Retro-Commissioning for Energy Efficiency

Transcription

1 High Performance Buildings 2006 AABC Commissioning Group (ACG) April 6, 2006 Retro-Commissioning for Energy Efficiency Making buildings work. Better. Tom Poeling, P.E., CEM, LEED AP E M C Engineers, Inc. Agenda Retro-Commissioning for Energy Efficiency What is Retro-Commissioning? Define Benefits of RCx Define RCx Process Discuss RCx Findings 2 1

2 What is Retro-Cx (R-Cx Cx) Systematic process for improving the current condition and operation of an existing building.. Typically addresses: HVAC, Controls Lighting Controls Envelope Evaluates the condition of building s systems and optimizes the operation, performance, and maintenance in accordance with the Owner's current operational needs, including reducing energy consumption. Typically performed on a building which was never commissioned. 3 Why R-CxR Anything? Poor initial design, equipment selection Space complaints temperature, IAQ, etc. Multiple renovations Room changes from original intent Modifications to system components Changes to controls sequences, set points Building is not operating efficiently against benchmarks THINK ABOUT IT AS A BUILDING TUNE TUNE-UP!!!! 4 2

3 Beyond Quick-fix Retro-commissioning (Retro-Cx) goes beyond quick fix Determine root causes of problems Optimize building systems Control sequences that are optimized for efficient and effective operation Often reduces or eliminates need for capital improvements 5 Retro-Commissioning Benefits Corrections are typically low cost measures to implement Savings are realized in energy cost, O&M costs, avoided capital typically typically 5% to 20% in energy costs alone Paybacks typically 6 mo to 2 years 50% to 200% ROI Allows for training O&M staff to sustain ongoing building performance improvement 6 3

4 Retro-Cx Addresses - Energy Savings Demand Savings (less opportunity than electrical consumption savings) Natural Gas Savings Operational Issues (IAQ, comfort problems, broken systems, etc.) Deferred Maintenance Issues 7 Where does Our Energy Go? Transportation 27% in 1997 and 2004 Industrial 38% in 1997, 33% in 2004 Buildings 36% in 1997, 40% in 2004 In Buildings - Approximately half in Residential and half in Commercial Electrical Capacity 70% to Buildings *Source: Energy Information Agency 8 4

5 Retro-Commissioning Process Retro-Commissioning Phases Planning Phase Assess BAS capabilities, potential opportunities, and Investigation approach. Investigation Determine how systems are supposed to operate, monitor how they operate, and prepare a prioritized list of the operating opp s. Implementation Implement opportunities and verify proper operation. Operating Phase Report operating improvements made and train the building operator how to sustain efficient operation implement capital improvements 10 5

6 Planning Phase Planning Phase Assess BAS capabilities, potential opportunities, and Investigation approach. Operating Phase Investigation Implementation 11 Kick-off meeting Obtain building data Benchmark performance (EUI comparisons) Review building operational issues Quantify range of potential savings Develop RCx Plan Planning Phase 12 6

7 Building Based: Benchmarking Annual Utility Consumption from Billing Calculate EUI (energy use per SF) Compare to databases available: SIC, NAICS, CalArch,, EIA, others Use EUI to identify Retro-Cx potential and best candidates for Retro-Cx Consider any unique differences in your building systems or equipment as compared to typical buildings in the benchmark database 13 Benchmark Example Natural Gas High Usage Normalized Monthly Natural Gas Use- CH 1 Natural Gas (Therms) 10,000 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1, Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 14 7

8 Benchmark Example Natural Gas Lower Usage Normalized Monthly Natural Gas Use - CH 2 7,000 6,000 Natural Gas (Therms) 5,000 4,000 3,000 2, ,000 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 15 Building Floor Area Benchmarking Example Annual Electricity Use Ann. Peak Electrical Demand Annual Natural Gas Use Annual Electricity Costs Annual Natural Gas Costs Annual Utility Consumption Data Energy Use Index (kbtu( kbtu/sf-year) Total Utility Costs (ft 2 ) (kwh/yr) (kw) (therms/yr) ($) ($) ($) CH 1 126,972 2,435, ,246 $308,081 $51,997 $360,078 CH 2 110,286 1,473, ,934 $188,376 $33,762 $222,138 Building Peak Annual Electrical Demand Electricity EUI Electricity EUI Natural Gas EUI Natural Gas EUI Total EUI W/ft 2 (kbtu/ft 2 ) (kwh/ft 2 ) (kbtu/ft 2 ) (therms/ft 2 ) (kbtu/ft 2 ) CH CH

9 Benchmarking Energy Use Index Natural Gas EUI Electricity EUI EUI (kbtu/sf) ` CM CH SM CH BH CH ML CH EM CH EL CH WH CH DN CH BL CH PL HQ 17 Benchmark Example Benchmark Against Database CAL-ARCH DATABASE: Your whole building EUI is 127 kbtu/ft2-yr, which is higher than 92 % of comparison buildings shown. OTHER DATABASES: Energy Star (EPA) Commercial Buildings Energy Consumption Survey (CBECS) 18 9

10 RCx Plan - Purpose Identify the approach in the Investigation Phase Building Issues: Energy Usage Comfort Indoor Air Quality Noise Approach: Controls/Trending Design Maintenance Issues TAB 19 Investigation Phase Planning Phase Operating Phase Investigation Determine how systems are supposed to operate, measure and monitor how they operate, and prepare a prioritized list of the operating opportunities. Implementation 20 10

11 Investigation Phase What is the equipment actually doing? Validate the direct digital control (DDC) system Trend system points Document conditions Identify changes to setpoints, schedules, & sequences and cost/benefits 21 Evaluate Trend Data Mountain America Credit Union Cooling tower unable to maintain setpoint at full fan speed. Condenser Water maintianed at 70F Current (Amps); OA Temp (F); RH (%) Cooling tower fans cycle between high and low speeds System operates 6 am to 6 pm weekdays and 6 am to 1 pm Saturday :00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0: Chilled Water maintianed at 50F 10.0 CHW Supply-Return Temps (F) 0.0 OA Temp (*F) Wet Bulb Temp (*F) Chiller Current (Amps) Cooling Tower Fan #2 East (Amps) Chilled Water Supply Temperature (*F) Chilled Water Return Temperature (*F) 22 Cond Water Supply Temperature (*F) Cond Water Return Temperature (*F) 11

12 Investigation: DDC vs. Pneumatics Can you RCx pneumatics? DDC Trending analysis Pneumatics Point to point verification, calibration Look for the signs Disconnected linkages, actuators Inspect pressure gauges Review condition of control air Look at compressor station Regular PM program? 23 Investigation Phase Identify broken subsystems and equipment repair if needed for testing Perform TAB measurements (system level) Perform updated HVAC load study Identify opportunities for implementation 24 12

13 Investigation Phase Investigation report documents the retro-commissioning effort As-found conditions Adjustments or repairs made to systems (if any) Results of evaluation and Implementation plan Implementation costs and savings estimated Remaining issues that could not be resolved without upgrade-repair-replacement project Identify any capital projects to address current operational needs or correct problems Provide budget cost estimate for more capital intensive projects 25 Implementation Phase Planning Phase Operating Phase Investigation Implementation Implement opportunities and verify proper operation 26 13

14 Implementation Phase Implement recommended opportunities and correct operational deficiencies to achieve improved performance and energy savings Performed by: Internal maintenance staff Program manager, controls, mechanical, service, TAB, electrical contractor 27 Implementation Phase - Verification Verify modifications are in place Perform functional tests to assure modifications are operating as designed Trend performance to verify energy savings 28 14

15 Verify Modifications Hot Deck Reset Temperature Control Santa Monica Courthouse Hot Deck Reset AH-1 (11/28-05 to 12/1/05) Hot Deck Temperature (Deg F) Hot water system enabled Outsid Air Temperature (Deg F) 29 Track System Level Metrics Simultaneous Heating and Cooling 30 15

16 Operating Phase Planning Phase Investigation Implementation Operating Phase Report operating improvements made and train the building operators how to sustain efficient operation implement capital improvements 31 Operating Phase Provide on-site training how is the building suppose to operate to sustain improvements Update O&M data Document setpoints and settings for systems 32 16

17 Sustaining Improvements Continuous Cx Track monthly building energy use Compare similar months, different years Compare energy usage vs. OAT metric Sub-meter major HVAC systems if possible Cooling plant, heating plant, ventilation fans Verify operation of energy conservation strategies Track equipment run times (schedules) Track temperatures against set points 33 Operation Phase - Verification Overall Performance Comparison kw Significant Demand and Overall Energy Reduction during similar load periods. Overall Reduction of Base Load :00 AM 6:00 AM Outside Air Temperature 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM Time kw-2005 kw-2004 OAT-2005 OAT

18 Verify Energy Conservation Strategies Space Temperatures WHAT YOU SEE Scheduled Start/Stop Control Ventilation Control Chiller Sequencing Fan Speed Control Simultaneous Heating & Cooling WHAT YOU DON T SEE 35 Typical Retro-Cx Project Timeline Planning Investigation Implementation Verification 4 to 6 weeks 12 to 24 weeks 8 to 16 weeks 4 to 8 weeks 36 18

19 Retro-Commissioning Findings Top 10 HVAC Opportunities Found 10. Verify lighting controls schedules/effectiveness 9. Terminal unit tune-ups dampers & valves 8. Improve clg. tower sequencing/lower cond. wtr. temps 7. Improve chiller sequencing 6. Return VFDs to variable speed operation 5. Optimize supply air static pressure set points 4. Ensure proper ventilation airflow rate 3. Optimize/restore economizer operation 2. Implement reset schedules to eliminate simultaneous heating and cooling 1. Turn off equipment when not needed (Scheduled S/S) 38 19

20 Top 5 Gas Opportunities 5. Improve boiler efficiency (tune-up or replace) 4. Implement aggressive air and water temperature reset strategies (HWS vs OA, MAT vs RAT, night setbacks, space temperatures) 3. Tune-up terminal units to eliminate simultaneous heating and cooling (valve leakage) 2. Optimum start/stop vs. scheduled start/stop (close OSA!! let Building coast to end of day) 1. Turn off heating plant when not needed (Scheduled S/S) 39 PreFx Phase Controls Checkout Typical Point to Point Findings: Sensors out of calibration Inoperative dampers (pneumatic control, transducers, actuators, linkages, dampers) Minimum OA damper settings Inoperative control valves Inoperative CHW/HW control valves Inoperative variable frequency drives (VFDs( VFDs) 40 20

21 PreFx Phase Air/Water TAB Typical TAB Findings: Inadequate supply/return fan capacity Duct leakage / Duct obstructions Static pressure set points Maintenance Issues: Dirty filters/broken fan belts Terminal unit issues: Thermostats out of calibration Reheat valves stuck or leaking by Inoperative damper actuators Air flow at terminal unit outside acceptable tolerances 41 Example RCx Process Building Issues (Interview): Difficult to maintain comfort interior zones (no reheat) versus exterior zones (reheat) Source of many hot complaints Design issue?? Point to Point Analysis: Chilled water valve stuck open on AHU-3 Supply air temperature maintained at 52 F Noted as deficiency during PreFx Phase 42 21

22 Example RCx Process (cont.) Test and Balance: Could not achieve design air flow at zone level Functional Test Results: Bad duct pressure transmitter AHU VFD actually controlling to 0.6, instead of 1.2 Chilled water valve (AHU-3) connected to main air (20 psi), branch line bypassed 43 Example RCx Process (cont.) Implementation: Put CHW valve back on branch pressure control Replaced duct pressure sensor transmitter Performed test and balance to design conditions Restored outside air economizer capability Implemented discharge air temp. reset strategy 44 22

23 Example RCx Process (cont.) 45 Indicators of HVAC Opportunities Changes to operating sequences Deferred basic maintenance Complex controls beyond O&M staff control Lack of system documentation Comfort complaints (hot or cold calls) Interim fixes to respond to localized requests Rising energy consumption demand (kw) or consumption (kwh) check EUI!! 46 23

24 Economic Benefits Existing Buildings Study*: 59 Buildings $0.26/sf-yr median normalized energy cost savings 0.7 years median payback * The Cost-Effectiveness of Commercial Buildings Commissioning A Meta- Analysis of Existing Buildings and New Construction in the United d States, Nov 23, 2004 Lawrence Berkeley National Laboratory, Portland Energy Conservation Inc., Energy Systems Laboratory-Texas A&M University 47 Benefits of HVAC Tune Ups Cost depends on systems selected, size of building, type of building Budgetary estimates: RCx from $0.30 to $0.70 per SF depending on scope of services required, size & type of building ROI & Payback Excellent (<1 yr typical) Energy savings typically 5 to 15% Existing buildings account for over 95% of building SF most operate inefficiently ACEEE 2003 Study RCx 2 nd best savings potential out of 38 evaluated processes!!! What is the cost of loss of comfort resulting in loss of productivity in poor building environment? 48 24

25 Example Resources Portland Energy Conservation Inc Building Commissioning Association, Practical Guide to Commissioning Existing Buildings, Haasl & Sharp, 1999, ateam.lbl.gov/mv/docs/retrocommissioningguide.pdf ASHRAE, Guideline , , The HVAC Commissioning Process, Continuous Commissioning Guidebook for Federal Energy Managers U.S. DOE / FEMP, GSA Commissioning Handbook, CBECS, Energy Star Portfolio Manager, 49 Question & Answers 25

26 Thank You! 51 26