Bài giảng Green energy course syllabus - Chapter 4: Solar resource - PV materials - Nguyễn Hữu Phúc
Green Energy Course-
Renewable Energy Systems
Biên sọan: Nguyễn Hữu Phúc
Khoa Điện- Điện Tử- Đại Học Bách Khoa TPHCM
The Solar Resource
• Before we can talk about solar power, we need to talk
about the sun
• Need to know how much sunlight is available
• Can predict where the sun is at any time
• Insolation : incident solar radiation
• Want to determine the average daily insolation at a site
• Want to be able to chose effective locations and panel
tilts of solar panels
The Sun and Blackbody Radiation
• The sun
– 1.4 million km in diameter
– 3.8 x 1020 MW of radiated electromagnetic energy
• Blackbodies
– Both a perfect emitter and a perfect absorber
– Perfect emitter – radiates more energy per unit of surface area
than a real object of the same temperature
– Perfect absorber – absorbs all radiation, none is reflected
The Solar Resource
• Before we can talk about solar power, we need to talk
about the sun
• Need to know how much sunlight is available
• Can predict where the sun is at any time
• Insolation : incident solar radiation
• Want to determine the average daily insolation at a site
• Want to be able to chose effective locations and panel
tilts of solar panels
Plank’s Law
• Plank’s law – wavelengths emitted by a blackbody
depend on temperature
3.74108
E
(7.1)
14400
5 exp
1
T
• λ = wavelength (μm)
• Eλ = emissive power per unit area of blackbody
(W/m2-μm)
• T = absolute temperature (K)
Electromagnetic Spectrum
Visible light has a wavelength of between 0.4 and 0.7 μm, with
ultraviolet values immediately shorter, and infrared immediately longer
Source: en.wikipedia.org/wiki/Electromagnetic_radiation
288 K Blackbody Spectrum
The earth as a blackbody
Figure 7.1
Area under curve is the total radiant power emitted
Stefan-Boltzmann Law
• Total radiant power emitted is given by the Stefan –
Boltzman law of radiation
E AT 4
(7.2)
• E = total blackbody emission rate (W)
• σ = Stefan-Boltzmann constant = 5.67x10-8 W/m2-K4
• T = absolute temperature (K)
• A = surface area of blackbody (m2)
Wien’s Displacement Rule
• The wavelength at which the emissive power per unit
area reaches its maximum point
2898
max
(7.3)
T
• T = absolute temperature (K)
• λ = wavelength (μm)
• λmax =0.5 μm for the sun , T = 5800 K
• λmax = 10.1 μm for the earth (as a blackbody), T = 288 K
Extraterrestrial Solar Spectrum
Figure 7.2
Air Mass Ratio
As sunlight passes through the
atmosphere, less energy arrives at the
earth’s surface
Figure 7.3
• h1 = path length through atmosphere with sun directly
overhead
• h2 = path length through atmosphere to spot on surface
• β = altitude angle of the sun
Air Mass Ratio
h2 1
air mass ratio m =
h sin
(7.4)
1
Figure 7.3
• Air mass ratio of 1 (“AM1”) means sun is directly
overhead
• AM0 means no atmosphere
• AM1.5 is assumed average at the earth’s surface
Solar Spectrum on Surface
M increases
as the sun
appears
lower in
the sky. Notice
there is
a large loss
towards the blue
end for higher m,
which is why the
sun appears
reddish at sun
rise and sun set
ECE 333 (398RES)
Renewable Energy Systems
Lecture 23
The Solar Resource
Professor Tom Overbye
Department of Electrical and
Computer Engineering
Announcements
• Homework 11 is 7.3, 7.14 (use approximation equations
given in book rather than table data), 7.15, 7.17. It is due
on Thursday April 30.
• Reading: Chapters 7 and 8
• Final exam is on Friday May 8 from 8 to 11am. Because
of the class size we have two rooms, 106B8 Eng. Hall and
163 Everitt.
– Last name starting with A through J go to 163, otherwise 106B8.
– Final is comprehensive, with more emphasis on solar (since it
wasn’t on an earlier exam)
– Same procedure except you can bring in one new notesheet and
your two previous notesheets.
Another Projection on How Quickly
Our Resources will Vanish
However New Reserves and Sources
Often Appear: Uranium Example
• Chart shows uranium resources at 59 years at current
production levels.
• In 2006 worldwide production of uranium ore was
about 40,000 tonnes. Economicially viable reserves
now at about 5.5 million tonnes, a value that has
recently increased because of the increase in price.
• There are estimated to be 35 million tonnes than could
eventually be mined economically.
• Uranium can be extracted from sea water giving an
ultimate potential of about 4.6 billion tonnes, enough
for 100,000 years at the current rate of consumption.
Solar Spectrum on Surface
M increases
as the sun
appears
lower in
the sky. Notice
there is
a large loss
towards the blue
end for higher m,
which is why the
sun appears
reddish at sun
rise and sun set
In the News: Solar for Chicago
• On 4/22/09 Exelon announced plans to build a solar
power plant on Chicago’s South Side.
• The $60 million solar power plant will provide a
maximum of about 10MW. Exelon will be relying on
loan guarantees from the US DOE as part of the
economic stimulus plan
• The solar plant will be located in the West Pullman
neighborhood
• Assuming a 25% capacity factor, a zero percent interest
rate, $0.15 electricity, payback time on the plant will be
$60,000,000/(0.15*8760*10,000*0.25) = 18.3 years
The Earth’s Orbit
• One revolution every 365.25 days
• Distance of the earth from the sun
360(n 93)
d 1.5108 10.017sin
km (7.5)
365
• n = day number (Jan. 1 is day 1)
• d (km) varies from 147x106 km on Jan. 2 to 152x106
km on July 3 (closer in winter, further in summer)
• Note that the angles in this chapter are in degrees
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