Intro to Solar Energy
UCSD
Many slides courtesy of Prof. Tom Murphy
Lecture 9
Spring 2008
UCSD
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Intro to Solar Energy
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above the atmosphere
at ground level
O2
H2O
Atmospheric absorption
H2O
H2O,CO2
H2O, CO2
much room for improvement/growth, but going backwards!
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ranges in W/m2:
< 138
138–162
162–185
185–208
208–231
> 231
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divide by 24 hr to get average kW/m2
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Solar Land Area Requirements
6 Boxes at 3.3 TW Each
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Question
Question
How was the midterm?
Green houses get hotter than the outside air because A. About right
B. Too hard
C.  Too long
D.  Too short or too easy
E. I won't know until I get my score!
A. Glass is transparent to IR allowing the heat energy in
B. Glass is transparent to visible light but opaque to IR
C. The glass prevents wind from carrying away the heated air
D. Glass amplifies the solar energy
E. Both B. and C. 21
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Question
Does the Sun provide enough energy to meet all current
human needs? A. Yes
B. Eventually yes, but current technology is not available
C.  Maybe yes, if humans can reduce their need for energy
D.  No, current human use is more than the Sun provides
E.  It is not clear at the present time
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Power Tower in Barstow, CA
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photon of light
electric field
n-type silicon
electric field
n-type silicon
p-type silicon
p-type silicon
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liberated electron
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current flow
external load
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0.58
+0.58 +0.58 +0.58 +0.58 +0.58
3.5 volts
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Question
The energy from the Sun is 100% used in which of the
following?
A. Silicon photovoltaic solar cells
B. Photosynthesis
C. Passive solar space heating
D. Flat plate solar thermal water heating
E. Non of the above
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Question
In planning a rooftop solar system, how many watts per
square meter should you use? A. About 1386 W/m2
B. About 1/2 of 1386 W/m2
C. About 500 W/m2
D. About 171 W/m2
E. None of the above
flat arrangement
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tilted arrangement
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based on clear, sunny days
overall winner
Lecture 9
better in
summer
good in
winter
2nd place
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