MSE 156 - Solar Cells, Fuel Cells and Batteries: Materials for the Energy Solution

Course Information

Instructor: Professor Bruce Clemens 356 McCullough Building 650 725 7455 bmc@stanford.edu

Course Assistant: Vardaan Chawla 210 McCullough Building 650 723 6778 chawla@stanford.edu

Location and Time: 11:00-12:15, Tuesday, Thursday Room 120, Building 60

Grading: Homework 25% Labs 20% Project 20% Midterm 35%

Course Assignments: Homework – four problem sets Labs – two labs with write-up Project - device construction Exams - In-class midterm

Safety Training: Required! Procedure TBA

MSE 156 - Solar Cells, Fuel Cells and Batteries: Materials for the Energy Solution

The energy problem: causes, scope and scale Energy usage Global warming Peak oil Assessing energy resources

Solar Cells Solar spectrum Basic semiconductor physics Electron and hole energy bands p-n junctions

Photovoltaic effect Solar cell operation and characteristics Fill factor Efficiency

Materials issues in solar cells

Emerging solar cell technology

Photovoltaic systems Grid tied versus battery backup

Batteries Basic electrochemistry Thermodynamic concepts Cell potentials Cell reactions and half reactions Hydrogen reference electrode Reaction kinetics

Battery technologies Basic battery construction Lead-acid Alkaline Ni-metal hydride Li ion Li polymer

Battery lifetime and operation issues Charging and re-charging cycle Temperature effects Degradation

Fuel Cells Basic fuel cell operation Fuel cell reactions: thermodynamics and kinetics Differences from batteries

Advantages and issues in fuel cells

Types of fuel cells Proton exchange membrane (polymer electrolyte membrane) Solid oxide Emerging technologies and materials issues

Course Outline

Resources

Energy and Global Warming Richard Heinberg “The Party’s Over: Oil, War and the Fate of Industrial Societies” David Goodstein “The End of the Age of Oil” Jared Diamond “Collapse: How Societies Choose to Fail or Succeed” Mark Bowen “Thin Ice: Unlocking the Secrets of Climate in the World’s Highest Mountains” Basil Gelpke, Ray McCormack “A Crude Awakening: The Oil Crash” Al Gore “An Inconvenient Truth” Fred Krupp and Miriam Horn “Earth: The Sequel” Godfrey Boyle “Renewable Energy”

Solar Cells Jenny Nelson “The Physics of Solar Cells” Antonio Luque and Steven Hegedus “Handbook of Photovoltaic Science and Engineering Thomas Markvart “Solar Electricity (Second Edition)”

Batteries David Linden, Thomas B. Reddy “The Handbook of Batteries” (available online at http://www.knovel.com/knovel2/Toc.jsp?BookID=627) Almost any chemistry text, e.g. Gordon Brown “Physical Chemistry”

Fuel Cells Ryan O’Hayre, Suk-Won Cha, Whitney Colella, Fritz B. Prinz “Fuel Cell Fundamentals”

Energy

The property of matter and radiation that is manifest as a capacity to perform work (Apple Dictionary)

Several different forms, such as kinetic, potential, thermal, electromagnetic, chemical, nuclear, and mass have been defined to explain all known natural phenomena (Wikipedia)

The strength and vitality required for sustained physical or mental activity (Apple Dictionary)

Definition:

Units and Conversions:

• the energy required to lift a small apple (102 g) one meter against Earth's gravity. • the amount of energy, as heat, that a quiet person produces every hundredth of a second. • the energy required to heat one gram of dry, cool air by 1 degree Celsius. • one hundredth of the energy a person can get by drinking a single 5 mm diameter droplet of

beer.

Si Unit of energy is Joule (J) Mechanical work increases energy of a body (kinetic or potential)

1 Joule is:

force distance

Power time

1 electron Volt = 1.602 x 10-19 J

Forms of Energy Kinetic energy – the energy possessed by a moving mass Kinetic energy = (mass x speed2)/2

Kinetic energy within a body determines its temperature - matter consists of atoms or molecules - atoms or molecules in have kinetic energy manifested as vibration or motion - the higher the temperature the faster the atoms or molecules are moving - this atomic scale kinetic energy is known as thermal energy

Potential or gravitational energy Potential energy = mass x acceleration due to gravity x height

Force Distance

At the atomic scale gravitational force is insignificant and electrical force (forces between charges) dominates

- Electrical energy is the energy associated with electrical forces - At the atomistic scale this electrical energy is chemical energy (the energy associated with chemical bonds)

Forms of Energy

Macroscopically (and technologically) electrical energy is manifested as electrical currents driving loads. For example a current of one amp through a load of one ohm resistance operating for one second is our old friend a Joule.

Electrical energy is also associated with fields (electrical and magnetic) Light is a form of electromagnetic energy

• Nuclear energy is the energy associated with the forces between the particles in the atoms nucleus

• At the sub-atomic length scales of the nucleus, these forces are much stronger than electrical forces

• Nuclear reactions convert mass to energy E = mc2

The first law of thermodynamics says that in all processes, energy is conserved; neither created or destroyed (must include mass energy if considering nuclear processes).

However, the second law of thermodynamics says that in converting from one form of energy to another, the useful output is always less than the input

Energy Conversion

The efficiency is the ratio of useful output to required input

Typical efficiencies

Water turbine 90 %

Electrical Motor 90 %

Coal fired power station 35 – 40 %

Internal combustion engine 10 – 20 %

Solar cells 10 – 40 %

Energy Content

With a conversion efficiency of 37.5 %, one metric ton produces 15.75 GJ or 4.5 MWh of electrical energy

1 metric ton (tonne) oil = 1000 kg = 7.33 barrels = 307.9 gallons

Burning 1 metric ton oil releases 42 x 109 J or 12 MWh

Efficiency of Use - Electrical Energy Conversion Example

Energy Unit toe (tonne oil equivalent) 1 toe is the energy content of a tonne of oil

1 toe = 42 GJ 1 Mtoe = 42 x 1015 J = 42 PJ

This is the energy content of a tonne of oil

When comparing energy forms it is important to compare apples to apples. A power plant needs about 2.7 tonnes of oil to produce 1 toe of electrical energy.

World Energy Consumption BP Statistical Review of World Energy June 2007

Distribution of Energy Consumption

http://www.skyscrapercity.com/showthread.php?t=326298

The world at night

Distribution of Energy Consumption BP Statistical Review of World Energy June 2007

Are We Running Out of Oil?

As we near peak: • Exponential growth of

energy usage will slow • Demand will outstrip

supply • Price will rapidly

escalate (no elasticity in demand - we are addicted to energy!)

Other Energy Reservoirs

Shepard Glacier, Glacier National Park, Montana

1913

http://www.livescience.com/environment/060324_glacier_melt.html

2005

“Climate change and trace gases”, James Hanse, Makiki Sato, Pusker Kharecha, Gary Russell, David W. Lea and Mark Siddall. Philosophical Transactions of the Royal Society A, 365, 1925-54, (2007).

http://www.worldviewofglobalwarming.org/

Are We Cooking the Earth?

3 kg of CO2 released for each kg oil burned

E H

z

Electromagnetic Radiation

Wavelength

Permittivity Permeability

of free space

Speed of light

Quantized energy: Frequency: