hydropower (2)

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Source: Department of Energy

The energy to drive the hydrologic cycle isgained from the sun. Thus, hydropower is arenewable energy source and one that isprevalent all over the earth.

ENERGY PRODUCING SYSTEMS

HHYYDDRROO PPOOWWEERRIINNTTRROODDUUCCTTIIOONNHumans have used the power of flowingwater for thousands of years. Earlycivilizations used wooden paddle wheels togrind corn and wheat to flour. The wordHydro comes from the Greek word forwater. Hydropower traditionally representsthe energy generated by damming a riverand using turbine systems to generateelectrical power. However, there areseveral other ways we can generate energyusing the power of water. Ocean waves,tidal currents and ocean water temperaturedifferences can all be harnessed to generateenergy. More than 70 percent of the earth iscovered in water. In many ways the earthis a water planet and the water is inconstant motion thanks to the hydrologiccycle (see diagram).

The United States is one of the worlds topproducers of hydropower (see chart). Asmuch as 12 percent of the electrical energygenerated in the U.S. is currently derivedfrom hydropower systems. Parts of thePacific Northwest generate as much as 70percent of their electricity usinghydroelectric sources. More than half therenewable energy generated in the UnitedStates comes from hydroelectric dams.Hydroelectric power is currently the leastexpensive source of electrical power and ismuch cleaner than power generated usingfossil fuels.

HYDRO POWER PRODUCTION

Energy For Missouri: Today and Tomorrow - Educator's Guide

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Worldwide 20 percent of all electricity isgenerated using hydropower. Norwayproduces 99 percent of its electrical needsusing hydropower and New Zealandprovides 75 percent of its electrical needswith hydropower. Most of the rivers in theUnited States already have one or moredams constructed along their course.However, most of these dams are not used togenerate energy. Only two percent of themore than 75 thousand dams in the U.S. arecurrently used to generate electrical power.Most dams are designed to createrecreational opportunities (lakes), providewater for farm irrigation, serve as a source ofpublic drinking water, or are used as a formof flood control (See chart).

TTYYPPEESS OOFF HHYYDDRROOPPOOWWEERR SSYYSSTTEEMMSS

• IMPOUNDMENT

This type of hydropower system takes advantage of the conversion ofpotential energy of a dammed river to kinetic energy. The water is releasedfrom the dam through a series of pipes and used to operate turbine systemsand generate electrical power. The lake volume can be regulated andrepresents a source of stored energy. These systems can be very efficientwith as much as 90 percent of the energy being converted to electricalpower.

In some cases impoundment systems are used specifically to store energy.One of the first installations of this type of pumped storage system wascarried out by Ameren UE on a tributary of the Black River near Pilots Knobin Missouri. Electrical power generated from other sources is used to pumpwater up hill and fill a large storage impoundment. Typically this occurs atnight when electrical consumption is low. The stored water is then “tapped”during peak energy demands to provide additional power, such as on veryhot summer days when air-conditioning needs are great.


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Source: INEL/DOE

Pump storage systems offer a solution tothe intermittent nature of some energysources such as solar or wind power.During sunny or windy days electricalpower can be used to pump water uphill toan impoundment for storage. Duringcloudy days or during periods of low windthe impoundment then serves as a back-upenergy source. Such approaches allowrenewable energy sources such as solar orwind power to provide consistent anduninterrupted electrical power, regardlessof changes in solar availability or windvelocity.

• DIVERSION SYSTEMS

Diversion hydropower systems essentially channel the flow of a river or aportion of the flow to a turbine system used to generate electrical power. Aset of pipes or canals is used to redirect the flow and such systems usually donot require a dam. Such systems are only applicable to very fast flowingbodies of water and the amount of power produced is very dependent on theflow. These systems cannot store power in the way a dam does and are bestapplied for smaller scale local power applications in remote locations awayfrom main utility power grids.

• WAVE POWERAny one who has gone swimming in the ocean canattest to the power of even small waves. Wave powersystems involve constructing artificial canyons ortroughs designed to channel the power of each wave.This motion is then used to drive turbines, compressair, or lift hydraulic pumps designed to generateelectrical power. These systems are often applied togenerate specific local electrical power needs such aslighting a marker buoy or providing power to aremote lighthouse. However, entire systems could bebuilt along stretches of coast line and provide formuch larger power needs.


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• TIDAL ENERGY

The moon exerts a strong gravitational force on our planet. This forcecombined with the rotational movement of our planet creates uplift in ourocean surface every 12 hours. The level of this tidal effect is greatlyinfluenced by the depth of the water, local ocean currents, and geologicalconstrictions that amplify the effect. Tides can be as small as a few incheson some coastal regions (west Florida coast) to as much as 30 feet or more inother locations (upper Baja peninsula). Tidal energy systems typicallyinvolve erecting a dam across the opening of a bay. As the tide comes in theflow of water is directed towards a series of turbines to generate electricalpower. As the tide recedes the flow reverses and can again be captured togenerate power. Some systems use the incoming tide to fill a large reservoirsystem then the gates close and power is generated from the controlledoutflow. This type of power system has been successfully operated inFrance and currently provides power to 240,000 homes.

• OCEAN THERMAL ENERGY

These systems take advantage of the temperature difference in ocean waterwith depth. The radiant energy from the sun causes surface waters to besignificantly warmer than colder deep water. Such systems require at least a40 degrees Fahrenheit difference between surface and deeper waters. Thewarmer surface waters are used to vaporize a working fluid with a lowboiling point (such as ammonia). The expanding vapor is used to drive aturbine and generate electricity. The working fluid is re-condensed usingcolder deep-sea water and the process repeated. Some systems use oceanwater itself as the working fluid and have the advantage of producing freshwater in the process (via distillation). Such systems can be a significantadvantage in areas of the world where fresh water is limited. Ocean thermalenergy systems have been successfully piloted in Japan and Hawaii.However, the power generated from these systems is still currently moreexpensive than electricity generated by other means (fossil fuels,hydropower, etc). In the future, as the technology for ocean thermal energysystems is refined, both energy and fresh water may be routinely obtainedfrom the sea. Sixty percent of the world’s population is located near coastalregions and could greatly benefit from this emerging technology.


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HYDROPOWER POTENTIALAlaska through Missouri

Source: INEL/DOE

HYDROPOWER POTENTIALMontana through Wyoming

Source: INEL/DOE

SSPPEECCIIFFIICC CCHHAARRAACCTTEERRIISSTTIICCSS OOFF HHYYDDRROOPPOOWWEERR

Forty years ago as much as 40percent of the electricitygenerated in the United Statescame from hydroelectric dams.Coal-fired power utilitiescurrently provide the majority ofour electrical power and only 12percent of electricity consumed iscurrently generated usinghydropower. Hydropowersystems represent a renewableenergy source driven by thehydrologic cycle.

However, rivers and coastal areasare critical habitat for asubstantial amount of the lifefound on earth. Dams certainlychange the characteristics ofrivers and can have drasticallynegative impacts on fishpopulations and other aquaticorganisms. A dam on a river canmitigate the natural flood cyclesrequired by some fish forbreeding, can limit migrationsand can significantly alter thetemperature of the water. Manydam installations have beenshown to increase the processesof anaerobic degradation oforganic matter resulting inincreased levels of atmosphericcarbon dioxide. Dams alsocompete with other water needssuch as crop irrigation, drinkingwater and aquatic habitat


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TTHHEE FFUUTTUURREE OOFF HHYYDDRROOPPOOWWEERRIINN MMIISSSSOOUURRII

Missouri currently has nine pumpedstorage facilities, and twentyconventional hydroelectric plants. TheBagnell Dam on the Osage River(pictured above) produces 176megawatts of power and helps avoidthe emission of 220 tons per hour ofcarbon dioxide that would result froman equivalent coal-fired power plant. Atotal of 29 additional hydroelectric siteshave been identified for Missouri (1993U.S. Department of Energy study).Several of these sites are located onOzark rivers where development wouldbe inappropriate for environmental andcultural reasons. Even thoughMissouri’s potential concerninghydroelectric power is less than manyother states, hydroelectric power willbe an important part of a morediversified, localized powerdistribution system. Recentdevelopments in microturbinetechnologies set the stage for thedevelopment of smaller localizedapplications of hydropower.

protection. Water itself is becoming aprecious resource as evidenced by themany lawsuits filed over water rightsbetween the western states. In manyparts of the world entire countries are indispute over water rights. The ColoradoRiver, for example is so heavily utilizedalong its course that it no longerconsistently flows from the United Statesthrough Mexico to the sea. The last onehundred miles of riverbed is often dry asa result of water diversion associatedwith agricultural irrigation and drinkingwater needs.

However, many river systems in theUnited States already have one or moredams installed along their path to the seaand only three percent of such dams arecurrently used to generate electricalpower. Such dams could be retrofittedwith turbine systems and electricalpower obtained through modification ofpre-existing facilities. Hydropower hasthe potential to be critical facet in theapplication of other renewable energysystems. Wind power and solar powersystems are intermittent sources ofenergy. Pumped storage systems can beused to generate conventionalhydropower during time frames when theprimary source of power (wind or solar)is unavailable. New developments intidal, wave and thermal ocean energyalso promise to aid in establishing cleanand renewable energy sources. As thesetechnologies mature their practicalapplication will increase helping toprovide power for coastal populations.

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Bagnell dam-Ameren UE


hydropower (2)

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