Improve Facility Operation through Commissioning-A Case Study

1. Improve Facility Operation through Commissioning-A Case Study Mingsheng Liu, Ph.D., P. E. University of Nebraska

2. Outline • Facility information • Commissioning measures • Measured results and conclusions

3. 1. 1 Building and AHUs Information

4. 1.2 Control Systems Information • A modern DDC system was installed in 1995 as part of energy retrofit project • Provide remote control on each AHUs, pump, and terminal box • Provide remote monitoring on critical parameters

5. 1.3 AHUs Information • All single duct systems are converted into VAV system with modern DDC control • All systems have economizers • All AHUs reset supply air temperature according to the outside air temperature • New control valves and dampers were installed as part of the energy retrofit project in 1995.

6. 1.4 Boiler Plant Information • New boilers were installed in 1995 • Boiler 1-250 HP (8 MMBtu/hr) • Boiler 2-500 HP (17 MMBtu/hr) • Boiler 3-700 HP (23 MMBtu/hr)

7. 1.5 Thermal Storage System

8. 1.6 Measured Hourly Electricity Consumption Before Commissioning

9. 1.7 Measured Hourly Gas Consumption Before Commissioning

10. 1.8 Operation Problems and Concern • Thermal Storage System: 1,760 kW peak demand in 1997 (expected to be 1,400 kW) • Overall retrofit savings: significantly smaller than the projected value • EMCS systems: lack of confidence of smooth operation

11. 2.1 Commissioning Measures • Energy Management and Control Systems • Buildings • Thermal storage systems • Boiler systems

12. 2.2 Measures for EMCS Systems • Point by point check software • Verify hardware in the field • Optimize/modify control algorithms • Terminal box • AHUs • Chilled water loop • Hot water loop

13. 2.2.1 Example: VAV Fan Speed Control Existing schedule: Modulate the fan speed to keep at least one of the five terminal box damper at 90%.

14. 2.2.2 Real Operation • One of the room temperature set point was 72°F. The occupant wanted to be 76°F. She could not change the set point since it was programmed by the EMCS system. • A foot heater is used to make 76°F • The box is open to fight the heater • The fan is speed up to satisfy the box

15. 2.2.3 Solutions

16. 2.3 Measures for Buildings • Chilled water loop balance • Hot water loop balance • Air flow balance • Thermostats and terminal box check up • Dampers and linkage check up/repair/replace

17. 2.4 Measures for Thermal Storage System • Loop differential pressure set point optimization • Chiller on/off schedule • Tank charge rate optimization • Off-peak demand reduction

18. 2.5 Measures for Boilers • Decrease steam pressure from 60 psig to 40 psig at night and weekends • Use smaller boiler/boilers

19. 3.1 Comparison of Whole Campus Electricity Consumption

20. 3.2 Comparison of Campus Hourly Gas Consumption (ft3/hr)

21. 3.3 Comparison of Measured Peak Demand • 1785 kW in 1997 (Before commissioning) • 1483 kW in 1998 (During commissioning) • ???? In 1999 (After commissioning)

22. 3.4 Comparison of Costs and Savings • The measured annual energy savings based on paid utility bills: $146,581 • $69,669 for electrical energy • $24,462 for peak demand • $52,670 for gas • The total contract amount: $143,000 • The project duration: 10 months (3-98 to 12-98)

23. 3.5 Conclusions • Look for significant amount of energy savings from commissioning • Look for significant operating improvement from commissioning