Hi all,

Having some difficulty in an App. G model for a 6-floor 14,000 m2 GFA Hotel
in zone 1B (Abu Dhabi). Assuming standard design for each, should a proposed
VAV system out-perform window AC units (the baseline)?

Proposed:
VAV with 2 Air-cooled centrifugal chillers, chiller COP = 3.1 (2.8 if
condenser fan energy included)
Envelope - Better windows decrease heating demand by 8% rest of envelope is
minimum required for compliance

Baseline:
System Packaged terminal heat pump, COP = 3.52

Using Energyplus v6.0 the results are;

Site Energy in End Uses BL Proposed COP5
MWh MWh MWh
Space Cooling 747.5 1052.0 715.6
Heat Rejection 0.0 0.0 0.0
Space Heating 1.3 0.1 0.1
Pumps 0.0 60.0 60.0
Fans - Interior 42.2 137.7 137.7
Fans - Car park 0.0 0.0 0.0
Interior Lighting 530.5 530.5 530.5
Exterior Lighting 0.0 0.0 0.0
Service Water Heating 0.0 0.0 0.0
Receptacle/Process Equipment 146.3 146.3 146.3
Data Centre Equipment 0.0 0.0 0.0
Elevators and Escalators 0.0 0.0 0.0
Total Site Energy 1467.9 1926.6 1590.2

I have the energy for the baseline, the proposed with COP = 3.1, and then
trying COP = 5. It seems that even if we drastically increase the COP of the
chiller plant in the proposed VAV system, we still can't get any energy
savings. Is this realistic, an artifact of the simulation, or just an error
on my part?

Any guidance would be appreciated,

Marcus Jones, LEED AP