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FUNDAMETALS OF ENERGY CONVERSIONS Doc. Ing. Tomáš Dlouhý, CSc.

FUNDAMETALS OF ENERGY CONVERSIONS Doc. Ing. Tomáš Dlouhý, CSc. ENERGY. What is energy? Energy can be defined as the ability to do work If an object does work (exerts a force over a distance to move an object) the object uses energy 1st law of thermodynamic

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FUNDAMETALS OF ENERGY CONVERSIONS Doc. Ing. Tomáš Dlouhý, CSc.

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  1. FUNDAMETALS OF ENERGY CONVERSIONSDoc. Ing. Tomáš Dlouhý, CSc.

  2. ENERGY • What is energy? • Energy can be defined as the ability to do work • If an object does work (exerts a force over a distance to move an object) the object uses energy • 1st lawofthermodynamic • energycanbeconvertedfromoneform to another but cannotbecreatedordestroyed

  3. ENERGY FORMS AND CONVERSIONS • The five main forms of energy are: • Heat • Chemical – fuels and food • Electromagnetic • radiation • electricity • Nuclear • Mechanical • Energy can be changed from one form to another. • Changes in the form of energy are called energy conversions.

  4. ENERGY CONVERSIONS • Example - automobile engine • fuel is burned to convert chemical energy into heat • the heat energy is then changed into mechanical energy

  5. PRIMARY AND SECONDARY ENERGY • primary energy-comes from the direct exploitation of energy sources as theyexist in the nature • fossilfuels – gas, coal, oil, … • renewables – solar, hydro, wind, geothermal, ocean, biomass, … • nuclear • secondary energy - is generated from primary energy through a conversionsrequiringtechnicalmeans

  6. ENERGY CONVERSIONAND TECHNICAL MEANS

  7. THERMAL ENERGY CONVERSIONS • 2nd lawofthermodynamics • it is not possible convert ALL of the thermal energy derived from a high temperature source to mechanical energy • some thermal energy must be rejected to a low temperature sink • efficiencyofconversion

  8. CARNOT VAPOR CYCLE The thermal efficiency of this cycle is given as

  9. CARNOT VAPOR CYCLE • The thermal efficiency in any power cyclecanbeimproved by • increase ofthe maximum temperature at which heat is added • decreaseof the minimum temperature at which heat is rejected • Reasons why the vaporCarnot cycle is not used: • pumping process 1-2 requires the pumping of a mixture of saturated liquid and saturated vapor at state 1 and the delivery of a saturated liquid at state 2. • to superheat the steam to take advantage of a higher temperature, elaborate controls are required to keep TH constant while the steam expands and does work. • To resolve the difficulties associated with the Carnot cycle, the Rankine cycle was devised.

  10. RANKINE VAPOR CYCLE The simple Rankine cycle continues the condensation process 4-1 until the saturated liquid line is reached. Ideal Rankine Cycle Processes Process Description • 1-2 Isentropic compression in pump • 2-3 Constant pressure heat addition in boiler • 3-4 Isentropic expansion in turbine • 4-1 Constant pressure heat rejection in condenser

  11. SIMPLE VAPOR POWER PLANT

  12. CYCLE WITH GAS TURBINE Braytoncycle

  13. INTERNAL COMBUSTION ENGINES Two-stroke engine Four-stroke engine Diesel engine

  14. STIRLING ENGINES externalcombustionengine

  15. SOLAR THERMAL ENERGY CONVERSIONS concentratedsolarpowerplant solarpowertower

  16. WIND ENERGY CONVERSION Horizontal and vertical - axis windturbines

  17. ENERGY CONVERSIONS OF THE GEOTHERMAL RESOURCE Hot dry rock geothermalsystem 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock

  18. OCEAN ENERGY TECHNOLOGY • Tidal power • Wave power • Marine current power • Osmotic power • Ocean thermal energy

  19. DIRECT ENERGY CONVERSIONS • heating • chemical – combustionoffuels • solar – solarcolectors • geothermal • electricity • solar – photovoltaiccells • chemical – fuelcells

  20. Solar thermalenergy

  21. Solar photovoltaicelectricityproduction

  22. Fuelcells

  23. Requirements • Each student iscalled to elaborate • writen report (3-5 pages) • presentation (10 slides - max. 10 minutes) describingoneoffollowingitems: • Steampower plant • GasTurbines • InternalCombustionEngines • HydraulicTurbines • StirlingEngines • Solar ThermalEnergyConversion • WindEnergyConversion • EnergyConversionoftheGeothermalResource • OceanEnergy Technology • Direct EnergyConversion - Solar PhotovoltaicCells • Direct EnergyConversion - FuelCells • Dateofpresentation: 13.12.2011

  24. http://strojarna.jecool.net/

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