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Power
Choices
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| Pick
a common source of “power” and describe the various influences
necessary before it came into widespread us. Use a concept map. |
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Alternate
Energy Source
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| Pick
a nontraditional source of energy that may be used for societal needs.
Discuss the pros, cons, fundamental force, what is needed to capture
the energy and transform into useful work, and what is needed to foster
widespread use in our society. |
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Food
Chain
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| Draw
a pyramid to represent the food chain. Assume that a human’s
only sustenance is fish. Trace through the food chain to determine
how many plants are needed to sustain a human for 1 year. |
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US
Energy Sources
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| Which
energy sources do we (the USA) use most and where do they come from?
State in percentages. Which are nonrenewable versus renewable? Note
that the definition of renewable depends on the ability of the resource
to be replaced within a relatively short time period in our societal
frame of reference. |
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Transformation
of Energy
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| Trace
the transformations of energy from kinetic to potential (and indicate
the fundamental force) for a pot of water boiling on an electric stove
that is powered by a coal-fired power plant. |
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Power
Plant
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A 600-MWe power plant has an efficiency of 36% with 15% of the waste
heat being released to the atmosphere as stack heat and the other
85% taken away in the cooling water (see figure below). Instead of
drawing water from a river, heating it, and returning it to the river,
this plant uses an evaporative cooling tower wherein heat is released
to the atmosphere as cooling water is vaporized. At what rate must
15°C makeup water be provided from the river to offset the water
lost in the cooling tower? |
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Electric
water heater
(mass and energy transfer)
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| An
electric water heater heat at 140°F is kept in a 70°F room.
When purchased, its insulation is equivalent to R5. An owner puts
a 25-ft2 blanket on the water heater, raising its total
R-value to 15. Assuming 100% conversion of electricity into heated
water, how much energy (kWhr) will be saved each year? If electricity
cost 8.0 cents/kWhr, how much money will be saved in energy each year? |
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Reducing
Pollution by Adding Ceiling Insulation
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A
home with 2000ft2 of poorly insulated ceiling is located
in an area with an 8-month heating season during which time the outdoor
temperature averages 40°F while the inside temperature is kept
at 70°F (this could be Chicago, for example). It has been proposed
to the owner the $2000 be spent to add more insulation to the ceiling.
raising its total R value from 11 to 30 (ft2-°F-hr/Btu). The house
is heated with electricity that cost 8 cents/kWhr.
a. How much money would the owner expect to save each year and how
long would it take for the energy savings to pay for the cost of insulation?
b. Suppose 1 million homes served by coal plants could achieve similar
energy savings. Estimate the annual reduction in SO2, particulate,
cooling water, bottom ash, and carbon emissions that would be
realized.
Assume:
1kWhr electricity results in: 450 g coal used (250g C, 45g fly ash
(particulates), 9g S) 13.5g bottom ash 6120 kJ cooling water |
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