2003 ASHRAE Annual Meeting Kansas City

Energy Conservation Benefits of a DOAS with Parallel Sensible Cooling

by Ceiling Radiant Panels

Jae-Weon JeongStanley A. Mumma, Ph.D., P.E.

William P. Bahnfleth, Ph.D., P.E.

Department of Architectural EngineeringThe Pennsylvania State University

(e-mail: jqj102@psu.edu)

2003 ASHRAE Annual Meeting Kansas City

Presentation Outline

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

DOAS/CRCP system

2003 ASHRAE Annual Meeting Kansas City

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

2003 ASHRAE Annual Meeting Kansas City

DOAS with Parallel Cooling

2003 ASHRAE Annual Meeting Kansas City

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)

2003 ASHRAE Annual Meeting Kansas City

Pilot System Configuration

Two 5-ton Air Cooled

Chillers

Enthalpy Wheel

8 rows, 2’ X 13’ CRCPs

3-Way Valve(SA Temp Control)

3-Way Valve(Panel CHW Supply

Temp Control)

Cooling Coil

High InductionDiffuser

Variable Speed Drive(modulated EW speed)

2003 ASHRAE Annual Meeting Kansas City

System Operating Stages

Maintain Space DPT& DBT set-point

If Space DBT > 75F (set-point)when SA = 52F (lower limit)

Panel Pumpis activated

Tp = Space DPT + 3F

2003 ASHRAE Annual Meeting Kansas City

EW and C/C controls

A

B

C

EA

SA DPT (= 52˚F)

hEA

EW – OffC/C – Modulate (maintain SA condition)

EW – Full SpeedC/C – Modulate (maintain SA condition)

EW – Speed Modulation (maintain SA DPT)C/C – Modulate or Off (maintain SA condition)

2003 ASHRAE Annual Meeting Kansas City

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

2003 ASHRAE Annual Meeting Kansas City

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

2003 ASHRAE Annual Meeting Kansas City

Cooling Coil Load

57% of Peak C/C Load is shifted

to the EW

VAV

DOAS/CRCP

VAV DOAS/CRCP

Operated for more hours

7.6 % of Annual C/C Load was reduced

2003 ASHRAE Annual Meeting Kansas City

Chiller Energy 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)

29% reduction

25% reduction

2003 ASHRAE Annual Meeting Kansas City

Fan and Pumping Energy

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

37% of VAV

71% Reduced

nearly twice

2003 ASHRAE Annual Meeting Kansas City

Total Energy Consumption

DOAS/CRCP VAV

Chiller

PumpFan

42% Reduced !

19 MWh

11 MWh

2003 ASHRAE Annual Meeting Kansas City

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

2003 ASHRAE Annual Meeting Kansas City

Questions?