Transcript ENERGY SOURCES CHAPTERS 15 AND 16

ENERGY SOURCES
CHAPTERS 15 AND 16
We Need Energy To Power Our Vehicles And To
Generate Electricity
• Most electrical plants are attached to a grid.
• Grids connect power plants to each other and their
customers.
• Peak demand is when the most electricity is needed.
Late afternoon.
• Brownout- grid does not fail, but not enough
electricity can be produced.
• Blackout- there is a malfunction in the grid.
• Rolling blackout- areas lose power sequentially
when demand is greatest.
Nuclear power Geothermal,
6%
solar, wind 2.5%
Nuclear power
8%
Geothermal,
solar, wind 1%
Hydropower
4.5%
Hydropower,
3%
Natural gas 23%
Natural gas 21%
Biomass 11%
Coal
23%
Coal
22%
Oil 33%
World
Biomass 3%
Oil
39%
United States
Fig. 15-3, p. 373
Fossil Fuels
• Coal
• Natural gas – 50-90% methane plus other gases
like butane and propane
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LPG- butane and propane are liquified and removed
LNG- methane is liquefied for transportation
Unconventional natural gas –coal bed methane
And methane hydrate-methane trapped in icy water
molecules under arctic permafrost
• Oil
– Tar sands - bitumen
– Shale oil - kerogen
Products Which Are Made From Petroleum Products
• Product list
STAGES IN COAL FORMATION
Increasing heat and carbon content
Increasing moisture content
Lignite
Peat
(brown coal)
(not a coal)
Anthracite
(hard coal)
Bituminous
(soft coal)
Heat
Heat
Heat
Pressure
Pressure
Pressure
Partially decayed plant
matter in swamps and
bogs; low heat content
Low heat content; low
sulfur content; limited
supplies in most areas
Extensively used as a fuel
because of its high heat
content and large supplies;
normally has a high sulfur
content
Highly desirable fuel
because of its high heat
content and low sulfur
content; supplies are
limited in most areas
Stepped Art
Fig. 15-11, p. 383
We Can Convert Coal into Gaseous and Liquid Fuels (synfuels)
• Conversion of solid coal to
– Synthetic natural gas (SNG) by coal gasification
– Methanol or synthetic gasoline by coal liquefaction
Requires more mining of coal
Expensive
Low net energy yield
• Methane hydrate- nature gas trapped in water
molecules under the arctic permafrost
too expensive and could release CH4 which is a
ghg
CLEAN COAL-processes that reduce the negative environmental
effects of burning coal.
• Crush and wash the coal to remove impurities
• Wet scrubbers, or flue gas desulfurization systems-Capture
the SO2 gases (flue gases)in scrubbers:
• Fluidized-bed combustion –Limestone and dolomite are added
during the combustion process to mitigate sulfur dioxide
formation. Limestone mixed with water removes SO2 and combines to
make a paste or powder. Forms gypsum which is used in drywall
• Electrostatic precipitators remove particulates that aggravate
asthma and cause respiratory ailments by charging particles
with an electrical field and then capturing them on collection
plates.
• Integrated Gasification Combined Cycle (IGCC) – Heat and
pressure are used to convert coal into a gas or liquid that can
be further refined and used cleanly. The heat energy from the
gas turbine also powers a steam turbine.
• Bag filters- traps coal particles
Nuclear Energy
• When the nucleus splits (fission), nuclear energy is
released in the form of heat energy and light
energy.
• Nuclear energy is also released when nuclei collide
at high speeds and join (fuse). This is called fusion
and is how the sun creates its energy.
How Does a Nuclear Fission
Reactor Work?
• Controlled nuclear fission reaction in a reactor
A neutron hits the nucleus of an atom which
releases more neutrons which hit more nuclei
which release more neutrons which hit more….
This is called a chain
reaction.
How Does a Nuclear Fission Reactor Work?
• Controlled nuclear fission reaction in a
reactor
– Light-water reactors
• Fueled by uranium ore and packed as pellets
in fuel rods and fuel assemblies (U-235)
• Control rods absorb neutrons in
order to control the
rate of the reaction.
What Is the Nuclear Fuel Cycle?
• Mine the uranium
• Process the uranium to make the fuel
– Mill (concentrate) the ore to make yellowcake,
uranium oxide
– Convert into uranium hexafluoride (UF6) gas
– Enrich gaseous UF6 to have a higher concentration of
uranium – 0.7% to 5% U-235 – cooled into a solid
– Fuel fabrication to convert into useable fuel
• Use it in the reactor
• Safely store the radioactive waste
• Decommission the reactor
Dealing with Radioactive Wastes Produced by Nuclear Power Is
a Difficult Problem. Possible Methods of Disposal and their
Drawbacks
High-level radioactive wastes must be stored safely for 10,000–
240,000 years
1. Bury it deep in the ground
2. Shoot it into space or into the sun or to the moon
3. Bury it under the Antarctic ice sheet or the Greenland ice
cap
4. Dump it into descending subduction zones in the deep
ocean
5. Bury it in thick deposits of muck on the deep ocean floor
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How much energy is wasted??
“The outdated four”
Incandescent bulb
90-95%
Motor vehicle
94%
Nuclear energy
92%
Coal fired power plant
75-80%
Net Energy Efficiency—Honest Energy Accounting
• Net energy efficiency
– the only energy that counts
Net energy is important!!
Net Efficiency= % energy available from
source X energy efficiency for that step
100 x 0.95=95%
0.95 x 0.57=54%
Net energy efficiency for heating two well insulated homes
a) Electricity from nuclear power plant
b) Heated passively by direct solar energy
Cogeneration (combined heat and power)
• The waste from one form of energy is used by
another company.
• Steam produced in generating electricity is
used to heat the plant or nearby buildings.
We Can Design Buildings That Save Energy and
Money
• Green architecture -energy efficient and money saving, makes
use of natural lighting, passive solar heating, recycled building
materials, rainwater collection, etc
• Living or green roofs – covered with soil and vegetation
– Reduce runoff, improve air quality, save energy
• Straw bale houses - -stack hay and cover with plaster (super
insulator)
• Superinsulation• U.S. Green Building Council’s Leadership in Energy and
Environmental Design (LEED)
– Green building certification exists in 21 countries
Two Buildings That Were Designed With Energy In Mind
– Georgia Power Company in Atlanta, GA (U.S.) – uses
60% less energy than conventional buildings
• Largest portion of building faces south-solar energy
• Each floor extends out over one below it(blocks out summer
sun reduces AC cost)
• Compact fluorescent lighting over work
areas
– Ministry of Science and Technology
Building in Beijing, China
– Porous bricks, solar cells, solar hot
water heating system, roof garden,
concrete building blocks filled with insulating foam
Roof Top Vegetation
• Can improve the air quality by acting as a filter to trap airborne
dust particles.
• Alleviating Urban Heat Island Effect- reductions in temperature are
due mainly to the shading of the heat absorbing roof surfaces as
well as the evapo-transpirational cooling effects of the plants in the
roof gardens.
• Improving Water Quality.-Depending on the thickness of the
various layers of the roof garden, a green roof is able to filter out
heavy metals and nutrients present in rainwater
• Improving Stormwater Management - Roof gardens retain
rainwater on the roof through the various layers and significantly
reduce the peak discharge flow rate into
the stormwater drainage system.
Good for the environment, but very costly
Hydroelectricity
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Provides about 7% of electricity in US
Hoover Dam- largest in US
3 Gorges Dam- largest in the world
No CO2 emissions
Moderate to high net energy
High construction costs, danger of collapse,
decreases flow of natural fertilizer (silt) to land
below the dam, high environmental impact from
forming the reservoir
Wind Energy- the most rapidly growing
source of electricity
• What is the source of wind?
• The sun!
• US has largest wind energy generating capacity,
then Germany and Spain- but US gets only 1% of
electricity from wind (Ca and TX)
• Nondepletable
• Off-grid residents use batteries (expensive) to
store electricity
SOLAR ENERGY
• Passive – large windows or attached green houses
face south
• Active- capture sun’s energy with solar water
heating systems, photovoltaic cells and solar
thermal systems for electricity generation- uses
pumps or fans
• Photovoltaic cells- wafer thin sheets of silicon
imbedded with boron impurities- when photons
strike the glass plate, electrons are emitted from the
wafer, creating a current
• Solar thermal electricity- sun’s rays are focused on a
system filled with a heat absorbing liquid. Liquid
heats the water, creating steam to spin a turbine.
Biomass (solid)- carbon based fuel source like wood, manure, charcoal,
plants- number 1 use of renewable energy in US- can be burned
directly as a solid fuel or converted into gaseous or liquid biofuels
• Biofuel (liquid) – alcohols made from switch grass, hemp, corn,
sugarcane sugars
• Ethanol- made from the fermentation/distillation of sugars in plants
such as sugarcane, corn and switchgrass (U.S. uses corn, Brazil,
sugarcane)
• usually mixed with gasoline in a ratio of 1/9 parts gasoline = gasohol10% ethanol:90% gasline
• switch grass--grows faster than corn, disease resistant, drought
tolerant, grown on land unfit for crops
• No net increase in CO2 emissions since CO2 is cycled in a short time
• Rainforests have been negatively impacted!, increase soil
degradation, erosion, decrease biodiversity, increase global warming
• Biodiesel- made by extracting oil from algae and plants like soybeans
and oil. Also, vegetable oils from restaurants are used!
• Methanol- derived from wood, wood waste,
crop residues and sewage sludge.
• High net energy yield and reduce agricultural
wastes.
• Biogas digesters – anaerobic bacteria that
decompose animal waste to produce methane.
Methane combustion creates heat.
• Municipal sewage treatment plants use the
methane produced to run their operations.
Geothermal- energy from the natural radioactive
decay of elements deep in the earth
• Hot water can be piped directly to homes
• Heat exchangers collect heat by circulating
cool liquid underground which gets hot and
returns to the surface. 87% of homes heated
this way in Iceland.
• Can make electricity.
• Heat from decaying elements is
nondepletable, but the water is not.
Tidal Energy
• Most effective when there is a large
difference in tide heights- 26 feet
• When tide comes in, water spins a turbine
and when the tide goes out, the water still
spins the turbine
• Big disadvantage is the damage done to
inlets, bays and estuaries if the dam is built
across them. Siltation and loss of breeding
areas.
Different types of fuel for vehiclesgasoline powered cars emit nearly 20 pounds
of CO2 for every gallon (6 pounds) burned
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Electric (EV)
Hybrid electric
Plug in hybrid electrics- have an added battery
Hydrogen- hydrogen fuel cell- water vapor is the
only emission
• Flex-fuel – run on E-85 (85% ethanol) or gasoline
CAFE Standards
Corporate Average Fuel Economy
• Transportation needs consume 2/3 of petroleum
use and this use is increasing faster than all
other uses of petroleum.
• These standards are the average fuel economies
of a manufacturers fleet of cars or light trucks.
• Guidelines follow the EPA guidelines.
• Standards achieved by better engine design,
efficiency and weight reduction. Average
standard is 27.5 mpg.
Alternatives to the car
• Mass transit
– light rail, buses, subways, airlines, ferries
California’s Efforts to Improve Energy
Efficiency
• Population 37 million-uses less energy per person
than any other US state
• High electricity costs
• Reduce energy waste
• Use of energy-efficient devices
• Strict building standards for energy efficiency
Rocky Mountain Institute-think tank
for energy efficiency
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99% of hot water supplied by sun
95% of daytime lighting supplied by sun
90% of household electricity supplied by sun
ALL FROM PASSIVE SOLAR HEATING, HEAVY
ROOF INSULATION, THICK STONE WALLS,
ENERGY EFFICIENT WINDOWS
• GETS ELECTRICITY FROM SOLAR CELLS, SELLS
EXCESS POWER
• ELECTRIC BILL IS LESS THAN $50 A YEAR!!
Main problems with wind, solar and tidal are cost
and limitations of energy storage technology
• Solutions:
• Tax industries that emit CO2
• Nonrenewable resources become more expensive
for the consumer
• Require that a certain percentage of energy come
from renewable energy
• Regional Greenhouse Gas Initiative (RGGI) – 10
states have committed to reducing ghg emissions
from electricity generation by 2018
Which is a source of high net energy?
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Tar sands
Wind
Fission
Synthetic natural gas
Geothermal
• WIND
The fastest growing renewable energy
resource today is ___
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Nuclear
Coal
Wind
Large-scale hydroelectric
Geothermal
• WIND
THE LEAST-EFFICIENT ENERGY CONVERSION
DEVICE LISTED IS ____.
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STEAM TURBINE
FUEL CELL
FLUORESCENT LIGHT
INCANDESCENT LIGHT
INTERNAL COMBUSION ENGINE
• INCANDESCENT LIGHT
WHICH OF THE FOLLOWING IS NOT A
UNIT OF POWER?
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BTU
Horsepower
Kilowatt
Joule
All are units
• Joule- it is a unit of energy!
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Which country has made the largest
commitment to increasing its share of
renewable resources?
The US
Russia
China
Saudi Arabia
Japan
• CHINA
Which has the least environmental
impact?
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Gasoline
Coal
Oil shale
Tar sands
Natural gas
• NATURAL GAS
• Tar sands news clip
Which of the following is NOT considered
to be a source of ethanol?
sorghum
sugar beets
potatoes
corn
rice
potatoes
Which of the following sources represented the
highest total cost of producing electricity (in U.S. cents
per kilowatt hour)?
solar cells
coal
wind
nuclear
Solar cells
Which has the highest net energy for
heating homes?
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Coal
Nuclear
Hydroelectric
Biomass
Natural gas
• COAL
• If your laptop computer uses 50 watts per
hour and you use it for three hours per day,
how much will the electricity cost to run the
computer for one year if your utility charges
$0.08 per kilowatt hour?
• $ 4.38
• 50 w x 3h/day x 365 days/year x kw/1000w x
$0.08/kWh