Improve Facility Operation through Commissioning-A Case

StudyMingsheng Liu, Ph.D., P. E.

University of Nebraska

Outline

1. Facility information

2. Commissioning measures

3. Measured results and conclusions

1. 1 Building and AHUs Information

Building Floor Area # of AHU Function500 33,399 4 Office517 25,136 2 Dormitory518 28,108 5 Adolescent center537 25,136 2 Office541 13,745 2 Dental Office650 98,070 17 Dormitory673 49,651 5 Office, operating units, and others675 72,146 16 Dormitory, and kitchen679 72,146 16 Dormitory, and kitchen682 12,550 1 Class rooms684 12,500 4 Chapel691 33,048 9 Gym, library, and others725 23,721 6

Total 499,356 89

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

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.

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)

1.5 Thermal Storage System

Chiller plant275 ton

Bldg675

Chiller plant425 ton each

Chiller plant200 ton

Bldg691

Bldg684

Bldg725

Bldg537

Bldg650

Bldg682

Bldg517

TES

1.6 Measured Hourly Electricity Consumption Before Commissioning

1.7 Measured Hourly Gas Consumption Before Commissioning

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

2.1 Commissioning Measures

• Energy Management and Control Systems

• Buildings

• Thermal storage systems

• Boiler systems

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

2.2.1 Example: VAV Fan Speed Control

Supply Air Fan

Dampers

OA

RA

Filter

CC

Zone

P

VAVDamper

Duct StaticPressure Sensor

HCVFD

EA

Existing schedule: Modulate the fan speed to keep at least one of the five terminal box damper at 90%.

Existing schedule: Modulate the fan speed to keep at least one of the five terminal box damper at 90%.

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

2.2.3 Solutions

Max VAVDamper Position

95% PID

VFDStatic Pressure

PIDResetToa

Min

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

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

2.5 Measures for Boilers

• Decrease steam pressure from 60 psig to 40 psig at night and weekends

• Use smaller boiler/boilers

3.1 Comparison of Whole Campus Electricity Consumption

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

3.3 Comparison of Measured Peak Demand

• 1785 kW in 1997 (Before commissioning)

• 1483 kW in 1998 (During commissioning)

• ???? In 1999 (After commissioning)

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)

3.5 Conclusions

• Look for significant amount of energy savings from commissioning

• Look for significant operating improvement from commissioning