Conventional Energy Alternatives

Alternatives to Fossil Fuels

• Our global economy is largely powered by fossil fuels– Over 80% of our energy comes from oil, coal and

natural gas and generate 2/3rds of electricity

• Because fossil fuels are nonrenewable energy experts accept that we need to shift from fossil fuels to energy sources that don’t deplete as quickly and are better for the environment

Alternatives to Fossil Fuels

• We have developed a range of alternatives to fossil fuels, most of which are renewable with very little environmental impact

• However most remain more expensive than fossil fuels

– In the short term

– Once we invest in infrastructure to better transmit power from renewable sources prices should go down

Alternatives to Fossil Fuels

• Three alternative energy sources are currently the most developed and most widely used

– Nuclear Power

– Hydroelectric Power

– Biomass energy (Bioenergy)

• These exert less environmental impact than fossil fuels but more impact than “new renewable” alternatives

Alternatives to Fossil Fuels

• World’s Energy– Biomass/fuelwood provides 10%

– Nuclear power provides 6%

– Hydropower provides 2%

• Although their global contributions to overall energy supply is low, these energy sources contribute greatly to our generation of electricity– Nuclear and Hydropower together account for nearly

30% of the world’s electricity generation

Top Producers

Nuclear Power Produced in

gigawatts

Number of plants

United States 100.7 104

France 63.1 58

Japan 46.8 54

Russia 22.7 32

Germany 20.5 17

Hydropower produced (terawatt-hours)

China 485

Brazil 374

Canada 369

United States 276

Russia 179

Alternatives to Fossil Fuels

• Energy consumption patterns in the US are similar to those globally

– Except the US relies less on biomass and more on fossil fuels/nuclear power

• Sweden, on the other hand, has decreased its fossil fuel use by 36% since 1970

– Nuclear power, bioenergy and hydropower power provide Sweden with 60% of its total energy and almost 100% of all electricity

Where are Nuclear Power Plants located?

Nuclear Power

• Nuclear power occupies and odd and conflicted position in our modern debate over energy

– It is free of air pollution

– But there is the dilemma of radioactive waste disposal, nuclear weaponry and power plant accidents

NUCLEAR ENERGY

• A 1,000 megawatt nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day.

Figure 16-20

Nuclear Power

• Developed commercially in the 1950s

– Experienced the most growth in 1970

• The U.S. generates the most electricity from nuclear power

– Only 20% of electricity comes from nuclear sources

Nuclear Power

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

• We harness this energy by converting it to thermal energy which is then used to generate electricity

Nuclear Power

• The reaction that drives the release of nuclear energy in power plants is nuclear fission

– The splitting apart of atomic nuclei

– Each split nucleus emits energy in the form of heat, light and radiation as well as releasing multiple neutrons

• These neutrons also split thus resulting in a self sustaining chain reaction

How is Nuclear Fission Energy produced?

Nuclear Power

• 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

Nuclear Power

• For fission to begin in a nuclear reactor, the neutrons bombarding uranium are slowed down with a substance called a moderator

• Control rods = made of a metallic alloy that absorbs neutrons, and are placed into the reactor among the water-bathed fuel rods

• Containment buildings are constructed to prevent leaks of radioactivity due to accidents or natural catastrophes such as earthquakes

Nuclear Power

• If not controlled this chain reaction becomes a runaway positive feedback releasing enormous amounts of energy

– This type of power can create a nuclear bomb

• In a power plant fission is controlled so that only one of the two or three neutrons emitted with each fission even goes to induce another one

Nuclear Power

• We generate electricity from nuclear power by controlling fission in nuclear reactors

• The process begins when the naturally occurring element uranium is mined from underground deposits

• Uranium containing minerals are uncommon and uranium ore is in finite supply

– Considered nonrenewable

A typical light water reactor

Nuclear Reactors

Fig. 16-16, p. 372

Small amounts of radioactive gases

Uranium fuel input (reactor core)

Control rodsContainment shell

Heat exchanger

Steam TurbineGenerator

Waste heat

Electric power

Useful energy 25%–30%Hot

water output

Coolant

Moderator

Cool water input

Waste heat

Shielding Pressure vessel

Coolant passage

Water CondenserPeriodic removal and storage of radioactive wastes and spent fuel assemblies

Periodic removal and storage of radioactive liquid wastes

Water source (river, lake, ocean)

How does a Nuclear Power Plant Work?

Nuclear Power

• Uranium is used because it is radioactive

• Radioactive isotopes emit subatomic particles and high energy radiation as they decay

• The isotope uranium-235 decays and eventually forms into lead-207

• Each radioisotope decays at a rate determined by its half-life– The time it takes for half of the atoms to give off

radiation and decay

– The half life of Uranium-235 is 700 million years

Nuclear Waste

• Plutonium, cesium, strontium, and other “-ium” elements created in a nuclear reactor emit dangerous radiation that can literally knock electrons off the atoms of our cells, disrupting or destroying cell function or even causing cells to mutate into cancer cells.

• Radioactive elements emit radiation because they are unstable; they’d rather be something else.

• They achieve this by going to pieces; emitting particles and waves billions of times per second. This process is called a half-life.

What is a Half-Life?• Every radioactive element has a half-life

• Half-life is the time it takes for half of its atoms to decay.

• Half-lives range from a fraction of a second to billions of years –– 4.5 billion for uranium 238.

– 704 million for uranium 235

• The longer the half-life, the less intense the radiation.

• After 10 half-lives, an element is usually harmless

Nuclear Power

• Uranium-238 occurs naturally (over 99% of all uranium in nature)

• However, Uranium-238 does not emit enough neutrons to maintain a chain reaction when fissioned we use Uranium-235 for commercial energy

• Mined uranium ore must be processed to enrich concentration of U235 to at least 3%

• The enriched uranium is formed into pellets which are incorporated into metallic tubes called fuel rods

Nuclear Power

• When isotopes of uranium and plutonium undergo controlled nuclear fission, the resulting heat produces steam that spins turbines to generate electricity.

– The uranium oxide consists of about 97% nonfissionable uranium-238 and 3% fissionable uranium-235.

– The concentration of uranium-235 is increased through an enrichment process.

Nuclear Power

• After several years in a reactor enough uranium has decayed so that the fuel no longer generates adequate energy it must be replaced with new fuel

• Most spent fuel rods is disposed of as radioactive waste

NUCLEAR ENERGY

• After three or four years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete container.

Figure 16-17

NUCLEAR ENERGY

• After spent fuel rods are cooled considerably, they are sometimes moved to dry-storage containers made of steel or concrete.

Figure 16-17

Nuclear Power

• Control rods are made of a metallic ally and absorb neutrons – Placed into the reactor among the water-bathed

fuel rods

– Engineers move these control rods into and out of the water to maintain the fission reaction at the desired rate

– All of this takes place within the reactor core and is the first step in the electricity-generating process

Nuclear Power

• Using fission, nuclear power plants generate electricity without creating air pollution

– Compared to fossil fuels that emit sulfur dioxide, particulate matter, carbon dioxide and other GHGs

– nuclear power helps avoid emitting 600 million metric tons of carbon each year

• Equivalent to 7% of global GHG emissions

Nuclear Power

• Nuclear power has many advantages over coal

– Nuclear power poses far fewer chronic health risks from pollution for people living near power plants

– Uranium generates far more power than coal by weight or volume

• Less needs to be mined less damage to the environment

– Nuclear power plants are safer for workers than coal-fired plants

Nuclear Power

• Nuclear power is an extremely rich energy source.

• One gram of Uranium-235 delivers as much energy as 3.5 metric tons of coal!!!

• One in every 5 houses in the U.S. is supplied with nuclear energy.

Nuclear Power

• Nuclear power does have drawbacks

– The waste produced is radioactive

• It must be disposed on in a way that minimized danger to present and future generations

– If an accident occurs at a power plant (or if it is sabotaged) the consequences can be catastrophic

Nuclear Power

• Many governments, although not necessarily citizens) have judged the good to outweigh the bad

• Today the world has ~439 operating nuclear power plants in 30 nations

Nuclear Power

• Nuclear Fusion- the process that drives our sun’s vast output of energy and the force behind hydrogen bombs (thermonuclear)

• Involves forcing together the small nuclei of lightweight elements under extremely high temperature and pressure

• Fusion requires temperatures of many millions of degrees Celsius– Therefore not yet been developed for commercial

power

Nuclear Power

• Fusion experiments in the lab still require scientists to input more energy than they produce

• However, if we were able to develop a way to control fusion in a reactor we could produce vast amounts of energy using water as a fuel

• It would create only low level radioactive waste, no pollution emissions and no risk of accidents/sabatoge/weapons

Nuclear Power

• Three events have had influence in shaping public opinion about nuclear energy

– Three Mile Island

– Chernobyl

– Fukushima

Nuclear Power

• Three Mile Island

– Happened in Pennsylvania in 1979

– Worst nuclear disaster on US soil

– Nuclear meltdown (coolant water began draining, temperatures rose inside the reactor core and metal surrounding uranium fuel rods began to melt releasing radiation)

– Most radiation remained trapped inside the containment building

Nuclear Power

• Chernobyl– At the Chernobyl plant in Ukraine in 1986 and

explosion occurred

– Destroy the reactor and sent clouds of radioactive debris billowing into the atmosphere

– Radiation continued to escape from the plant for 10 days while countryside residents stayed in their homes• 10 days after the explosion the Soviet gov’t evacuated more

than 100,000

– Emergencies crews risked their lives to put out fires (some later died from radiation exposure)

Nuclear Power

• The accident killed 31 people directly and sickened or caused cancer in thousands more

• Health authorities estimate that most of the over 4,000 cases of thyroid cancer diagnosed in people who were children at the time resulted from radioactive iodine spread by the accident.

The Chernobyl accident

The destroyed reactor was encased in a massive concrete sarcophagus to contain further leakage

Nuclear Power

• Fukushima Nuclear Crisis-– On March 11, 20121 the Fukushima Nuclear Power

Station, just north of Tokyo suffered multiple reactor failures • After a 9.0 magnitude earthquake and 10m high tsunami

– Heat generated by the fuel rod meltdown caused reactor water to boil to steam, exposing the fuel rods to air• Produced hydrogen gas

– In a last resort to cool the fuel rods engineer pumped seawater into the coolant system• Much of that water became radioactive and was dumped

back out into the ocean

NUCLEAR ENERGY

• Scientists disagree about the best methods for long-term storage of high-level radioactive waste:

– Bury it deep underground.

– Shoot it into space.

– Bury it in the Antarctic ice sheet.

– Bury it in the deep-ocean floor that is geologically stable.

– Change it into harmless or less harmful isotopes.

• High-level radioactive waste- the form used in fuel rods.

• Low-level radioactive waste- the protective clothing, tools, rags, and other items used in routine plant maintenance.

Radioactive Waste

Nuclear Power

• Waste disposal remains a problem– What do we do with spent fuel

rods and other radioactive waste?

– The waste will continue emitting radiation for thousands of years because of the half-lives of uranium and plutonium

– We must place radioactive waste in an unusually stable and secure locations

Nuclear Power

• For many years the U.S., Soviet Union and more than a dozen other nations routinely dumped radioactive waste into the oceans

– Believed the barrels would not leak

– Believed if they leaked radioactive waste would be diluted by seawater

Nuclear Power

• Currently nuclear waste from power generation is being held in temporary storage

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

• However 3/4ths of the U.S plants now have no room left for this type of storage

• In total the U.S. power plants are storing over 60,000 metric tons of high-level radioactive waste

Storage of high-level radioactive waste

Nuclear Power

• The sites are vulnerable to terrorists attacks– especially poorly protected pools and casks that

store spent nuclear fuel rods.

– Terrorists could wrap explosives around small amounts of radioactive materials that are fairly easy to get, detonate such bombs, and contaminate large areas for decades.

• Over 161 million U.S. citizens live within 75 miles of temporarily stored waste

Nuclear Power

• Nuclear waste managers would prefer to send all waste to a central repository that can be heavily guarded

– Yucca Mountain was chosen

Nuclear Power

• Yucca Mountain

– Remote site in the desert of southern Nevada about 100 miles away from Las Vegas

– $13 billion was spent on its development but in 2010 support for the project ended

– It was a good place because it was remote and unpopulated, minimal risk of earthquakes, receives little rain to contaminate groundwater

Yucca Mountain, Nevada

Nuclear Power

• Concerns arose about the possibility of earthquakes or volcanic activity might destabilize the site’s geology

• Another concern was the idea of transporting radioactive waste across country

– “Mobile Chernobyls”

Cons Concerning Transportation of Nuclear Waste

• “Mobile Chernobyls” to carry 154 million pounds of radioactive waste through America’s heardland.

• Every year starting around 2010, 175 train and truck convoys filled with nuclear waste would pass through counties where more than a third of all Americans live.

• If an accident occurred en route, the nuclear fallout could kill thousands.

• Traveling convoys may become terrorists target.• Current mishap rates for trains and trucks suggest there would

be nearly 100 rail accidents and one or two truck accidents over the 24 years the Yucca Mountain would be accepting waste. (No harmful radiation is LIKELY to leak in those accidents…)

• About 6.5 million pounds of waste would be hauled 1 million miles by train and 100,000 miles by truck each year for 24 years.

• Waste will travel through 45 states!• Some politicians are in favor of Yucca Mountain only because it

will get their nuclear waste out of their back yard.

Failure of Yucca Mountain

Nuclear Power

• Without Yucca Mountain the U.S. has no place designated to dispose of its radioactive waste from commercial nuclear power plants

• It had expected to begin receiving radioactive waste in 2017

• Waste would be stored in a network of tunnels 1,000 feet underground (but 1,000 feet above the water table)

Pros about Long Term Storage at Yucca Mountain

• Storage in the middle of the desert is far safer for radioactive waste than scattered around the country in temporary holding facilities.

• Yucca Mountain is remote, has a sparse population, and is made of hard-rock formations.

• Yucca Mountain is a compromise between leaving radioactive waste at the surface where it is accessible but exposed and putting it thousands of feet below the surface where it cannot be retrieved.

• Yucca Mountain is the most studied geological formation ever!

Cons about Long Term Storage at Yucca Mountain

• The EPA has ruled that the DOE must demonstrate that Yucca Mountain can meet EPA standards for public and environmental health for 10,000 years. Does that mean radioactivity won’t be a threat after 10,000 years? NOPE! The peak radiation dose to the environment will occur after 400,000 years!

• Yucca mountain is only about 100 miles north of Las Vegas, a major metropolis.

• Scientific studies are incomplete making the decision to use Yucca Mountain “weak to moderate”.

• Scientists cannot agree if Yucca Mountain is watertight. Water could corrode containers and contaminate the surrounding landscape, seeping into groundwater.

• Tests showed that water seeped inside the mountain at a more rapid rate than government computers initially estimated.

• It’s only a matter of TIME before Yucca Mountain FAILS…

Nuclear Power

• Nuclear Power growth has slowed

• Since 1980 nuclear power has grown by 2.5% per year worldwide

• Public anxiety after Chernobyl made utilities less willing to invest in new plants

• Every nuclear plant has been far more expensive than expected

• Plants ages more quickly than expected– Including corrosion in coolant pipes

What Happened to Nuclear Power?

• After more than 50 years of development and enormous government subsidies, nuclear power has not lived up to its promise because:– Multi billion-dollar construction costs.

– Higher operation costs and more malfunctions than expected.

– Poor management.

– Public concerns about safety and stricter government safety regulations.

Advantages Disadvantages

No air pollution is produced Possibility of accidents

Countries can limit their need for imported oil

Disposal of the radioactive waste

Advantages and Disadvantages of Nuclear

Energy

Bioenergy

• Also known as biomass energy is obtained from biomass resources

• Biomass- organic material derived from living or recently living organisms and it contains chemical energy that originated ultimately with sunlight and photosynthesis– Plant matter- wood, charcoal from wood charred

in the absences of oxygen, matter from agricultural crops as well as combustible animal waste products (cattle manure)

Bioenergy

• To a poor farmer in a developing country bioenergy is cutting wood from trees and collecting livestock manure by hand to burn for heat and cooking

• To an industrialized farmer it means shipping his grain to a hi-tech refinery that converts it to liquid fuel to run automobiles

Bioenergy• In principal, bioenergy is renewable and releases no

net carbon dioxide into the atmosphere• It is renewable only if it is not overharvested

– Leads to deforestation– Soil erosion– Desertification– Damages biodiversity

• Heavily populated arid regions that support meager woodlands are most vulnerable to overharvesting– Africa and Asia

• Another drawback of bioenergy is it can be a health hazard as an indoor air pollutant when used for cooking and heating

Bioenergy

• Although most of the world still relies on fuelwood, charcoal and manure new bioenergy approaches are being developed

– Biopower- burning in power plants to generate heat and electricity

– Biofuels- liquid fuels used to power automobiles

• These are being developed in wealthier, industrialized nations like the U.S. and Sweden

Bioenergy

• Biopower

• Many sources for Biopower include waste products of existing industries or process

– Woody debris in logging operations/saw mills/paper mills

– Residue from agricultural crops (cornstalks and cornhusks), animal waste from feed lots, and methane from landfills

Bioenergy

• Bioenergy crops

– We are beginning to grow certain types of plants as crops to generate biopower

– Usually fast growing like bamboo, fescue, switchgrass, and willows

• Mainly used to produce biofuels

Bioenergy

• Combustion strategies

• Power plants used to combust biomass operate similarly to those fired by fossil fuels

– Combustion heats water, makes steam to turn turbines and creating electricity

– Usually biomass plants are located where they can take advantage of forestry waste

Bioenergy• Advantages

– Enhances energy efficiency

– Recycles waste products

– Lead us towards sustainability

– Mitigates climate change by reducing carbon dioxide emissions

– Capturing methane at landfills reduces GHG emitted into the atmosphere

– Geographically widespread/dispersed

– By replacing coal fired power plants it reduces sulfur dioxide emissions which would increase human health

Bioenergy

• Disadvantages

– If we burn crops/plant matter for power we deprive the soil of the nutrients it would have gained if we allowed the material to decompose

• Decrease soil fertility

– Concern of using more land just for biofuels-decrease biodiversity

Bioenergy

• Biofuels

– Two primary biofuels developed thus far are:

• Ethanol (for gasoline engines)

• Biodiesel (for diesel engines)

Bioenergy• Ethanol is the alcohol in beer, wine and liquor

• Produced as a biofuel by fermenting biomass by carbohydrate rich crops

• Ethanol is widely used in the US to reduce automotive emissions– Over 10.7 billion gallons of ethanol was produced

• Mostly from corn

– Any vehicle with a gasoline engine runs well on gasoline blended with up to 10% ethanol but more vehicles are being produced that can run primarily on ethanol

– Flexible fuel vehicles run on E-85- a mix of 85% ethanol and 15% gasoline

Bioenergy

• In Brazil, sugarcane residue is crushed to make bagasse- a material that is then used to make ethanol

• Ethanol from sugarcane accounts for 40% of all automotive fuel that Brazil drivers use

Bioenergy

• Growing corn to make ethanol exerts considerable impacts on ecosystems

– Increases pesticide use, fertilizer use

– Increase freshwater depletion

– Consequences of monocultural industrialized agriculture

– Takes up land that would otherwise be left in its natural condition

• If the US replaced all of its fuel with ethanol we’d have to expand corn acreage by 5x

Bioenergy

• Ethanol competes with food production and drives up food prices.

• About 21% of U.S. corn crop it used to make ethanol

• As farmers shifted move corn crops to ethanol in 2006-2008 corn supplies for food dropped and international corn prices skyrocketed

– Made it difficult for the poor to afford food

Bioenergy

• Growing corn to make ethanol requires substantial inputs of energy

• Oil is used for the farm equipment (to spray fertilizers and pesticides)

• Oil is also used to transport corn to processing plants

• Fossil fuels are used at the refineries to heat the water so ethanol can be distilled

• Therefore simply shifting from gasoline to ethanol for transportation needs would not eliminate our reliance on fossil fuels

Bioenergy

• Ethanol yields only a modest amount of energy relative to the energy that needs to be inputted

– In order to gain 1.5 units of energy from ethanol we need to expend 1 unit of energy

Bioenergy

• Biofuels

– Drivers with diesel engines can use biodiesel

• a fuel produced from vegetable oil/cooking grease/animal fat

– The oil is mixed with small amounts of ethanol or methanol (wood alcohol)

– In the U.S. we mainly use soybean oil

– Vehicles with diesel engines can run on 100% biodiesel

Bioenergy

• Biodiesel cuts down on emissions compared to petrodiesel

• Nontoxic and Biodegradable• Using waste oil as a biofuel is sustainable but

most biodiesel, like most ethanol, comes from crops specifically grown for that purpose– Has the same environmental impacts as growing corn

for ethanol– Growing soybeans, however, increases tropical

rainforest deforestation since most soybeans are grown in Brazil and Southeast Asia

Bioenergy

• The “next generation” of biofuel comes from algae

– Even jet fuel can be produced by algae

• Several species produce large amounts of lipids that can be converted to biodiesel

• Alternatively, carbohydrates in algae can be fermented to create ethanol

Bioenergy

• Algae can be grown in open ponds including raceway ponds that circulate algae around a racetrack

• Algae grow much faster than terrestrial crops and could be harvested every few days and produce many more times more fuel than other biofuel crops

• Algae farms can be set up just about anywhere

Bioenergy

• Because algae need nutrients waste water from sewage treatment plants could actually be a good source of water

• Piping in carbon dioxide speeds their growth

– Could make use of smokestack emissions

Bioenergy

• Energy from biomass is carbon-neutral

– It releases no NET carbon into the atmosphere

– Burning biomass does emit carbon dioxide but it is balanced by the fact that photosynthesis had pulled this amount of carbon from the atmosphere

Bioenergy

• However, bioenergy is not carbon neutral if natural forests are destroyed in order to plant bioenergy crops

– Forests sequester more carbon than crop plants

• It is also not carbon neutral if we have to input fossil fuels energy to produce the biomass

– Driving tractors, using and applying fertilizers and applying pesticides)

Hydroelectric Power

• We use kinetic energy of moving water to turn turbines and generate electricity

• Accounts for 2.2% of the world’s energy supply and 15.6% of the world’s electricity production

• For nations with large amounts of river water and the economic resources to build dams hydroelectric power has been a keystone of their development and wealth– China, Brazil, Norway, Austria, Switzerland and

Venezuela obtain large amounts of energy from hydropower

Hydroelectric Power

• Most hydroelectric power comes from impounding water in reservoirs behind concrete dams that block the flow of river water and then letting that water pass through the dam

• Because immense amounts of water are stored behind the dams we call this the storage technique– Hoover Dam on the Colorado River is an example

Hydroelectric Power

• The run of the river approach generates electricity without greatly disrupting the flow of rover water– Sacrifices the reliability of water flow across

seasons compared to the storage technique

– One method is to divert a portion of a river’s flow through a pipe and passing it through a power house and then returning it to the river

– Another method is to flow river water over a dam small enough not to impede fish passage

Hydroelectric Power

• Dam building began in the 1930’s in the United States when the federal government constructed dams as public projects partly to employ people and help end the economic depression

• U.S. dam construction peaked in the 1960s

– 3,123 dams were completed in a single year

Hydroelectric power

• For producing electricity hydroelectric power has two advantages over fossil fuels– Renewable

– No carbon compounds are burned in the production• No pollutants are emitted

• However, fossil fuels are used in the construction and maintenance of dams

• New evidence suggests large reservoirs release methane as a result of anaerobic decay in deep water

• But overall it accounts for only a small fraction of GHG emissions compared to fossil fuel combustion

Hydroelectric Power

• It is efficient with an EROI (energy returned on investment) ratio of 10:1

Hydroelectric Power

• Has it’s drawbacks– Damming rivers destroys habitats for wildlife as

riparian areas above dam sites are submerged and those below dam sites are often starved of water• Riparian- relating to or living or located on the bank of

a natural watercourse (as a river) or sometimes of a lake or a tidewater

– Natural flooding cycles are of rivers are disrupted• Prevents floodplains from receiving fresh nutrient laden

sediments

• Sediments become trapped behind dams

Hydroelectric Power

• Create thermal pollution

– Water downstream may become unusually warm if they are kept at unnaturally shallow levels

– If cold water is released rapidly in warm waters it can create thermal shock which can kill many aquatic organisms

• Dams also block the passage of fish by fragmenting the river

– Reduced biodiversity

Hydroelectric Power

• The weight of water in a large reservoir has also been known to cause geologic impacts (earthquakes) when water seeps intro fractures of bedrock

• If a dam collapses it can result in an earthquake or landslide resulting in death among people downstream

Hydroelectric Power

• China recently completed Three Gorges Dam

– World’s largest dam

– Its reservoir displaced over 1 million people

– Soon will generate as much electricity as dozens of coal fired or nuclear plants

Hydroelectric Power

• Unlike other renewable energy sources hydroelectric power is not likely to expand much more

– Many of the world’s largest rivers are already dammed

– People have grown more aware of the ecological impacts of dams

• Many people want to dismantle some dams and restore river habitats