[EnergyPlus_Support] Re: PTHP Baseline outperforming VAV

["Jean marais" <jeannieboef@xxxxxxxxx>]

Hi Markus,

For a large performance differace, look to the facade. Example: Proposed building has three pane glass, but the total window to wall ratio is 80%. baseline has single pane, but 40%. Baseline outperforms proposed because you simply can't compare 100 mm thick glass and 300 mm brick interms of conduction and Solar gain into the space.

PS example is not accurate and a little over played, but you get my meaning. Otherwise, I find it unlikely that the window units outperform a central unit, unless their are scheduling differences, or you zone dampers are not working.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Marcus" <clasz14@...> wrote:
>
> 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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