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Hydropower History: Greeks
- 1. Waterwheels (4000 BC)
- -The water wheel is an ancient device that uses flowing or falling water to create power by means of a set of paddles mounted around a central wheel or axle.
- -Grind wheat into flour
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Gravitatational Potential energy: equation
PE = mgh
- m:mass
- g:gravitational acceleration
- h:altitude
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Hydropower equation
m = pV
- p:density of water
- V:volume of water
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Hydropower conversion efficiency
1. Gravitatational Potential Energy-----Kinetic Energy-------Electrical Energy
90%
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The latent heat(energy) of evaporation of water
2.27 x 10^6 Jkg^-1
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Approximately_____of the kinetic energy of flowing rivers is currently converted to electricity,
Approximately 10% of the kinetic energy of flowing rivers is currently converted to electricity,
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Run-of-the-river hydroelectric plants
- 1. In locations where there is a substantial natural river gradient (e.g. waterfalls), rivers can be diverted into turbines to generate electricity
- 2. The most Cost-effective and least environmentally damaging
- Ex. Niagara falls On
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Hyroelectric dams
1. Impound a reservoir of water that can flow through a turbine electric generators on demand
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Pumped Hyroelectric storage
1. Energy can be efficiently stored by pumping water into elevated reservoirs and then retrieved by letting the water flow back down
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Overall efficiency of Pumped Hydroelectric storage
75%
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Gravity dams are most often built in
wide canyons
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Arch and cupola dams are built of _____and most often built in _____
Arch and cupola dams are built of reinforced concrete and are most often built in steep canyons
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The goal of the dam builder is to
find a site that will provide the most water storage for the least cost
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The average EPR for hydroelectric systems
225, the highest of all energy systems
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Dam ownership and Operation in US
- 1. construction peaked in 1970s
- 2. 75,000 damns, oly 2,400 used for hydropower
- 3. Owned and operated by a variety of organizations, mostly private
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Dam Economic issues
- 1. Benfits of dam projects have been systematically overestimated
- 2. Reduced river flows
- 3. Increased evaporation rates
- 4. Short lifetime: 50 years
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Human and Environmental Costs of Dams
- 1. Loss of land due to permanent flooding
- -Displacement of indigenous human populations
- -permanent loss of wild river canyons, wildlife, recreation
- 2. Effects on river ecosystems
- -reduced downstream annual flow interfere with river ecosystems, nutrients, and farming
- -Barriers to upstream and downstream fish migration (salmon)
- 3. Greenhouse gas emissions due to the decomposition of submerged vegetation
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Notable dam failure
- 1975 Banqioa Reservoir Dam in China
- -caused 36,000 deaths downstream
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Stone Canyon Reservoir
- 1. Built in 1921
- 2. Capacity of 3.4 million gallons
- 3. UCLA lies in the floodplain
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Dam Removal
- 1. Growing pressure to remove dams and resotr river canyons to their natural state
- 2. 600 dams have been removed in the last 50 years
- 3. Cost effective
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Limitations to expand Hydropower
- 1. Earth's water cycle
- 2. Unavailability of sutiable sites to develope on
- 3. Uncertainties in climate predictions
- 4. Environmental tradeoffs
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