Solar Energy
Raymond F. Carl
1
History of Solar Energy
 Types of Solar Energy Technologies
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 Passive
 Concentration
 Photovoltaic
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Photovoltaic Cell (Solar Cells)
 Materials
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
and Efficiency
Inorganic
Organic
 Concerns
about risks of toxic materials in PV Cells
2
The History of Solar Energy
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Greeks used passive solar to heat Buildings (400 BC)
Romans improved by using glass to trap heat in the
buildings and green houses (100 AD)
1700: Antoine LaVoisier built a solar heater
1839: French physicist Antoine-Cesar Becquerel
observed that shining light on an electrode submerged
in a conductive solution would create an electric
current.
1860: The First Solar Motor, heated water used to
drive a steam motor, Auguste Mouchout
1883: American Charles Fritts described the first solar
cells, which was made from selenium wafers
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The History of Solar Energy
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1900: The photoelectric effect was discovered.
1904: Henry E. Willsie first use of solar energy at night.
1916: Millikan provided experimental proof of the
photoelectric effect
1918: Polish scientist Czochralski developed a way to grow
single-crystal silicon.
1941: American Russell Ohl invented a silicon solar cell
1954: Bell Labs researchers Pearson, Chapin, and Fuller
reported their discovery of 4.5% efficient silicon solar cells
1950’s: Solar cells developed for satellites
1960: Hoffman Electronics achieved 14% efficient PV cells.
1973: OPEC Energy Crisis causes US to re-examine use of
renewable energy sources; federal and state tax credits result
in rapid growth for a new solar industry.
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Passive
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Direct Solar Gain
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South facing large
windows
Floors, walls, ceiling
used to trap heat. The
heat is released at
night
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Passive
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Indirect Solar Gain
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Thermal storage
materials are placed
between the interior
habitable space and
the sun
Can use vents in wall
to help circulate hot air
through room
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Passive
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Isolated Solar Gain:
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Uses a fluid (liquid or air)
to collect heat in a flat
plate solar collector
attached to the structure.
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Concentration
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Power towers
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Large field of mirriors
is used to concentrate
the sunlight.
Concentrated Sunlight
is used to heat molten
salt
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Concentration
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Trough Collectors
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Uses parabolic mirrors
to heat a fluid in an
absorbing tube.
Hot fluid is used to boil
water to run a steam
generator.
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Photovoltaic Cells (Solar Cells)
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Photoelectric effect
PN junction directly
converts sunlight into
electricity.
Electricity can be stored
for later useage or used
on demand.
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Photovoltaic Cells (Solar Cells)

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Multiple PN junction Cell
has multiple transparent
layers
Top layer absorbs the
high energy light and
passes rest through
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Photovoltaic Cells (Solar Cells)
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Solar Cells transform light
to electricity
Controller regulates were
the charge is directed
Batteries store the energy
Inverter converts from DC
to AC
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Photovoltaic Cells (Solar Cells)
Inorganic Materials

Thick Crystalline Materials
 Crystalline Silicon
 Single-crystal
 Multicrystalline
 Edge-defined
film-fed growth
 Dendritic

Gallium Arsenide (GaAs)
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Photovoltaic Cells (Solar Cells)
Inorganic Materials
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Thin Film Materials
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Amorphous Silicon (a-Si)
Cadmium Telluride (CdTe)
Copper Indium Diselenide (CuInSe2, or CIS)
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Inorganic Materials

Concerns:
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Use of toxic metals like Cadmium
Use of toxic gasses in the manufacturing of
PV, silane, hydrogen selenide
Can the materials be recycled or are they
destined for landfills
15
Inorganic Materials
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Concerns Answered
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Cd is produced as a byproduct of Zn production and can either
be put to beneficial uses or discharged into the environment
CdTe in PV is much safer than other current Cd uses.
CdTe PV uses Cd 2500 times more efficiently than NiCd
batteries
􀂄Occupational health risks are well managed 
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􀂄Absolutely no emissions during PV operation
􀂄Risk from fire emissions is minimal
􀂄Disposal of spent modules is an environmental issue –
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Continuous vigilance is required
Reducing the amount of CdTe will alleviate the problem
Recycling will resolve most environmental concerns
Burning of Coal produces 140 g Cd/GWh in fine dust
Burning of Coal produces 2 g Cd/GWh be emitted from the stack
(for plants with perfectly maintained electrostatic precipitators or
baghouses operating at 98.6% efficiency
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Inorganic Materials
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Concerns Answered
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Manufacturers use gas handling systems to reduce risk, and use
careful engineering and administrative controls to prevent
exposure of workers or the public.
Landfill leaching is a modest concern only, because PV materials
are largely encased in glass or plastic and many are insoluble.
Because of dispersed use, and small amounts of semiconductor
material per cell, PV recycling will be challenging. Machinery for
dismantling modules for recycling has been developed, and
recycling systems for batteries and electronics provide useful
models.
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Photovoltaic Cells (Solar Cells)
Organic Materials
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Pure and chemically
modified fullerenes
polythiophene derivatives
polyphenylene vinylene
18
Organic Materials
 Current obstacles
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All of the PV cells made from Organic molecules
decompose rapidly.
Only 3-6 % conversion of solar energy to electricity
19
Conclusion
Using a combination of Passive solar
energy and photovoltaic cells can lessen
pollution.
 Concerns with use of Cadmium in PV cells
is exaggerated when compared to
electricity produced from coal
 More research is needed and being done
 Cost of Solar system will come down in
price when production increases

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Sources
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http://www.abc.net.au/rn/science/earth/stories/s225110
.htm
http://www.solarenergy.com/info_history.html
http://pvpower.com/pvtechs.html
http://www.adsdyes.com/fullerenes.html
http://www.azsolarcenter.com/design/pas-2.htm
http://www.eere.energy.gov/RE/solar_concentrating.ht
ml
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