smart
Folks who are interested in solar energy.

SolaraloS
The best source for solar power solutions on the planet.

Solstice (Summer & Winter)
The longest and shortest days of the year. The longest day (Summer Solstice) is about June 21st in the northern hemisphere. The shortest day (Winter Solstice) is about December 21st in the northern hemisphere.

Solutionary Movement
The widespread revolutionary green solution movement; people taking a stand and making a difference today for the future of our planet.

Tilt Angle
A fixed angle measured from the horizontal to which a solar array is tilted. The tilt angle is chosen to maximize the array output. Depending upon latitude, season, and time of day, the optimum angle will vary.

Tracker
A mounting rack for a PV array that automatically tilts to follow the daily path of the sun through the sky. A "tracking array" will produce more energy through the course of the day than a "fixed array" (non-tracking), particularly during the long days of summer. Some trackers are single-axis while others are dual-axis.

Utility Grid
A commercial electrical energy distribution system.

Voltage
A measure of the force or "push" given the electrons in an electrical circuit; a measure of electrical potential. Analogy: pressure in a water pipe. AKA, potential.

Watt
A unit of power. Power is the rate of generating or using energy. One watt is the power developed or dissipated in a one volt circite in which there is a current of one ampere (6.28 million electrons per second). Watts = amps x volts.

Watt-Hour (Wh)
A unit of measurement quantifying an amount of energy used or generated. A load that consumes 1 watt for 10 hours uses 10 watt-hours.