Glossary

Air Mass: The relative thickness of the atmosphere that solar radiation passes through to reach the Earth’s surface.

Analog Meter: Measures the energy consumption as it comes from the grid in kilowatt-hour.

Diffused Radiation: The radiation that has been scattered or reflected by water vapor, clouds, dust, air molecules, and pollutants.

Direct Radiation: The radiation that reached the Earth’s surface without being absorbed, scattered, or reflected. Sometimes called ‘beam radiation’.

Energy: (physics) The property of matter and radiation (solar energy is radiant) that manifests as a capacity to perform work (such as causing motion or the interaction of molecules).

Equinox: Earth’s orbital position when solar declination is equal. When day and night are of equal length. The Equinox occurs on March 21st and September 21st.

Incidence Angle: The angle between the sun’s rays and a line perpendicular to the array surface.

Insolation: Incident solar radiation. The annual energy output of the entire world is equivalent to the amount the sun produces in about five billionths of a second. However, most of the radiation disappears and only a very small fraction of the sun’s radiant energy, or insolation, reaches the Earth’s atmosphere. And only about half of that reaches the surface of the Earth.

Junction Box: A container for electrical connections, usually intended to conceal them from sight and deter tampering. A small metal or plastic junction box which forms part of an electrical conduit wiring management system.

Kilowatt hour (kWh): The kilowatt-hour is a unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour. Energy bills are expressed in terms of kilowatt hours.

***Understanding Kilowatt-hours***
A heater rated at 1,000 watts (1 kilowatt), operating for one hour, uses one kilowatt-hour of energy. A 40-watt light bulb operating for 25 hours uses one kilowatt-hour. Electrical energy is sold in kilowatt-hours, and the cost of running equipment is the product of power in kilowatts multiplied by running time in hours and price per kilowatt-hour. In the standard utility model, the unit price of electricity may depend upon the rate of consumption and the time of day. Industrial users may also have extra charges according to their peak usage and the power factor – solar does not.

Net Meter: Measures the energy consumption and production of energy taken from, and put into, the grid in kilowatt-hour. **As energy is consumed, the meter spins forward and the consumer is charged for the energy. ***As energy is produced, the meter spins backward and credits the consumer.

Peak Sun Hours: The equivalent number of hours per day when solar irradiance averages 1 kW/m2. For example, six peak sun hours means that the energy received during total daylight hours equals the energy that would have been received had the irradiance for six hours been 1 kW/m2 (or 1000 w/m2).

Photovoltaics (PV): A method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect.

Photovoltaic Effect: The creation of voltage or electric current in a material upon exposure to light. The photovoltaic effect refers to photons of light exciting electrons into a higher state of energy, thus allowing them to act as charge carriers for an electric current.

Photovoltaic System: (PV System or Solar Energy System) An arrangement of components designed to supply usable electric power for a variety of purposes, using the sun as the power source.

PV systems may be built in various configurations:

a.) Off-grid without battery (array-direct)
b.) Off-grid with battery storage for DC-only appliances
c.) Off-grid with battery storage for AC and DC appliances
d.) Grid-tie without battery – offered by Brite Energy
e.) Grid-tie with battery storage

Radiant Energy: Energy that is transmitted in the form of (electromagnetic) radiation; energy that exists in the absence of matter.

Solar Array: An arrangement of solar panels used to power a structure.

Solar Cell: The basic building block of PV system. A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. Assemblies of solar cells are compiled to create solar panels.

Solar Constant: The amount of energy received at the top of the Earth’s atmosphere on a surface oriented perpendicular to the sun’s rays. The solar constant of 1368 W/m2 is a satellite-measured yearly average.

Solar Energy: Radiant energy emitted by the sun.

Solar Insolation: The solar energy received over one day (kWh/m2 /day).

Solar Irradiance: (W/m2) The power of solar radiation per unit area.

Solar Panel: A set of solar photovoltaic modules electrically connected and mounted on a supporting structure. One of the standard Solar Panels used on homes is 250kW. 4 panels x 250 W= 1kW (the average home is 6kW or 24 250 watt solar panels).

Solar Radiation: The general term for the electromagnetic radiation/energy emitted by the sun.

Solstice: The Earth’s orbital position when solar declination is at its minimum or maximum.

Racking: The mechanical connection between the roof or ground and the photovoltaic module.

Utility Disconnect: Many utilities require a visible-blade, lockable-open disconnect in the AC output circuit of the inverter. This disconnect is usually located within sight of the service entrance meter so that emergency response people can easily find it.

Watt: The watt (symbol: W) is a derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt (1736–1819). The unit, defined as one joule per second, measures the rate of energy conversion or transfer.

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