Retro-Cx.ppt

1、Retro-Commissioning: A Tool for Improving HVAC Systems and Energy Cost Reduction Speaker: William McGuire, P.E.,Retro-Commissioning of Existing Buildings Why Retro-Cx What is Retro-Cx ? How do you do it / what to look for Case Studies Take-Away,AGENDA,Why Retro-Cx,Older bldgs. (Pre 1990) on average

2、consume more energy Antiquated control systems that dont work Energy saving control strategies missed in design Neglected maintenance wasting energy and/or causing IAQ problems System upgrades that miss the mark Building usage / floor plans changed,Why Retro-Cx,Energy cost are only expected to rise

3、Economic outlook may prevent new construction Employee / Community goodwill “Its the right thing to do” Owners learn more about their own facilities Benefits intended to be long lasting Simple payback typically less than two years,Why Retro-Cx,Leased Buildings LEED EB / ENERGY STAR buildings may bec

4、ome a differentiator High energy costs translate into increased rent cost,Why Retro-Cx,Source: US Government Energy Information Administration,Consumption in Gross Energy by Year Constructed - 2003,45% less energy consumed,New buildings 35% to 57% more efficient,Energy intensity 10% less,Why Retro-C

5、x,A study by Lawrence Berkeley National Laboratory (LBNL) - 2004 Retro-Cx results Whole-building electricity savings range from 5% to 15% Gas savings range from 1% to 23% Payback ranged from 0.2 to 2.1 years The bigger the building typically the better the payback period Small buildings have opportu

6、nity as well Source: A RetroCommissioning Guide for Building Owners - PECI,Why Retro-Cx,Lawrence Berkeley National Laboratory (LBNL) 2004 Value of Energy Savings$0.11 - $0.72/ft2 Value of Non Energy Savings$0.10 - $0.45/ft2 Non Energy: Equip Life, thermal comfort, IAQ, productivity, liability, etc.,

7、1996 PECI/EPA/DOE Study of 60 Commercial Buildings:,40%,33%,15%,HVAC Problems,Sensors not operating properly,Missing Equipment,Why Retro-Cx,Why Retro-CxRetro-Commissioning X-nth Examples,Retro-commissioning is “GREENER”,If Retro-commissioning our existing buildings can save just 10% energy consumpti

8、on,Reduce oil imports by 50%. Almost meets Kyoto Protocol.,Exploit our existing buildings, not the environment !,Green Moment,What is Retro-Commissioning?,DISCOM,What is Retro-Cx,Design Installation Set-up / TAB Controls / Optimization Operation Maintenance,RETRO-Commissioning is evaluating and perf

9、ormance testing an Existing buildings HVAC.,Reveals hidden deficiencies that could have been avoided by commissioning. Highlights O design oversight? Can save pump energy by going variable primary (add drives). $20,000 VAV with Reheat many are reheating. Min cfm setting could be lowered to avoid reh

10、eating. And SATR logic can be implemented. Save +/- $big,PROBLEMSAVINGS DISCO&M Cooling Tower Operation:$24,000 O Hot Water Boiler Sequence:$20,000 IS Chilled Water: Low Delta-T Syndrome$80,000 D or I AHU Static Pressure Setpoint Optimization:$50,000 S Constant pump CHW system with 2-way valves :$20

11、,000 D VAV re-heating setpoints:$ big S Total:$200,000 per year.,Baseline Savings: $200,000 /yr ($0.50 / sf),Retro-Commissioning Results,Retro-Commissioning DISCO&M Case Study #3,Not-For-Profit Hospital,“O&M” Looking for HIDDEN CAPACITY resulting from possible improper operation.,Hospital BAS Interr

12、ogation - Typical Air Handling Unit,1. Chilled Water Valve failed open, making 49.6F air. 5.4F colder than set point 2. Supply Fan VFD is at 100%, no spare capacity for filter loading 3. Outdoor air damper Software Override (SWO), changed from design setpoint,Hospital BAS Interrogation - Chiller Pla

13、nt,Return Chilled water temperature is too low. The return temperature should be 58F. Too many chilled water coils are over-flowing, and producing low return water temperatures. Another LOW DELTA-T PROBLEM. The flow of 1149 gpm and the calculated tons of 359, calculate a flow rate of 3.2 gpm/ton. Th

14、e secondary CHW is pumping over 50% more chilled water than it should be due to failed open AHU chilled water valves.,6 of 30 Air Handling Units had hidden cooling coil valve problems. Heating boilers are re-heating the overcooled air. The spare central plant capacity that was discovered: Cooling:14

15、2 Tons (new spare capacity) Heating: 1.7 million btuh(25% of one big boiler),Baseline Savings: $200,000 /yr ($0.90 / sf) Retro-Cx Investment: 1 day ( Incidental) Value: Defer new 1000 ton chiller ($1000/ton),Retro-Commissioning Case Study #3: Summary Not-for-profit Hospital,Retro-Commissioning DISCO

16、&M Case Study #4,For-Profit Hospital,“DISCO&M” Administration wanted energy savings. Facilities Staff did not want anyone (us) to look at their system and find potential problems it might make them look bad.,Hospital BAS Interrogation - Chiller Plant Logic Problems,Improper Chiller OFF Logic Operati

17、ng more pumps & towers than necessary,Building Load 1000 tons. (2 chillers needed),Three 550 ton chillers ON. (1650 tons),For-Profit Hospital: Improper Constant Volume Pump Set-up,Circuit Setter 80% Closed. Should have trimmed impeller,For-Profit Hospital: AHU Investigation Improper Design,Original

18、Design / Construction Problems: Low first cost solutions = high long term operating costs,PROBLEMSAVINGSDISCO&M AHU Supply Air Temp Reset Logic$72,000D Condenser Water Reset Temp Reset Logic$33,000D Chiller ON/OFF Logic$10,000D Pump Valve Adjustment$26,000S AHU Device Tune-up$58,000O&M Modify AHU Re-he