Pouls, Jazz (Solar Cells)

7/23/2019 Pouls, Jazz (Solar Cells)

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Solar Cells

Jazz Pouls



Why solar cells?

Global Warming Rising Oceans/Melting Ice

Fossil Fuel Dependency

Rising price of gas



What is a solar cell?

A device that absorbs light from the sun and

produces electrical current



History of the Solar Cell

Edmond Becquerel 1839

o Discovers photovoltaic effect

Russell Ohl 1946

o

Patents the modern p-n junction solar cell

Bell Laboratories 1954

o First practical solar cell: 6%



How does a solar cell work?

Photovoltaic Effect

o Photons knock electrons out of atom

o Electrons move upwards throughsemiconductor, then to an external

circuit, thus creating current



n-type dopate: 5 valence electrons

in the Si crystal, free electron

p-type dopate: three valence electrons

in the Si crystal, positively charged “hole”




p-n junction: where the two doped silicons

meet

depletion zone: creates an electric field

within the cell




A solar cell in action

When hit with a photon of sufficient energy, electrons

jump from the valence band to the conduction band. The energy necessary to make this jump in energy is

called the band gap. Semiconductors are perfect for solar cells

because they only conduct when theirelectrons absorb photons from the sun




Electrons in the conduction band leave

behind positively charged “holes” in thecrystal.

Electrons could “recombine” but...




The electric field created by depletion zone

only allows electrons to go upwards.

This creates a diode, due to the p-n

junction.




17:54




front surface contacts

substrate

external circuit



Solar Cell Efficiency

Power of incident light is calculated by:

o Irradiance x Surface Area

Power of incident light

Power of electric current produced



Shockley-Queisser Limit

Major Assumptions: 1 junction, 1 material, unconcentrated sunlight

1.34 eV



Why the limit?

Energy is lost because:

o the sun’s energy is converted to heat

o recombination occurs

o photons pass through the cell

Not to mention: reflection



How to beat the system!

Concentrate the light

Multijunction cells



But unfortunately...

Commercial solar cell/panel efficiencies

range from 10% to 20%



Applications

Solar panels first relevant in space

Power output to Weight ratio is high

Space programs willingly to pay a premium



Applications

Solar panels have become increasingly

attractive for home and business owners as

efficiencies have gone up and prices have

gone down. Solar energy is a low-maintenance

investment for many.



Applications

Although solar cars are not going to be

practical anytime soon, solar energy could

be used to create hydrogen for fuel cell

vehicles.



Applications

Large scale:

o Huge arrays with lots of surface area

o Preferably in flat deserts with little cloud cover

o Sun-tracking devices

o Concentrators/Reflectors



Further Technologies

Thin-Film Solar Cells

Common materials:

o a-Si:H, CdTe, Cu(In,Ga)Se2

Proso Easier to manufacture

o Lower cost

o Less material used

o Often flexible

Cons:

o Lower efficienc




Thin-Film Solar Cells




Transparent Solar Cells

UCLA





Only absorb photons that are invisible tohumans, letting visible light through

MIT





Applications

o Windows

o Cellphones

o Computers

Only 2% efficiencies so far

Lots of room for improvement



Joseph-Louis Lagrange

Lived 1736-1813

(kinda) French mathematician,

astronomer and physicist

Given Legion of Honor byNapoleon

Involved in both the Prussian

and French Academy of

Sciences




Tautochrone curve

Lagrangian points

Lagrangian Mechanicso energy and momentum

o not forces




Number Theory

Algebra

Calculuso Helped create calculus of variations

o Euler-Lagrange equation

o Lagrange error bound



William Rowan Hamilton

Lived 1805-1865

Irish physicist, astronomer and

mathematician



Reformulated classical and

Lagrangian mechanics

Resulted in Hamiltonian Mechanics

o

Hamilton’s principle function Served as base for quantum

mechanics

Optics

o Wave Theory of Light

Quaternions

William Rowan Hamilton where



References

Anthony, Sebastian. "MIT Startup Makes Transparent Solar Panel." ExtremeTech. N.p., 25 Feb. 2013. Web. 18 July 2013.

Hamakawa, Yoshihiro. Thin-film Solar Cells: Next Generation Photovoltaics and Its Applications. Berlin: Springer, 2004. Print.

Hurley, Tracy, and Jane Alba. "Solar Panels." Animation. Sumanas, Inc., 2008. Web. 20 July 2013.

Jha, A. R. Solar Cell Technology and Applications. Boca Raton: Taylor & Francis, 2010. Print.

"MIT Startup Makes Transparent Solar Panel." ExtremeTech. N.p., 25 Feb. 2013. Web. 18 July 2013.

Nelson, Jenny. The Physics of Solar Cells. London: Imperial College, 2003. Print.

Reddy, P. Jayarama. Science & Technology of Photovoltaics. Leiden: CRC Taylor and Francis Group Balkema, 2010. Print.

"Solar Efficiency Limits." Solar Efficiency Limits. Four Peaks Technologies, 2011. Web. 22 July 2013.

Wrenn, Eddie. "Scientists Create Transparent Solar Panels." Mail Online. Daily Mail, 24 July 2012. Web. 18 July 2013.

Würfel, Peter. Physics of Solar Cells: From Basic Principles to Advanced Concepts. Weinheim: Wiley-VCH, 2009. Print.

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