1. Solar Radiation Characteristics
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Solar Radiation Characteristics
المــــركــز الوطنــــــي لبحــــــوث الطـــاقــــــة
National Energy Research Center

2. Solar Radiation Characteristics
Eng. Firas Alawneh
Head of Photovoltaics (PV) Division
National Energy Research Center (NERC)
Royal Scientific Society (RSS)
Amman-Jordan

3. Solar Radiation Solar radiation as a fuel for solar cells
Why do we need Solar Radiation Data?
How do we use Solar Radiation Data for Renewable Energies?
Solar Radiation Concepts
The Sun
Extraterrestrial solar radiation (radiation outside Earth’s atmosphere)
Terrestrial solar radiation (radiation inside Earth’s atmosphere)
Solar radiation at the Earth’s surface
Solar Radiation Measurements
Global Horizontal Irradiance (GHI)
Direct Normal Irradiance (DNI)
Diffused Horizontal Irradiance (DHI)
Solar Radiation Potential Assessment
Analysis of Solar Irradiance Data Sets (A case study for Jordan)
Averages and Sums of Solar Radiation (Hourly, daily, monthly and yearly)

4. Fuel of Solar Cells + - intermittent Solar Cell Solar Radiation
Electrical Power (Type: DC)
Sun Rays
Power (W) = Voltage (V) x Current (A)
[W/m2]
voltage
current
Incident Solar Irradiance (Instantaneous Power Density)
200
1000 + -
Solar Radiation
intermittent
Solar cells are rated at 1000 W/m2

5. Standard Solar Day on a Horizontal Surface (Clear sky without clouds)
Time of day
Sunrise
Sunset
Noon
Solar Irradiance (W/m2)
Sunshine Duration Hours
Area Under the Curve = Daily Total Solar Radiation in kWh/m2/day

6. Annual Global Solar Radiation (kWh/m2.a) in the World

7. Why Do We Need Solar Radiation Data?
• Agriculture Photosynthesis
• Astronomy Solar Output Variation
• Atmospheric Science Numerical Weather Prediction
• Climate Change Energy Balance
• Health UV effects on skin
• Hydrology Evaporation
• Materials Degradation
• Oceanography Energy Balance
• Photobiology Light and Life
• Renewable Energy Sustainability

8. How Do We Use Solar Radiation Data for Renewable Energies?
• Technology Selection
• Site Selection
• System Design
• Performance Monitoring

9. Solar Radiation Concepts
The Sun
Extraterrestrial solar radiation
(radiation outside Earth’s atmosphere)
Terrestrial solar radiation
(radiation inside Earth’s atmosphere)
Solar radiation at the Earth’s surface

10. The Sun
The sun is a hot sphere of gas whose internal temperatures reach over 20 million degrees Kelvin due to nuclear fusion reactions at the sun's core which convert hydrogen to helium.
The total power emitted by the sun is calculated by multiplying the emitted power density by the surface area of the sun which gives 9.5 x 1025 W.

11. Sun is ultimately the source of all usable energies
Non-RES
Sun is ultimately the source of
all usable energies
RES
indirect
direct
RES
RES
RES
RES

12. Solar Electromagnetic Spectrum
The light that we see everyday is only a fraction of the total energy emitted by the sun incident on the earth. Sunlight is a form of "electromagnetic radiation" and the visible light that we see is a small subset of the electromagnetic spectrum (response band of solar cells)

13. Solar Radiation in Space
The solar radiation outside the earth's atmosphere is calculated using the radiant power density at the sun's surface (5.961 x 107 W/m2), the radius of the sun and the distance between the earth and the sun. The calculated solar irradiance at the Earth's atmosphere is about 1.36 kW/m2.

14. Solar Spectrum / Air Mass
Solar cells are rated at 1.5 AM

15. E = hc /λ λ
Theoretical PV Efficiency Limit

16. What Influences the Amount of Solar Radiation?
• Solar output 11 year solar cycle
• Earth-Sun distance % annual variation
• Clouds Dominant factor
• Water vapor Selective absorber
• Air pollution % less direct
• Smoke from forest fires Natural or man-made
• Volcanic ash Global effect for years
• Location
• Time of day Solar position
• Season

17. Solar Radiation at the Earth’s Surface
Sunlight reaching the ground must first pass through the earth’s atmosphere. It reaches the outer atmosphere at an average rate of 1,366.1 W/m2, on a plane perpendicular to the path from the sun. On clear days, the majority of solar energy reaching the earth comes on a path directly from the sun. The intensity of the sun’s power on the earth’s surface is reduced to 800 to 1,100 W/m2, depending on the clearness of the atmosphere and the altitude of the location. (At high altitudes, there are reduced atmospheric gases to scatter and absorb solar radiation).

18. Atmospheric Effects

19. Seasons Variation

20. Sun Paths at Different Locations on Earth

21. Sun Position

22. Sun Path Diagrams

23. Shading Analysis to Check Solar Access
manual
Solar Pathfinder
Automatic
Solmetric SunEye

24. Monthly Solar Access Averages

25. Solar Radiation Measurements on a Horizontal Surface
Global Horizontal Irradiance (GHI)
Direct Normal Irradiance (DNI)
Diffused Horizontal Irradiance (DHI)

26. Solar Radiation Measurements
Global Horizontal Irradiance (GHI) - [W/m2]
Direct Normal Irradiance (DNI) - [W/m2]
Diffused Horizontal Irradiance (DHI)- [W/m2]

27. Pyranometer
It is not hard to measure energy from the sun at Earth's surface.
Pyranometers are designed specifically for this purpose.
The name pyranometer stems from Greek, "pyr" meaning "fire" and "ano" meaning "sky“.

28. GHI, DNI and DHI Relationship
Global Horizontal (GHI) = Direct Normal (DNI) X cos(θ) + Diffuse Horizontal (DHI)
Horizontal Plane
Zenith θ
DNI
GHI
DHI

29. What are Solar Radiation Measurements?
DNI
Measured by a
Pyrheliometer on a
sun-following
tracker
GHI
Measured by a
Pyranometer with a
horizontal sensor
DHI
Measured by a
shaded Pyranometer
under a tracking ball or
an adjustable ring

30. Clear Sky
Time

31. Partly Cloudy Sky
Time

32. Solar Radiation on Arbitrary Tilted and Oriented Surfaces
Global = Direct + Diffuse + Albedo
Albedo is known as surface reflectivity of sun’s radiation. The term has its origins from a Latin word albus, meaning “white”. It is quantified as the proportion, or percentage of solar radiation of all wavelengths reflected by a body or surface to the amount incident upon it. An ideal white body has an albedo of 100% and an ideal black body, 0%. The typical amounts of solar radiation reflected from various objects are shown in the table shown right.

33. Thank You!