lecture09 - Sun Power II Solar Heating Heat Engines Solar...

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ENGRI 1290 1 Sun Power II Solar Heating Heat Engines Solar Collectors
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ENGRI 1290 2 Lecture’s objectives • Understanding the principles of heat engines and solar heating • Learning the different types of solar collectors
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ENGRI 1290 3 Solar power Solar heating happens at all wavelength providing that the system can absorbe the radiations. What is the power density of sun light above the atmosphere? 1.36 kW/m 2 What is the power density at sea level ? 1 kW/m 2 However 30% of this light is diffuse light and cannot be used directly for solar heating. As a result the total useable “peak” power is 700 W/m 2 This is also 1 horsepower/m 2
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ENGRI 1290 4 How to use heat to produce work What is heat ? Heat is motion at the microscopic scale (atoms, …) What is work ? Work is motion at the macroscopic scale (us, machines,…) Transforming microscopic motion into macroscopic motion is the job of a heat engine . Useful work comes from motion along one direction However heat is random motion. How to turn random motion into directed motion? Force the heat to move in that direction… by connecting it to a cold source This creates a heat flow which can be harnessed to produce mechanical work.
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ENGRI 1290 5 The heat engine
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This note was uploaded on 09/14/2011 for the course ENGRI 1290 taught by Professor Gourdain during the Fall '10 term at Cornell University (Engineering School).

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lecture09 - Sun Power II Solar Heating Heat Engines Solar...

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