Solar Radiation Characteristics Sponsored by Solar Radiation Characteristics المــــركــز الوطنــــــي لبحــــــوث الطـــاقــــــة National Energy Research Center

Solar Radiation Characteristics Eng. Firas Alawneh Head of Photovoltaics (PV) Division National Energy Research Center (NERC) Royal Scientific Society (RSS) Amman-Jordan firas.alawneh@nerc.gov.jo

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)

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

Standard Solar Day on a Horizontal Surface (Clear sky without clouds) Time of day Sunrise Sunset Noon Solar Irradiance (W/m2) Sunshine Duration Hours 800 - 1100 Area Under the Curve = Daily Total Solar Radiation in kWh/m2/day

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

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

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

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

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.

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

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)

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.

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

E = hc /λ λ Theoretical PV Efficiency Limit

What Influences the Amount of Solar Radiation? • Solar output 11 year solar cycle • Earth-Sun distance 3.5% annual variation • Clouds Dominant factor • Water vapor Selective absorber • Air pollution 40% less direct • Smoke from forest fires Natural or man-made • Volcanic ash Global effect for years • Location • Time of day Solar position • Season

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).

Atmospheric Effects

Seasons Variation

Sun Paths at Different Locations on Earth

Sun Position

Sun Path Diagrams

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

Monthly Solar Access Averages

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

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

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“.

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

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

Clear Sky Time

Partly Cloudy Sky Time

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.

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