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Energy and Power

Energy and Power. Topic 8. Power production. Energy transformations. Chemical or nuclear energy in fuel. Thermal energy in steam. Rotational mechanical energy. Electrical energy in generator. Output 30% Electrical energy. Fuel. boiler. turbine. Input 100% Chemical energy. 10%

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Energy and Power

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  1. Energy and Power Topic 8

  2. Power production

  3. Energy transformations Chemical or nuclear energy in fuel Thermal energy in steam Rotational mechanical energy Electrical energy in generator

  4. Output 30% Electrical energy Fuel boiler turbine Input 100% Chemical energy 10% Thermal energy Friction in turbine 20% Thermal energy boiler 40% Thermal energy exhaust gas out chimney

  5. World energy use

  6. The SUN The sun is the energy source for most types of energy source. (except nuclear and tidal) Fossil fuels come from organic matter decomposed under high temperatures and pressure over millions of years. The organic materials required the sun to grow.

  7. Energy density • Energy density is used to compare different types of fuels. • Formula: De=E/m Units: J/kg • Fuels with higher energy density cost less to transport

  8. FuelEnergy Density (MJ/kg) Fusion fuel-300,000,000 MJ/kg Uranium-235:90,000,000 MJ/kg Natural gas-53.6 MJ/kg Gasoline (Petrol)-46.9 MJ/kg Diesel-45.8 MJ/kg Biodiesel-42.2 MJ/kg Crude oil-41.9 MJ/kg Coal-32.5 MJ/kg Sugar-17.0 MJ/kg Wood-17.0 MJ/kg Cow dung-15.5 MJ/kg Household waste-10 MJ/kg

  9. An oil fired power station produces 2000MW of power. • Determine the amount of energy produced in a day. • Estimate how much oil the power station needs each day.

  10. Solar power An active solar heater, whose efficiency is 35%, is used to heat 1500 kg of water from 20C to 60C. The average power received from the sun in that location is 0.82 kW/m2. a)Determine the amount of energy needed to heat the water. b)Calculate the area of the solar heater needed to heat the water in 3.0 hours.

  11. Photovoltaic cells A photovoltaic cell, with an area of 0.75 m2. Is placed in a location where the power received from the sun is 0.95 kW/m2. a)If the cell is 22% efficient, determine the amount of power produced. b)If the potential difference across the cell is 5.0 mV, how much current does it produce?

  12. Basic features of a horizontal axis wind turbine: a) Tower to support rotating blades. b) Blades that can be rotated to face into the wind. c) Generator. d) Storage system or connection to a distribution grid

  13. Wind generator

  14. Power equation

  15. Wind turbine practice • A wind turbine has a diameter of 45 m and the speed of the wind is 27 ms-1 on a day when the air density is 1.3 kgm-3. Calculate the power that could be produced if the turbine is 35% efficient.

  16. Energy in a wave • The energy in a wave is determined by the • Amplitude of the wave • Velocity of the wave • Gravity • Density of the water

  17. Wave power equation

  18. Power per unit length

  19. Wave calculation practice • Waves of amplitude 2.4 m roll onto a beach with a speed of 12 ms-1. (density of salt water is 1025 kgm-3) • Calculate how much power they carry per meter of shoreline. • Calculate the power along 2 km of shoreline.

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