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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. 1 of 33 © Boardworks Ltd 2006 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. 2 of 33 © Boardworks Ltd 2006 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. 3 of 33 © Boardworks Ltd 2006 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? 4 of 33 © Boardworks Ltd 2006 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. 5 of 33 • Thermal Towers boil water into steam to turn turbines that drive generators and produce electricity. © Boardworks Ltd 2006 • Demo solar furnace 6 of 33 © Boardworks Ltd 2006 • 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. 7 of 33 © Boardworks Ltd 2006 How do solar cells work? 8 of 33 © Boardworks Ltd 2006 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. 9 of 33 © Boardworks Ltd 2006 Pros and cons of solar power 10 of 33 © Boardworks Ltd 2006 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 11 of 33 How could you improve the experiment to make it more precise, more accurate, more reliable? © Boardworks Ltd 2006 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 12 of 33 © Boardworks Ltd 2006