Copyright © 2013 Pearson Canada Inc. © 2010 Pearson Education Canada 17 Energy Alternatives PowerPoint ® Slides prepared by Stephen Turnbull Copyright

Copyright © 2013 Pearson Canada Inc.

© 2010 Pearson Education Canada

17

Energy Alternatives

PowerPoint® Slides prepared by Stephen Turnbull


17-1



Upon successfully completing this chapter, you will be able to• Discuss the reasons for seeking alternatives to fossil fuels

• Summarize the contributions to world energy supplies of conventional alternatives to fossil fuels

• Describe the scale, methods, and environmental impacts of hydroelectric power, nuclear power, and biomass energy

• Outline the major “new renewable” alternative sources of energy and assess their potential for growth

• Describe a variety of new biomass, solar, wind, geothermal, and ocean energy technologies, and outline their advantages and disadvantages

• Explain the benefits of hydrogen and fuel cells and assess future options for energy storage and transportation

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Central Case: Harnessing Tidal Energy at the Bay of Fundy

• Large tidal ranges makes the Bay of Fundy one of the most suitable locations in the world for generating power from ocean tides

• Site of three tidal power plants

• Tidal power does not entail negative impacts of traditional hydroelectric dams

• Major impacts involve interference with normal currents and with marine life

“Not only will atomic power be released, but someday we will harness the rise and fall of the tides and imprison the rays of the Sun.”—THOMAS A. EDISON, 1921

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Alternatives to Fossil Fuels

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Hydropower, nuclear power, and biomass energy are conventional alternatives

• They exert less environmental impact than fossil fuels but more impact than the “new renewable” energy sources

• Each has benefits and drawbacks

• These are best viewed as intermediates along a continuum of renewability

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Hydropower, nuclear power, and biomass energy are conventional alternatives (cont’d)

• Fuelwood and other biomass sources provide 10% of the world’s energy, nuclear power provides 6.3%, and hydropower provides 2.2%

• Nuclear energy and hydropower each account for nearly one-sixth of the world’s electricity generation

• Canada relies heavily on hydropower

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Hydroelectric Power

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Modern hydropower uses two approaches

• Hydroelectric power = uses the kinetic energy of moving water to turn turbines and generate electricity

• Approaches:

- Storage technique = impoundments harness energy by storing water in reservoirs behind dams

- Run-of-river approaches generates energy without greatly disrupting the flow of river water

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© 2010 Pearson Education Canada17-10





Hydropower generates relatively little air pollution

• The great age of dam building began in the 1930s

• Hydropower accounts for 2.2% of the world’s energy supply and 16% of the world’s electricity production

- This is considerably higher in Canada

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Hydropower generates relatively little air pollution (cont’d)

• Hydropower has advantages over fossil fuels for producing electricity:

- It is renewable: as long as precipitation fills rivers we can use water to turn turbines

- It is clean: no carbon dioxide is emitted

- It is efficient: has an EROI of 10:1, as high as any modern-day energy source

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Hydropower has negative impacts, too

• Dams:

- Destroy habitats

- Disrupt natural flooding cycles

- Cause thermal pollution downstream and thermal shocks which can eliminate fish populations

- Block passage of fish, fragmenting the river and reducing biodiversity

- Have geological impacts (e.g. earthquakes)

- Have other social and economic impacts on local communities

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Hydropower may not expand much more• China’s Three Gorges Dam is the world’s largest dam

- Displaced over 3 million people, ecological impacts

• Hydropower not likely to expand much more

- Most of the world’s large rivers have already been dammed

- People have grown aware of the ecological impact of dams

- Developing nations will probably increase hydropower if they have rivers

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Nuclear Power

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Nuclear Power

• Public safety concerns and the costs of addressing them have constrained the development and spread of nuclear power in the Canada, Sweden, and many other nations

• 20% of U.S. electricity comes from nuclear sources

• Canada generates 15% of its electricity with nuclear power

• France receives 75% of its electricity from nuclear power

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Fission releases nuclear energy

• Nuclear energy = the energy that holds together protons and neutrons within the nucleus of an atom

• Nuclear fission = the splitting apart of atomic nuclei

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Enriched uranium is used as fuel in nuclear reactors

• Nuclear reactors = facilities within nuclear power plants

• Nuclear fuel cycle = the process when naturally occurring uranium is mined from underground deposits

• Radioisotopes = emit subatomic particles and high-energy radiation as they decay into lighter radioisotopes, ultimately becoming stable isotopes

• Most spent fuel is disposed of as radioactive waste

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Fission takes place in nuclear power plants• The neutrons bombarding uranium fuel in a reactor are

slowed down with a substance called a moderator (most often water)

• Control rods = soak up excess neutrons produced and are placed into the reactor among the fuel rods

• Some reactors (CANDU) make use of 238U an instead of 235 U-enriched fuels

- Breeder reactors

- Generate new fissile fuel at a faster rate than they are used up, less waste

- More expensive and more susceptible to explosive accidents

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Nuclear power generates little air pollution

• Generates electricity without creating air pollution from stack emissions

• International Atomic Energy Agency – 150X lower than fossil fuel combustion

- Took into account not only emissions but mining, transport of fuel, manufacturing of equipment, construction of power plants, disposal of wastes and decommissioning of plants

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Nuclear power generates little air pollution (cont’d)

• Advantages of nuclear power over fossil fuels:

- helps us avoid emitting 600 million metric tons of carbon each year

- Less damage to landscapes and less waste than coal mining

- Plants are safer for workers than coal-fired plants

• Drawbacks of nuclear power:

- Nuclear waste is radioactive

- Accidents can be catastrophic

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Coal versus nuclear power

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Nuclear power poses small risks of large accidents• 1979: Near-miss at the Three Mile Island plant in

Pennsylvania

• Meltdown = coolant water drained from the reactor vessel, temperatures rose inside the reactor core, and metal surrounding the uranium fuel rods began to melt, releasing radiation

• Most radiation remained trapped inside the containment building

- Cleanup lasted for years

- Residents have shown no significant health impacts

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Nuclear power poses small risks of large accidents (cont’d)

• 1986: explosion at the Chernobyl plant in Ukraine caused the most severe nuclear power plant accident the world has ever seen

- For 10 days, radiation escaped from the plant while crews tried to put out the fire

- The Soviet Union evacuated more than 100,000 residents

- The landscape around the plant for 19 miles remains contaminated

- The accident killed 31 people directly and up to several thousand developed fatal cancers

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• Atmospheric currents carried radioactive fallout across much of Northern Hemisphere

• Fallout was greatest where rainstorms brought radioisotopes down from the radioactive cloud

• Parts of Sweden received the highest fallout

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• March 11, 2011, a megathrust earthquake of magnitude 9.0 struck off the coast of Tōhoku, Japan

• It generated a massive tsunami that killed more than 15,000 people and inundated the Fukushima Dai-ichi power plant

- Nuclear reactors shut down automatically but fission continues in the reactor cores

- Backup generators failed due to the flooding

- Subsequent overheating set off fires, explosions, and core meltdowns – released radioactive materials

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Radioactive waste disposal remains problematic

• The long half-lives of uranium, plutonium, and other radioisotopes will cause them to continue emitting radiation for thousands of years

• Must be stored in unusually stable and secure locations and monitored for years

• Currently nuclear waste from power generation is held in temporary storage at nuclear power plants in Canada and other places around the world

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Radioactive waste disposal remains problematic (cont’d)

• Spent fuel rods sunken in pools of water to minimize radiation leakage

• Some store wastes in thick casks of steel, lead, and concrete

• In Lac du Bonnet, Manitoba, scientists are testing proposals for long-term storage deep underground in the stable, ancient crystalline rocks of the Canadian Shield

- Geological isolation

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Waste storage by geological isolation17-32



Multiple dilemmas have slowed nuclear power’s growth

• It is enormously expensive to build, maintain, operate, and ensure the safety of nuclear facilities

• Electricity is more expensive than from coal and other sources

• Nuclear power plants in Western Europe will be retired by 2030

• Asian nations are increasing nuclear capacity; 15 plants are under construction

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More Nuclear Power?

• Do you think Canada as a whole, or your province in particular, should expand its nuclear power program?

•Why, or why not?

weighing

the issues

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Fusion remains a dream

• Nuclear fusion = forcing together the small nuclei of lightweight elements under extremely high temperature and pressure

- Have not yet developed “cold” fusion for commercial power generation

- If we could control fusion, we could produce vast amounts of energy from water

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Traditional Biomass Energy

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Biomass energy means different things to different users

• Biomass = organic material that makes up living organisms

• People harness biomass energy from many types of plant matter

- Wood from trees

- Charcoal from burned wood

- Matter from agricultural crops

- Combustible animal waste products

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Traditional biomass sources are widely used in the developing world

• Over 1 billion people still use wood from trees as their principal energy source

• Fuelwood, charcoal, and manure account for 35% of energy use

- In the poorest nations it may be up to 90%

• Fuelwood and other biomass sources constitute 80% of all renewable energy used worldwide

• By the year 2030, 2.6 billion people will be using traditional fuels for heating and cooking in unsustainable ways

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Traditional biomass energy has environmental pros and cons

• It is essentially carbon-neutral, releasing no net carbon into the atmosphere

- Carbon released is carbon that was used in photosynthesis

- Only if biomass sources are not overharvested

- If overharvested leads to deforestation, soil erosion, and desertification

- Damaging landscapes, diminishing biodiversity, and impoverishing human societies

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“New” Renewable Energy Sources

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“New” renewable energy sources

• Energy from sunlight, wind, geothermal heat, ocean water, and hydrogen, as well as new technologies for biomass energy

• Three major applications:

- Power generation

- Space heating

- Fuel

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“New” renewable contributions are small but growing quickly

• Globally, we obtain only 0.5% of our energy from new renewable energy sources

• In Canada, only about 6% of electricity generation comes from renewable sources other than large hydro

• Most in Canada comes from wind, followed by small hydro (run-of-river) installations and biomass

• Wind power has grown by 50% each year from 1970s

• Rapid growth is likely to continue as population and consumption grow

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The transition won’t happen overnight

• Still technological, economic, and social barriers

• Most remaining barriers are political and economic

• Companies have not been eager to invest in the transition from fossil fuels to renewable energy due to limited profits and subsidies, tax breaks, and other incentives

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Biofuels and Biopower

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Biomass can be processed to make vehicle fuels

• Biofuels = biomass sources converted into fuels to power vehicles

- Corn, soybeans, plant matter

• Biopower = produced when biomass sources are burned in power plants, generating heat and electricity

- Crop residues, landfill gas, livestock waste

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Biomass can be processed to make vehicle fuels (cont’d)

• Ethanol = produces as a biofuel by fermenting carbohydrate-rich crops (corn)

• Any vehicle will run well on gasoline blended with up to 10% ethanol

• Flexible fuel vehicles = run on 85% ethanol

• Biodiesel = biofuel for diesel engines produced from vegetable oils (canola)

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Electricity can be generated from biomass

• Many sources of biomass can be used

- Waste products of existing industries or processes

- Woody debris from logging operations and sawmills

- Crops can be specifically grown, such as fast-growing willow trees or bamboo

- Co-firing combines biomass with coal

- Bacterial breakdown of waste to produce methane and other gases (landfill gas)

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Biofuels have environmental and economic benefits

• Adding biofuels helps fossil fuels combust more completely, reducing pollution

• Replacing gasoline with biofuels reduces emissions of nitrogen oxides, greenhouse gases, and other pollutants

• Reduces sulphur dioxide emissions when used instead of coal

• Economic benefits such as supporting rural communities and help reducing dependence of fossil fuel imports

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Biofuels also brings drawbacks

• Growing crops exerts tremendous impacts on ecosystems

- Fertilizers and pesticides

- Land is converted to agriculture

• Biofuel is competing with food production

• Substantial inputs of energy are required

- Fossil fuels are used in refineries to heat water to distil pure ethanol

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Solar Energy

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Passive solar heating is simple and effective

• Passive solar energy = the most common way to harness solar energy

• Buildings are designed to maximize direct absorption of sunlight in winter and keep cool in summer

• Low south-facing windows maximize heat in the winter and overhangs on windows block light from above in the summer

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Passive solar heating is simple and effective (cont’d)

• Thermal mass = construction materials that absorb, store, and release heat- Straw, brick, concrete - Strategically located to capture sunlight in cold

weather and radiate heat to the interior, and absorb heat during warm weather

• Planting vegetation in strategic locations• By heating buildings in winter and cooling them in

summer, passive solar methods conserve energy and reduce costs

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Active solar energy collection can heat air and water in buildings • Active solar energy collection = uses

technology to focus, move, or store solar energy

• Solar energy has been used for hundreds of years

• Flat plate solar collectors (solar panels) = one active method for harnessing solar energy

- Water, air, or antifreeze pass through the collectors, transferring heat throughout the building

- Heated water is stored and used later

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Active solar energy collection can heat air and water in buildings (cont’d)

• Power tower = mirrors concentrate sunlight onto receivers to create electricity

• Solarwall = combination of active and passive technologies

- Bombardier’s Canadair plant in Montreal

- South-facing wall with millions of tiny holes which allow air to pass

- Air passing through absorbs solar-generated heat and circulated through buidling

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Power-tower in Southern California, largest such facility in the world

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PV cells generate electricity directly

• Photovoltaic (PV) cells = collect sunlight and convert it into electrical energy

- These are used with wind turbines and diesel engines

• Photovoltaic (photoelectric) effect = occurs when light strikes one of a pair of metal plates in a PV cell, causing the release of electrons, creating an electric current

• A PV cell has two silicon plates, the n-type layer (rich in electrons) and the p-type layer (electron poor)

- Sunlight causes electrons to flow from the n-type to the p-type layer, generating electricity

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Copyright © 2013 Pearson Canada Inc.A typical photovoltaic cell17-60


Solar power offers many benefits

• The Sun will burn for 4 - 5 billion more years• Solar technologies are quiet, safe, use no fuels, contain no

moving parts, and require little maintenance• They allow local, decentralized control over power• Developing nations can use solar cookers, instead of

gathering firewood• Net metering = PV owners can sell excess electricity to their

local power utility• New jobs are being created• Solar power does not emit greenhouse gases and air

pollution

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Location and cost can be drawbacks• Not all regions are sunny enough to provide

adequate power

• Daily or seasonal variation in sunlight can pose a problem in stand-alone systems

- Far northern locations

• Up-front cost of equipment

- Currently can pay for themselves in 10-20 years

- Future technology could make this fall to 1-3 years

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Wind Energy

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Wind Energy

• Wind energy = energy derived from moving air masses (an indirect form of solar energy)

• Wind turbines = devices that harness power from wind

- Windmills have been used for 800 years to pump water to drain wetlands and irrigate crops and to grind grain into flour

• The largest wind power producer in Canada is the Le Nordais project in the Gaspé Peninsula

• Today, wind power produces electricity for nearly the same price as conventional sources

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Modern wind turbines convert kinetic energy to electrical energy

• Wind turns the blades that rotate machinery inside a compartment called a nacelle (gearbox, generator, and equipment to monitor the activity)

• Higher in height is better to minimize turbulence and maximize wind speed

• Turbines rotate in response to wind direction

• Doubled wind velocity results in an eightfold increase in power output

• Often erected in groups called wind farms

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Wind is the fastest-growing energy sector• Wind power grew 26% per year globally between

2000 and 2005, then quadrupling between 2006 and 2009

• Germany is world leader in installed wind capacity

• In Denmark, wind supplies 20% of nation’s electricity and is world’s leading producer of wind turbines

• In Canada, wind power could meet 15% of the nation’s electrical needs

• Wind speed are roughly 20% greater over water than over land and wind is less turbulent

• Winter weather also promotes stronger wind conditions

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Wind power has many benefits

• Wind produces no emissions once installed

• It prevents the release of large levels of CO2

• It is more efficient than conventional power sources • Turbines also use less water than conventional power

plants • Farmers and ranchers can lease their land

- Produces extra revenue - Landowners can still use their land for other uses

• Advancing technology is also driving down the cost of wind farm construction

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Wind power has some downsides – but not many• We have no control over when wind will occur • Companies have to invest a lot of research before

building a costly wind farm • Good wind sources are not always near population

centers that need energy • When wind farms are proposed near population

centers, local residents often oppose them (NIMBY)• Wind turbines also pose a threat to birds and bats,

which can be killed when they fly into rotating blades; however, there are ways of deflecting them

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Wind and NIMBY

•How would you react if your electric utility proposed to build a wind farm atop a ridge running in back of your neighbourhood, such that the turbines would be visible from your house?

• Would you support or oppose the development? Why?

• If you would oppose it, where would you suggest the farm be located? Do you think anyone might oppose it in that location?

weighing

the issues

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Geothermal Energy

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Geothermal energy

• Renewable energy is generated from deep within the Earth

• Radioactive decay of elements under extremely high pressures deep inside the planet generates heat

- This heat rises through magma, fissures, and cracks

• Geothermal power plants use heated water and steam for direct heating and generating electricity

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Geothermal energy (cont’d)

• But if a geothermal plant uses heated water faster than groundwater is recharged, the plant will run out of water

- Operators have begun injecting municipal wastewater such as Napa Valley, California

- Reinjecting water after it is used, back into the ground to replenish the supply

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We can harness geothermal energy for heating and electricity

• Geothermal ground source heat pumps (GSHPs) use thermal energy from near-surface sources of earth and water

- The pumps heat buildings in the winter by transferring heat from the ground into buildings

- In the summer, heat is transferred through underground pipes from the building into the ground

- Highly efficient, because heat is simply moved

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Use of geothermal power is growing

• Currently, geothermal energy provides less than 0.5% of the total energy used worldwide

- It provides more power than solar and wind combined

- But, much less than hydropower and biomass

• Commercially viable only in British Columbia

• Used extensively in Iceland

• In the right setting, geothermal power can be among the cheapest electricity to generate

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Geothermal power has benefits and limitations• Benefits:

- Reduces emissions

- It does emit very small amounts of gases

• Limitations:

- May not be sustainable

- Water is laced with salts and minerals that corrode equipment, shorten lifetime of plants, and add to pollution

- Limited to areas where the energy can be trapped

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Ocean Energy

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We can harness energy from tides, waves and currents

• The rising and falling of ocean tides twice each day throughout the world moves large amounts of water

• Differences in height between low and high tides are especially great in long narrow bays, like the Bay of Fundy or Skookumchuck Narrows

• These areas are best for harnessing tidal energy by erecting sluices across the outlets of tidal basins

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We can harness energy from tides, waves and currents (cont’d)

• Wave energy can be developed at a greater variety of sites than tidal energy

• The motion of wind-driven waves at the ocean’s surface is harnessed and converted from mechanical energy into electricity

• Offshore or coastal

• Wave energy is greatest at deep-ocean sites

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We can harness energy from tides, waves and currents (cont’d)

• Ocean currents are a third potential source of kinetic energy

• The Gulf Stream is an ideal spot

• Underwater wind turbines have been erected in European waters to test this idea

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Hydrogen Fuel and Power Storage

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Hydrogen fuel and power storage

• The development of fuel cells and hydrogen fuel shows promise to store energy in considerable quantities

- To produce clean, efficient electricity

• A hydrogen economy would provide a clean, safe, and efficient energy system

• Fuel cell = utilize chemical energy like batteries; Ballard- a leader

• Hydrogen could alleviate dependence on foreign fuels and fight climate change

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Copyright © 2013 Pearson Canada Inc.A typical hydrogen fuel cell

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Hydrogen fuel may be produced from water or other matter

• Electrolysis = electricity is input to split hydrogen atoms from the oxygen atoms of water molecules

2H2O 2H2 + O2

- Produces pure hydrogen

- Will cause some pollution depending on the source of electricity, but less than than other processes

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Fuel cells can be used to produce electricity

• Once isolated, hydrogen gas can be used as a fuel to produce electricity within fuel cells

• The chemical reaction involved in that fuel cell is the reverse of electrolysis

2H2 + O2 2H2O

• The movement of the hydrogen’s electrons from one electrode to the other creates electricity

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Hydrogen and fuel cells have many benefits

• We will never run out; hydrogen is the most abundant element in the universe

• Can be clean and nontoxic to use

• May produce few greenhouse gases and other pollutants

• Can be no more dangerous than gasoline in tanks

• Cells are energy efficient

• Fuel cells are silent and nonpolluting and won’t need to be recharged

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Conclusion• Many people are convinced that we need to shift to

renewable energy sources that will not run out and will pollute far less

• Renewable sources include solar, wind, geothermal, and ocean energy sources and hydrogen fuel

• Renewable energy sources have been held back by inadequate funding and by artificially cheap prices for nonrenewable resources

• Whether we can also limit environmental impact will depend on how soon and how quickly we make the transition

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Copyright © 2013 Pearson Canada Inc. © 2010 Pearson Education Canada 17 Energy Alternatives PowerPoint ® Slides prepared by Stephen Turnbull Copyright