Energy Systems & Sustainability

Freshman Seminar 2008

The Issue Before Us

“One of the greatest challenges facing humanity during the twenty-first century must surely be that of giving everyone on the planet access to safe, clean & sustainable energy supplies.”

Some basic definitions (1)

Energy… modern sense of this word appeared in the 1800’s :

Described transfer of heatMotion of planetsOperation of machineryFlow of electricity

Some basic definitions (2)

TODAY…TODAY… Energy = capacity to do work. That is, to

move an object against a resisting force Unit --- Joules

Power = the rate of doing work or rate at which energy is converted from one form to of energy to another Unit -- Watts = Joules/second

Some basic definitions (3)

What about sustainable? What about sustainable? Word introduced by the UN report

“Our Common Future”Brundtland Commission in 1987

sustainable = development that meets the needs of the present without compromising the ability of future generations to meet their own needs

Some basic definitions (4)

Sustainable energy sources means: that are not substantially depleted by continues

use; the use of which does not entail the emission of

pollutants or other hazards to the environment on a substantial scale; and

the use of which does not involve the perpetuation of substantial health hazards or social injustices.

P.S. Others prefer the emphasize P.S. Others prefer the emphasize renewablerenewable energy energy insteadinstead

Energy Sources

• Fossil Fuels– Coal– Oil– Natural gas

• Nuclear energy– Fission– Fusion

• Bioenergy– Burning wood– Animal dung– Wastes– Alcohol (ethanol)

• Gasohol

• Hydroelectric• Solar energy• Wind energy• Wave power• Tidal energy• Geothermal

– Earth internal heat originates mainly from the decay of long lived radioactive elements

% contributions of energy sources to world’s consumption (2000)

0

5

10

15

20

25

30

35

OilCoalN. GasBioenergyNuclearHydroOther

Why bother to learn about this now?

• Problems with current energy producing fuels• It is hypothesized that by 2050 we will have run

out of economically recoverable fossil fuels

Growing Population

No More Fossil Fuel? Need For New Energy Sources

• If we continue to burn fossil fuels for energy, they will only last another few hundred years.

• This means that an energy shortfall could occur within the next fifty years.

Some basic facts about

• Fossil Fuels– Coal– Oil– Natural gas

75% of our current source of energy

Coal

• Abundant• Burns dirty• Causes acid rain and

air pollution– Greenhouse gas

problems

Oil

• Flexible fuel source with many derivatives

•Transportable

•Finite supply

•Causes air pollution

Natural Gas

• Burns cleanly• Transportable• Finite supply• Dangerous to

handle

Nuclear Power (7%)

• Clean

• No CO2

• No immediate pollution

• Problems with waste disposal

• Safety concerns

Other Alternative Sources (18%)

• Water Power

• Solar Power

• Tidal Power

• Wind Power

• Geothermal Power

20% of the energy needed for an estimated world population of 10 Billion in 2050

WHY?

We need to look at each source in more detailed

Few comments about...

Nuclear Fusion

Introduction

• “Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements”

-Carl Sagan, 1991

Our Sun

Fusion Advantages• Abundant fuel, available to all nations

– Deuterium and lithium easily available for thousands of years

• Environmental Advantages– No carbon emissions, short-lived radioactivity

• Modest land usage– Compact relative to solar, wind and biomass

• Can’t blow up– Resistant to terrorist attack– Less than 5 minutes of fuel in the chamber

• Not subject to daily, seasonal or regional weather variation– No large-scale energy storage nor long-distance transmission

• Can produce electricity and hydrogen– Compliments other nearer-term energy sources

Fusion Disadvantages

• Huge research and development costs• Radioactivity

Background

Fusion Basics

Basic Physics

Energy-Releasing Reactions

Chemical Fission Fusion

Sample Reaction

C + O2 CO2 n + 235U 143 Ba + 91 Kr + 2 n 2H +3H 4He + n

Typical Inputs

(to Power Plant)

Bituminous Coal UO2 (3% 235 U+ 97% 238U) Deuterium & Lithium

Typical Reaction Temp. (K)

700 1000 108

Energy Released per kg of Fuel (J/kg)

3.3 x 107 2.1 x 1012 3.4 x 1014

What is an atom?

Nuclear Power

• Nuclear fission– Where heavy atoms,

such as uranium, are split apart releasing energy that holds the atom together

• Nuclear fusion– Where light atoms,

such as hydrogen, are joined together to release energy

States of Matter

• Plasma is sometimes referred to as the fourth state of matter

Plasma makes up the sun and the stars

Plasma Atoms

• In plasma the electrons are stripped away from the nucleus

• Like charges repel

– Examples of plasma on earth:

• Fluorescent lights

• Lightning

• Neon signs

Other Typical Plasmas

• Interstellar

• Solar Corona

• Thermonuclear

• Laser

Characteristics of Typical Plasmas

Basic Characteristics

• Particles are charged

• Conducts electricity

• Can be constrained magnetically

Fusion Fuel

• Tritium

• Deuterium

The fuel of fusion

Inexhaustible Energy Supply

• Deuterium– Constitutes a small percentage of the hydrogen in water

• Separated by electrolysis• 1 barrel (42 gallons) water ¾ oz.

• Tritium– n + Li T + He– Lithium is plentiful

• Earth’s crust• Oceans

– Savannah, Georgia– Canada, Europe, Japan

Fusion Fuel: Deuterium

Other Possible Fusion Fuels

Helium-3 Nuclear Fusion

Proton Proton NeutronProton

Where is Helium-3?

• Helium-3 comes to us from the sun on the solar wind

• It cannot penetrate the magnetic field around the earth, so it eventually lands on the moon

• One shuttle load- 25 tons- would supply the U.S. with enough fuel for one year

HOW FUSION REACTIONS WORK

Two Main Types of Fusion Reactions: P-P

"P-P": Solar Fusion Chain

Two Main Types of Fusion Reactions: D-T

D + T => 4He + n

More on Fusion Reactions

An enormous payoff

• The fraction of “lost” mass when H fuses into He is 38 parts out of 10,000

• This lost mass is converted into energy

• The energy released from 1 gram of DT = the energy from about 2400 gallons of oil

The result

• Inexhaustible fuel source– Seawater & Lithium

• The MOST “bang for your buck”• Inexpensive to produce• Widely distributed fuel source

– No wars

• No pollution– Helium is not polluting

• Fuel that is non-radioactive– Residue Helium-4 is non-radioactive

• Waste reduction

More of Fusion Radioactivity

• Stray Tritium– Relatively benign

• Doesn’t emit strong radioactivity when it decays– So only dangerous when ingested or inhaled

• Shows up in one’s body as water– Easily and frequently flushed out

• Half-life of 12 years– No long-term waste problem– Won’t decay while in one’s body

– Less than natural exposure to radon, cosmic rays and much less than man-made x-rays

More on Fusion Radioactivity

• Reactor Structure– Development of special “low-activation”

structural materials• Vanadium• Silicon-carbide

– Wait ten to fifteen years after shutdown• The reactor will be less radioactive than some

natural materials (particularly uranium ores)• Recycle into a new fusion reactor

Waste Reduction

Power Source Total Waste (m3) High-Level RAD Waste

Coal 10,000 (ashes) 0

Fission 440 120

Fusion:

Today’s Materials 2000 30

Advanced Materials 2000 0

So why aren’t fusion plants already in operation?

How fusion works and the obstacles in the way

The Problems

• Harnessing the Energy

• Achieving & sustaining high temperatures– The reaction takes place at a temperature hotter

than the surface of the sun– 0.1 seconds

• Containing the fuel & the reaction

• Money for research and development

Harnessing the Energy

Achieving ignition temperatures

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