EE535: Renewable Energy: Systems, Technology

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EE535 Renewable Energy Systems, Technology
Economics

• Session 4 Solar (1) Solar Radiation

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Solar Radiation
Energy from the sun in the form of ultra-violet,
visible and infra-red electromagnetic radiation
is known as solar radiation

• 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

Ultraviolet 0.20 - 0.39µ Visible 0.39 -
0.78µ Near-Infrared 0.78 - 4.00µ Infrared 4.00 -
100.00µ
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Orientation
Z
P
z
d
?

• Flux of solar radiation incident on a surface
  placed at the top of the atmosphere, depends on
  time t, geographical location (latitude f,
  longitude ?, and on the orientation of the surface

Horizon
Equator
E(t, ?, ?) S(t)cos ?(t , ?, ?) S(t) is known
as the solar constant
d is the declination of the sun ? is the hour
angle of the sun ? 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).
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Solar radiation spectrum for direct light at both
the top of the Earths atmosphere and at sea
level

• 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

http//en.wikipedia.org/wiki/Solar_radiation
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Solar Quantities

• The sun generates approximately 1.1 x 10 E20
  kilowatt-hours every second.
• The earths 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 earths 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 suns rays through
  the earths atmosphere is shortened.
  Consequently, less solar radiation is scattered
  or absorbed, and more solar radiation reaches the
  earths surface.
• The amounts of solar energy arriving at the
  earths 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.

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Solar Absorption and Reflection
Direct Solar Radiation Solar radiation at normal incidence in the direct beam from the sun
Diffuse Solar Radiation Scattered radiation on a horizontal surface
Global Solar Radiation Sum of the direct beam plus the diffuse component on a horizontal surface
Infra-red Radiation Terrestrial infra-red radiation emitted by the sky on the Earth's surface
Net Radiation balance Combined downward solar radiation and sky infra-red minus upward reflected solar and terrestrial radiation
Turbidity Measure of the amount of scattering in the atmosphere

• 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 Earths atmosphere
• A0 E (1-a0)

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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_fi
g.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/(kWpy) (kilowatt hours per year
per kilowatt peak rating).
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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 gt dci (1) gt 0.2 gt dci (2) gt 0.02 gt dci (3) gt 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

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

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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.

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Declination Angle
d
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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.

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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

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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.

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Pemodelan Radiasi Matahari
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Data dan Software

• Data Klimatologi
• Profil Atmosfer
• Tabel Efisiensi Solar Sel dan Grafik Tanggapan
  Spektral
• Model SMARTS v2.9.5
• Surfer

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Efisiensi Semikonduktor

• Efisiensi Semikonduktor dalam Solar Cell

Semikonduktor Efisiensi () Tempat Pengujian
GaInP a-Si CdTe GaAs InP multi-Si Mono-Si ZnO/CIGS 31.3 1.5 12.1 0.7 16.5 0.5 27.6 1.0 24.3 1.2 20.3 0.5 24.7 0.5 18.4 0.5 NREL (1/03) NREL (10/96) NREL (4/00) Sandia (5/91) NREL (2/91) NREL(5/04) Sandia (3/99) NREL (2/01)
Tabel Efisiensi Semikonduktor (Sumber Green,
2006)
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Interface SMARTS Model
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Input
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Grafik Tanggapan Spektral
(sumber Field, 1997)
Setiap jenis semikonduktor memiliki spectral
response yang berbeda-beda.
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Hasil Peta Spasial Rata-rata Bulanan Daya
Radiasi Matahari (th. 1988-2002) Hasil Estimasi
Model SMARTS
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Hasil Perhitungan Daya Listrik untuk Solar Sel
Jenis GaInP