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

1. 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@psu.edu)

2. Presentation Outline • Research background • Pilot DOAS/CRCP system • Energy simulation overview • Energy conservation effects of the DOAS/CRCP system

3. 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

4. DOAS with Parallel Cooling

5. 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)

6. Pilot System Configuration 3-Way Valve (Panel CHW Supply Temp Control) Two 5-ton Air Cooled Chillers 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

7. System Operating Stages Panel Pump is activated Maintain Space DPT & DBT set-point Tp = Space DPT + 3F If Space DBT > 75F (set-point) when SA = 52F (lower limit)

8. 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 (= 52˚F)

9. 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 Manufacturer’s EW performance data • General Fan and Pump models were used

10. 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

11. 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

12. 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

13. 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

14. DOAS/CRCP VAV Total Energy Consumption 42% Reduced ! 19 MWh 11 MWh Fan Pump Chiller

15. 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

16. Questions?