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Solar irradiance Pakistan
1. Solar Resource Assessment
Renewable Energy Course
EEM-405
Institute of Business Management
Karachi
Syed Akhtar Ali-Visiting Professor
CEO-PROPLAN
proplanassociates@gmail.com
2. • Average insolation (kWh/m2/day)
• Amount of electromagnetic energy (solar
radiation) incident on the surface of the earth.
Also referred to as total or global solar
radiation.
• Midday insolation (kWh/m2/day)
• Average insolation available within 1.5 hours
of Local Solar Noon.
3. • Clear sky insolation (kWh/m2/day)
• Average insolation during clear sky days (cloud
amount < 10%).
• Clear sky days (days)
• Number of clear sky days (cloud amount <
10%).
4. PARAMETERS FOR SIZING AND
POINTING OF SOLAR PANELS AND FOR
SOLAR THERMAL APPLICATIONS:
5. • Insolation on horizontal surface (kWh/m2/day)
• Amount of electromagnetic energy (solar radiation)
incident on the surface of the earth. Also referred to as
total or global solar radiation. The average and percent
difference minimum and maximum are given.
• Diffuse radiation on horizontal surface (kWh/m2/day)
• Amount of electromagnetic energy (solar radiation)
incident on the surface of the earth under all-sky conditions
with direct radiation from the Sun's beam blocked by a
shadow band or tracking disk at the Earth's surface.
• Direct normal radiation (kWh/m2/day)
• Amount of electromagnetic energy (solar radiation) at the
Earth's surface on a flat surface perpendicular to the Sun's
beam with surrounding sky radiation blocked.
6. • Insolation at 3-hourly intervals (kW/m2)
• Amount of electromagnetic energy (solar
radiation) incident on the surface of the earth.
• Insolation clearness index (dimensionless)
• Fraction of insolation at the top of the
atmosphere which reaches the surface of the
earth.
• Insolation normalized clearness
index (dimensionless)
• Zenith angle-independent expression of the
insolation clearness index
7. • Clear sky insolation (kWh/m2/day)
• Average insolation during clear sky days (cloud amount
< 10%).
• Clear sky insolation clearness
index (dimensionless)
• Fraction of insolation at the top of the atmosphere
which reaches the surface of the earth during clear sky
days (cloud amount < 10%).
• Clear sky insolation normalized clearness
index (dimensionless)
• Zenith angle-independent expression of the clear sky
insolation clearness index.
•
9. • Solar Noon (GMT time)
• The time when the sun is due south in the
northern hemisphere or due north in the
southern hemisphere.
• Daylight Hours (hours)
• Time between sunrise and sunset.
10. • Daylight average of hourly cosine solar zenith
angles (dimensionless)
• The average cosine of the angle between the sun
and directly overhead during daylight hours.
• Cosine solar zenith angle at mid-time between
sunrise and solar noon (dimensionless)
• Approximate monthy average ratio of horizontal
surface solar beam radiation to direct normal
radiation.
11. • Declination (degrees)
• The angular distance of the sun north (positive) or south
(negative) of the equator.
• Sunset Hour Angle (degrees)
• The angle that the earth has rotated between the time of
solar noon and sunset.
• Maximum solar angle relative to the horizon (degrees)
• The maximum vertical angle of the sun above the horizon.
• Hourly solar angles relative to the horizon (degrees)
• Hourly solar azimuth angles (degrees)
• The arc of the horizon measured clockwise from true north,
to the point where a vertical circle through the sun intersects
the horizon
13. • Radiation on equator-pointed tilted
surfaces (kWh/m2/day)
• Radiation on tilted surfaces is calculated from
the monthly average insolation on a horizontal
surface. Tilt angles are 0, latitude - 15,
latitude, latitude + 15, 90, and the optimum
angle. The optimum angle provides the
monthly averaged maximum radiation.
14. • Minimum radiation for equator-pointed tilted
surfaces (kWh/m2/day)
• Radiation on tilted surfaces is calculated from
the monthly minimum insolation on a
horizontal surface. Tilt angles are 0, latitude -
15, latitude, latitude + 15, 90, and the
optimum angle. The optimum angle provides
the monthly averaged maximum radiation.
15. • Maximum radiation for equator-pointed
tilted surfaces (kWh/m2/day)
• Radiation on tilted surfaces is calculated from
the monthly maximum insolation on a
horizontal surface. Tilt angles are 0, latitude -
15, latitude, latitude + 15, 90, and the
optimum angle. The optimum angle provides
the monthly averaged maximum radiation.
16. Cloud Information:
• Daylight cloud amount (percent)
• Percent of cloud amount during daylight within a
region.
• Cloud amount at 3-hourly intervals (percent)
• Percent of cloud amount within a region.
• Frequency of cloud amount at 3-hourly
intervals (percent)
• Percent of time the cloud amount is less than
10%, between 10 - 70%, and greater than 70%
within a region.
17. Meteorology (Temperature):
• Air Temperature (° C)
• Daily Temperature Range (° C)
• Difference between the average daily maximum and
average daily minimum.
• Cooling Degree Days above 18° C (degree days)
• The monthly accumulation of degrees when the
daily mean temperature is above 18° C.
• Heating Degree Days below 18° C (degree days)
• The monthly accumulation of degrees when the
daily mean temperature
18. Earth Skin Temperature (° C)
• Daily Mean Earth Temperature minimum,
maximum and amplitude (° C)
• Minimum: 22-year average of the minimum daily
mean earth temperature for each month.
• Maximum: 22-year average of the maximum daily
mean earth temperature for each month.
• Amplitude: One half of the difference between the
average daily earth temperature minimum and
maximum.
19. Supporting Information
• Top-of-atmosphere insolation (kWh/m2/day)
• Amount of electromagnetic energy (solar radiation)
incident at the top of the atmosphere.
• Surface Albedo (dimensionless)
• Fraction of insolation reflected by the surface of the
earth