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[EnergyPlus_Support] PTHP Baseline outperforming VAV

Hi all, please excuse cross-posting to Bldg-sim;

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
-- 
Marcus Jones, LEED AP, M.Sc.
Freelance energy consultant
Vienna, Austria




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