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Conserving Energy

Learn important basic ideas for conserving energy, the biggest savings opportunities, space heating strategies, energy in transportation, improving engine efficiency, alternative fuels, benefits of recycling, and more. Discover practical ways to reduce energy consumption and make cost-effective improvements in various applications.

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Conserving Energy

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  1. Conserving Energy As in, not wasting it

  2. Basic Conservation Ideas • Biggest savings are possible: • applications with greatest consumption • greatest unit cost • cheapest improvements • Efficiency vs. Sacrifice

  3. Space Heating

  4. Q DT = –kA Dt Dx Conductive Heat Loss • Fourier Heat Conduction Law • rate of heat transfer: • Q is heat transferred • Dt is time increment • k is thermal conductivity, W/mK or Btu/ft·h°F • A is cross-sectional area • DT/Dx is temperature gradient

  5. Degree-Days (In/Out Temperature Difference)  (Number of Days) Or, DTDt Note that Q = –kADTDt/Dx Proportional to energy demand

  6. Q = –ADT /R Dt R-value • Thermal resistance of a material • RDx/k • So rate of heat transfer is • Unit: m2K/W or h·ft2·°F/Btu • Series R-values are additive

  7. Common Heat Losses • Air infiltration • substantial heat loss • benefit of ventilation • Standard fireplaces

  8. Energy in Transportation Capacity and Demand

  9. Engine Efficiency • Best at optimal power, rpm • Normal operation gives varying demand • efficiency gains from evening demand

  10. Power F·v

  11. Prominent forces • Acceleration F = ma • Hill climbing F = mgs Energy could be reclaimed by regenerative braking • Drag F v2 Lost to air turbulence

  12. Hybrid Vehicles • Regenerative braking • Peak power • More efficient engine, operating conditions

  13. Alternate fuels • Biodiesel, ethanol • Hydrogen • Methanol

  14. Fuel Cells • Not heat engines! • Less stringent constraint to efficiency • Fuels: Hydrogen, maybe methanol

  15. Lighting • Incandescent lighting is horribly inefficient • Fluorescent and LED are better • longer lifetime • issues with spectral quality • higher initial cost • hazardous materials in fluorescent tubes

  16. Recycling • Especially beneficial for aluminum • high energy cost to make metal from ore • Added benefit of reducing landfill use

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