Solar Energy Workshop

Alexis Ostrowski and Bright WalkerSponsored 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

Renewable EnergyRenewable sources of energy will never run out.

Wind

Geothermal

Solar

Water

Biomass

WIND

Kineticenergy electricity

e-

WATER

Kineticenergy electricity

e-

BIOFUELS

Chemicalenergy

kineticenergy

GEOTHERMAL

Thermalenergy Electricity

e-

SOLAR

Light energy electricity

e-

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

Lets build a solar car!

Photo by Bright Walker