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Energy Efficient Heating Ventilating and Air Conditioning

Energy Efficient Heating Ventilating and Air Conditioning. Facility Energy Balance. Fundamental Equation. Qf = [(A/R + V pcp) (Tia – Toa) – Qint] / Eff A = area of envelope R = thermal resistance of envelope V = air flow rate pcp = product of air density and specific heat

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Energy Efficient Heating Ventilating and Air Conditioning

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  1. Energy Efficient Heating Ventilating and Air Conditioning

  2. Facility Energy Balance

  3. Fundamental Equation • Qf = [(A/R + V pcp) (Tia – Toa) – Qint] / Eff • A = area of envelope • R = thermal resistance of envelope • V = air flow rate • pcp = product of air density and specific heat • Tia = inside air temperature • Toa = outside air temperature • Qint = internal heat gain • Eff = efficiency of heating equipment

  4. Energy Saving Opportunities • Increase insulation: R • Decrease outdoor air flow rate: V • Decrease inside air temperature: Tia • Maximize utilization of internal heat: Qint • Increase efficiency: Eff

  5. Increase Insulation

  6. Insulate Un-insulated Walls/Ceilings Diminishing return of increasing insulation Adding R=10 hr-ft2-F/Btu and (Tia – Toa) = 35 F

  7. Insulate Metal Walls Insulate walls with spray-on cellulose or closed-cell foam

  8. Cover Single-pane Glass with Double-Wall Polycarbonate Sheets

  9. Replace Single Pane Skylights with Double-Wall Polycarbonate R = 1 to R = 4 Heating Cost Saving = $0.90 /ft2-yr Cost = $2 / ft2

  10. Insulate Dock Doors

  11. Reduce Air Flow

  12. Air Flow Fundamentals • Air flow in = Air flow out • Most plants exhaust more air than MAUs supply • Causes negative pressure and infiltration • Infiltration air reduces comfort, and heating energy

  13. Close Doors and Openings Install garage-door openers on lift-trucks to close shipping doors!

  14. Close Doors and Openings • Install garage-door openers on lift-trucks • Observation: Heating energy varies by 3X at same temp! • Discovery:Didn’t close shipping doors!

  15. Seal Unused Exhaust Fans

  16. Reduce Stack-Driven Infiltration

  17. Turn Off Excess Exhaust/Ventilation

  18. Turn Off Dust Collectors When Not In Use

  19. Shut Blast Gates to Dust Collectors When Not In Use

  20. Filter and Return Clean Air to Plant

  21. Filter and Return Clean Air to Plant Scrap Paper Collector

  22. Install VFDs on Vent Hoods

  23. Supply Outside Air to Exhaust Air Locations

  24. Supply Outside Air to Exhaust Air Locations Scrap Transport System

  25. Reverse Exhaust Fan Direction to Utilize Heat from Equipment

  26. Balance Plant Air Pressure with Differential Pressure Controlled MAUs • Manometer measures pressure difference and adjusts MAU air flow • Good choice if ventilation requirements change frequently (paint booths, etc.) • Minimizes infiltration and facilitates lower inside air temperature

  27. Use Indoor Heaters For Envelope Loss and Make-up Air Units to Heat Outside Air • Unit/IR/air rotation heaters • Reheat indoor air/space • 80% efficient since exhaust combustion gasses • Direct-fire make-up air units • Bring in and heat outside air • 100% efficient since combustion gasses added to outside air • Selection: • Heating outside air, even at 100% efficiency, requires more energy than re-heating inside air at 80% efficiency. • Use unit/IR heaters to make up envelope losses • Use make-up air units to heat outside air

  28. Reduce Indoor Air Temperature

  29. Move Thermostat Off Exterior Walls

  30. Use Programmable Thermostats • Lower/increase interior set-point temp during unoccupied periods • Important because heating/cooling load proportional to (Tia – Toa) • Example: If Toa = 50 F, then reducing Tia from 70 F to 60 F decreases heating load by 50% • However, thermal mass limits temperature drop and reduces savings

  31. Reduce Temperature Stratification With High-Volume Low-Velocity Fans • Problem • Excess temperature stratification • Solution • Install destratification fans

  32. Reduce Temperature Stratification With Gas-Fired Infrared Heaters • Problem • Warm air removed by exhaust fans or openings • Excess temperature stratification (warm air near ceiling) • Solution • Install radiant heaters

  33. Decrease Space Cooling Energy

  34. Replace Dark Roof with White Roof White roofs reflect sunlight and reduce roof cooling load by over 50%

  35. Use Economizer For Year-round Cooling • Economizers vary positions of dampers to use outdoor air when Toa < Treturn

  36. Identify Economizer Failure with LEA Cooling slope should flatten at low temps Broken and missing damper gears

  37. Verify Economizer Savings • In year-round cooling, can reduce cooling electricity use by ~40%

  38. Increase Cooling Air Set-point Temperature During Cool Weather Higher cooling air set-point temperature: Increases cooling load offset by economizer Decreases re-heat (if any) Decreases compressor load.

  39. Purchase High-Efficiency Roof-top Units

  40. Case Study 1 • Reduce winter ventilation & balance air pressure • Weather-adjusted gas use reduced by 51%.

  41. Case Study: Reduce Winter Ventilation & Balance Air Pressure

  42. Case Study: Reduce Winter Ventilation & Balance Air Pressure • Reduce Winter Ventilation & Balance Air Pressure • Weather-adjusted baseline gas use reduced by 51%.

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