Energy Emergency and New Materials Lei Zhang & Yanli Ding

9/7/2015 Energy Use Household Energy ConsumptionEnergy Consumption by sector and region Source: US Energy Information Adminastration

9/7/2015 US Energy Consumption 2008 Source: US Energy Information Adminastration, 2008

China Energy Consumption 2008 “Coal production ramp up from million tons of oil equivalent in 1999 to 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

5 Fossil Fuel Consumption Climbing Source: solarnavigator.net

9/7/2015 Expanding Population

7 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.”

9/7/2015 Greenhouse 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

9/7/2015 The Hidden Cost of Fossil Fuels: Pollutants Particulates Sulfur Dioxide: acid rain damage ecosystems, historical buildings and materials (corrosion) Nitrogen Oxides Ozone

9/7/2015 Outdoor air pollution kills 1.3 million each year Source: World Health Organization(2010)

12 Mapping air pollution using corn grown in US fields Source: Geophysical Research Letters.(2007)

Rhett Allain,Southeastern Louisiana University GeothermalSolar Hydroelectric Wind Renewable Energy Nuclear Fission

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:

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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/m 2

Absorption of Light Electrons can jump between “bands” Incident light with energy ≥ than the “band gap” energy can be used to excite the electrons

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:

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  cm 2 )

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:

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