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Name:
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ELTRY250
Chap 02
Quiz 02 Practice
Solar Radiation
Describe the following terminologies in PV systems
1
Solar
Irradiance
(Solar power)
Intensity of the solar radiation
Expressed in W /m2 or KW / m2
2
Solar
Irradiation
(Solar Energy)
Total amount of solar irradiance on an area over time
Expressed in Wh /m2 or KWh / m2
3
Air mass
Is a representation of the relative distance of atmosphere that
solar radiation must travel through to reach Earth’s surface.
AM = 1.0 (AM1.0), when sun is directly overhead (zenith) at
sea level.
4
Zenith angle
Angle between sun and the zenith (a point in sky directly
overhead a particular location)
5
Peak Sun hour
Number of hours required for a day’s total irradiation to
accumulate at peak sun condition.
i.e. A day with an average irradiance of 600 W /m2 over 8 hr
 Peak sun hour = 600 * 8 / 1000 = 4.8 Hours
6
Pyranometer
A sensor that measures only total (Direct and reflected) solar
irradiance (solar power) in atmosphere.
7
Solar
declination
The angle between equatorial plane and the line joining the
centers of the sun and earth in the ecliptic plane
8
Solar noon
Solar noon is the exact moment when sun crosses a local
meridian and is at its highest position of the day.
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ELTRY250
Chap 02
Quiz 02 Practice
Please Print
Name:
KEY
Solar Radiation
Solar time
A timescale based on apparent motion of the sun crossing a
local meridian.
10
Standard time
A timescale based on apparent motion of the sun crossing a
Standard meridian (Multiple of 15o east or west of the zero
longitude).
11
Solar azimuth
angle
Is the horizontal angle between due south and the sun
-180o to +180o
East of due south is + angle
West of due south is - angle
12
Solar altitude
angle
Is the vertical angle between sun and horizon
0o to 90o
Complements the zenith angle
13
Zenith angle
Angle between sun and zenith (vertical line from location in to
the sky)
14
Sun path chart
Charts showing solar azimuth angle versus solar altitude which
indicated the range of the sun for a given location
15
Solar window
The area of sky between sun paths at summer solstice and
winter solstice for a particular location
16
Array tilt angle
Vertical angle between horizontal and the array surface
9
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Page 2 of 3
Please Print
Name:
KEY
ELTRY250
Chap 02
Quiz 02 Practice
Solar Radiation
17
Array azimuth
angle
The horizontal angle between due south and the direction of the
array surface
18
Incidence angle
The angle between the direction of the direct radiation and a
line exactly perpendicular to the array surface
19
Single-axis
tracking
Sun tracking system that rotates one axis to approximately
follow the position of the sun
20
Dual-axis
tracking
Sun tracking system that rotates two axes independently to
exactly follow the position of the sun
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