Solar Dictionary: All Terms

Absorber   the plate in a solar hot water collector or pool collector that converts solar radiation to heat energy. Generally matte black or selective surfaces on copper.
  Solar Domestic Hot Water  Solar Pool Heat

Absorptance   the ratio of energy absorbed by a surface relative to the energy striking it. Thermal collectors have high absorptive coatings resulting in absorptance of .95 to .98
  Solar Domestic Hot Water  Solar Pool Heat

AC Disconnect   one of the balance of system components, this utility serviceable disconnect switch allows the current being produced from the photovoltaic system to be isolated from the utility feed during times of maintenance, service or repair.
  Solar Electric

Alternating Current (AC)   the type of current that most utility interconnected homes and commercial structures run on. The direction of this type of current reverses at regular intervals usually 120-reversals or 60-cycles per minute making it easy for the utility providers to control.
  Solar Electric

Ambient Temperature   temperature of the surrounding outside air
  Solar Domestic Hot Water  Solar Pool Heat

Ampere (A)   a unit of electrical current which measures the flow of electrons (similar to the measure of flow rate of water through a hose).
  Solar Electric

Amp-hour Capacity (Ah/AM)   referring to the size of a battery, this is a measurement of the flow of current per hour.
  Solar Electric

Angle Of Incidence   the angle at which solar radiation strikes a surface (collector).
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Array   a group of thermal collectors or photovoltaic modules organized to produce a desired amount of energy.
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Balance of System Components   all components of a solar system other than the actual array (includes everything from design costs through installation and service/maintenance).
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Battery Back-up   a photovoltaic system designed with batteries of a specified amp-hour capacity to provide current to a residential or commercial structure or its key loads for a predetermined period of time.
  Solar Electric

British Thermal Unit (BTU)   the quantity of heat needed to raise 1 pound of water by 1 Fahrenheit. 8 BTU's will raise 1 gallon of water 1
  Solar Domestic Hot Water  Solar Pool Heat

Charge Controller   utilized only in systems which incorporate batteries, this component controls the flow of current to and from the batteries to protect them from over-charging and over-discharging.
  Solar Electric

Collector (Solar Collector)   device that collects solar radiation and converts it to heat
  Solar Domestic Hot Water  Solar Pool Heat

Collector Efficiency   the radio of usable heat energy extracted from a collector to the solar energy striking the cover
  Solar Domestic Hot Water  Solar Pool Heat

Collector, Evacuated Tube   a collector which consists of parallel rows of glass tubes connected to a header pipe. Each tube has the air removed from it to eliminate heat loss through convection and radiation.
  Solar Domestic Hot Water

Collector, Flat-Plate   a flat, rectangular, insulated, weatherproof box containing an absorber plate under a cover plate.
  Solar Domestic Hot Water

Conduction   heat flow in any direction due to temperature variations within a material
  Solar Domestic Hot Water  Solar Pool Heat

Convection   the motion of a fluid by which heat may be transported. See also 'Thermosyphoning', 'Conduction', and 'Radiation'
  Solar Domestic Hot Water  Solar Pool Heat

Cover Plate   also referred to as glazing, usually a sheet of tempered glass or transparent plastic placed above the absorber in a flat plate collector
  Solar Domestic Hot Water

Current   the flow of electrical energy measured in amperes (A)
  Solar Electric

DC Disconnect   a disconnect switch which isolates the photovoltaic array from the other system components during times of maintenance/service.
  Solar Electric

DHW (SDHW)   solar domestic hot water
  Solar Domestic Hot Water

Direct Current (DC)   a type of electricity which flows through a conductor in only one direction with low voltage and high current. Most standard appliances will not work on DC, so the electricity must be inverted to AC.
  Solar Electric

Emittance   a measure of the propensity of material to radiate energy to its surroundings. Solar collectors have low emissivity coatings.
  Solar Domestic Hot Water  Solar Pool Heat

FSEC   Florida Solar Energy Center, organization that provides research, testing, and certification of solar thermal collectors and systems
  Solar Domestic Hot Water  Solar Pool Heat

Galvanic Corrosion   condition caused as a result of a conducting liquid making contact with two different metals which are not properly isolated
  Solar Domestic Hot Water  Solar Pool Heat

Grid-tied   the photovoltaic system that is connected to the utility grid allowing the system and the grid to interact (allows for net-metering).
  Solar Electric

Header   tubes running horizontally across the bottom and top of absorber plates. See also 'Risers'
  Solar Domestic Hot Water  Solar Pool Heat

Heat Exchanger   a device, such as a copper coil, immersed in a tank or tube of water, used to transfer heat from one fluid to another
  Solar Domestic Hot Water  Solar Pool Heat

Heat Exchanger, Double Wall   heat exchangers using a non-potable (antifreeze) heat transfer fluid that is separated from the potable water by two walls and a small gap, thus allowing a leak of heat transfer fluid to become visible rather than enter the potable water. These heat exchangers are required by most plumbing codes.
  Solar Domestic Hot Water

Hybrid System   often referring to solar pool heating, is a system which uses solar collectors in addition to a conventional heater
  Solar Pool Heat

Insolation   the total amount of solar radiation - direct, diffused, and reflected - striking a surface exposed to the sky
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Inverter   the component of a photovoltaic system which changes DC to AC (essential in both grid-tied and stand-alone systems).
  Solar Electric

Junction Box (PV)   an enclosure on the back of a module where photovoltaic modules are connected to form a string.
  Solar Electric

Junction Box (roof)   an enclosure mounted near the array where strings come together to be run to the inverter.
  Solar Electric

Kilowatt (kW)   a unit of electrical power; equals 1000-watts
  Solar Electric

Kilowatt-hour (kW h)   a unit of energy; equals 1000-watts acting over one hour.
  Solar Electric

Magnetic South   the direction on a compass pointing due-South, away from the North Pole.
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Megawatt (MW)   a unit of electrical power; equals 1000-kilowatts
  Solar Electric

Module   a collection of photovoltaic cells connected together, as well as other components (i.e. junction box, frame, wires, etc.), designed to produce a specified number of watts under standard test conditions (STC). Also referred to as a solar panel.
  Solar Electric

NABCEP   North American Board of Certified Energy Professionals, organization providing certification of solar installers
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

National Electric Code (NEC)   the guidelines for all types of electrical installations.
  Solar Electric

Net-metering   an agreement with the utility provider which allows grid-tied systems to back-feed the grid during times when production exceeds usage. During these times the utility meter actually runs backwards, creating a "debit and credit" situation between the producer and the utility provider.
  Solar Electric

Orientation   the direction that a solar array faces with regard to magnetic directions (N, E, S, W).
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Passive System   a system which converts solar energy into usable thermal energy without using mechanical power. See 'thermosyphon'
  Solar Domestic Hot Water

Photovoltaics (PV)   the conversion of light into electricity.
  Solar Electric

Racking (rails)   the components used to secure a domestic hot water, pool, or photovoltaic system in place; can be ground, deck, roof or pole mounted depending on the application and the orientation of available space.
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Radiation   the flow of energy across open space via electromagnetic waves, such as visible light
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Resistance (R)   a unit measured in ohms, it is the opposition to the flow of electrons produced by a conductor.
  Solar Electric

Risers   tubes that run vertically, inside the absorber plate, between the headers.
  Solar Domestic Hot Water  Solar Pool Heat

Seasonal Efficiency   the ratio, over an entire heating season, of solar energy collected and used against the solar energy striking the array
  Solar Domestic Hot Water

Selective Surface   a surface used for absorber plates that absorbs radiation of one wavelength (i.e. sunlight) but emits little radiation of another wavelength (i.e. heat)
  Solar Domestic Hot Water

Solar Access   the amount of sunlight a photovoltaic array should receive based upon orientation, obstructions and average annual sun hours.
  Solar Electric

Solar Cell   the smallest element in a solar module, it is directly responsible for the conversion of light into electricity. Usually made of mono- or poly-crystalline or amorphous silicone.
  Solar Electric

Solar Index   the ratio of measured solar radiation to an expected number if the sky is clear, with an average clear sky day being 100%
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Solar Noon   the time the sun crosses the meridian of the site, this is the highest point the sun gets in a day. Also referred to as Solar South
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Solar South   see 'Solar Noon'
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

SRCC   Solar Rating and Certification Committee. Organization that rates collector and system performance.
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Stagnation   in a closed loop glycol system, when the pump does not operate as intended and fluid sits in the collectors under full sunshine. The fluid may be damaged from extreme high temperatures and a pressure relief valve may open.
  Solar Domestic Hot Water

Standard Test Conditions (STC)   conditions under which a module is tested in a laboratory; each manufacturer has slightly different STC's, but most center around the following criteria: 25 degrees Celsius, 1.5 atmospheres of air pressure and 1000-watts per square meter of light energy.
  Solar Electric

Standby Heat Loss   heat lost through storage and piping, even when not hot water is used
  Solar Domestic Hot Water  Solar Pool Heat

Thermistor   an electric device which changes its resistance based upon temperature
  Solar Domestic Hot Water  Solar Pool Heat

Thermosyphon   a process which makes water circulate automatically from a warm collector or heat exchanger to cooler water above it
  Solar Domestic Hot Water

Tilt Angle   the angle a collector or module surface forms with the horizon
  Solar Domestic Hot Water  Solar Pool Heat  Solar Electric

Volts (V)   the unit that measures electrical force (the force required for one amp to flow through a resistance of one ohm).
  Solar Electric

Watt (W)   the basic unit of electrical power.
  Solar Electric