Bio 111 Alternative Energy Options Week10
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Transcript of Bio 111 Alternative Energy Options Week10
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Alternatives to Fossil
Fuels
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Nuclear Energy
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Atomic structure
all matter made of atoms
each atom composed of anucleus that contains protons(+ charge), and neutrons
(neutral) nucleus surrounded by a
cloud of orbiting electrons (-charge)
interesting factoid: orbitingelectrons moving at almostthe speed of light!
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Isotopes
in most atoms, # of protons = # of neutrons, butnot always
# of neutrons can vary
different forms of an element called isotopes
most elements a mixture of isotopes - some stable,but some not
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Radioactive decay
unstable isotopes throw off particles and emit
radiation from their nuclei as they decay
referred to as radioisotopes
over time, mass of radioisotopes actually
decreases measure of the decrease (rate of decay) called
half-life
half life - length of time it takes for 1/2 of theradioactive mass to decay to a stable form
half lives of isotopes vary from a fraction of asecond to tens of thousands of years
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Half life of isotopeslength of time until half of the material decays
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Chain reactions
nuclear fission gives off enormous amounts ofenergy
opportunity exists for a chain reaction - series ofsteps that occur one after the other, in sequence
example: forest fire if heat from one tree spreads to second tree and
second to third - fire burns at steady rate
but if one burning tree ignites two other trees and each
of these two ignite two more and so on, rate of burningwill speed up
acceleration called a branching chain reaction
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if a branching chain reactioncontinues rapidly, energy isreleased at an increasing rate
results in an atomic explosion
(see a movie of an atomic explosion at
http://www.youtube.com/watch?v=H1sS1TmXF38
if the chain reaction is carefully
controlled, energy can be releasedslowly for useful purposes
http://www.youtube.com/watch?v=H1sS1TmXF38http://www.youtube.com/watch?v=H1sS1TmXF38http://www.youtube.com/watch?v=H1sS1TmXF38http://www.youtube.com/watch?v=H1sS1TmXF38 -
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Nuclear fission
process starts when a neutron strikes a U-235nucleus
nucleus splits
kinetic energy released as fission products flyapart
flying fragments hit other atoms and transferenergy - releases heat
energy released by nuclear reactions muchgreater than amount released by chemicalreactions
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Nuclear power production
less than 1% of mineduranium contains theisotope needed fornuclear fission
processed (enriched)uranium formed intopellets
pellets inserted into
thin tubes called fuelrods (about 12' long,1/2" diameter)
pellets of enriched uranium
on palm of hand
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fuels rods are bundledand lowered into the
core of the reactor
control rods fitbetween the fuel rods
control rods can beraised or lowered tocontrol the rate offission
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fuel rods inserted intoposition in the reactorcore
the reactor core is
contained by a reactorvessel with 6" steelcasing
in most countries,
reactor vessel housedin a containmentbuilding with 4' thickcement walls
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Nuclear power plants
similar to coal plants in that heat is used toproduce steam to drive a turbine
energy released from nuclear fission in the fuelrods heats water bathing the reactor core
to avoid radioactive contamination, the wateris contained in huge pipes in the wall of thereactor vessel
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not all reactors havecomplete containment
buildings nuclear reactor at
Chernobyl had onlypartial containment
proved inadequate inthe accident in 1986
20 of the former
Soviet Union's 44reactors now inoperation have thesame design
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Radioactive waste about 1/3 of old fuel
rods (40-60 rods) arereplaced annually
entire assembly,
containing unuseduranium, newly formedplutonium, and wasteproducts, is removed
all components willcontinue to beintensely radioactivefor a long period of
time
storage of nuclear wasteremains a problem - oneproposed solution - storagetunnels under Yucca Mountain,
Nevada
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most people in the world stillget their energy from burningplant or animal products
people who burn wood indeveloped countries do so outof choice, but for most of theworld's poor, fossil fuels are
simply not available or tooexpensive
wood or cow dung are theonly possible alternatives
this has caused timberdepletion and deforestationaround the world
biomass is renewable only ifnot overharvested
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Problems with biomass fuels
wasted time and potential
in rural areas wood is scarce - people spend a large portion oftheir time simply finding the fuel needed to cook their meals
Africa - women and children often travel 50 km/day hunting forfuel wood (wasted time on this task prevents girls and womenfrom getting an education and seeing to other needs)
Asia - common for families to spend 1/4 of their income or 1/4 oftheir time obtaining fire wood
Andes Mountains of South America - families must support anextra donkey just to collect and haul fire wood
wasted resources when manure is burned instead of wood, this represents the loss
of a potential source of fertilizer
a conflict arises - when the dung is burned to cook today's dinner,there's less fertilizer available to grow food for the following
season
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biogas - creative, low-tech solution to both theenergy and fertilizer problems
manure from cattle dung and night soil is converted into a clean source of energy.helps in conservation of fuel wood, improves sanitation and generates
employment in rural areas.
manure
biogas generator
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Biogas
when sewage, garbage, manure, or cropresidues decompose in the absence of oxygen,methane (natural gas) is released
methane produced in this manner is calledbiogas
methane produced from wastes is identical tomethane extracted from underground deposits
Basics of biogas conversion
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Basics of biogas conversionNote: this would be a great time to review the action
of decomposers in ecosystems!
fermentation of manure generates methane
anerobic bacteria feed on the undigestedvegetation in the manure and perform cell
respiration to convert food energy to ATP energy because cell respiration in occurring in a low
oxygen environment, the waste product producedis methane (instead of carbon dioxide)
the methane gas is used for cooking, lighting andelectricity generation
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Biogas residue makes excellent fertilizer
review: mineral nutrients contain no foodenergy and aren't biodegradable
after the biogas is released, the decomposed
manure is removed and spread on farm fields asa high quality fertilizer
construction costs are returned in 1-3 years byfuel savings
tens of thousands of units have been built inChina and elsewhere through Asia
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manure to energy projects work in developedcountries too! example: dairy farm operated oncow manure
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Waste to energy
about 300 plants worldwide burn municipalgarbage to generate electricity or produce steamto heat homes and offices
largest facility - Rotterdam, Germany - 550
megaWatt plant (about half the output of alarge nuclear reactor) operates entirely onrefuse
Munich, Germany - generates 12% of itselectricity by burning garbage
North America - is a largely unexploited resource
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conversion of municipal solid waste to energy
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Cost/benefit analysis from U.S. projects
Modesto, CA - methane from sewage treatment iscollected and used in city vehicles
cost of setting up the system and maintenance is equivalent tobuying gasoline at 30 cents/gallon
Brooklyn, NY - drilled more than 100 gas wells into thecore of an extensive landfill outside the city
about 3.5 million cubic feet of methane are collected every dayfrom decomposing garbage
city realized a profit of $600,000 in the first year of operation of
the wells 25,000 homes are supplied with heating and cooking gas from a
source that otherwise would have been wasted
Bi f l t l t i it d
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Biofuels can generate electricity andpower vehicles
fermentation of vegetation producesethanol
energy conversion from crop to fuel is quitelow - some plants more efficient than
others the higher the % of cellulose in the
vegetation, the better the conversion, butcorn is quite low in fiber
sources with the potential for higherefficiency: lumber waste (from sawmills),reeds and other marsh plants, algae, fungi
Drawbacks to biofuel production to
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Drawbacks to biofuel production topower vehicles
methane isclean in regardto many airpollutants, butstill releasescarbon dioxide(majorgreenhousegas)
FYI - methaneis a greenhousegas too
Drawbacks to biofuel production to
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Drawbacks to biofuel production topower vehicles
ethanol from corn, sugar beets, sugar cane, and biodieselfrom oil seeds, all require high-quality agricultural land forgrowth
in U.S, large quantities of fossil fuels used to plant, harvest,
and transport the corn that's used to produce ethanol additional fossil fuels used to manufacture fertilizers and
pesticides
more fuel needed to cook the grain, warm the sugar as itferments, and distill the mixture to obtain pure alcohol
therefore, when the whole process is taken into consideration,there's little real conservation of fossil fuels
in less industrialized countries, such as Brazil, farmers usemore manual labor and less fuel to raise crops, so the energybalance in ethanol production is more favorable
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Drawbacks to biofuel production topower vehicles
ethanol productionhas raised world foodprices
more difficult to raisethe money forimported food indeveloping countries
Source: USDA NationalAgricultural Statistics Service
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Solar Energy
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Passive solar design
simplest way to use solar energy - design andorient a house so that the structure itself collectsand stores heat from the sun
many ancient civilizations used passive solar
design was standard in ancient Greece and Rome - in
Vesuvius, Romans had solar bath houses
Greek playwright Aeschylus believed onlyuncivilized barbarian societies didn't understandthe concept of solar design
what do you think?
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passive solar used inthe Americas sincethe Anasazi built cliffdwellings in the
American Southwest
they chose southfacing cliff sites fortheir homes
Gila cliff dwellings New Mexico
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Canyon de Chelly, Arizona
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in winter, the sun shines directlyinto the buildings providing heat
in summer, the sun is higher in
the sky
the edge of the cliff acts as anawning to provide cooling shade
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Gila cliff dwellings New Mexico
view from inside the cliff dwellings
H l d f th t?
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Have we learned from the past?
today many
people in theSouthwest livein rectangularhouses
oriented andconstructed sothat largeamounts offossil fuels areneeded toprovide heat
and cooling
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basics of passivesolar design
use heat-absorbingconstructionmaterials
south facingwindows maximize
sunlight capture inwinter
plant trees and othervegetation around
buildings
H d l k?
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How does solar power work?
active solar -
photovoltaic (PV)cells contain siliconand other elements
sunlight excites
electrons which areejected from thesilicon atoms
ejected electronsflow out of the PVcells through awire, producing
electricity
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passive solar home
active solar home
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i t lli l l k fl t f
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installing solar panels - works on any flat surface
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PV cells Georgetown University Intercultural Center
can supply half of the building's electricity needs
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PV panels can be fragile and expensive
new, improved products are on the market
these are solar shingles (thin film solar cells)
less fragile, much cheaper, more durable
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this is the coolest thing since sliced bread - solar paint!
several years in development, seems to be about ready to
hit the market http://news.nationalgeographic.com/news/2005/01/0114_
050114_solarplastic.html
http://news.nationalgeographic.com/news/2005/01/0114_050114_solarplastic.htmlhttp://news.nationalgeographic.com/news/2005/01/0114_050114_solarplastic.htmlhttp://news.nationalgeographic.com/news/2005/01/0114_050114_solarplastic.htmlhttp://news.nationalgeographic.com/news/2005/01/0114_050114_solarplastic.html -
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these examples and thefollowing are just for fun, butthey can be useful
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I saw this guy in the airport andasked if I could take his photo - thebackpack charges his laptop(plugged in inside) while he walksaround
I have a radio similar to thisand they work great -especially for a day at thebeach
solar car race from DC to California - colleges and universities entered
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solar car race from DC to California colleges and universities enteredcarsthe race started at L'Enfant Plaza a few years ago, so I was able to getthese photos
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New solar technologieslearn more at
http://www.nanosolar.com/
G th l
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Geothermal energy energy from the heat in the earth's crust
core of the earth is a large mass of moltenmaterial called magma - temperature upto 800F.
in most places, magma is many miles
below ground, but some locations, itcomes close to the surface and createshot spots
when groundwater comes in contact withhot spots, the water turns to steam
example: geysers in Yellowstone NationalPark
see some cool video athttp://www.yellowstonenationalpark.com/
geysers.htm
Geothermal
http://www.yellowstonenationalpark.com/geysers.htmhttp://www.yellowstonenationalpark.com/geysers.htmhttp://www.yellowstonenationalpark.com/geysers.htmhttp://www.yellowstonenationalpark.com/geysers.htm -
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Geothermalpower
Geothermal power
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Geothermal power the steam is used to spin
turbines that drive
electric generators
problem: the steam oftencontains minerals thatcan clog and corrode the
generating equipment U.S. has 1.8 million acres
of land wheregeothermal energy is
known to exist has potential to become
an important source ofelectricity
geothermal power plant - Iceland
H d l i
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Hydroelectricpower
turbine hydroelectric power
Interesting wind power factoids
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Interesting wind power factoids
since ancient times, people
have harnessed wind energy over 5,000 years ago,
Egyptians used windmills to sailships on the Nile River
later, people built windmills togrind wheat and other grains
earliest known windmills usedin Persia (present day Iran)
American colonists usedwindmills to grind wheat andcorn, to pump water, and tooperate sawmills
Wi d
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Wind power
fastest growingenergy sector
estimated that windgeneration could
produce about 40%of the country'spresent energy needs
technology needed to
build infrastructure isrelatively simple andcommerciallyavailable
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just wanted you tosee the real size ofcommercialwindmills
use the person onthe top for size
comparison
of course they comein small, residentialsizes too
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here's a coolcombinationof wind andsolar
when the sunisn't shiningthe wind isprobablyblowing
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The Pickens Plan
T. Boone Pickens, founder/chairman of BP Capital Mgmt.(huge energy-oriented investment fund - $4 billion - and
heavily invested in the oil industry)
despite this, he has a plan to help make the U.S. energy
independent that involves, wind, solar, and natural gas
what do you think of his ideas?
http://www.pickensplan.com/theplan/
(scroll down to see the details of the plan)
Hydroelectric Power
http://www.pickensplan.com/theplan/http://www.pickensplan.com/theplan/ -
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Hydroelectric Power
water turns
the blades ofthe turbine
the turbinedrives the
generator
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water over the dam
(sorry - I couldn't help myself)
Co-generation
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Co generation(also called combined heat and power - CHP)
simultaneousgeneration ofheat and power
instead of
releasing the heatas a wasteproduct, thereleased heat
provides spaceheating or heatswater to producesteam
the diagram in the following slide represents an idealized co-
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the diagram in the following slide represents an idealized cogeneration and energy sharing system
generation of electricity (blue lines) and steam heat (red
lines) comes from multiple sources besides traditional power plants that supply electricity to
substations for distribution, incineration plants and combinedheat and power plants (CHP) would play a larger role inenergy production
both of these plants could also supply steam for heat and forindustrial processes
waste heat from industrial plants can be piped throughturbines to create additional electricity
small individual CHP generators are now available and can beinstalled in homes and offices to provide both heat and power- they feed any excess electricity back into the grid
Source: Scientific American, January 2009
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