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Period 25: Energy from Wind and Biomass
Activity 25.1: Causes of Winds
1) The Earth’s winds
a) What causes wind circulation from the equator to the high latitudes?
The uneven heating of the Earth’s surface causes convection currents.
b) What causes these north-south winds to be deflected to the east or west?
Winds are deflected due to the spinning of the Earth, which produces
the Coriolis effect.
c) On a sunny day, which surface heats more quickly – land or water? Land
Which surface cools more quickly at night? Land
d) What causes land and sea breezes? What role do convection currents play?
During the day, air above the land is heated more quickly than air
above water. Warm air rises, creating a region of low pressure above
the beach. Air above the water moves inland toward this region of low
pressure. This circulation creates convection currents.
At night, warm air above the water rises, creating a region of low
pressure above the water. Air from the land moves seaward toward
the region of low pressure. The night time breeze moves in the
direction opposite to the day time breeze (out to sea).
e) Your instructor will demonstrate land and sea breezes. Does this demonstration
represent a daytime breeze or a night time breeze?
Activity 25.2: Generating Electricity from Wind Power
2) Generating Electricity from Winds
Your instructor will demonstrate a model wind electric generator.
a)
How can the moving blades of a wind turbine generate electricity?
The moving blades of the wind turbine turn a shaft that is
connected to an electrical generator. The motion of the turbine
blades causes magnets to spin near coils of wire in the
generator, producing electricity.
b)
What types of locations can provide the most wind power?
The best locations for wind farms include shorelines with their
constant land and sea breezes, flat plains with little topography
to interrupt wind flow, and mountain ridges at higher altitudes
than the surrounding landscape.
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c)
What are the advantages of generating electricity using wind power?
A renewable resource, no atmospheric pollution
d)
What (if any) are the environmental concerns about using wind power?
The environmental impact of wind turbines is primarily on
organisms in the atmosphere: birds, bats, and insects. Even
organisms not directly struck by the turbine blades can be killed
by the pressure of the spinning blades. To reduce damage to
birds, some wind farms have agreed to suspend operations
during night time migration of bird flocks in the spring and fall.
e)
Group Discussion Question: Why are there often objections to the
installation of wind farms from local residents?
Nearby residents may be bothered by the noise of the spinning
blades. Visitors to shorelines may complain that offshore wind
farms spoil their view.
Activity 25.3: Payback Time
3)
Payback Time for the Cost of Electricity
Some locations have sufficient wind power to use a windmill to generate
electricity for home use.
a) If a backyard windmill could generate an average of 628 watts of power
(0.628 kilowatts), how many kilowatt-hours of energy could this windmill
generate each year?
Find total hours of use:
Multiply kW by hrs:
24 hours
365 days
x
day
year

8 ,760 hours
year
0.628 kW x 8,760 hours = 5,501 kWh/year
year
b) Suppose that you have been given the choice of purchasing electricity or
generating your own electricity using a backyard windmill. Answer the
questions below to find how much money could you save in 10 years by
using the windmill as your only source of electric power.
1) If electricity costs $0.12 per kilowatt hour and you use 5,500 kWh
per year, how much would you pay for purchased electricity for ten
years?
Purchasing electricity for 10 years costs
$0.12
5,500 kWh
x
x 10 years
kWh
year
2

$6,600
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2) If the windmill costs $3,000 to purchase and install and $200 per
year for upkeep, how much would it cost you to generate your own
electricity for ten years?
Using the windmill for 10 years costs
 $200

$3,000  
x 10 years  $3,000  $2 ,000 
 year

3) How much money (if any) would the windmill save you after 10
years?
$5,000
You save $6,600 - $5,000 = $1,600 after 10 years.
4) Is the payback time for the windmill more or less than 10 years?
_less_
Activity 25.4: Energy from Biomass
4)
Using Biomass for Energy
a)
What is biomass?
Plant material or animal waste used as a fuel is called biomass.
b)
What are the common types of biomass used as biofuels?
Common types of biomass include wood, other plant material,
including algae, and animal waste.
Some biomass, such as
wood, is used directly as fuel, while some sources are converted
into other compounds, such as corn into ethyl alcohol (ethanol),
an additive to gasoline.
c)
How can biofuels be produced from algae?
Algae are small aquatic plants that can grow in fresh water, salt
water, or waste water. Algae can turn carbon dioxide and
radiant energy from the Sun into energy. Some types of algae
store energy as oils, which can be extracted to make fuel. Algae
can be grown in large tanks on land that is otherwise not
suitable for agriculture.
d)
How can biofuel be produced from animal waste?
Cow manure is collected and heated in a digester tank. The
decomposition of the mature produces methane gas. Methane is
burned for heating or to produce electricity.
4)
Bioethanol and biodiesel used for transportation
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a)
What is bioethanol?
Bioethanol is ethyl alcohol that is distilled from plant material,
such as corn, sugar cane or switchgrass.
b)
Much gasoline contains some ethanol; for example, E85 is 15% ethanol.
What advantage does E85 have over straight gasoline as a vehicle fuel?
Adding ethanol, which is derived from corn, to gasoline reduces the
amount of fossil fuel necessary to power vehicles and reduces the
particulate matter produced by them.
Alcohol combustion produces less soot than oil.
c)
What economic consequences are there to using large quantities of corn
to produce ethanol for vehicle fuel?
Higher food prices, higher value of agricultural land.
d)
How does biodiesel differ from bioethanol?
Bioethanol is produced from plant material. Biodiesel is
produced from vegetable oils and animal fats. Used cooking oil
can be a source of biodiesel.
e)
Group Discussion Question: Does the combustion of biodiesel and
bioethanol produce greenhouse gases?
Yes. However, in some cases, the carbon dioxide released by the
burning of biofuel is equal to the uptake of carbon dioxide from
the atmosphere by the plants that produced the biofuel. In this
case, the fuel is considered carbon neutral.
Activity 25.5: The Carbon Cycle
5)
The Carbon Cycle
a) What is the carbon cycle?
The carbon cycle is the exchange of carbon between living organisms
and the environment.
b) Where is carbon sequestered (stored) in the environment?
The oceans, the terrestrial biosphere and in sediments
c) What activities add carbon to the atmosphere?
Combustion of fossil fuels, respiration by animals and plants.
d) What activities remove carbon from the atmosphere?
Photosynthesis by green plants, carbon dioxide dissolved in the oceans
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6)
The Carbon Budget
a) What is the Earth’s carbon budget?
The carbon budget is the balance of the carbon exchanges between
carbon sinks and sources.
b) What are carbon dioxide sinks?
A carbon sink is a component of the carbon cycle that absorbs and
stores more carbon than it releases.
c) What are carbon dioxide sources?
A carbon source emits more carbon than it absorbs.
d) What role do the oceans play in the carbon budget?
The oceans are the largest active carbon sink on the planet.
e) Group discussion Question: How have human activities changed the balance of
the Earth’s carbon budget?
Human activity has altered the carbon budget of the Earth by:
the combustion of fossil fuel
deforestation, the clearing of trees for agricultural use, that results in
plant cover that can absorb less carbon dioxide than the original
vegetation.
acid rain has made sea water more acidic, which adversely affects coral
reefs, another carbon sink.
the manufacture of concrete also adds carbon dioxide to the
atmosphere.
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