Download 8. Renewable Energy - Wind and Water - science

23 May, 2017
Solar Power
Objectives
Be able to describe how electricity can be produced directly
and indirectly from the Sun’s rays and describe how the
intensity of the Sun effects the output power.
HSW: AF5: Working critically with evidence.
AF1: Thinking scientifically.
Will use again in:
Used before in:
PLTS: Independent enquirers: support conclusions, using reasoned arguments and evidence.
Used before in:
Will use again in:
Keywords
Light, heat, infra-red, thermal, photo-voltaic, intensity, precise,
accurate, reliable.
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Outcomes
All students should be able to:
 Be able to describe that electricity can
be produced from the Sun’s light and
heat.
Most students should be able to:
 Carry out an investigation into how the
voltage of a solar cell varies with light
intensity.
Some students should be able to:
 Evaluate the method used and suggest
improvements.
 Explain how a photovoltaic cell works.
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Solar Power
• Electricity can be produced by the
heating effect of the Sun or by directly
transforming light into electricity.
• These are called passive solar heaters.
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What is passive solar heating?
Passive solar heating involves any system that can capture
the Sun’s energy directly. This can be done using a simple
solar collector or by the design of a building.
For example, the heat of the Sun
can be focused on one spot
using a curved mirror.
Solar cookers work on this
principle and so require no fuel.
Other examples of passive solar
heating include a greenhouse or
a south-facing window.
What do you think are the advantages and disadvantages
of passive solar heating?
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Solar thermal power stations
• Some solar power
stations use curved
mirrors, which focus
solar energy onto pipes
containing water. This
heats the water and
forms the steam needed
to drive a turbine.
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• Thermal Towers boil
water into steam to
turn turbines that
drive generators and
produce electricity.
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• Demo solar furnace
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• Solar Cells use the light and transform
it directly into electricity in a
photovoltaic cell. (photo-light; voltaicvoltage making)
• Demo calculator(!)
• Demo solar powered car.
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How do solar cells work?
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Butt Head - Explanation
• A solar panel is made of silicon crystal.
• An atom of silicon contains a nucleus and
electrons.
• Student model
• Light is used to raise electrons from lower
energy levels to higher ones.
• When electrons are knocked loose, they flow
freely and create an electrical current.
• Photocells tend to be about 25% efficient.
• In other words only a quarter of the light has
enough energy to knock the electrons loose to
flow freely.
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Pros and cons of solar power
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PRACTICAL TIME!
How does the light intensity
affect the voltage output?
Method
Set up the equipment:
Distance
(cm)
0
7
14
21
Voltage
(V)
Analysis:
Draw a graph:
V/V
The light intensity goes
down as the light is further
away from the solar cell but
does the voltage?
d/cm
28
35
42
49
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How could you improve the experiment
to make it more precise, more accurate,
more reliable?
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Plenary: Mark your partners book. Tell them
WWW and EBI and give them a grade.
All students should be able to:
 Be able to describe that electricity can
be produced from the Sun’s light and
heat.
C
Most students should be able to:
 Carry out an investigation into how the
voltage of a solar cell varies with light
intensity.
B
Some students should be able to:
 Evaluate the method used and suggest
improvements.
 Explain how a photovoltaic cell works. A
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