Right-Sized: Equipment and Controls for Super Efficient Buildings--Energy Flows - Landry
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presented at the Seminar/Training series "Getting to AIA+2030/SB2030 Energy Goals"
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Right-Sized: Equipment and Controls for Super Efficient Buildings--Energy Flows - Landry
- 1. RIGHT-SIZED: Equipment and Controls for Super Efficient Buildings |March 9, 2012| PRESENTERS: Jim Keller, Jay Denny, Russ Landry, Julianne Laue Funded By: ARRA Funds Energy Resource Developed By: In partnership with: Manage office Minnesota
- 2. Special Thanks to: Erik Kolderup, PE, LEED AP Kolderup Consulting www.kolderupconsulting.com erik@kolderupconsulting.com (415) 531-5198 Funded By: ARRA Funds Energy Resource Developed By: In partnership with: Manage office Minnesota
- 3. Learning Objectives • Right-sizing after applying passive energy conservation strategies • Utilize controls to optimize the efficiency of equipment • Energy efficient strategies to maintain occupant comfort • Understanding energy flows in a building 3
- 4. Agenda • Part 1 (12:30-2:00) – IAQ and Ventilation – Thermal Comfort – HVAC Loads – Energy Flows • Break • Part 2 (2:10-3:00) – HVAC System Alternatives – “Right-Sizing” HVAC Components – HVAC Controls – Selecting an HVAC System – The Architect’s Role • Break • Exercise (3:10-3:40) • Right Sizing in Practice (3:40-4:00) • Case Studies (4:00-4:20) • Wrap Up (4:20-4:30) 4
- 5. Energy Flows 5
- 6. Three Key Energy Flow Issues Heat Flow from One “Thing” Moving Heat from One Place to Another to Another Moving Heat “Uphill” 6
- 7. Getting Heat from One “Thing” to Another • Heat Naturally Flows “Downhill” from Hot to Cold – The bigger the temperature difference, the faster the heat flows – The bigger the area, the faster the heat flows 7
- 8. Carrying Heat from One Place to Another • Heat Carried by Water or Air – Depends on temperature change (TD or T) – Depends on water or air flow rate Energy Per Pound = Temperature 8
- 9. Carrying Heat from One Place to Another • Refrigerants-- Evaporation(Boiling)/ Condensing is “Freeze- Dried” Version Energy Per Pound – Can carry a lot of energy with little fluid Boiling or Condensing – Little temperature change needed – Used in Refrigeration systems (evaporation = boiling) Temperature 9
- 10. Carrying Heat from One Place to Another • Refrigerants—Controlling Temperature of Heat – Change pressure to control temperature of evaporation/condensing – Pressurize to move heat uphill Boiling/ Condensation Temperature Pressure 10
- 11. Carrying Heat from One Place to Another • Refrigerants—Controlling Temperature of Heat – Change pressure to control Condensation --> temperature of Energy Per Pound evaporation/condensing Evaporation --> – Pressurize to move heat uphill Boiling/ Pressure Condensation Temperature Pressure Temperature 11
- 12. Moving Heat “Uphill” (aka Refrigeration) – Energy must be added to move heat uphill – That extra Temperature energy ends up as more heat – The farther “uphill” the heat is moved, the more energy it takes 12
- 13. Moving Heat “Uphill” (aka Refrigeration) – Energy must be added to move heat uphill – That extra Temperature energy ends up as more heat – The farther “uphill” the heat is moved, the more energy it takes 13
- 14. Moving Heat “Uphill” (aka Refrigeration) – Energy must be added to move heat uphill – That extra Temperature energy ends up as more heat – The farther “uphill” the heat is moved, the more energy it takes 14
- 15. Room Heat Gain & Loss Components External heat gains Solar radiation through Internal heat gains windows Lighting Conduction Occupants through windows Office equipment Conduction Infiltration through through Other? opaque cracks envelope
- 16. Getting Heat Into a Space in a Building: “Typical” Central System Gas, Coal or Oil 3,500 – 4,000 F Boiler Boiler Water 180 F ~350 to 400 F 180°F 160°F Air Handler/VAV Radiators 140°F 120°F Heated Air 100°F Mix 80°F Space 60°F 40°F Mixed or Cooled Air 20°F 0°F -20°F 16
- 17. Getting The “Rated” Efficiency Out of Condensing Boilers (>90% Efficiency) 100% Condensing Boiler 95% Boiler Efficiency 90% Heated Air 85% EnergyStar Min 80% Natural Draft 75% 80°F 100°F 120°F 140°F 160°F 180°F Entering Water Temperature 17
- 18. _______ Chart for Showing Moisture in Air Issues • Curve at Top Shows When Air Can’t Hold Any More Moisture (aka saturated) Amount of Moisture (aka Steam) in Air • Once At the Top, Cooling More Condenses Moisture Out of Air 60 F 100 F 140 F Air Temperature 18
- 19. Getting The “Rated” Efficiency Out of Condensing Boilers (>90% Efficiency) 100% Condensing Boiler 95% Boiler Efficiency 90% Direct-Fired Heater Heated Air 85% EnergyStar Min 80% Natural Draft 75% 80°F 100°F 120°F 140°F 160°F 180°F Entering Water Temperature 19
- 20. _______ Chart for Showing Moisture in Air Issues • Moisture is Much More Diluted in Direct-Fired Heater Amount of Moisture (aka Steam) in Air • It Reaches a Lower Temperature, but Never Condenses (THANK GOODNESS!) Direct Fired Heater 60 F 100 F 140 F Air Temperature 20
- 21. Getting Heat Into a Space in a Building: “Typical” Central System Gas, Coal or Oil 3,500 – 4,000 F Boiler Boiler Water 180 F ~350 to 400 F 180°F 160°F Air Handler/VAV Radiators 140°F 120°F Heated Air 100°F Mix 80°F Space 60°F 40°F Mixed or Cooled Air 20°F 0°F -20°F 21
- 22. Getting Heat from One “Thing” to Another • Heat Naturally Flows “Downhill” from Hot to Cold – Via conduction (key in solids), convection (moving gas or liquid), and/or radiation – The bigger the temperature difference, the faster the heat flows – The bigger the area, the faster the heat flows • Moving Heat “Uphill” Takes Energy – There’s a minimum possible energy required for a given rise in temperature – The farther “uphill” the heat is moved, the more energy it takes – All Forms of Energy Put into Something Eventually End up as Heat 22
- 23. Central System Designed for Condensing Boilers Gas at 3,500 F Boiler 180°F Boiler Water 160 F Average + 160°F Air Handler/VAV Radiant 140°F Radiators Floor 120°F Heated Air 100°F Mix 80°F Space 75 F 60°F 40°F Mixed or Cooled Air 20°F 0°F -20°F 23
- 24. Central System Designed for Condensing Boilers 60 F Drop 180°F Traditional 20 F Drop 160°F Boiler Water 150 F Average 140°F 120°F 100°F 80°F Space 75 F 60°F 40°F 20°F 0°F -20°F 24
- 25. Getting The “Rated” Efficiency Out of Condensing Boilers (>90% Efficiency) 100% 60 F Drop 95% Boiler Efficiency 90% Traditional 20 F Drop Heated Air 85% EnergyStar Min 80% Natural Draft 75% 80°F 100°F 120°F 140°F 160°F 180°F Entering Water Temperature 25
- 26. Getting Heat Into a Space in a Building: Heat Pumps—Air Source & Ground Source Air Source 120°F 100°F Heated Air Air Source HP Mix Mix Air Source HP 80°F Space 60°F 40°F 20°F 0°F -20°F 26
- 27. Getting Heat Into a Space in a Building: Heat Pumps—Air Source & Ground Source Air Source Ground Source 120°F 100°F Heated Air Ground Source HP Air Source HP Mix Mix Air Source HP 80°F Space 60°F Ground 40°F Water/Glycol 20°F 0°F -20°F 27
- 28. Getting Heat Out of a Space in a Building: Typical Systems Air Cooled Water Cooled Higher Peak Lift Lower Peak Lift 120°F Refrigerant in Chiller 100°F Cooling Tower Water 80°F Chiller DX Chiller Space Mix Mix 60°F Cooled Air Chilled Water 40°F Refrigerant in Chiller 20°F 0°F -20°F 28
- 29. _______ Chart for Showing Moisture in Air Issues • Air Cooled Refrigerant Loses Heat to Air Temperature Amount of Moisture (aka Steam) in Air • Evaporation Loses Heat to a Lower Temperature (Wet Bulb) 55 F 75 F 95 F Air Temperature 29
- 30. Getting Heat Out of a Space in a Building: Economizer Recirculated & Economizer Cooled Air (Outdoor Air) 120°F 100°F 80°F Space Mix 60°F Cooled Air Chilled Water 40°F Refrigerant in Chiller 20°F At Mild Temperatures At Low Temperatures All Outdoor Air Does Mixing Outdoor and 0°F Part of Cooling Room Air Does All Cooling -20°F 30
- 31. Moving Heat from One Place to Another Air Water Refrigerant Temperature Drop 20 10 - Heat Carrying Capacity: 5 10 50 BTU per Pound Fluid Transport Energy Factor: 0.17 0.04 0.27 Watts per lb/hr Heat Transport Enegy Factor: 35 4 5 Watts per BTU/hr 31
- 32. Water vs. Air • Water good… – Moving heat via water typically requires less energy – Pipe much smaller than equivalent duct • But… – Still need ventilation in many cases • May need a fan and duct anyway – Air distribution system typically less expensive – Air system can provide “free” cooling with outdoor air 32
Notas do Editor
- My intent is to provide a glimpse into some of the key physical principles impacting HVAC system energy use and efficiency. In other words, I want to show a version of what one engineer “sees” when looking at different buildings and systems while minimizing the superfluous jargon. In addition to trying to improve non-engineers’ insight into key energy performance issues, I’d like to challenge the other engineers to go even further than I am to be sure that other members of the design teams you work with understand the key issues for your projects that are behind the trendy technological terms. Jim has already described the two key functions of HVAC systems—providing fresh air and thermal comfort—and I’ll lay out the basic energy flow and efficiency issues for these, but I’m going to switch the order.
- Now at the risk of the University deciding that I can never again set foot in the Mechanical Engineering building of my alma mater, I’m going to try and get through this without using the word “thermodynamics” again.
- Systems are eitherrecirculating or
- Here’s the chart that must not be named for showing how moisture in air issues.When natural gas burns the chemical reaction forms water, which is in the form of steam at that high temperature. However, the steam is so diluted that it doesn’t start to condense until it is cooled down to around 130F.The energy given up when steam condenses (or boils) is the same as the energy in a 1,000F temperature change of water. It’s easier to think about the energy when water boils to steam, so maybe it will help to think of condensing drops as if they were drops of superconcentrated 5 hour energy.
- --Now you see how that several percentage jump in efficiency depends on having water coming into the boiler that is cool enough to take advantage of the “steam”.--Now I’ve added direct-fired heaters, which are a simpler way to beat traditional equipment, but which are often incorrectly assumed to have 100% efficiency. So if you architects want to watch for a chance to correct a mechanical equipment guy, bring up direct-fired heaters. Direct-fired heaters put all of the heat right into the air they are mixed with so why wouldn’t they be 100% efficient?
- Well, the “steam” made by burning natural gas in air gets so diluted that it doesn’t condense when it’s mixed with the cooler air. They just don’t get the extra boost from having moisture condensation.
- The simplistic approach is to use the same pieces like radiators and heating coils and just make them bigger. Other options are radiant floor heating or reducing the water flow rates while only slightly increasing equipment size.
- This shows two other lower price strategies: 1) OA reset 2) reduce flow rateThis shows how about the same average water temperature with half the flow rate leads to a much lower boiler system minimum temperature—which is the key to getting the extra benefit of condensing. Dramatic flow rate reduction at off-design conditions can often be accomplished without any increase in heat exchanger size.
- When natural gas burns the chemical reaction forms water, which is in the form of steam at that high temperature. However, the steam is so diluted that it doesn’t start to condense until it is cooled down to around 130F.
- The simplistic approach is to use the same pieces like radiators and heating coils and just make them bigger. Other options are radiant floor heating or reducing the water flow rates while only slightly increasing equipment size.
- Systems are designed to be able to get rid of heat at worst case conditions, and often have built-in or artificial control limits on how much the maximum refrigerant condensing temperature can be brought down.--Note impact of HX size.
- Systems are designed to be able to get rid of heat at worst case conditions, and often have built-in or artificial control limits on how much the maximum refrigerant condensing temperature can be brought down.