energy systems & sustainability freshman seminar 2013 mayda m. velasco oct. 1, 2013
Post on 27-Dec-2015
217 Views
Preview:
TRANSCRIPT
Energy Systems & Energy Systems & SustainabilitySustainability
Freshman Seminar 2013Mayda M. VelascoMayda M. Velasco
Oct. 1, 2013Oct. 1, 2013
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
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
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
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
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
Basic Characteristics
• Particles are charged• Conducts electricity• Can be constrained magnetically
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
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
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 WastePower Source Total Waste (m3) High-Level RAD WasteCoalCoal 10,000 (ashes) 10,000 (ashes) 0 0
FissionFission 440 440 120 120
Fusion:Fusion:Today’s MaterialsToday’s Materials 2000 2000 30 30Advanced MaterialsAdvanced Materials 2000 2000 0 0
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
top related