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.

Fig. 15-3, p. 373

Nuclear power 6%

Geothermal, solar, wind 2.5% Nuclear power

8%Geothermal, solar, wind 1%

Hydropower 4.5%

Coal 23%

Biomass 3%

Hydropower, 3%

Natural gas 23%Natural gas 21%

Oil 33% Oil 39%

Coal 22%

World United States

Biomass 11%

Fossil Fuels• Coal• Natural gas – 50-90% methane plus other gases

like butane and propane– 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

• Product list

Products Which Are Made From Petroleum Products

STAGES IN COAL FORMATION

Fig. 15-11, p. 383

Increasing moisture content Increasing heat and carbon content

Peat (not a coal)

Lignite (brown coal)

Bituminous (soft coal)

Anthracite (hard 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

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 liquefactionRequires more mining of coal

Expensive Low net energy yield

• Methane hydrate- nature gas trapped in water molecules under the arctic permafrosttoo 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 reactorA 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 chainreaction.

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 ground2. Shoot it into space or into the sun or to the moon3. Bury it under the Antarctic ice sheet or the Greenland ice cap4. Dump it into descending subduction zones in the deep ocean5. Bury it in thick deposits of muck on the deep ocean floor

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

http://www.google.com/url?sa=i&rct=j&q=roof+gardens+advantages+for+environment&source=images&cd=&cad=rja&docid=IAnHrOTot-S1qM&tbnid=-7ahrIvFBP_UIM:&ved=0CAUQjRw&url=http://www.roofgreen.org/resources/&ei=l9wNUe7nGpH69gTD_4DgCw&psig=AFQjCNFwof1X8YFDKJKV4PYYVIFeS2hU6w&ust=1359948983491457

Hydroelectricity

• 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 = gasohol- 10%

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 vehicles-gasoline powered cars emit nearly 20 pounds

of CO2 for every gallon (6 pounds) burned

• 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 StandardsCorporate 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

• 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?

• Tar sands• Wind• Fission• Synthetic natural gas• Geothermal

• WIND

The fastest growing renewable energy resource today is ___

• Nuclear • Coal• Wind• Large-scale hydroelectric• Geothermal

• WIND

THE LEAST-EFFICIENT ENERGY CONVERSION DEVICE LISTED IS ____.

• STEAM TURBINE• FUEL CELL• FLUORESCENT LIGHT• INCANDESCENT LIGHT• INTERNAL COMBUSION ENGINE

• INCANDESCENT LIGHT

WHICH OF THE FOLLOWING IS NOT A UNIT OF POWER?

• BTU• Horsepower• Kilowatt• Joule• All are units

• Joule- it is a unit of energy!

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?

• 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 cellscoalwindnuclear

Solar cells

Which has the highest net energy for heating homes?

• 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