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Transcript of Energy
Wood (renewable energy sources) served as main form of energy up until the Industrial Revolution.
During Industrial Revolution, coal (non-renewable) surpassed wood's usage.
Coal was overtaken by petroleum during mid 20th century.
Natural gas and coal experienced rapid development in second half of 20th century.
US was self-sufficient in energy until late 1950's, when consumption outpaced domestic production, leading to oil imports.
Industrial sector in US uses largest share of energy, followed by transportation and then residential & commercial uses.
Coal was once main form of energy in industrial sector but gave way to natural gas and petroleum in late 1950's.
By 1998, net imports of oil surpassed domestic oil supply in the US.
US accounts for 25% of world's petroleum consumption
the ability to do work
In the SI system, the unit for energy is the
is work divided by time
The unit of power is the joule(s) aka a
Power and Units
the amount of work done per time. The most common unit of power is the kilowatt-hour (kWh)
Laws of Thermodynamics
energy cannot be created or destroyed
when energy is converted from one form to another, a less useful form results (energy quality). Energy cannot be recycled to a higher quality. Only 20% of the energy in gasoline is converted to mechanical energy. The rest is lost as heat and is known as low-quality energy.
Sample Conversion Problem #1
Thorpeville is a rural community with a population of 8,000 homes. It gets its electriciy from a small, municipal coal-burning power plant just outside of town. The power plant's capacity is rated at 20 megawatts with the average home consuming 10,000 kilowatt hours (kWh) of electricity per year. Residents of Thorpeville pay the utility $012 per kWh. A group of entrepreneurs is suggesting that the residents support a measure to install 10 wind turbines on existing farmland. Each wind turbine is capable of producing 1.5 MW of electricity. The cost per wind turbine is $2.5 million dollars to purchase and operate for 20 years.
(a) The existing power plant runs 8,000 hours per year. How many kWh of electricity is the current plan capable of producing?
(b) How many kWh of electricity do the residents of Thorpeville consume in one year?
(c) Compare answers (a) and (b). What conclusions can you make?
(d) Assuming that the population of Thorpeville remains the same for the next 20 years, and that electriciy consumption remains stable per householdd, what would be the cost (expressed in $ per kWh) of electricity to the residents over the next 20 years if they decided to go with wind turbines?
(e) What are the pros and cons of the existing coal-burning plant compared with the proposed wind farm?
Sample Conversion Problem #2:
(a) An electric heater requires 0.30 kWh to heat a gallon of water. The thermostat is set to 150F. The cost of electricity is $0.20 per kWh. A washing machine with a flow rate of 6.0 gallons per minute runs four times each Saturday. Each time it runs, it takes in water for a total of 15 minutes. How much total water does the washing machine use in one year?
(b) Calculate the annual cost of the electricity for the washing machine, assuming that 3.0 gallons per minute of the water used by the machine comes from the hot-water heater.
Forms of Energy
two types of mechanical energy (potential ex. a book sitting on a table) & (kinetic ex. a baseball flying through the air)
heat is the internal energy in substances - the vibration and movement of atoms and molecules within substances
: chemical energy is stored in bonds between atoms in a molecule
electrical energy results from the motion of electrons
: nuclear energy is stored in the nuclei of atoms. It is released by either splitting or joining of atoms
: electromagnetic energy travels by waves
Units of Energy / Power
Btu (British Thermal Unit):
this unit is used in US; in most countries it's been replaced with the joule. Btu is amount of heat required to raise the temp of one pound of water by 1 degrees F. 1 watt is approx. 3.4 Btu/hr. 1 horsepower is approx. 2,540 Btu/hr. 12,000 Btu/hr is referred to as a "ton" in many air conditioning applications.
used in the automobile industry. 1 horsepower (HP) is equivalent to 746 watts
1,000 or 10 to the 3rd. 1 kW = 10 to the 3rd watts
Mega (M) -
1,000,000 or 10 to the 6th. 1 MW = 10 to the 6th watts
Kilowatt hour (kWh):
equal to 1,000 watt hours or 3.6 megajoules. A kilowatt hour is most commonly known as a billing unit of energy delivered to consumers by electric utilities. Ex) a heater rated at 1,000 watts (1 kilowatt), operating for one hour uses one kilowatt hour (equivalent to 3.6 megajoules of energy. Using a 60 watt lghbulb for one hour consumes 0.06 kilowatt hours of electricity. Using a 60 watt lightbulb for 1,000 hours consumes 60 kilowatt hours of electricy
Present Global Energy Use
In US, most energy derived from nonrenewable sources such as coal, petroleum, natural gas, propane, and uranium.
"Nonrenewable" because resources don't accumulate as quickly as they're used.
Renewable energy sources include biomass, geothermal, hydropower, solar, and wind energy.
Termed "renewable" because they are replenished in relative short time.
Future Energy Needs
Future Energy Needs
Although the US's energy history is one of large scale change as new forms of energy were developed, the outlook for the next few decades is for continued growth and reliance on the three major fossil fuels: petroleum, natural gas, and coal. The most realistic, economical, and viable resources of future energy needs for the immediate future are clean coal, methane hydrates, oil shale, and tar sands.
Global coal supply capable of meeting energy demands for decades
Clean-coal technology refers to processes that reduce negative environmental impacts
ex) washing coal to remove impurities, capturing sulfur dioxide & carbon monoxide from flue gases
Methane hydrates (methane locked in ice) recently discovered source of methane that form at low temps. and high pressure
Found in two types of geological settings:
in permafrost regions
beneath ocean floor at depths greater than 1,640 ft.
Some believe there's enough methane in form of hydrates to supply energy for hundreds of thousands of years
Natural gas expected to have larger role in power generation
This is due to increased pressure for clean fuels and low cost of constructing new natural gas-fired power plants
US natural gas expected to increase 40%
Demand expected to grow due to use as transportation fuel and also as source of alternative liquid fuels and source of hydrogen for fuel cells
Main waste associated with natural gas is carbon dioxide - greenhouse gas that contributes to global warming
Oil shales contain organic matter called kerogen
If oil shale heated in absence of air, kerogen is converted to oil
Approximately 3 trillion barrels of recoverable oil from oil shale globally, of which 750 billion is in the US
Oil shale extracted through either surface mining or
methods (extracted oil & gases through pumping)
Most oil shale in US found in Wyoming, Utah, & Colorado
Largest world reserves found in Estonia, Australia, Germany, Israel, & Jordan
Surface mining oil shale negatively impacts environment
Blasting, drilling, crushing, and heating involved in extraction
methods can impact aquifer
Tar sands contain bitumen, a semisolid form of oil that doesn't flow
Specialized refineries convert bitumen to oil
Tar sand deposits mined using strip-mining
methods use steam to extract bitumen from tar sands
Sulfur content from tar sands is high (5%)
Most deposits located in CA, Venezuela, and Canada (most concentrated, therefore most economical to mine
Oil from tar sands represents 2/3 of total global oil reserves
Environmental issues similar to those of oil shale
In free-market economy, energy price driven by supply and demand
Sudden shifts occur if either supply or demand change
Sometimes energy crisis brought on by failure of world markets to adjust to prices in response to shortage
Oil supply controlled by nations with reserves such as Saudi Arabia and Venezuela, who belong to OPEC (Organization of Petroleum Exporting Countries).
OPEC controls supply and can regulate price
Most of global energy supplied by burning oil
At current rates of consumption, reserves expected to last 50 years (US oil reserves expected to last 25).
Industrialization of China will significantly reduce these predicted estimates
Increased prices of crude oil make other sources (shale oil & tar sands) more economical
Fossil Fuel Resources & Use
Fossil Fuel Resources & Use
Coal is created by partial decomposition of organic material (286 mya) subjected to high temps. and pressure
Sulfur from decomposition of hydrogen sulfide by anaerobic bacteria became trapped in coal
Three types of coal exist:
lignite: brown, softest, lowest heat content
bituminous: soft, high sulfur content, constitutes 50% of US reserve
anthracite: hard, highest heat content, low sulfur content, constitutes 2% of US reserve
Peat is precursor to coal; used in some countries for heat; lowest heat content
Coal supplies 25% of global energy (China & US biggest consumers)
In US 87% used in power plants to generate electricity
Clean Air Act requires up to 90% reductions in release of sulfur-containing gases.
Oil is a fossil fuel formed from decomposition of deeply buried organic material under high temps. and pressure for millions of years
Compounds derived from oil are known as petrochemicals (used to manufacture paints, drugs, plastics, etc.)
Natural gas (known as methane or CH4) produced by decomposition of ancient organic matter under high heat and pressure
Conventional sources of methane associated with oil deposits
Unconventional sources include coal beds, shale, gas hydrates, and tight sands
Methane can be liquified (LNG), which allows for worldwide distribution
Two main methods of mining coal:
Preparation for extracting underground coal intensive:
must remove overburden
screen for size
wash to remove contaminants
Today, we're able to convert solid coal into gas or liquid fuel via clean-coal technology
Oil occurs at various depths in the crust
Extraction is expensive and difficult
Usually found trapped in layer of porous sandstone, subducted under nonporous rock such as limestone
Other times, oil is trapped at fault
Natural gas typically found just below nonporous layer and immediately above oil
Below oil, sandstone typically saturated with water
Oil extracted via drilling a well and puncturing limestone layer
Pressurized oil naturally flows upwards
Oil sent to refinery where it is "cracked" or refined via boiling at different temps
Finished products include: gasoline, heating oil, diesel oil, asphalt, etc.
Arctic National Wildlife Refuge (ANWR):
largest national wildlife refuge in US
located in NE Alaska
19 million acres
since 1977, question whether to drill for oil has been ongoing political controversy
debate ranges over accessibility to oil, world market reserves, and harm to environment
Keystone Pipeline System:
proposal to construct pipeline to transport synthetic crude oil and diluted bitumen from oil sands in Canada to multiple destinations in US. Plan stalled in Congress since Oct. 2012
Natural gas typically flows from wells under its own pressure
Collected by small pipelines that feed large gas transmission pipelines
In US, approx. 20 trillion cubic feet of gas produced each year
Natural gas from shale rock formations once uneconomical to extract now becoming fastest growing source of natural gas in US
Potential to become new global energy source
Process involves chemicals mixed with water and sand and injected into wells at high pressure to create fractures in rock, allowing oil and natural gas to escape upwards
Studies estimate up to 80% of natural gas wells drilled in next decade will require hydraulic fracturing
extraction time is short
well can deliver 20-40 years
allows for extraction in areas previously cost prohibitive
allows greater independence from foreign energy
creates jobs, stimulates economy
dangerous chemicals can contaminate water table
toxic, radioactive, & caustic liquid waste by-products pose storage, treatment, and disposal issues
no adequate safeguards or regulations in place
process results in contaminated water, air, destruction of streams, etc.
World Reserves & Global Demand
Coal, oil, and natural gas are nonrenewable energy resources. Following is a brief description of the known world reserves of these energy sources and their expected demands in the future.
Coal is currently world's single largest source of fuel used to produce electricity.
US has the largest proven recoverable coal reserves in world.
China is world's largest producer of coal.
Global coal reserves are estimated to last about 300 years at current levels of extraction.
45 - 70% of global oil reserves has already been depleted
Estimated to have 50 year supply on Earth remaining
US owns 3% of global oil reserves - but uses 30% of oil extracted globally each year
Increased competition from China & India increases cost
2/3 of oil used in US goes towards transportation
1/4 used in industrial processes
Oil imports decreased recently due to improvements in efficiency (higher fuel economy standards)
Majority of natural gas reserves located in Middle East (34%)
Russia & Kazakhstan together have 40% of global reserves, Middle East has 25%, & US has 3%
Based on our production levels in US, there is enough natural gas to last 75 years of domestic production
Estimates do not consider increased levels of domestic production or accessing restricted reserves in Arctic National Wildlife Refuge
Synthetic Fuel (synfuel):
any fuel produced from coal, natural gas, or biomass through chemical conversion.
Conversion process creates substances that are chemically the same as crude oil or processed fuels, but were synthesized through artificial means.
Raw materials used to produce synfuels subjected to intense chemical & physical changes to be used as crude oil or processed fuel.
Example: synthetic natural gas (SNG), which is produced from coal liquefaction
Pros & Cons of SNG
Solid Coal to Synthetic Natural Gas (SNG, Methanol, or Synthetic Gasoline
easily transported via pipelines
produces less air pollution
large supply of raw material
can produce gasoline, diesel, or kerosene without reforming or cracking
low net energy yield
requires energy to convert to SNG
increases depletion of coal
more expensive than petroleum products
Environmental Advantages / Disadvantages of Sources
abundant, established reserves will last 300 years at current rate of consumption
unidentified reserves estimated to last 1,000 years
US reserves estimated to last 300 years
high net-energy yield
US subsidies keep prices low
stable, non-explosive, not harmful if spilled
extraction done via strip mining or underground mining
above methods can disrupt land through erosion, runoff, and decrease biodiversity
up to 20% of coal ends up as fly ash, boiler slag, or sludge
combustion of coal leads to mercury, sulfur, & radioactive particulates in air
35% of all carbon dioxide released due to coal combustion
underground mining is dangerous / unhealthy
expensive to process & transport
pollution causes global warming, scrubbers, etc. are expensive
high net-energy yield
ample supply for immediate future
large US subsidies
versatile - used to manufacture many products (paints, medicines, plastics, etc.)
global reserves limited
produces pollution (SO2, NOx, CO2)
production releases contaminated waste-water & brine
oil spills, erosion, etc.
disruption of wildlife habitat
supplies are politically volatile
pipelines for distribution in place
easily transported as LNG over rail / ship
viewed by many as transitional fossil fuel as world moves towards alternative energy sources
global reserves to last 125 years at current rate of consumption
high net energy yield
produces less pollution than other fossil fuels
extraction is not as damaging to environment
H2S and SO2 are released during processing
LNG processing expensive and dangerous
Leaking of CH4 had greater impact on global warming than CO2
Disruption to collection areas
Extraction releases contaminated waterwater & brine
During nuclear fission, an atom splits into two or more smaller nuclei along with by-product particles (neutrons, photons, gamma rays, and beta & alpha particles). The Reaction gives off heat (exothermic). If controlled, the heat that is produced is used to produce steam that turns generators that then produce electricity. If the reaction is not controlled, a nuclear explosion can result.
The amount of potential energy contained in nuclear fuel is
10 million times
more than that of more traditional fuel sources such as coal and petroleum. The downside is that nuclear wastes remain highly radioactive for thousands of years and are difficult to dispose. The most common nuclear fuels are U-235, U-238, and Pu-239.
differs from U-238 in ability to produce a fission chain reaction
min. amount of U-235 required for chain reaction called
low concentrations of U-235 can be used if speed of neutrons is slowed
less than 1% of natural uranium on Earth is U-235
Uranium that's been processed to separate out U-235 is called "enriched uranium"
nuclear weapons contain 85% or more U-235; nuclear power plants contain about 3% U-235
Half life of U-235 is 700 million years
most common (99.3%) isotope of uranium
has half life of 4.5 billion years
when hit by neutron, decays into Pu-239, which is used as fuel in fission reactors
most depleted uranium is U-238
has half life of 24,000 years
produced in breeder reactors from U-238
plutonium fission provides 1/3 of total energy produced in typical commercial nuclear power plant
control rods in power plant need to be changed frequently due to buildup of Pu-239 that can be used for nuclear weapons due to buildup of Pu-240, a contaminant
international inspections of nuclear power plants regulate amount of Pu-239 produced by plants
Nuclear energy in US emerged in 1960's and increased rapidly until late 1980's
Decline due to cost overruns, higher operating costs, safety issues, and disposal of waste issues
Due to electricity shortages, cost increases of fossil fuels, and global warming, there is renewed interest
As of 2005, nuclear power plants provided 6% of world's energy and 15% of energy in US
By 2007, there were 439 nuclear reactors worldwide
US produces most of the nuclear energy, with 19% of households consuming it
Proponents of nuclear energy assert it is sustainable and reduces carbon and dependence on foreign oil
Operational safety record is also good in comparison to other fuel types
Critics assert it is dangerous and hazardous to store radioactive waste
Nuclear Reactor Types
Various reactor types are in use:
All have several commonalities:
a) core contains up to 50,000 fuel rods containing pellets
b) all use enriched or concentrated U-235 as fuel, able to produce 10 million times the energy than combustion of atom of coal
c) control rods move in and out of the core to absorb neutrons
d) a neutron moderator is a medium that reduces velocity of fast neutrons. Moderators can be water, graphite, or deuterium oxide (heavy water)
e) coolant removes heat and produces steam to generate electricity
Types of Reactors
: moderator and coolant are light or normal water
also known as "deuterium oxide" is form of water in which each hydrogen in the water molecule contains one proton, one electron, and one neutron, basically increasing efficiency of the nuclear reaction
: uses light water, graphite for moderation, and uranium for fuel. This type of reactor, built by the Russians, was very unstable and is no longer produced (see Chernobyl case study)
fast-breeder reactors and other experimental installations are in this group. They produce more fissionable material than they consume
Environmental Advantages / Disadvantages of Nuclear Power
no air pollutants
releases 1/6 CO2 as fossil fuel plants
water pollution is low
disruption of land is low to moderate
waste takes millions of years to degrade
not easily stored
decommissioning of older plants may cost $300 million or more
low net-energy yield energy required for mining uranium, processing ore, building and operating plant, dismantling plant, and storing waste
safety & malfunction issues
Safety Issues (Radiation & Human Health)
US DOE estimates up to 50,000 radioactive contaminated sites within US require cleanup with projected cost of $1 trillion dollars. Situation is many times worse in the former USSR
Chernobyl, Ukraine (1986):
Explosion in a nuclear power plant sent highly radioactive debris throughout northern Europe. Estimates run as high as 32,000 deaths, and 62,000 square miles remain contaminated. About 500,00 people were exposed to dangerous levels of radiation. According to the World Health Organization, the Chernobyl nuclear disaster will cause 50,000 new cases of thyroid cancer among young people living in the areas most affected by the nuclear disaster, and the incidence of thyroid cancer in children rose tenfold in the Ukraine region. In certain parts of Belarus, 36% of children who were under four when the accident occurred can expect to develop thyroid cancer. Cost estimates run as high as $400 billion. The cause was determined to be both design and human error.
occurs when extremely high temperatures are used to fuse together nuclei of isotopes of lightweight atoms, causing large amounts of energy to be released
A coal-fed electrical plant producing 1,000 megawatts of electricity in one day produces 30,000 tons of CO2 gas, 600 tons of SO2 gas, and 80 tons of NO2 gas.
In contrast, a fusion plant producing the same amount of electricity would produce 4 pounds of harmless helium as a waste product
dams built to trap water, channel water through turbines that generate electricity. Hydroelectric power supplies 10% of the electricity used in US and approximately 3% globally.
dams control flooding
low operating costs
no polluted waste products
long life spans
moderate - high net-useful energy
areas of water recreation
dams create flooded areas which displace residents
destruction of wildlife - disallow fish from migrating
sedimentation requires dredging
expensive to construct
subjected to Earth Quakes
Methods to control floods include:
straighten & deepen streams: Cons: removes bank vegetation & increases stream velocity = erosion; may increase downstream flooding & sedimentation
dams store water in reservoirs; during excess rainfall, dams can be overwhelmed
Identify & Manage Flood-Prone Areas:
precautionary building practices such as floodways, building elevation, & pump stations can be adopted
Levees or Floodwalls:
levees are raised embankments that prevent rivers from overflowing. They can break - Hurricane Katrina, 2005
this technique prevents natural flood plains & maintains biodiversity
Estimated 74,993 dams in America, blocking 600,000 miles of previously free-flowing rivers
Salmon are migratory fish that hatch in streams & rivers before swimming downstream to the ocean where they live most of their lives
Return to rivers & streams to spawn
In Sacramento Valley, CA, less than 5% of original salmon habitat available
Due to habitat destruction, at least 106 major US west coast salmon runs are extinct
Dams also change character of rivers, creating slow-moving warm pools ideal for salmon predators
Cutting overhead trees creates siltation, reducing O2 and increased temps = kill salmon eggs
Remediation Measures Taken:
creation of fish passage facilities (fish ladders) that help salmon migrate over or around dams
water released from upstream storage reservoirs used to increase velocity and reduce temp, improving migration conditions
juveniles also manually transported downstream in barges & trucks
Silting & Other Impacts
dam reservoirs in tropics, due to slow movement, serve as breeding grounds for mosquitoes, snails, and flies - vectors that transmit malaria, schistosomiasis, & river blindness
flooded areas behind dams destroy rich croplands & displace people
Effects on Watershed:
downstream areas are deprived of the nutrient-rich silt that would revitalize depleted soil profiles
Impact on Wildlife:
migration and spawning cycles are disrupted
occurs when silt (particles between sand and clay) settles out behind dams. Over time, silt must be dredged
freshwater evaporates and seepage via porous rock beds
a joint program between US EPA and US DOE. It's designed to protect environment through energy-efficient products and practices. Programs coordinated through Energy Star saved enough energy in 2005 to avoid greenhouse gas emissions equivalent to 23 million cars and $12 billion in utility bills. The symbol shown below appears on products that meet Energy Star standards.
Transportation consumes 2/3 of petroleum in US
This sector of energy consumption increases fastest among all sectors
Imports of crude oil expected to increase 66% by 2020
CAFE (Corporate Average Fuel Economy) standards are the avg. fuel economies of a manufacturer's fleet of passenger cars or light trucks
Testing follows guidelines established by EPA
Estimated that CAFE result in savings of over 55 billion gallons annually and 10% reduction in CO2
CAFE standards achieved via better engine design, efficiency, and weight reduction
Avg. CAFE standard of 27.5 mpg for cars has not increased in US since 1996
Improvements to fuel economy could be achieved by expanding CAFE standards to include:
reduced tire-rolling resistance
transition to higher voltage electric systems
performance-based tax credits
Hybrid Electric Vehicles
Should be capable of: driving at least 300 miles between refueling, be refueled quickly, keep up with other traffic
Gas powered cars meet requirements but produce large amounts of pollution & get poor gas mileage ex) 1 gallon of gasoline weighs 6 pounds. When burned, the carbon in it combines with oxygen from the air to produce 20 pounds or carbon dioxide. Electric car produces almost zero pollution but has limited range between charges. Hybrid vehicle attempts to increase mileage AND reduce emissions significantly while overcoming shortcomings of electric car.
Gasoline-hybrid cars contain FIVE features:
1) it has an engine
2) fuel tank (gasoline has much higher energy density than batteries (ex. 1,000 pounds of batteries needed to store as much energy as 1 gallon of gas or 6 lbs of gasoline)
3) advanced electronics allow electric motor to act as generator - can draw on batteries to accelerate engine
4) generator similar to electric motor but acts only to produce electrical power
5) batteries on hybrid car are energy storage device for electric motor - electric motor on hybrid car can put energy into batteries as well as draw energy from them
Parallel vs Plug-in Hybrids
contains fuel tank supplying gasoline to engine and set of batteries that supply power to electric motor. Both engine and electric motor power car simultaneously
hybrid cars with added battery. Can be plugged in to a 120 volt outlet and charged. Stored energy provide up to 60 miles per charge. Once charge used up, fuel in tank powers car
Alternative Fuels (LNG and CNG)
Natural Gas Vehicle (NGV):
alternative vehicle that uses compressed natural gas (CNG).
In 2010, there were 12.7 million natural gas vehicles globally
NGV require high compression, hence thick walled tanks, adding to material cost and weight
CNG is lighter than air, dispersing upwards in case of leak
Cost of CNG much cheaper than oil - some places in US sell for $1.09 per gallon equivalent of gasoline
NGVs and CNGs tend to corrode and wear out less rapidly than gas powered engine
Able to drive 500,000 miles on a CNG engine is not uncommon
Emissions are cleaner with NGVs, less wasted fuel, and lower emission of carbon and particulates
an automobile propelled by an electric motor that uses electrical energy stored in batteries
Popular in late 19th and early 20th century prior to advances in internal combustion engines
Renewed interest occurring in mid 2000s due to increasing cost of fuel prices
reduction of air pollution
reduced dependence on foreign oil
expensive (cost of lithium-ion battery)
drivers fear of batteries running out
includes rail, bus service, subways, airlines, ferries, and so on.
Often deciding factor as to where people live, work, and how much air pollution they're subjected to
In US, private cars are primary mode of transportation
Rest of the world uses mass transit as primary form of transportation ex) in US 3% of population use mass transit, in Japan, 47% use it!
Use of mass transit rises sharply with population density
Mass transit can be more efficient than private care in urban areas
consists of trains that share space with road traffic and trains that have their own right-of-way and are separated from road traffic
Bus Rapid Transit:
includes bus-dedicated and grade-separated right-of-ways, bus lanes, bus signal preference and preemption, bus turnouts, bus-boarding islands, curb realignment, off-bus fare collection, and level boarding
model of car rental where people rent cars for short periods of time. Promoted as alternative to owning a car and where people primarily use mass transit; not limited by office hours as with rental agencies; car sharing is basically for those who typically use mass transit but must travel greater distances from city every so often
consists of collecting & harnessing radiant energy from sun to provide heat and/ or electricity; can be generated via photovoltaic cells, solar collectors or central solar-thermal plant
uses sun's energy to heat water or air inside home, etc. Requires electrical input for pumps and fans; requires NO MOVING PARTS; structure is built to maximize solar capture ex) large, south-facing windows
supply for energy is limitless
reduces reliance on foreign oil
only pollution is in manufacturing of collectors
can store energy during day / release at night
inefficient where sunlight is limited
maintenance costs are high
systems must be periodically replaced
efficiency between 10 - 25% and not expected to increase soon
Hydrogen Fuel Cells
Most hydrogen used by industry in refining, treating metals, and processing foods
Enough hydrogen produced in US to power 20 - 30 million cars or 5 - 8 million homes
Hydrogen fuel cell similar to battery; has two electrodes, an anode, and a cathode, separated by a membrane
Oxygen passes over one electrode and hydrogen over the other
Hydrogen reacts with catalyst on anode that converts hydrogen gas into negatively charged electrons and positively charged hydrogen ions
Electrons flow out of cell to be used as electrical energy
Hydrogen ions move through the electrolyte membrane to the cathode, where they combine with oxygen and electrons produce water
Unlike batteries, fuel cells never run out
Hydrogen Cells - Pros & Cons
waste product is pure water
ordinary water (fresh or salt) can be used to obtain hydrogen
does not destroy wildlife habitats, etc.
energy used to produce hydrogen could come from renewable source
easily transported through pipelines
can be stored in compounds to make safe to handle
requires energy to produce hydrogen from either water or methane
changing current fossil fuel system into hydrogen-based system expensive
hydrogen is explosive
currently, difficult to store hydrogen gas for personal cars
any carbon-based, biologically derived fuel source such as wood, manure, charcoal, or bagasse grown for use as a biofuel. ex) biodiesel, methanol, and ethanol. Plants suitable for biofuel include switch grass, hemp, corn, & sugarcane. Biomass can also be used for building materials and biodegradable plastics and paper. Approximately 15% of global energy supply is derived from biomass; most common in developing nations.
renewable energy source
can be sustainable if deforestation controlled
could supply 1/2 of global energy demand
plantation (cottonwoods, poplar, sycamores, switch grass & corn) can be located in less desirable locations, reduce erosion, restore degraded land
requires water & fertilizer
uses inorganic fertilizers, pesticides, etc.
corn diverted to ethanol raises food prices
could cause massive deforestation
creates large levels of air pollutants
expensive to transport (heavy)
inefficient - 70% of energy lost as heat
is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. Currently used as biofuel and in manufacture of paper and building materials. For each 10 tons of sugarcane crushed, a sugar factory produces nearly 3 tons of bagasse. High moisture content of bagasse, typically 40 - 50%, is drawback to use as fuel. Approximately 90% of the cars in Brazil run on either alcohol or gasohol (a mixture of gasoline and ethanol) produced from sugarcane grown in Brazil.
Using the by-product of agricultural crops such as bagasse for paper production rather than wood, does offset commercial forestry practices and reduces rate of conversion of rain forest to commercial tree stock; however, this is offset by the clearing of tropical rain forests to areas suitable for growing sugarcane.
Bagasse has been used as sorbent material to clean up oil spills and to make disposable food containers, replacing materials like styrofoam.
How it works:
wind turns giant turbine blades that then power generators. Turbines can be grouped in clusters called wind farms.
entire US electrical needs could be met by wind in North Dakota, South Dakota, and Texas
wind farms can be quickly built as w built on out-on sea platforms
moderate-to-high energy yield
land underneath wind turbines can be used for agriculture
requires steady wind (few places available)
requires backup system in place when wind not blowing
visual & noise pollution
may interfere with migratory patterns of birds
may interfere with communication such as microwaves, TV & cell phone
utilizes small turbines connected to generators submerged in streams to generate power. Capacity tends to be 100 kW or less. Technology does not impede stream navigation or fish movement and is attractive in remote areas where power lines are not available
Factors to consider when installing small-scale hydro-power:
amt. of flow available on consistent basis
amount of drop (head) the water has between intake and output
Ocean Waves & Tidal Energy
How it Works:
natural movement of tides and waves spin turbines that generate electricity. Only a few plants currently operating globally (north coast of France and Bay of Fundy between US & Canada
minimal environmental impact
net-energy yield is moderate
construction is expensive
few suitable cases
equipment can be damaged in storms, etc.
How it works:
heat contained in subsurface rock and fluids from magma, etc. produce pockets of underground dry steam, wet steam, and hot water. This steam is then used to drive turbines, which generates electricity. Geothermal energy supplies less than 1% of energy needed in US. Currently being used in Hawaii, Iceland, Japan, Mexico, New Zealand, Russia, and CA. Tend to be situated near tectonic plate boundaries
moderate net energy yield
limitless & reliable energy source
little air pollution
reservoir sites are scarce
source can be depleted if not managed properly
noise, odor, land subsidence
can degrade ecosystem
Renewable Energy Law, China (2007):
rapid development in China resulted in significant increase in energy consumption, leading to rise in harmful emissions & power shortages.
China's 2007 Renewable Energy Law requires:
power grid operators to purchase resources from registered renewable energy producers
offers financial incentives & discounted lending for renewable energy projects
law designed to protect environment , prevent energy shortages, and reduce dependence on imported energy
includes use of photovoltaic and active solar water heating
imposes penalties for noncompliance
a bloom box is a collection of solid oxide fuel cells that use liquid or gaseous hydrocarbons (such as gasoline, diesel, or propane produced from fossil or bio sources) to generate electricity on the site where it will be used. 20% of Bloom Box cost savings result from avoiding transfer losses associated with transmitting energy over an electric grid. 15% of the power at eBay is currently created with Bloom Boxes. Other large companies that are using Bloom Boxes include Google, Staples, Walmart, FedEx, Coca-Cola, and Bank of America
Quick Review Checklist
forms of energy
power & units
laws of thermodynamics
present global energy use
energy production vs. consumption
energy production by sector
Future Energy Needs
Fossil Fuel Resources & Use
oil, natural gas
world reserves & global demand
coal, oil, natural gas, synfuels
Environmental Advantages / Disadvantages of Sources
coal, oil, natural gas
nuclear reactor types
pros and cons
silting & other impacts
hybrid electric vehicles
electric motor/drive assist
automatic start / shutoff
group / personal rapid transit
automated highway systems
bus rapid transit
solar (pros vs. cons)
hydrogen fuel cells
diagram & pros vs. cons
Brazil and biomass
diagram & pros vs cons
diagram & pros vs cons
Ocean Waves & Tidal Energy
diagram & pros vs cons
hot dry rock
pros vs. cons
Renewable Energy Law (China, 2007)
Based on Barron's AP ES, Princeton Review, Kaplan & Miller Text
Summarized by C. Chigounis
Methane Hydrate Formation
Methane Hydrate: Undersea Fuel of the Future
Tar Sands and Oil Shale
Algae Oil Biodiesel
Active vs. Passive Solar Power
Hydrogen Fuel Cell
LNG - Safe Fuel of the Future
Hybrid Electric Cars
Hydrofracking - A Closer Look