7
Renewable Energy Sources—Solar
and Wind
Think About It Date
Page R72 Page #
· How can your
community take
advantage of solar energy
to meet its energy needs?
· Is your community
windy enough to make
wind power feasible for
electricity generation?
Renewable Energy Sources—Solar
and Wind
Investigate Part A Date
Pages R73-74 Page #
1b. Prepare a data table.
4a. What is the output of
your solar water heater
in Btu/ft2/min?
4b. Convert the output
of your solar water
heater from Btu/ft2/min
to Btu/ft2/hour.
4c. What would be the
output of sunlight per
day?
4d. Convert this value to
kWh/m2/day.
5a.How does the average
daily solar radiation per
for January compare
with that of July?
Explain.
5b. Record the values for
average daily solar
radiation for January and
July in your community.
5c. How does the daily
output of your solar
water heater compare to
the average daily solar
radiation for the two
months shown?
5d. Calculate the
estimated efficiency of
your solar water heater.
Renewable Energy Sources—Solar
and Wind
Investigate Part B Date
Pages R74-76 Page #
5a. Keep a record of the
wind speeds you are
measuring.
6a. Is the wind speed
the same in the
morning; the afternoon;
the evening?
6b. Is it windier in other
locations?
6c. Do trees or buildings
block the wind?
7a. Make a plot of wind
velocity throughout the
day.
8a. What percentage of
your household
electricity needs does
this represent?
8b. How much wind
power could be produced
with a 3-m blade?
9a. How did your
calculations compare
with those of others?
9b. What are the
characteristics of the
locations of homes that
have the highest wind
velocities?
9c. What are the
characteristics of those
with the lowest wind
velocities?
9d. Overall, how well
suited is your community
for wind power?
9e. Which locations in
your community are
optimally suited for wind
turbines?
9f. How realistic is the
assumption that two days’
worth of measurements
can be extrapolated to
yearly averages?
9g. For how long should
measurements of wind
velocity be taken to get
an accurate measure of
wind velocities in you
community?
Activity 8
Renewable Energy Sources—Solar and Wind
Digging Deeper Date
Pages R77-81 Page #
Solar energy forms include:
•direct solar radiation
•indirect solar radiation
•wind
•photovoltaic
•biomass
Nuclear fusion in the sun’s core is what keeps the sun hot
The surface of the sun radiates electromagnetic energy in all directions in the visible, ultraviolet and infrared ranges of the spectrum
The sun’s energy travels at the speed of light, reaching Earth in about eight minutes
Only a small fraction of this energy reaches the Earth, because the Earth is small and very far away from the sun
However, the sun is far more than enough to provide all of the Earth’s energy needs (if it could be harnessed in a practical way)
Insolation the rate at which a given area of land receives solar energy
Insolation depends on:
•latitude
•season of the year
•time of day
•cloudiness of the sky
•clearness of the air
•slope of the land surface
Earth its axis of rotation is tilted 23.5° as it orbits the sun
Earth points toward the sun at one end of its orbit (summer), and away from the sun at the other end (winter)
In summer, the sun is at a high angle in they sky, causing the days to be long
In winter, the sun is at a low angle in the sky, causing the days to be short
http://www.eram.k12.ny.us/education/sctemp/533f6c792a28a4a3199aff54741a3dbc/1248403241/solarAngle.swf
Solar heating there are two basic types:
systems
1. active
2. passive
Active system special equipment, in the form of a solar collector, is used to collect and distribute solar energy
Passive system the home is designed to let in large amounts of sunlight; the heat produced from the light is trapped inside
Passive systems do not rely on mechanical equipment, but they are not as effective as active systems
Solar water have two main parts:
heating systems
1. a solar collector
2. a storage tank
The solar energy is collected with a thin, flat, rectangular box with a transparent cover
The bottom of the collector box is a plate that is coated black on the upper surface and insulated on the lower surface
The solar energy that strikes the black surface is converted to heat, while cool water is circulated through pipes from the hot collector box to a storage tank
The water is warmed as it passes through the collector box
Solar collectors can be used in large commercial buildings for heating and cooling
Photovoltaic cells/ convert light energy directly into
system electricity
Even though the efficiency of these systems is not high, they are often the cheapest form of electricity
Wind power has been increasingly used over the past 25 years to create electricity
Wind power can be used on a large scale to produce electricity for communities (wind farms) or it can be used on a smaller scale to meet part or all of the electricity needs of a household
Wind energy California leads the country in
in the U.S. the generation of electricity from wind turbines
Other areas that have potential include:
•the Rocky Mountains
•the flat Midwest states
•Alaska
Cost of wind in 2000, the cost of wind power
power was less than six cents per kilowatt-hour, making it competitive with electricity produced by coal-fired plants
Renewable Energy Sources—Solar
and Wind
Check Your Understanding Date
Page R81 Page #
1. How does the sun
produce solar energy?
2. What factors determine
the rate at which solar
energy is received by a
given area of the Earth’s
land surface?
3. What are the
differences between
passive and active solar
heating systems?
4. Why must solar
energy systems occupy
a much larger area, per
unit of energy produced,
than conventional
systems that burn fossil
fuels?
Renewable Energy Sources—Solar
and Wind
Understanding and Applying Date
Page R82 Page #
1a. What size of a system
would be required to
meet these heating
requirements?
1b. What would the
system cost?
1c. Find out how much it
costs to heat a home for
five months in the winter
where you live.
Calculate how many
years it would take to
recover the cost of the
solar water-heating system.
2a. Why is metal used for
tubing in flat plate solar
collectors?
3. Why is wind power
more efficient than
generating electricity
from all the methods
that involve heating
water to make steam?
4. Why is wind power
less efficient than
hydropower?
5. Calculate the wind
energy generated in the
two windy hours
compared with the 22
less windy hours.
6. Looking at the U.S.,
where does your
community fall in terms
of wind potential?
7a. Determine the number
of wind turbines that
would be needed to
produce the electricity
equivalent to a large
electric power plant.
7b. Calculate the
reduction in the amount
of SO2 emitted per year.
7c. What are some
problems that might be
encountered with the
wind farm?
Renewable Energy Sources—Solar
and Wind
Inquiring Further Date
Page R83 Page #
1. Solar-thermal
electricity generation
Research how a solar
thermal power plant,
like the LUZ plant in the
Mojave Desert in
California, produces
electricity. Diagram how
such a system works.
what are the kilowatt-
hour costs of producing
electricity using this
method? What does the
future hold for power
plants of this kind?
2. Photovoltaic electricity
Investigate photovoltaic
electricity generation and
discuss the results of
your investigation with
the class.
3. History of wind energy
or solar energy
Investigate how people
in earlier times and in
different cultures have
harnessed the sun or
wind energy. What
developments have taken
place in the past hundred
years? How is wind
energy being used today?
include diagrams and
pictures.
4. Wind farms
Prepare a report on how
electricity is generated
on wind farms. Describe
types of wind generators,
types and sizes of wind
farms, the economics of
electricity production on
wind farms, and the
locations of currently
operating wind farms in
the U.S. Include diagrams.