Solar Terminology
What do all those strange words mean?

We put together a list of some of the common terminology used in solar applications.
If you don't see what you are looking for, let us know and we will add it to the list.

Absorber Surface - The surface of the collector plate witch absorbs solar energy and transfers it to the collector plate.

Absorptance - The ratio of the amount of radiation absorbed by a surface to the amount of radiation incident upon it.

Absorptivity - The capacity of a material to absorb radiant energy.

Active Solar System - An assembly of collectors, thermal storage device(s) and transfer media which converts solar energy into thermal energy, and in which energy in addition to solar is used to accomplish the transfer of thermal energy.

Array - More than one collector forming a system

Azimuth Angle (Solar) - The angular direction of the sun with respect to true south.

Collector (Solar Collector) - An assembly of components intended to capture usable solar energy.

Collector Plate - The component of a solar collector that transfers the heat from solar energy to a circulating fluid.

Emissivity - The property of a surface that determines its ability to give off radiant energy.

Emittance - The ratio of the radiant energy emitted by a body to the energy emitted by a black body at the same temperature.

Fixed Collector - A permanently oriented collector that has no collector that has no provisions for seasonal adjustment or tracking of the sun.

Flat Plate Collector - A collector without external concentrators or focusing devices, usually consisting of an absorber plate, cover plate, back and side insulation and a container.

Incident Angle - The angle at which insolation strikes a surface.

Insolation - The total amount of solar energy reaching a surface per unit of time.

Nocturnal Radiation - Loss of energy by radiation to the night sky.

Passive Solar System - An assembly of collectors, thermal storage devices, and transfer media which converts solar energy into thermal energy and in which no energy in addition to solar energy is used to accomplish the transfer of thermal energy. The prime element in a passive solar system is usually some form of thermal capacitance.

Reflected Insolation - The portion of the total solar energy reaching a surface (window, wall, collector) which has been reflected by an adjoining surface.

Retrofit Solar - Altering an existing structure by adding solar equipment or device.

Selective Surface <- A surface with wave length dependent properties.

Shading Loss - The loss of collector efficiency caused by the shading of the absorber plate by collector edges or components. The shading loss usually varies with the angle of incidence of insolation.

Solar Angle - The angular elevation of the sun above the horizon.

Solar Collector - Any device which collects solar energy and transforms it into another usable form of energy.

Tracking Collector - A solar energy collector that constantly positions itself perpendicular to the sun as the earth rotates.



Collector Efficiency Plot (Ti - Ta )/Ht

Ti = Collector inlet Temperature

Ta = Outdoor Ambient Temperature

Ht = Total solar radiation falling on the collector