EE535: Renewable Energy: Systems, Technology & Economics

EE535: Renewable Energy: Systems, Technology & Economics Session 4: Solar (1): Solar Radiation S Daniels

Annual solar radiation on a horizontal surface at the equator is over 2000kWh/m2 In Northern Europe this falls to about 1000kWh/m2 (per annum) The tilt between the sun and the land reduces the intensity of the midday sun Solar Radiation Energy from the sun in the form of ultra-violet, visible and infra-red electromagnetic radiation is known as solar radiation Ultraviolet 0.20 - 0.39µ Visible 0.39 - 0.78µ Near-Infrared 0.78 - 4.00µ Infrared 4.00 - 100.00µ S Daniels

Flux of solar radiation incident on a surface placed at the top of the atmosphere, depends on time t, geographical location (latitude φ, longitude λ, and on the orientation of the surface Orientation Z P z δ ώ Horizon Equator E(t, Ф, λ) = S(t)cos Ф(t , Ф, λ) S(t) is known as the solar constant δ is the declination of the sun ώ is the hour angle of the sun Ф is the angle between the incident solar flux and the normal to the surface The solar constant is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) (roughly the mean distance from the Sun to the Earth). S Daniels

The sun produces light with a distribution similar to what would be expected from a 5525 K (5250 °C) blackbody, which is approximately the sun's surface temperature Radiation interacts with matter in several ways: Absorption Transmission Scattering Reflection Solar radiation spectrum for direct light at both the top of the Earth’s atmosphere and at sea level http://en.wikipedia.org/wiki/Solar_radiation S Daniels

Solar Quantities • The sun generates approximately 1.1 x 10 E20 kilowatt-hours every second. • The earth’s outer atmosphere intercepts about one two-billionth of the energy generated by the sun, 1.5 x 10 E18 kilowatt-hours per year. • Because of reflection, scattering, and absorption by gases and aerosols in the atmosphere, only 47% of this, (7 x 10 E17 ) kilowatt-hours, reaches the surface of the earth. • In the earth’s atmosphere, solar radiation is received directly (direct radiation) and by diffusion in air, dust, water, etc., contained in the atmosphere (diffuse radiation). The sum of the two is referred to as global radiation.The amount of incident energy per unit area and day depends on a number of factors, e.g.: • Latitude • local climate • season of the year • inclination of the collecting surface in the direction of the sun. • TIME AND SITE • The solar energy varies because of the relative motion of the sun. This variations depend on the time of day and the season. In general, more solar radiation is present during midday than during either the early morning or late afternoon. At midday, the sun is positioned high in the sky and the path of the sun’s rays through the earth’s atmosphere is shortened. Consequently, less solar radiation is scattered or absorbed, and more solar radiation reaches the earth’s surface. • The amounts of solar energy arriving at the earth’s surface vary over the year, from an average of less than 0,8 kWh/m2 per day during winter in the North of Europe to more than 4 kWh/m2 per day during summer in this region. The difference is decreasing for the regions closer to the equator. • The availability of solar energy varies with geographical location of site and is the highest in regions closest to the equator. S Daniels

Solar Absorption and Reflection • When a photon is absorbed, its energy is changed into a different form: electrical or heat • A fraction of the incoming solar radiation is reflected back into space – this is known as the albedo (a0) of the earth-atmosphere system • Annual average of a0 is 0.35 • Reflection from clouds – 0.2 • Reflection on cloudless atmosphere (particles, gases) - 0.1 • Reflection on the earths surface – 0.05 • Radiation absorbed by the Earth’s atmosphere • A0 = E (1-a0) S Daniels

Solar Corrections • Direct normal solar radiation • is the part of sunlight that comes directly from the sun. This would exclude diffuse radiation, such as that which would through on a cloudy day. Indication of the clearness of the sky. • Diffuse sky radiation • is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. • It is also called skylight, diffuse skylight, or sky radiation and is the reason for changes in the colour of the sky. • Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation. • Global Horizontal Radiation • total solar radiation; the sum of direct, diffuse, and ground-reflected radiation; • however, because ground reflected radiation is usually insignificant compared to direct and diffuse, for all practical purposes global radiation is said to be the sum of direct and diffuse radiation only. http://rredc.nrel.gov/solar/pubs/shining/page12_fig.html [Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter (W/m2) per day. In the case of photovoltaics it is commonly measured as kWh/(kWp·y) (kilowatt hours per year per kilowatt peak rating). ] S Daniels

Clouds • Cloudfree (direct beam insolation) and cloudy periods (prevailing diffuse radiation) average to a mean irradiance • For the assessment of solar power plant sites, short interval recordings of sunshine, direct and diffuse radiation are required • Clouds can be classified by their optical depth • 2 > dci (1) > 0.2 > dci (2) > 0.02 > dci (3) > 0 • Cloud Free Line Of Sight Probabilities (CFLOS) are available (World Atlas) • indicates for a given time and location to what percentage the sky is cloudfree S Daniels

European Irradiation S Daniels The European Commission's Joint Research Centre, Institute for Environment and Sustainability

Typical Figures • The intensity of the sunlight that reaches the earth varies with time of the day and year, location, and the weather conditions. The total energy on a daily or annual basis is called irradiation and indicates the strength of the sunshine. Irradiation is expressed in Wh/m² per day or for instance kWh/m² per day. • To simplify calculations with irradiation data solar energy is expressed in equivalents of hour's bright sun light. Bright sun light corresponds with a power of about 1,000 W/m² so one hour of bright sunlight corresponds with an amount of energy of 1 kWh/m². • This is approximately the solar energy when the sun shines on a cloudless day in the summer on a surface of one square meter perpendicular to the sun. • The optimum orientation and inclination angle will vary from site – to – site • On-site measurements essential • Ideally you want the cell oriented at 90 to the sun at all times S Daniels

Solar Panels • A solar panel produces electricity even when there is no direct sunlight. So even with cloudy skies a solar energy system will produce electricity (see How does it work). The best conditions, however, are bright sunlight and the solar panel facing towards the sun. To benefit most of the direct sunlight a solar panel has to be oriented as best as possible towards the sun. For places on the Northern Hemisphere this is south, for countries on the Southern Hemisphere this is north. • In practice, the solar panels should therefore be positioned at an angle to the horizontal plane (tilted). Near the equator the solar panel should be placed slightly tilted (almost horizontal) to allow rain to wash away the dust. • A small deviation of these orientations has not a significant influence on the electricity production because during the day the sun moves along the sky from east to west. S Daniels

Declination Angle d S Daniels

Solar Panel Tilt Angle • The sun moves across the sky from east to west. Solar panels are most effective when they are positioned facing the sun at a perpendicular angle at noon. • Solar panels are usually placed on a roof or a frame and have a fixed position and cannot follow the movement of the sun along the sky. Therefore they will not face the sun with an optimal (90 degrees) angle all day. The angle between the horizontal plane and the solar panel is called the tilt angle. • Due to motion of the earth round the sun there are also seasonal variations. In the winter the sun will not reach the same angle as in summer. Ideally, in the summer solar panels should be placed somewhat more horizontal, to benefit most from the sun high in the sky. However these panels will then not be placed optimally for the winter sun. S Daniels

Useful Solar Power • Solar Thermal – direct heating of buildings and water • Solar Photovoltaic – direct generation of electricity • Solar Biomass – using trees, bacteria, algae, corn, soy beans, or oilseed to make energy fuels, chemicals, or building materials • Food – feeding plants, humans, and other animals S Daniels

Global Averages • The average annual global radiation impinging on a horizontal surface which amounts to approx. • 1000 kWh/m2 in Central Europe, Central Asia, and Canada reach approx. • 1700 kWh/m2 in the Mediterannian. • 2200 kWh/m2 in most equatorial regions in African, Oriental, and Australian desert areas. • In general, seasonal and geographical differences in irradiation are considerable and must be taken into account for all solar energy applications. S Daniels

Pemodelan Radiasi Matahari ME4132 - Energi Angin & Matahari

Data dan Software • Data Klimatologi • Profil Atmosfer • Tabel Efisiensi Solar Sel dan Grafik Tanggapan Spektral • Model SMARTS v2.9.5 • Surfer ME4132 - Energi Angin & Matahari

Efisiensi Semikonduktor dalam Solar Cell Efisiensi Semikonduktor Tabel Efisiensi Semikonduktor (Sumber : Green, 2006)

Interface SMARTS Model ME4132 - Energi Angin & Matahari

Input S Daniels

S Daniels

Grafik Tanggapan Spektral (sumber: Field, 1997) Setiap jenis semikonduktor memiliki spectral response yang berbeda-beda.

Desember W/m2 Hasil : Peta Spasial Rata-rata Bulanan Daya Radiasi Matahari (th. 1988-2002) Hasil Estimasi Model SMARTS

Hasil Perhitungan Daya Listrik untuk Solar Sel Jenis GaInP

EE535: Renewable Energy: Systems, Technology & Economics