Solar Energy:
The Ultimate Renewable
Resource
What is Solar Energy?
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Originates from
nuclear fusion
reactions in the
sun
Nuclear Fusion Video (1.5")
Advantages and Disadvantages
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Advantages
 Chemical/radioactive pollutants remain on
sun
 Energy reaching the earth is incredible. By
one calculation, 30 days of sunshine striking
the Earth have the energy equivalent of the
total of all the planet’s fossil fuels, both used
and unused!
Disadvantages
 Sun does not shine consistently.
 Solar energy is a diffuse source. To harness
it, we must concentrate it into an amount and
form that we can use, such as heat and
electricity.
Putting Solar Energy to Use:
Heating Water
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2 methods of heating water:
passive (no moving parts) and
active (pumps)
In both, a flat-plate collector is
used to absorb sun’s energy to
heat water
Water circulates through the
closed system due to
convection currents
Tanks of hot water are used as
storage or to heat swimming
pools
Heating Water: Active System
Active System uses antifreeze so the liquid does not freeze if
outside temp. drops below freezing.
Active Water Heating Animation
Passive Heating of Living Spaces
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Best design of a building is for it to act as a
solar collector and storage unit. This is
achieved through three elements: insulation,
collection, and storage.
Efficient heating starts with proper insulation
on external walls, roof, and the floors. Doors,
windows, and vents must be designed to
minimize heat loss.
Collection: south-facing windows
Heating Living Spaces
Passive Solar
Passively heated
home in
Colorado
Heating Living Spaces
Passively heated homes use 60-75% of
solar energy that hits its walls and
windows
 A well-designed passive solar home can
reduce energy bills by 75% with an
added construction cost of only 5-10%
 About 25% of energy is used for water
and space heating
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Passive Solar Home Design Video (5")
Solar-Thermal Electricity:
Parabolic Dishes and Troughs
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Solar energy  electricity
Some solar power plants (see
picture from Mojave Desert) use
curved mirror called PARABOLIC
TROUGH to focus sunlight on a
pipe running down center of mirror.
Mirror focuses sunlight onto the
pipe, causing the water to boil and
produce steam. Steam can then be
used to turn a turbine to make
electricity.
Rows of solar mirrors are arranged
in "solar thermal power plants“.
They make electricity for more than
350,000 homes.
Solar-Thermal Electricity:
Power Towers
Sunlight is reflected off 1,800 mirrors
(HELIOSTATS) circling the tall tower.
 Fluid (liquid sodium) is heated by
sun's rays. The fluid is used to boil
water make steam  turn a turbine
and generator
 This experimental power plant is called
Solar II. It was built in California's
desert.
 Scientists say larger central tower power
plants can make electricity for 100,000
to 200,000 homes.
Solar Power Towers Animation (2.5")
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Direct Conversion into Electricity
Solar Cells or Photovoltaic Energy
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Sunlight converted directly to electricity using
solar cells
Solar cells also called photovoltaic cells (PV cells)
and can be found on many small appliances, like
calculators, and even on spacecraft
First developed in 1950’s for U.S. space satellites.
Made of silicon, special type of melted sand
Sunlight strikes solar cells and electrons (red
circles) are knocked loose. They move toward
treated front surface (dark blue color). When the
two surfaces are joined by a wire, a current of
electricity occurs between negative and positive
sides.
Solar cells  PV module  Array.
Some arrays are set on special tracking devices to
follow sunlight all day long.
Photovoltaic Energy Video
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Electrical energy from solar cells can be
used for lights/appliances
Solar energy can be stored in batteries
to light roadside billboards at night
Energy can be stored in a battery for
emergency roadside telephones where
no phone wires are around
Some experimental cars also use PV
cells. They convert sunlight directly
into energy to power electric motors
on the car.
Solar cells are used in satellites in outer
space. Here's a picture of solar panels
extending out from a satellite.
Rooftop PV
Modules