Re: [EnergyPlus_Support] Cooling consumption in winter

[Jason Kirkpatrick <jason.alan.kirkpatrick@xxxxxxxxx>]

Shane,

While it may be completely plausible that your building will require some cooling during the winter (depending on your buildings load characteristics .. surely a data center will have year round cooling), here are some things that you can check:

1)  Are you modeling infiltration at all?  for some guidance as to this, search the internet for 
"Infiltration Modeling Guidelines for Commercial Building Energy Analysis"

2)  check the SetpointManager that you are using for the air system.

you should have a single SetpointManager at the Supply Side Outlet Node of the AirLoopHVAC (Either  SetpointManager:Scheduled or  SetpointManager:OutdoorAirReset, depending on the control scheme you are using)

you should also have a single SetpointManager:MixedAir that takes the setpoint at the fan outlet, removes the calculated fan energy added to the airstream, and applies the modified setpoint to the outlets of the other equipment in the air handler.

an example of this is as follows:

  SetpointManager:Scheduled,
    AHU-1 SAT setpoint,  !- Name
    Temperature,             !- Control Variable
    Always 12.8,             !- Name
    AHU-1 Supply Fan Outlet; !- Setpoint Node or NodeList Name

SetpointManager:MixedAir,
    AHU-1 Mixed Air Temp Manager,                      !- Name
    Temperature,                                     !- Control Variable
    AHU-1 Supply Fan Outlet,                          !- Reference Setpoint Node Name
    AHU-1 Heating Coil Outlet,                          !- Fan Inlet Node Name
    AHU-1 Supply Fan Outlet,                          !- Fan Outlet Node Name
    AHU-1 Setpoint Nodelist;                           !- Setpoint Node or NodeList Name

Nodelist,
    AHU-1 Setpoint Nodelist,
    AHU-1 Mixed Air Outlet,                            ! Mixed air node
    AHU-1 Cooling Coil Outlet,                        ! CLG Coil Air Outlet
    AHU-1 Heating Coil Outlet,                        ! HTG Coil Air Outlet
    AHU-1 Heat Recovery Supply Outlet;                ! Enthalpy wheel outlet    

3) Check the Controller:OutdoorAir object to see if you are employing an outside air economizer. if you are, then the OutdoorAir:Mixer object should let in the appropriate amount of cold air to get the mixed air temp to the setpoint without using the cooling coil. Check the control scheme you are using for the Economizer to turn on. Are the conditions for it to turn on being met when you are getting the cooling in question? Are you placing a maximum limit on the outdoor air flow rate? 

4) Check Sizing:Zone  Sizing:System and DesignSpecification:OutdoorAir objects to make sure the appropriate amount of ventilation is being brought in, and also check the temperatures used for sizing the systems.

5) Are you controlling humidity? If so, your system may be cooling the air below the typical setpoint and then heating it back to get the appropriate temperature and humidity.

6) Run a simulation while reporting the temperatures and flow rates of each of the nodes that make up you airloop supply side (AHU). Particularly important will be the return air temperature, outdoor air flowrate, and the air temperature leaving the cooling coil.

7) If everything is working properly and you do in fact have a cooling load in the winter (maybe you can't use an airside economizer for whatever reason) then you might want to investigate a waterside economizer. There are example files demonstrating the use of this.

My guess is that you are not addressing infiltration and/or you have conflicting setpoints.


Hope this helps,

Jason

On Mon, Jan 10, 2011 at 2:33 AM, Shane Watson <mechenergy@xxxxxxxxx> wrote:

 

Dear All,

 

I am using simulating a VAV system for a cold climate, but getting cooling energy for winter season also, can some point out the mistake or suggest how can i check the system.

 

Thanks

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