Solar Energy Workshop Alexis Ostrowski and Bright Walker Sponsored by ConvEne-IGERT at UCSB.
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Transcript of Solar Energy Workshop Alexis Ostrowski and Bright Walker Sponsored by ConvEne-IGERT at UCSB.
It’s true: The kinetic energy of planets causes them to orbit the sun.
Energy Makes the World Go Round
Energy Cannot be Created or Destroyed
Energy is constantly changing from one form to another.
Nuclear
Electromagnetic
Thermal
Kinetic
Chemical
How We Use and Control Energy
Nuclear Reactor
Fire
Chemicalenergy
ThermalEnergy
Nuclearenergy
ThermalEnergy
Where Do We Get Energy From?
? ??
Sources: Coal Hydroelectric (Dams)Wind SolarNuclear GasolineNatural Gas
Oil (37%)
Natural Gas (23%)
Coal (25%)
Nuclear (6%)
Biomass (wood, 4%)
Water (dams, 3%)
Other (solar, wind, geothermal, <2%)
Over 85% of our energy comes from fossil fuels
Global Energy Usage
Fossil Fuels and Climate Change
CO2
Greenhouse gasses
1979 2003
• Burning fossil fuels releases CO2 and other greenhouse gasses into the air
• CO2 helps warm up the earth’s atmosphere
• This changes the earth’s weather patterns (polar ice melting)
Polar ice coverage
Fossil Fuels
Fossil fuels are not renewable--it takes millions of years to
form them
Fossil Fuels are made by millions of years of pressure and heat that turns dead plants and animals (fossils) into crude oil and coal
Cost of Renewable Energy
It costs more to produce renewable energy than it does to collect fossil fuels.
We need to research new ways to make renewable energy more affordable!
Silicon solar cells are very expensive to manufacture.
Energy research at UCSB
Light emitting diodes (LEDs)- To produce light using a minimum amount of energy
Solar cells-Direct conversion of sunlight into electricity
Solar CellsDirect conversion of solar energy into electricity!
•Clean•Renewable•Abundant•Easy to use
Lig
ht g
oes in
Semiconductor material
Electricity comes out
Many types:•Inorganic (Silicon)$$$•Organic/Plastic (Bucky balls)
COOL!!
Electrodes
Si
SiH Si
B-
Si
Si
Si SiSi
Si
Si
B-
Si Si Si Si
Si
Si
Si
B-
Si Si
Si
Si
Si
Si Si Si
Si
Si
Si
Si
B-
Si
SiH
Si
Si
Si Si Si
Si Si Si
Si SiSi
Si
Si
Si Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si Si
P+
SiSi
P+
Si
SiH Si Si Si
Si Si
Si P+
Si
Si
Si Si Si
P+
Si
Si Si
Si
Si
Si Si SiH
Inorganic Solar Cells
P doped region, consisting of stationary, negative Boron impurities and mobile positive charges called holes
Intrinsic, undoped region
N doped region, consisting of stationary, positive Phosophorus impurities and mobile negative charges called electrons
This assembly is collectively called a “PIN junction”.
P
I
N
Si
SiH Si
B-
Si
Si
Si SiSi
Si
Si
B-
Si Si Si Si
Si
Si
Si
B-
Si Si
Si
Si
Si
Si Si Si
Si
Si
Si
Si
B-
Si
SiH
Si
Si
Si Si Si
Si Si Si
Si SiSi
Si
Si
Si Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si Si
P+
SiSi
P+
Si
SiH Si Si Si
Si Si
Si P+
Si
Si
Si Si Si
P+
Si
Si Si
Si
Si
Si Si SiH
Inorganic Solar Cells
As soon as the junction is created, some of the mobile holes combine with the mobile electrons.
This leaves behind excess positive and negative charges in the doped regions, creating a strong electric field within the crystal
Elec
tric
Fie
ld
Electrons and holes are free to move around.
Si
SiH Si
B-
Si
Si
Si SiSi
Si
Si
B-
Si Si Si Si
Si
Si
Si
B-
Si Si
Si
Si
Si
Si Si Si
Si
Si
Si
Si
B-
Si
SiH
Si
Si
Si Si Si
Si Si Si
Si SiSi
Si
Si
Si Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si
Si Si
Si
Si
Si Si Si
Si Si Si
P+
SiSi
P+
Si
SiH Si Si Si
Si Si
Si P+
Si
Si
Si Si Si
P+
Si
Si Si
Si
Si
Si Si SiH
Inorganic Solar Cells
Elec
tric
Fie
ld
Anode
Cathode
Electrodes are applied to the PIN junction.
Absorption of light can cause the spontaneous generation of an electron-hole pair.
The elcectric field within the device causes the charges to move in opposite directions. This movement of charges creates a useable current at the anode and cathode.
Plastic Solar Cells
Transparent Electrode
Aluminum
1) Light Absorption
2) Exciton Diffusion
3) Charge Separation
4) Charge Transport
Positive and negative molecules mixed together between electrodes.
-Like a Spaghetti and Meatball Sandwich
Plastic Solar Cells
Apply Electrodes
Plastic solar cells are made out of
materials very similar to ink.
They are very easy to make!
Plastic Solar Cells
Low cost, low energy fabrication!
Large area potential!
Efficiency, stability lower than inorganic solar cellsStill a long way to go before having a big impact on overall energy problems
Nobel Lauriat Prof. Alan Heeger, enjoying his invention
Roll to roll printer
What you can do…
Use less energy
15 kWh/d5 kWh/d
40 kWh/d20 kWh/d
40 kWh/d5 kWh/d
Before: After:What youCan do
Food
Heating
Transportation
Eat vegetarian 6 days/wk
Put on a sweater
Carpool, walk, bike, or take the bus
3 simple things that make a difference
(avg 30 miles/day)
Skate or take a bus to school!
Summary
Solar Energy is a promising source of renewable energyWe need more efficient (and cheaper) solar cellsUCSB researchers are working hard to develop new technologies that solve energy problemsPlastic solar cells are a new technology that are cheaper and easier to make than silicon solar cellsYou can help with the energy problem by using less energyYou can also become a scientist and help discover new solutions to our energy problems