Exhaust Stack Discharge Velocity Reduction


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Higher Education Sustainability Conference - Best Practices Award - UCI ESDVR 06.22.10

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  • Here is an overview of what I plan to talk about. Lets take a few minutes to overview our Smart Lab concept
  • UC Irvine is a growing…
  • We are constantly challenging ourselves to save energy. Our recipe for taking on these ambitious projects is to have a multi-disciplinary team of professionals focused on a common goal.
  • Here is an overview of what I plan to talk about. Lets take a few minutes to overview our Smart Lab concept
  • Our goal at UC Irvine is to find the sweet spot where we balance lab safety and climate safety It is also our goal to outperform ASHRAE 90.1 or CA Title 24 by approximately 50%... To accomplish this we are…
  • The idea is to combine these ideas into one building, new or retrofit…
  • This CDCV system begins with: room sensors to measure the quality of the air in many locations of a building An air router pulls the air sample to the Centralized sensor suite that analyzes the air sample for… An information management server tells the VAV controller to increase or decrease air flow All this data is logged into a computer for analysis
  • The LFFH is a deeper hood with better capture and less turbulence so it can capture contaminants with less air flow. High performance fume hoods are more energy efficient than conventional hoods because of their lower total exhaust volumes. They are designed Low flow hoods take air entering through the sash opening and form a roll in the upper chamber called a vortex. This vortex enhances the hood’s containment capability and has been engineered so that it will not break down and collapse. A sensor within the hood sidewall prevents potential vortex collapse by automatically adjusting the rear baffle slots in real time. High Performance Fume Hood Components   Vortex Chamber has been designed to optimize the flow of the vortex within the hood to provide maximum containment at lower exhaust volumes and face velocities. Vortex Control System measures the stability of the vortex airflow pattern within the hood chamber and automatically adjusts the articulating baffle to maintain maximum containment.   Figure 4: High performance fume hood components   Articulating Baffles are designed so that the slot positions change when the baffle is adjusted by the Vortex controls.   Front Turning Vane increases the stability of the vortex within the fume hood.
  • We are reducing our lab lighting power density by 50% - Daylight sensors for fixtures near windows - Occupancy sensing by lab bay
  • The wind tunnel testing told us we can frequently save energy by: Raising stack heights Installing variable speed fans and reducing exhaust system flows, 15,000 cfm per stack Disabling existing by pass dampers Run more fans at lower speed
  • For Gross Hall… Reducing the kWh consumption kW is the (water pressure) SBD from SCE
  • Here is an overview of what I plan to talk about. Lets take a few minutes to overview our Smart Lab concept
  • What we are concerned about is the re-entrainment of contaminated air. We begin with a building and the prevailing wind. Within the building, contaminants are generated. An exhaust system needs to exhaust these contaminants out so they are not re-entrained into the building or to nearby individuals. Discuss components of system… Note the plumes and effects on dispersion of short/tall stacks and low/high exit velocities. So, we would likely select a taller stack for energy reduction which allows us to reduce the fan speed and exit velocity.
  • Using wind tunnel testing, we challenged the conservative assumptions on which buildings are designed. Wind tunnel testing is based on fluid dynamic similarity modeling—like wind tunnel tests of aircraft wings. Once the test is properly set up, we can measure in the wind tunnel almost anything related to wind and multiply it by the appropriate scale factor to determine the full-scale real-world value. The dilution of exhaust plumes is one of the wind-related parameters which can be well modeled in the wind tunnel. The wind tunnel is the only means available today to accurately model wind flow and related parameters around buildings. If you are considering using alternative methods such as desktop calculations or Computational Fluid Dynamics for this purpose, please talk to me off-line. I can provide references to articles in the technical literature which clearly describe the shortcomings of non-wind-tunnel approaches. The first step in setting up a wind tunnel test is to build an accurate scale model of the building under study and the buildings, terrain and trees around it. You need to extend the model out about ¼ mile in all directions to take account of the effects of upwind buildings, etc on the wind and turbulence at the building under study. Here we see the model used in this study for the Biological Sciences 3 and Natural Sciences 1 lab buildings. They are the blue buildings in the center. The model is at a scale of 1:200 and includes terrain and trees as well as buildings for ¼ mile radius. The accuracy of the model is directly related to the accuracy of the results. So it is important to put sufficient effort into recreating a model which accurately represents the existing buildings as well as those which are expected to be built within the next few years. The model is mounted on a turntable will is rotated by the wind tunnel operator to model different wind directions. In this photo, you are looking upwind and can see the wood blocks which are used to create the proper profile of wind speed and turbulence in the air approaching the test model—more about that a little later.
  • Tubes are installed in the model to take air samples at locations where the concentration of the exhaust plume might be important. The jargon term for these points is “receptors.” The locations are indicated by the numbered arrows. Note that some of the receptors use blue plastic fixtures which are designed to take their sample at a height of about 5 feet full scale. This is representative of the breathing zone for the average person.
  • Wind tunnel testing of exhaust dispersion is done in two primary modes. The first is smoke visualization as shown in this video clip. This allows us to see the plume and gives us a good idea of the flow phenomena controlling where the plume goes and how fast it is being diluted. This is very useful in understanding what is happening and devising alternative exhaust design approaches. The second mode of testing is the use of a precision tracer gas and analysis of its concentration in air samples at receptors to quantitatively specify the exhaust plume dilution. This is the fundamental set of measurements which tell us whether the maximum concentrations at receptors will exceed those allowed by health or odor standards.
  • Here is an artists rendering of stack heights increased 5 feet
  • Dynamic SP Reset based on demand inside the building
  • Exhaust Stack Discharge Velocity Reduction

    1. 1. 2010 Higher Education Sustainability Conference Los Angeles Trade Tech College June 22, 2010 Chris Abbamonto UC Irvine, Facilities Management
    2. 2. The University of California, Office of the President is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
    3. 3. Learning Objectives <ul><li>You will identify the criteria that exemplify new construction best practices in HVAC design and retrofitting. </li></ul><ul><li>The learner will identify the technologies useful for HVAC efficiency including indirect/direct evaporative cooling, a heat pipe heat recovery loop to dehumidify air in high-density areas, solar thermal installations, and the modification of exhaust stack height and discharge velocity. </li></ul><ul><li>You will compare and contrast the range of strategies and technologies to energy savings. </li></ul>
    4. 4. Agenda <ul><li>UC Irvine Campus Overview </li></ul><ul><li>Smart Lab Overview </li></ul><ul><li>Exhaust System Optimization </li></ul><ul><li>Questions and Discussion </li></ul>
    5. 5. University of California, Irvine <ul><li>Large research university </li></ul><ul><li>$16M annual utilities budget </li></ul><ul><li>Lab buildings consume 2/3 of campus energy </li></ul><ul><li>Many energy initiatives to reduce carbon footprint </li></ul>
    6. 6. Campus Energy Savings Team Synergy Safety Management Visionary & Supportive Upper Management Engineers Facility Managers Patience Supportive Users/ Researchers
    7. 7. Agenda <ul><li>UC Irvine Campus Overview </li></ul><ul><li>Smart Lab Overview </li></ul><ul><li>Exhaust System Optimization </li></ul><ul><li>Questions and Discussion </li></ul>
    8. 8. Balancing Lab Safety & Climate Safety <ul><li>Create lab buildings that out perform ASHRAE 90.1 / CA Title 24 by 50% </li></ul><ul><li>Combine energy initiatives such as </li></ul><ul><ul><li>Centralized demand controlled ventilation (CDCV) </li></ul></ul><ul><ul><li>Low flow (high performance) fume hoods </li></ul></ul><ul><ul><li>Energy-efficient lighting </li></ul></ul><ul><ul><li>Optimized Exhaust Systems </li></ul></ul>
    9. 9. Smart Lab Building Concept Building Exhaust System Labs w/CDCV real time lab air monitoring 4 ach occupied 2 ach unoccupied Energy efficient lighting Labs with low flow fume hoods (as appropriate )
    10. 11. Low Flow (high performance) Fume Hoods Sash Airfoil Work Surface Exhaust Plenum Baffle Increased Hood Depth Operate safely at lower face velocities (i.e. 70 FPM rather than 100 FPM)
    11. 12. Lighting Controls Reduce Power Density by 50% Lab Area LPD from 1.1 to 0.6 Lab Prep LPD from 1.0 to 0.4 Prep Room LPD from 2.0 to 1.0 Corridor LPD from 0.6 to 0.3
    12. 13. Exhaust Energy Reduction Solutions Slightly higher stacks, 4-5 feet Variable speed fans (reduce exhaust fan flows) Install wind responsive equipment (if needed) Reduce or eliminate bypass air
    13. 14. <ul><li>Estimated annual energy savings: </li></ul><ul><li>890,080 kWh electrical with 193 kW demand reduction </li></ul><ul><li>22,464 therms of natural gas </li></ul><ul><li>Estimated annual energy cost savings: </li></ul><ul><li>$ 110,980 at $0.105/kWh and $0.78/therm </li></ul><ul><li>Savings by Design payment of $ 397,836 </li></ul><ul><li>Exceeding Title 24 by 50% </li></ul><ul><li>Bid as a LEED New Construction (NC) Silver </li></ul><ul><li>Design Build contractor proposed to increase the sustainable features to achieve LEED NC Gold certification </li></ul>
    14. 15. Agenda <ul><li>UC Irvine Campus Overview </li></ul><ul><li>Smart Lab Overview </li></ul><ul><li>Exhaust System Optimization </li></ul><ul><li>Questions and Discussion </li></ul>
    15. 16. Lab Building Exhaust Wind Exhaust Fan Bypass Damper Plenum Fume Hood Supply Fan Duct Balcony Re-Entrainment of Contaminated Air
    16. 17. Wind Tunnel Testing Challenge Conservative Assumptions
    17. 18. Wind Tunnel Testing <ul><li>Build model of campus </li></ul><ul><li>Install model stacks </li></ul><ul><li>An abundance of air sampling point receptors </li></ul>
    18. 19. Wind Tunnel Testing Methodology <ul><li>Build model of campus </li></ul><ul><li>Install model stacks </li></ul><ul><li>Install air sampling points (“receptors”) </li></ul><ul><li>Ensure correct approach flow </li></ul><ul><li>Wind tunnel testing </li></ul>
    19. 21. Sprague Hall <ul><li>Install variable frequency drives (VFD) </li></ul><ul><li>Close bypass dampers </li></ul><ul><li>No stack extension needed </li></ul><ul><li>Energy Savings: </li></ul><ul><li>582,000 kWh </li></ul><ul><li>Cost: $197,000 </li></ul><ul><li>Simple Payback: 0.9 years </li></ul>
    20. 22. Croul Hall <ul><li>Install variable frequency drives (VFD) </li></ul><ul><li>8’ Stack Extensions </li></ul><ul><li>Static Pressure Reset </li></ul><ul><li>Energy Savings: </li></ul><ul><li>344,000 kWh </li></ul><ul><li>Cost: $307,000 </li></ul><ul><li>Simple Payback: 6.2 years </li></ul>
    21. 23. Natural Sciences II <ul><li>Install variable frequency drives (VFD) </li></ul><ul><li>Static Pressure Reset </li></ul><ul><li>4’ Stack Extensions </li></ul><ul><li>Energy Savings: </li></ul><ul><li>929,000 kWh </li></ul><ul><li>Cost: $331,000 </li></ul><ul><li>Simple Payback: 1.1 years </li></ul>
    22. 24. Hewitt Hall <ul><li>No Stack Extensions </li></ul><ul><li>Install variable frequency drives (VFD) </li></ul><ul><li>Static Pressure Reset </li></ul><ul><li>Energy Savings: </li></ul><ul><li>287,000 kWh </li></ul><ul><li>Cost: $365,000 </li></ul><ul><li>Simple Payback: 9.8 years </li></ul>
    23. 25. Summary of Savings 0.8 $ 224,910 $ 171,840 514,080 2,142,000 TOTALS: 9.8 $ 30,135 $ 296,120 68,880 287,000 Hewitt Hall 1.1 $ 97,545 $ 108,040 222,960 929,000 Natural Sciences 2 6.2 $ 36,120 $ 224,440 82,560 344,000 Croul Hall 0.9 $ 61,110 $ 57,320 139,680 582,000 Sprague Hall Years $ 0.105 Project Cost $ 0.24 kWh Savings Building Simple Payback Electrical Savings Net Incentive    
    24. 26. Keys to Success <ul><li>Next Steps </li></ul><ul><li>Wind Responsive Controls </li></ul><ul><li>Evaluation of Additional Facilities </li></ul><ul><li>Professional Risk Assessment </li></ul><ul><li>Challenging Engineering Rules of Thumb </li></ul><ul><li>Collaborative Cross Functional Team </li></ul><ul><li>Commitment of Resources to Energy Efficiency </li></ul>
    25. 27. Thank you for your time! QUESTIONS?? This concludes The American Institute of Architects Continuing Education Systems Program
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