Environmental
Science
Solar Energy
Lecture Notes
Solar Energy is RENEWABLE
Renewable vs. Nonrenewable
Energy Resources
DEMO:
Solar Energy can
be used 3 ways:
Solar Heating
Solar Heating  Electricity
Solar Radiation  Electricity
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Solar Hot Water
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1890: solar water heaters used in sunny
states like California, Arizona, and Florida
Artificial gas made from coal was available,
but cost 10X the price we pay for natural gas
today
1920: 1,000’s of solar water heaters had
been sold. BUT … large deposits of
oil/natural gas were discovered in U. S.
Solar water systems were replaced with
heaters burning these cheaper fossil fuels.
Solar collector for
heating water
A home in California in 1906
• Today, solar water heaters are
making a comeback (more than ½
million in California alone!).
• Heat water for homes/businesses
and swimming pools (see picture)
• Panels on roof contain water
pipes. Sun hits the panels and
pipes.
• Warmed water is then used in a
pool
Solar Thermal Electricity
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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.
These rows of solar mirrors
arranged in "solar thermal power
plants“. They make electricity for
more than 350,000 homes.
Solar Thermal Electricity
PROBLEM: Works only when sun is
shining. On cloudy days/at night, the
power plants can't make electricity.
 Some solar plants, use "hybrid"
technology During day they use sun. At
night/cloudy days they burn
natural gas to boil water to
generate electricity.
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SOLAR THERMAL ELECTRICITY
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Another form of solar power
(heat) to make electricity:
(Central Tower Power Plant) 
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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 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