Energy-Saving Designs for Existing Buildings

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Dan Watkins of Bornquist, Inc. in Chicago, IL presents Energy-Saving Designs for Existing Buildings focusing on pumping and boiler strategies. Presented at the February 9, 2010 Chapter Meeting & Seminar.

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Energy-Saving Designs for Existing Buildings

  1. 1. Energy-Saving Designs for Existing Buildings Presented by: Dan Watkins, LEED AP Bornquist, Inc.
  2. 2. Topics to Cover <ul><li>Designing for Efficiency </li></ul><ul><li>System Design Examples </li></ul><ul><ul><li>Variable Speed Pumping </li></ul></ul><ul><ul><li>Hot Water Boiler Systems </li></ul></ul><ul><li>Final Tips </li></ul>
  3. 3. Designing for Efficiency <ul><li>Equipment Efficiency </li></ul><ul><li>System Efficiency </li></ul><ul><li>Payback Considerations </li></ul>
  4. 4. Equipment Efficiency <ul><li>Equipment efficiency does play a role in increasing the overall efficiency of the system. The efficiency of some types of equipment are directly related to the system in which they are installed. Equipment efficiency can also be affected by the geographic area in which it is installed. </li></ul>
  5. 5. System Efficiency <ul><li>System Efficiency plays the biggest role in determining the overall affect of the replacement equipment. Designs should be based on overall system efficiency and not only based on individual equipment efficiency ratings. </li></ul>
  6. 6. Payback Considerations <ul><li>Payback is also a very big consideration, especially in retrofit projects. Sometimes the payback time period can dictate the design chosen. A good payback analysis blends initial cost with system efficiency, not just equipment efficiency. </li></ul>
  7. 7. System Design Examples <ul><li>Variable Speed Pumping </li></ul><ul><li>Boiler Systems </li></ul>
  8. 8. Variable Speed Pumping Applications <ul><li>Easy Pump Balancing </li></ul><ul><li>Variable Flow Systems </li></ul><ul><ul><li>Hot Water Pumps </li></ul></ul><ul><ul><li>Chilled Water Pumps </li></ul></ul><ul><ul><li>Condenser Water Pumps </li></ul></ul><ul><ul><li>Zone Pumps </li></ul></ul><ul><li>Pressure Booster Packages </li></ul>
  9. 9. Variable Speed Pumping <ul><li>VFD turns down the speed of the pump to match demand. </li></ul><ul><li>HP requirements drop significantly compared to flow rate reduction. </li></ul>
  10. 10. Variable Speed Pumping GPM 2 GPM 1 HEAD 2 RPM 2 RPM 1 HEAD 1 HP 2 HP 1 RPM 2 RPM 1 RPM 2 RPM 1 HP 2 HP 1 GPM 2 GPM 1 GPM 2 GPM 1 HEAD 2 HEAD 1 Affinity Laws 2 2 3 3 = = = = =
  11. 11. Variable Speed Pumping <ul><li>Easy Pump Balancing </li></ul>Pump Selected at: 1000 GPM @ 100’ 40 HP required. Duty Point: 30 HP Oversized by 15% 15’ head on TDV X
  12. 12. Variable Speed Pumping <ul><li>Easy Pump Balancing </li></ul>
  13. 13. Variable Speed Pumping <ul><li>Constant Volume Primary - Variable Volume Secondary </li></ul>
  14. 14. Variable Speed Pumping Example <ul><li>Pump Selected at: </li></ul><ul><li>1000 GPM @ 100’ </li></ul><ul><li>40 HP required. </li></ul><ul><li>Duty Point: 30 HP </li></ul><ul><li>Constant Volume Primary - Variable Volume Secondary </li></ul>
  15. 15. Variable Speed Pumping Example <ul><li>Constant Volume Primary - Variable Volume Secondary </li></ul>SENSOR ACROSS COIL Typical Setting Equals Design Pressure Drop Across the Coil, Control Valve, and Circuit Setter. Coil 10 - 15’ P.D. Control Valve 10 - 15’ P.D. Typical Total P.D. 20 -30’
  16. 16. Variable Speed Pumping Example <ul><li>Pump Selected at: </li></ul><ul><li>1000 GPM @ 100’ </li></ul><ul><li>Variable Speed and </li></ul><ul><li>System curves shown </li></ul><ul><li>20’ Control Head </li></ul><ul><li>725 RPM Minimum </li></ul><ul><li>Constant Volume Primary - Variable Volume Secondary </li></ul>
  17. 17. Variable Speed Pumping Example <ul><li>Constant Volume Primary - Variable Volume Secondary </li></ul>PE Motor
  18. 18. Variable Speed Pumping Example <ul><li>Savings not as great as compared to closed loop systems </li></ul><ul><li>Still should utilize hydro-pneumatic tanks </li></ul><ul><li>Better for pump life cycle </li></ul><ul><li>Does not require booster pump PRV’s </li></ul><ul><li>Variable Speed Domestic Pressure Boosting </li></ul>
  19. 19. Variable Speed Pumping Example <ul><li>Height of building – 12 stories </li></ul><ul><li>150 ft. static lift </li></ul><ul><li>30 PSI City pressure </li></ul><ul><li>30 PSI required at the top </li></ul><ul><li>50’ piping pressure drop at design flow </li></ul><ul><li>Variable Speed Domestic Pressure Boosting </li></ul>
  20. 20. Variable Speed Pumping Example <ul><li>Pump Selected at: </li></ul><ul><li>300 GPM @ 200’ </li></ul><ul><li>30 HP required. </li></ul><ul><li>Duty Point: 25 HP </li></ul><ul><li>2950 RPM </li></ul><ul><li>Minimum Speed </li></ul><ul><li>Variable Speed Domestic Pressure Boosting </li></ul>
  21. 21. Variable Speed Pumping Example <ul><li>Variable Speed Domestic Pressure Boosting </li></ul>
  22. 22. Efficient Boiler Design <ul><li>Boiler Types </li></ul><ul><ul><li>What is Efficiency? </li></ul></ul><ul><ul><li>Non-Condensing </li></ul></ul><ul><ul><li>Condensing </li></ul></ul><ul><li>Maximizing Efficiency </li></ul><ul><ul><li>Outdoor Reset </li></ul></ul><ul><ul><li>Short Cycle Prevention </li></ul></ul><ul><ul><li>Hybrid Systems </li></ul></ul>
  23. 23. Efficient Boiler Design <ul><li>Combustion Efficiency – 100 percent of efficiency minus the percentage of heat lost up the vent. </li></ul><ul><li>Thermal Efficiency – The combustion efficiency minus the jacket losses of the boiler. Based on ANSI Z21.13. For boilers 300,000 to 12.5 million Btu. </li></ul><ul><li>A.F.U.E. – The measure of annual efficiency of a boiler that takes into account the cyclic onoff operation and associated losses as it responds to changes in load. For boilers under 300,000 Btu </li></ul>
  24. 24. Efficient Boiler Design <ul><li>Non-Condensing </li></ul><ul><ul><li>Cast Iron </li></ul></ul><ul><ul><li>Steel Tube </li></ul></ul><ul><ul><li>Copper Fin </li></ul></ul><ul><ul><li>Modulating </li></ul></ul><ul><li>75-88% Efficiencies </li></ul>
  25. 25. Efficient Boiler Design <ul><li>Condensing </li></ul><ul><ul><li>Cast Aluminum </li></ul></ul><ul><ul><li>Stainless Steel </li></ul></ul><ul><ul><li>Cast Iron </li></ul></ul><ul><ul><li>Dual Heat Exchanger </li></ul></ul><ul><li>85-99% Efficiencies depending on operating conditions </li></ul>
  26. 26. Efficient Boiler Design <ul><li>120 o F return water </li></ul><ul><li>100% input </li></ul><ul><li>87% efficiency </li></ul><ul><li>Where is the condensation? </li></ul>
  27. 27. Efficient Boiler Design
  28. 28. Efficient Boiler Design <ul><li>Condensing Boiler Design Guidelines </li></ul><ul><li>Design system for lower water temperatures </li></ul><ul><ul><li>Use larger delta T’s </li></ul></ul><ul><ul><li>Radiant floor heat / snow melt </li></ul></ul><ul><ul><li>Water Loop Heat Pumps </li></ul></ul><ul><li>Select boiler plant for small turndown capabilities </li></ul><ul><li>Save initial cost by using both condensing and non-condensing boilers when possible </li></ul>
  29. 29. Efficient Boiler Design <ul><li>Outdoor Reset </li></ul><ul><ul><li>Designing a Reset Curve </li></ul></ul><ul><li>Cycle Efficiency </li></ul><ul><ul><li>How the cycle suffers </li></ul></ul><ul><ul><li>Adjusting the differential </li></ul></ul><ul><ul><li>Buffer Tanks </li></ul></ul><ul><li>Hybrid Systems </li></ul>Maximizing Efficiency
  30. 30. Efficient Boiler Design – Outdoor Reset
  31. 31. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>
  32. 32. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>Energy Use Per Unit of Load (e.g., HDDs) Energy Use (Therms, DecaTherms, etc.) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
  33. 33. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>New Energy Use Per Unit of Load (e.g., HDDs) Old Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
  34. 34. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>New Energy Use Per Unit of Load (e.g., HDDs) Old Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
  35. 35. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>New Energy Use Per Unit of Load (e.g., HDDs) Old Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
  36. 36. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>Energy Use Per Unit of Load (e.g., HDDs) Energy Use (Therms, DecaTherms, etc.) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
  37. 37. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>Total HDD x Best Therms/HDD = What’s Possible Total Therms – What’s Possible = What Was Wasted The E/L Curve Fast Calculation… Best ? Billing Period Therms HDDs Therms/HDD December January February March etc Total Therms Total HDD
  38. 38. Efficient Boiler Design <ul><li>Cycle Efficiency </li></ul>
  39. 39. Efficient Boiler Design <ul><li>How the Cycle Suffers </li></ul>10 GPM 10 GPM 60 GPM 20 Gallons in boiler at 170 °F. At 10 GPM and 100 MBH load At 800 MBH firing, boiler will hit 190 °F in about 20 seconds. BOILER 800 MBH Output
  40. 40. Efficient Boiler Design <ul><li>How the Cycle Suffers </li></ul>Added piping increases boiler volume…but to what extent? Adding 20 Ft. of 3” pipe adds 7.6 gallons Firing increases from 20 seconds to 25 seconds!
  41. 41. Efficient Boiler Design <ul><li>How the Cycle Suffers </li></ul>Using a buffer tank to add 200 gallons will increase firing to almost 3 minutes for a 20 °F delta T. Using reset on the system loop could allow for a 50 or 60 °F delta T. Using a 60 °F delta T would mean a minimum run time of over 8 minutes!
  42. 42. Efficient Boiler Design <ul><li>How the Cycle Suffers </li></ul>180 140
  43. 43. Efficient Boiler Design <ul><li>How the Cycle Suffers </li></ul>180 140
  44. 44. Efficient Boiler Design <ul><li>Hybrid Systems </li></ul>Condensing Boiler Non-condensing Boilers
  45. 45. Efficient Boiler Design <ul><li>Hybrid Systems </li></ul>Non-condensing Boilers BufferTank Condensing Boiler
  46. 46. Efficient Boiler Design <ul><li>General Guidelines </li></ul><ul><li>Utilize Buffer tanks and water temperature reset </li></ul><ul><li>Design for long on/off cycles </li></ul><ul><li>Boilers do not need to be same size/style </li></ul><ul><li>Use small, modulating boilers as a “jockey” boiler </li></ul><ul><li>Design for efficiency during light loads </li></ul>
  47. 47. Final Thoughts <ul><li>System design is typically more important than individual equipment selections. </li></ul><ul><li>Energy retro-fits should be based potential savings and initial cost. </li></ul><ul><li>Every building and every system is different, so there is no one-size-fits-all approach to Energy Saving Design. </li></ul>
  48. 48. <ul><li>Questions? </li></ul>
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