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Glossary of Solar Radiation Resource Terms |
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Other relevant glossaries
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Parabololic Collector Trough -
a system that tracks the path of the sun by pivoting on one axis (typically East-West or
North-South), using shiny parabolic troughs to heat the collector fluid that passes through
a tube at the focus. Below is an illustration from the
Solar Radiation Data Manual for Flat Plate and Concentrating
Collectors .
Passive Solar -
technology for using sunlight to light and heat buildings directly, with no circulating fluid or
energy conversion system.
Peak Watt -
the maximum amount of
power produced or demanded in a time interval, measured in
watts.
Percent Possible Sunshine -
the ratio of measured
bright sunshine
to the total possible bright sunshine in a given time period such as an hour or a day,
expressed as a percent.
Photoelectric -
pertaining to the conversion of
light (radiant energy) to electricity.
Photometer -
an instrument that measures illuminance.
Photon -
the fundamental particle or quantum of
electromagnetic radiation (radiant energy).
Photovoltaic -
technology for converting sunlight directly into electricity, usually with
photovoltaic cells.
Photovoltaic Cell -
a single semiconducting element of small size (for example, 1 cm2) that absorbs
light or other bands of the
electromagnetic spectrum and emits electricity.
Photovoltaic Module -
a unit comprised of several photovoltaic cells
that is the principal unit of photovoltaic array.
A photovoltaic module's size is on the order of 1 m2, although its size is governed
by convenience and application.
Photovoltaic Array -
a photovoltaic module
or set of modules used for converting
solar radiation to energy.
PMOD/WRC -
the Physikalisch-Meteorologisches Observatorium Davos /
World Radiation Center, at Davos, Switzerland. PMOD/WRC determines and maintains world-wide
standards for measurement of solar radiation,
including the World Radiometric Reference (WRR),
for the World Meteorological Organization.
Point-focusing Concentrator -
a solar power generator which uses a series of tracking mirrors
(heliostats), Fresnel lenses, or a
paraboloid (3-dimensional parabola, or dish) of
mirrors to focus solar energy onto a single central receiver such as a boiler,
engine, or photovoltaic array.
Polarimeter -
An instrument for determining the amount of polarization of light.
Ordinary light from the sun or a lamp is composed of disorderly waves that
vibrate in all directions perpendicular to the light beam. But polarized
light consists of orderly waves that vibrate in only one direction.
Power -
the amount of work or energy expended in a given amount of time.
For example, the watt is a unit of power, which is defined as a
joule per second.
Precipitable Water -
the amount of water in a vertical column of atmosphere. The unit of measure is typically the depth
to which the water would fill the vertical column if it were condensed to a liquid. For example,
6 centimeters of precipitable water (in the absence of clouds) indicates a very moist atmosphere.
Precipitable water is often used as a synonym for
water vapor.
PSP -
precision spectral pyranometer, a pyranometer
with an outer clear dome that can be replaced by colored domes that transmit specific bandwidths
of the solar spectrum. The PSP is a specific instrument of
Eppley Laboratory, Inc. Below is a picture of a PSP.
Pyranometer -
an instrument with a hemispherical field of view, used for measuring total or global solar radiation,
specifically global horizontal radiation;
a pyranometer with a shadow band or shading disk blocking the direct beam measures
the diffuse sky radiation,
as is illustrated in the picture below. A picture
of the Eppley PSP pyranometer is included in the PSP definition
above.
Pyrheliometer -
instrument with a narrow (
circumsolar) field of view
which measures direct normal irradiance.
Pyrheliometers are mounted on sun-following trackers so that the instrument is always aimed
at the sun. Below is a picture of two (silver) pyrheliometers mounted on a (white) tracker.
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