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Energy Efficiency Study on Student Recreation Center

Energy Efficiency Study on Student Recreation Center. Gang Wang, Ph.D., P.E. Civil and Architectural Engineering Texas A&M University - Kingsville. Outline. Background of Energy Conservation Studied Facility Information Purpose Energy Studies Current control sequences

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Energy Efficiency Study on Student Recreation Center

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  1. Energy Efficiency Study on Student Recreation Center Gang Wang, Ph.D., P.E. Civil and Architectural Engineering Texas A&M University - Kingsville

  2. Outline • Background of Energy Conservation • Studied Facility Information • Purpose • Energy Studies • Current control sequences • Energy performance • Improvement • Savings estimation • Troubleshooting • Conclusion

  3. Building Energy System • Mechanical system • Chilled water (chiller) • Heater (electrical/hot water) • Fan and pump (motor) • Lighting and power • Lighting • Office equipment • Motor (chiller, fan and pump) and electrical heater

  4. Mechanical or HVAC System • Remove impacts • People (250Btu/h & 0.2lbmv/h) • Lighting and power system • Climate and solar (envelope) • Create indoor environment • Temperature (75F) • Humidity (50%rh): 55F SAT • Indoor air quality: • 15CFM (ft3/min) OA or • Indoor CO2=700PPM + OA CO2 • Minimize energy usage • Chilled water (Chiller/electricity.) • Fan and pump (electricity) • Heating (hot water or electricity)

  5. Challenges • DOE: Buildings consume 40% of U.S. energy • HVAC (32%) • lighting and power (37%) • Electricity consumption • 4.3% per year increase • Natural gas ($/mmBtu): • $3.0 in 2002 to $14 in 2006. • TAMUK: $4M/yr • Improve energy efficiency • ASHRAE standard 90.1-2010 sets an energy savings target of 30%

  6. Energy Efficiency Measures • Electrical System • Reduce usage • Reduce HVAC load

  7. Energy Efficiency Measures • Electrical System • Reduce usage • Reduce HVAC load • Indoor Comfort and Health • SAT=55F (humidity control) • Maintain required OA intake (Annual $1.75 for 1CFM OA) • Partial Load Operation • Reduce fan speed • Avoid simultaneous cooling and heating

  8. Studied Facility Information • Student Recreation Center, built in 2010 • Floor area: 38,000 ft2 • Gym • Weights • Running track • Offices • Occupancy: • Design: 615 persons. • Actual: < 200 persons

  9. HVAC System Information • Air Handling Unit • AHU1 (SZ) : Gym • AHU2 (MZ) : Track • AHU3 (SZ) : Weights • AHU4 (SD) : Offices • AHU-OA • Chilled water • Electrical heating • Siemens APOGEE. • Variable frequency drive (VFD) on AHU fans

  10. Purposes • Identify energy efficiency measures • Minimize energy consumption • Improve indoor thermal condition • Increase physical plant cooling capacity • Develop energy efficiency control • Estimate cost savings

  11. AHU Schematics

  12. Control Sequencesby Design Engineer

  13. APOGEE PPCL Program by Control Engineer …… 00390 C SPEED CONTROL 00410 IF("%X%OCC") THEN GOTO 420 00412 SET(50,"%X%SVD") 00414 GOTO 430 00420 TABLE(SECND1,"%X%SVD",0,20,60,100) 00430 C DISCHARGE TEMPERATURE CONTROL 00450 LOOP(0,"B570.A01RMT","%X%LOOP","B570.A01RMSP",1000,100,8,1,50,0,100,0) 00460 IF("%X%HUMOVRD".EQ. OFF) THEN TABLE("%X%LOOP","%X%CCV",50,0,100,100) 00470 IF("%X%HUMOVRD".EQ. ON) THEN SET(100,"%X%CCV") 00480 DBSWIT(1,"%X%LOOP",40,45,"%X%EH1") 00490 DBSWIT(1,"%X%LOOP",25,40,"%X%EH2") 00500 DBSWIT(1,"%X%LOOP",5,20,"%X%EH3") 00510 C DAMPER CONTROL 00530 IF("%X%CO2" .LT. 700.0) THEN GOTO 570 00540 SET(100,"%X%OAD") 00560 GOTO 600 00570 LOOP(128,"B570.A02OAF","%X%OALOOP","B570.A02OASP",6,4,1,1,50,0,100,0) 00580 TABLE("%X%OALOOP","%X%OAD",0,15,100,100) 00600 GOTO 10

  14. Summary of Control Sequences OA flow is adjusted based on a design setpoint (615 vs. 200) OA is fully open if CO2>700ppm Space temperature is controlled by cooling coil or electrical heater Cooling coil is fully opened if space is humid Supply fan speed: 100% (no control) No supply air temperature control

  15. Outside Airflow (OA) Control Performance Low space CO2 Excessive OA intake Analysis Design OA flow setpoint, 8,200CFM Fault space CO2 setting: 700ppm (+OA CO2) Fault CO2 sensors Impact More chilled water Disturbance on indoor humidity

  16. Fan Speed Control • Performance: • Full speed: 24/7 • Analysis • No fan speed control • Impact • Waste fan power • Increase cooling load

  17. Space Air Temperature Control Performance Space air temperature is maintained

  18. Heating and Cooling Performance Performance Cooling coil and heater is hunting Analysis Single control loop with huge thermal capacity Impact Wastes chilled water and electricity

  19. Supply Air Temperature Control Performance Fluctuated SAT(≠55F) Simultaneous heating and cooling Analysis No SAT control Coil thermal capacity Impact High space humidity Waste chilled water and electricity

  20. Space Humidity Control

  21. Lighting Control Performance Lights are on during unoccupied hours Analysis Fault schedule Impact Waste electricity

  22. Improve Control(Lighting) Current Control On during weekday unoccupied time Improved control Off during unoccupied time

  23. Improve Control(Outside Air) Current Control Design OA flow setpoint, 8,200CFM Fault space CO2 control: 700ppm Troubleshoot Fault CO2 sensors Improved control OA flow setpoint: 3,000CFM based on actual occupancy Space CO2: 1000ppm Troubleshoot Calibrate CO2 sensors

  24. Improve Control(Fan Speed and Temperature) Current Control No supply air temperature (humidity) control No fan speed control Cooling coil and heater directly control space temperature Improved control Cooling coil is modulated to maintain SAT at 55F Fan speed is modulated to maintain space temperature. Heater is stepped on or off to maintain space temperature if airflow drops to min setpoint.

  25. Estimated Annual Savings

  26. Troubleshooting(Fault Cooling Coil Valve)

  27. Preliminary Results Baseline rate: 96kW Valve fault: 164kW $48,180/yr wasted Repair and preliminary control upgrade:90kW Final upgrade: 55kW $52,774/yr reduced

  28. Conclusion Identify energy efficiency measures Lighting control Outside air Integrate fan speed and cooling coil control Calibrate CO2 sensor and repair cooling coil valve Annual savings: $52,774 Electricity: 414,232kWh or 52% Chilled water: 2,955MMBtu or 45% No major retrofits

  29. Questions and Comments? Project team also includes Emmanuel Ayala, Joel Wright, Leah M. Ayala fromDepartment of Civil and Architectural Engineering and Ricardo Contreras Jr. from University Facilities.

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