Energy Emergency and New
Materials
Lei Zhang & Yanli Ding
Energy Use
Household Energy Consumption
Energy Consumption by sector and region
Source: US Energy Information Adminastration
4/13/2015
US Energy Consumption 2008
4/13/2015
Source: US Energy Information Adminastration, 2008
China Energy Consumption 2008
“Coal production ramp up from
645.9 million tons of oil
equivalent in 1999 to 1.552
billion tons in 2009” …… “but
the country was still forced to
increase coal imports by 42% in
order to meet demand”
China Daily
Source: US Energy Information Adminastration, 2008
Fossil Fuel Consumption Climbing
Source: solarnavigator.net
5
Expanding Population
4/13/2015
The Hidden Cost of Fossil Fuels
According to US Energy Information
Adminastration(EIA), “Energy
consumption grows by 53 percent
from 2008 to 2035”
“Oil prices rose in 2010 as a result of
growing demand associated with signs
of economic recovery and a lack of a
sufficient supply response.”
7
Greenhouse
4/13/2015
Source: US Energy Information Adminastration
More than CO2..
Air pollutant effects
• Particulates
PM10 particles: particles of 10 micrometers or
less, cause heart disease, lung cancer, asthma,
and respiratory infections.
• Sulfur Dioxide
• Nitrogen Oxides
• Ozone
The Hidden Cost of Fossil Fuels: Pollutants
• Particulates
• Sulfur Dioxide: acid rain damage ecosystems,
historical buildings and materials (corrosion)
• Nitrogen Oxides
• Ozone
4/13/2015
Outdoor air pollution kills 1.3 million each year
4/13/2015
Source: World Health Organization(2010)
Mapping air pollution using corn grown in US
fields
Source: Geophysical Research Letters.(2007)
12
Renewable Energy
Solar
Geothermal
Nuclear Fission
Hydroelectric
Wind
Rhett Allain,Southeastern Louisiana University
Solar Energy
• Energy produced by the sun
• Clean, renewable source of energy
• Harnessed by solar collection methods such as solar
cells
• Converted into usable energy such as electricity
• Consumes no fuel
• Wide power-handling capabilities
• High power-to-weight ratio
• It's time to go solar!
Energy from the Sun is Abundant
Source: http://www.ez2c.de/ml/solar_land_area/
• kdlai
Solar cells would need to cover an area comparable to the size of Texas to meet US
energy demand today
How does solar cell work?
• It's time to go solar!
Solar Energy Spectrum
Power reaching earth 1.37 KW/m2
Absorption of Light
• Electrons can
jump between
“bands”
• Incident light
with energy ≥
than the “band
gap” energy can
be used to
excite the
electrons
http://www.3dchem.com/molecules.asp?ID=135#
Crystalline Silicon
• monocrystalline
silicon (c-Si):
• polycrystalline silicon,
or multicrystalline
silicon, (poly-Si or
mc-Si)
• ribbon silicon
Polycrystalline silicon wafer
• Light with energy greater
than the band gap energy of
Si is absorbed
• Energy is given to an
electron in the crystal lattice
• The energy excites the
electron; it is free to move
• A positive “hole”
is left in the electron’s place
• This separation of electrons
and holes creates a voltage
and a current
Source: http://nanosense.org/activities/cleanenergy/solarcellanimation.html
• Expensive
– Made in high vacuum at high heat
– High manufacturing costs
• Need TLC
– Fragile, rigid, thick
• Long return on investment
– Takes 4 years to produce energy savings
equivalent to cost of production
Thin Films
• Produced from cheaper polycrystalline
materials and glass
• High optical absorption coefficients
• Bandgap suited to solar spectrum
CdTe/CdS Solar Cell
• CdTe: Bandgap 1.5 eV; Absorption coefficient 10 times that
of Si
• CdS: Bandgap 2.5 eV; Acts as window layer
• Limitation: Poor contact quality with p-CdTe (~ 0.1 Wcm2)
Dye-Sensitized Solar Cells
• Light with high enough energy
excites electrons in dye
molecules
• Excited electrons infused into
semiconducting TiO2,
transported out of cell
• Positive “holes” left in dye
molecules
• Separation of excited electrons
and “holes” creates a voltage
Source: http://nanosense.org/activities/cleanenergy/solarcellanimation.html
• Relatively inexpensive
– Made in non-vacuum setting mainly at room
temperature
– Relatively simple manufacturing process
• Need little TLC
– Thin, lightweight, flexible
• Short return on investment
– Takes approx 3 months to produce energy savings
equivalent to cost of production