env100 note 54.docx

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28 Mar 2012

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ENV100 Lecture Notes Mar 14, 2012
New Renewable Energy Alternatives continued
Readings: Chapter 17
Offshore and high-elevation sites can be promising for wind power
Wind speeds are 20% greater over water than over land
Less air turbulence over water than land
Wind power has many benefits
No emissions once installed
More efficient than conventional power sources
o EROI ≈ 18:1
Turbines use less water than conventional power plants
Farmers and ranchers can lease their land
o Produces extra revenue
o Landowners can still use their land for other uses
Advancing technology is also driving down the cost of wind farm construction
Wind power also has some drawbacks
No control over strength and timing of wind
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 (mainly noise concerns but some people just don’t like the turbines)
More up-front costs
Wind turbines may pose a threat to birds and bats, which can be killed when they fly
into rotating blades
Geothermal energy is from Earth’s interior
Most easily exploitable near active volcanoes or plate boundaries where heat flow is
Geothermal energy is inexhaustible, in principle
Radioactive decay of elements deep inside the planet generates heat
Geothermal power plants use heated water or steam for direct heating and generating
If heated water is used faster than groundwater is recharged, the plant will run out of
o Can inject wastewater into the ground to replenish the supply
Patterns of geothermal activity shift naturally
o An area that produces hot groundwater now may not always do so
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