Improve Facility Operation through Commissioning-A Case Study

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Improve Facility Operation through
Commissioning-A Case Study

• Mingsheng Liu, Ph.D., P. E.
• University of Nebraska

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Outline

• Facility information
• Commissioning measures
• Measured results and conclusions

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1. 1 Building and AHUs Information
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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

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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.

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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)

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1.5 Thermal Storage System
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1.6 Measured Hourly Electricity Consumption
Before Commissioning
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1.7 Measured Hourly Gas Consumption Before
Commissioning
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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

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2.1 Commissioning Measures

• Energy Management and Control Systems
• Buildings
• Thermal storage systems
• Boiler systems

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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

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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.
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2.2.2 Real Operation

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

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2.2.3 Solutions
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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

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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

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2.5 Measures for Boilers

• Decrease steam pressure from 60 psig to 40 psig
  at night and weekends
• Use smaller boiler/boilers

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3.1 Comparison of Whole Campus Electricity
Consumption
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3.2 Comparison of Campus Hourly Gas Consumption
(ft3/hr)
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3.3 Comparison of Measured Peak Demand

• 1785 kW in 1997 (Before commissioning)
• 1483 kW in 1998 (During commissioning)
• ???? In 1999 (After commissioning)

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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)

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3.5 Conclusions

• Look for significant amount of energy savings
  from commissioning
• Look for significant operating improvement from
  commissioning