Basic Science and Modeling of Solar Energy

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Basic Science and ModelingofSolar Energy
by Jeremy Parra and Sandrio Elim
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Topics

• Science of Solar Energy
• Technology Using Solar Energy

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Science of Solar Energy

• Resources
• Energy Flows
• Chemistry and Physics background

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The pp-chain (proton-proton chain) involves a
series of nuclear reactions that are responsible
for the generation of energy in the sun. The
basis for the suns energy is that four hydrogen
atoms fuse to form one helium atom whose mass is
slightly less than the mass of the combined four
hydrogen atoms. The missing mass is what was
converted to energy.     In the pp-chain, two
protons (moving at very fast velocities) fuse
together to create deuterium. A neutrino and a
positron are expelled in the process. Deuterium
(one proton and one neutron) fuse with one more
proton creating Helium-3. A photon is released in
this process and this is what gives the sun it's
energy. After Helium-3 is created, it fuses with
another of its type and 2 hydrogen atoms are
expelled. The result is one atom of Helium-4 and
2 atoms of Hydrogen to start the process all over
again. Even though the photons are accountable
for most of the sun's energy, about 5 of the
energy is given off in neutrinos. -bib. 1
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Solar fusion
Fig. 1 (copied ,bib.1)
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Hydrogen
Hydrogen(one proton)
electron
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Deuterium
neutrino
positron
Deuterium(one proton one neutron)
2
electron
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Helium
?
photon
Helium(two protons one neutron)
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Yield
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Sun Light
 
 
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Photon

• If when a photon strikes an electron it has the
  amount of energy to break the electron-electron
  bond( band gap) a free electron will result.
• This results in a positive hole and a negative
  electron.

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Photon
Free electron
Hole
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Semiconductors

• A semiconductor has electrical conductivity
  greater that insulators but less than good
  conductors.
• Silicon has four valence electrons.
• Pure silicon is in a perfect state of valence(has
  no free electrons).

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Si
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Silicon
electrons
nucleus
hole
Free electron
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Semiconductors

• When phosphorous is substituted for a silicon
  atom, there is one electron left
• The remaining electron is very loosely bound by
  the slightly more positive charge of the nucleus
  of the phosphorous atom.
• This electron travels easily around the
  phosphorous atom.
• Silicon that contains a large number of atoms
  with an extra valence electron is called n type
  silicon (n is for negative).

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N-Type
Extra Electron
Si
Si
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Semiconductors

• If a boron atom is substituted for a silicon
  atom, there is one valence electron which has no
  partner.
• This missing electron is a hole.
• This yields a positive charge (the absence of an
  negative electron).
• This is a p-type

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P-Type
Hole
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• The binding force of electron pairs is much
  stronger than the electromagnetic force between
  an electron and the nucleus
•  The extra electron moves from the n-type to the
  p-type
• And these electrons form valence pairs with the
  electrons that were missing a pair
• This results in a shift in charge that creates an
  electric field in the material.
• Now the n-side(doped with phosphorus) gains a
  positive charge.
• When the electron moved it left a proton
• Similarly, the boron atom is surrounded by one
  more electron than there are positive protons in
  the boron nucleus.

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Electric Field

• The n-type side doped with Phosphorus easily
  lends its free electron to the positive side
  (doped with boron).
• This leaves the n-type with one more proton than
  electron giving the n-type a positive charge.
• And the p-type now has one more electron the
  proton yielding a negative charge.
• This creates an electric field. With out this
  electric field the freed electron(freed by a
  photon) would just return to the same hole.
• But because of the electric field the freed
  electron will move from the negative area to the
  positive area creating an electric current. And
  the holes will move in the other direction.

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Technology Using Solar Energy

• Types of cells
• Crystalline Silicon
• a. Single crystal
• b. Multi-crystalline
• c. Ribbon
• d. Film
• Thin films materials
• a. Amorphous Silicon
• b. Cadmium Telluride
• c. Copper Indium Diselenide
• 3. Concentrators
• Components
• PV
• DC-AC Converter
• Backup Power Generator
• Stabilizer
• Electrical Panel

SourceDOE/GO-10097-377 FS 231 - March 1997
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Types of PV Cells

• Monocrystalline Silicon Cells
• Multicrystalline Silicone Cells
• Thick-film Silicon
• Amorphous Silicon
• Other thin films
• Cadmium telluride
• Copper indium diselenide
• Gallium arsenide
• Tandem cells

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1. Monocrystalline Silicon

• Most efficient PV tech
• Complicated process
• High Cost to manufacture

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2. Multicrystalline Silicon

• Cheaper
• Simpler process
• Less efficiency
• Granular texture

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3. Thick-film Silicon

• Continuous process
• Fine grained
• Bounded to aluminum frame

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4. Amorphous Silicon

• A thin homogenous layer
• More effective in absorbing lights
• Also known as thin film PV
• Efficiency about 6

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5. Other Thin Films

• a. Cadmium telluride and Copper indium diselenide
• Still in research
• Very inexpensive process
• Expected efficiency quite high
• b. Gallium arsenide
• High efficiency
• Relatively temperature independent
• For special purpose only
• c. Tandem cells
• Made of two different cells
• Usually from silicon and gallium arsenide
• Better use of incoming light

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Manufacturing
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How It Works
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Math Modeling
1. Optimal Conditions a. Equations b.
Independent Variables 2. Method of Data
Collection a. Software b. Units
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Bibliography

• 1) http//cosmos.colorado.edu/hairgrov/Sun's_Ener
  gy_Generation
• 2) http//www.wikipedia.org/wiki/Deuterium
• 3) http//pearl1.lanl.gov/periodic/elements/1.html
  
• http//www.nobel.se/chemistry/laureates/2000/publi
  c.html
• http//www.scolar.org.uk/html/pdf-page.html
• http//sol.crest.org/renewables/re-kiosk/solar/pv/
  theory/index.shtml
• http//www.fsec.ucf.edu/pvt/pvbasics/
• http//www.ips-solar.com/basics/solarbasics.htm
• http//acre.murdoch.edu.au/refiles/pv/text.html