Energy Conservation Benefits of a DOAS with Parallel Sensible Cooling by Ceiling Radiant Panels

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Energy Conservation Benefits of a DOAS with
Parallel Sensible Cooling by Ceiling Radiant
Panels

• Jae-Weon Jeong
• Stanley A. Mumma, Ph.D., P.E.
• William P. Bahnfleth, Ph.D., P.E.
• Department of Architectural Engineering
• The Pennsylvania State University
• (e-mail jqj102_at_psu.edu)

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Presentation Outline

• Research background
• Pilot DOAS/CRCP system
• Energy simulation overview
• Energy conservation effects of the DOAS/CRCP
  system

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Problems of All-Air VAV

• Multiple spaces equation (ASHRAE Std. 62)
• Does not guarantee that individual space will
  always receive the intended OA quantity
• Conditioning and transporting air
• Consumes large quantities of energy
• Part load humidity problem
• Space humidity is passively controlled

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DOAS with Parallel Cooling
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Pilot DOAS/CRCP system

• Space Conditions
• 3200 ft2 studio (43 X 74)
• 14 ceiling height with 8 rows of pendent
  illumination at the 9-ft plane
• 40 students
• Office equipments (desk lamps, personal computers)

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Pilot System Configuration
Two 5-ton Air Cooled Chillers
3-Way Valve (Panel CHW Supply Temp Control)
3-Way Valve (SA Temp Control)
High Induction Diffuser
Enthalpy Wheel
8 rows, 2 X 13 CRCPs
Variable Speed Drive (modulated EW speed)
Cooling Coil
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System Operating Stages
Panel Pump is activated
Maintain Space DPT DBT set-point
Tp Space DPT 3F
If Space DBT gt 75F (set-point) when SA 52F
(lower limit)
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EW and C/C controls
EW Full Speed C/C Modulate
(maintain SA condition)
hEA
A
EA
EW Off C/C Modulate (maintain SA
condition)
B
C
EW Speed Modulation (maintain SA
DPT) C/C Modulate or Off (maintain SA
condition)
SA DPT ( 52F)
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Energy Simulation

• Simulated the pilot system and a VAV serving the
  same space
• For DOAS/CRCP pilot system simulation
• General purpose equation solving software
• General reciprocating air-cooled chiller model
• Quasi-steady CRCP model
• Curve-fit of Manufacturers EW performance data
• General Fan and Pump models were used

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Energy Simulation

• For conventional VAV system simulation
• Commercial energy analysis program was used
• For common base simulation
• Identical chiller part-load characteristic
• Identical hourly space sensible latent loads
• Identical weather data (Williamsport, PA) were
  used

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Cooling Coil Load
VAV
57 of Peak C/C Load is shiftedto the EW
7.6 of Annual C/C Load was reduced
DOAS/CRCP
VAV
DOAS/CRCP
Operated for more hours
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Chiller Energy Reduction
29 reduction

• Chiller Size
• VAV system 14 ton
• DOAS/CRCP pilot system 10 ton
• Annual Chiller Energy Consumption
• VAV system 10.6 MWh/y (3.7 seasonal COP)
• DOAS/CRCP pilot system 7.9 MWh/y (4.5 seasonal
  COP)

25 reduction
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Fan and Pumping Energy
37 of VAV

• Fan Energy Reduction
• Design SA quantity DOAS 1200 scfm
  VAV 3220 scfm
• Annual Fan energy DOAS 2.33 MWh/y
  VAV 7.97 MWh/y
• Pumping Energy
• DOAS/CRCP system consumes as
  much pumping energy
• Counterbalanced by the greatly reduced fan and
  chiller energy

71 Reduced
nearly twice
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Total Energy Consumption
42 Reduced !
19 MWh
11 MWh
Fan
Pump
Chiller
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Conclusions

• Significant energy saving potential over 40
• Small SA quantity ? Fan energy reduction
• Total energy recovery ? Equipment size reduction
• Increased pumping energy
• Offset by reduced fan chiller energy
  consumption
• Real operation data of the pilot DOAS/CRCP system
  pending ASHRAE DOE funding
• More information http//doas-radiant.psu.edu

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Questions?