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Re: [EnergyPlus_Support] Re: Can HVAC system take air from earth tubes instead of ambient?



Hello all,

I would like to continue the discussion of the topic of EarthTubes as a source for pre-cooling the air prior to the HVAC systems and I apologise in advance for the length of my message.

In my project I'm working with 7 zones, each one has an attached AirLoop with a Unitary AirtoAir HeatPump and I'm running the model in mixed mode for the annual simulation.

I followed the approach explained by Jason Kirkpatrick, however I can not find a way for requesting the wet bulb temperature for the air leaving the EarthTube, so I left out of my coding all the "ETWB.csv" part. All I can get from the EarthTube object is Zone Air Inlet Temperature and I assume this is the dry bulb temperature.

In this way, my model is replacing the Outdoor Air dry bulb temperature at the Outdoor Air Inlet of the Unitary Heatpumps. One doubt would then be if the values for the cooling load reduction that result by changing only the dry bulb temperature would still be reliable.

Another thing I noticed is that sometimes during the winter season there is still need for mechanical cooling during the day (as the project is in a 2B climate and there are considerable internal gains), it seems to me that during this time it would be better for the Heatpumps to get the ventilation air directly from the outside, instead that from the EarthTubes so I wonder if it would be valid to set the ETDB.csv file equal to the OutdoorAir dry bulb temperatures from the weather file during the winter season, in order to represent the summer-only operation of the EarthTubes.

The final question or doubt I have is if by changing the values of the temperatures at the Heatpump's Outdoor Air Inlet would affect the calculations of heat transfer through the skin of the building and/or the operation of the Natural Ventilation.

Thank you very much for your comments and observations, I really appreciate them.

Sincerely,


Mauro Contreras
THREE Consultoría Medioambiental

PS: If it is any help, this is the adaptation I used from the code that Mr. Kirkpatrick sugested:

!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:ACTUATOR ===========
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override,        !- Name
    Air Loop Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_1,        !- Name
    Air Loop 1 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_2,        !- Name
    Air Loop 2 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_3,        !- Name
    Air Loop 3 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_4,        !- Name
    Air Loop 4 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_5,        !- Name
    Air Loop 5 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
! Name
! Component Name
! Component Type
! Control Variable
EnergyManagementSystem:Actuator,
    ET_OADB_Override_6,        !- Name
    Air Loop 6 Unitary HP AirToAir Outdoor Air Inlet,  !- Actuated Component Unique Name
    Outdoor Air System Node, !- Actuated Component Type
    Drybulb Temperature;     !- Actuated Component Control Type
 
 
 
 
!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:PROGRAMCALLINGMANAGER ===========
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_1,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_1;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_2,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_2;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_3,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_3;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_4,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_4;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name_5
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_5,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_5;                 !- Program Name 1
 
! Name
! EnergyPlus Model Calling Point
! Program Name 1
EnergyManagementSystem:ProgramCallingManager,
    Schedule OA_6,             !- Name
    AfterPredictorBeforeHVACManagers,  !- EnergyPlus Model Calling Point
    SchedOA_6;                 !- Program Name 1
 
 
!-   ===========  ALL OBJECTS IN CLASS: ENERGYMANAGEMENTSYSTEM:PROGRAM ===========
 
! Name
EnergyManagementSystem:Program,
    SchedOA,                 !- Name
    SET ET_OADB_Override = Earth_Tube_DB_Sched;  !- Program Line 1
 
! Name
EnergyManagementSystem:Program,
    SchedOA_1,                 !- Name
    SET ET_OADB_Override_1 = Earth_Tube_DB_Sched_1;  !- Program Line 1
 
! Name
EnergyManagementSystem:Program,
    SchedOA_2,                 !- Name
    SET ET_OADB_Override_2 = Earth_Tube_DB_Sched_2;  !- Program Line 1
 
! Name
EnergyManagementSystem:Program,
    SchedOA_3,                 !- Name
    SET ET_OADB_Override_3 = Earth_Tube_DB_Sched_3;  !- Program Line 1
 
! Name
EnergyManagementSystem:Program,
    SchedOA_4,                 !- Name
    SET ET_OADB_Override_4 = Earth_Tube_DB_Sched_4;  !- Program Line 1
! Name
 
EnergyManagementSystem:Program,
    SchedOA_5,                 !- Name
    SET ET_OADB_Override_5 = Earth_Tube_DB_Sched_5;  !- Program Line 1
 
! Name
EnergyManagementSystem:Program,
    SchedOA_6,                 !- Name
    SET ET_OADB_Override_6 = Earth_Tube_DB_Sched_6;  !- Program Line 1
 
 
!-   ===========  ALL OBJECTS IN CLASS: OUTPUT:ENERGYMANAGEMENTSYSTEM ===========
 
Output:EnergyManagementSystem,
    Verbose,                 !- Actuator Availability Dictionary Reporting
    Verbose,                 !- Internal Variable Availability Dictionary Reporting
    Verbose;                 !- EMS Runtime Language Debug Output Level
 
 
!-   ===========  ALL OBJECTS IN CLASS: SCHEDULE:FILE ===========
 
Schedule:File,
    EarthTubeDBSch,          !- Name
    Any Number,              !- Schedule Type Limits Name
    C:\EnergyPlusV6-0-0\CCSB\ETDB.csv,  !- File Name
    1,                       !- Column Number
    0,                       !- Rows to Skip at Top
    8760,                    !- Number of Hours of Data
    Comma;                   !- Column Separator

De: Jason Kirkpatrick <jason.alan.kirkpatrick@xxxxxxxxx>
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx
Enviado: Martes, 5 de julio, 2011 13:41:43
Asunto: Re: [EnergyPlus_Support] Re: Can HVAC system take air from earth tubes instead of ambient?
 
In my above method, simulation 1 will account for the free cooling / free heating effect of the earthtube.

simulation 2 will then read the outputs of simulation 1 as the input to the outdoor air node for the HVAC system thereby coupling the earthtube system to the HVAC system.  Just change the fields in yellow below to match the outdoor air intake of your HVAC system. Also you will need to input the location of your first simulations output in the blue fields.


EnergyManagementSystem:
Actuator,
    ET_OADB_Override, ! Name
    DOAS Outside Air Inlet, ! Component Name
    Outdoor Air System Node, ! Component Type
    Drybulb Temperature; ! Control Variable
   
EnergyManagementSystem:Actuator,
    ET_OAWB_Override, ! Name
    DOAS Outside Air Inlet, ! Component Name
    Outdoor Air System Node, ! Component Type
    Wetbulb Temperature; ! Control Variable

Schedule:File,
    EarthTubeDBSch, !- Name
    Any Number, !- ScheduleType
    W:\M\CALC\ETDB.csv, !- Name of File
    1, !- Column Number
    0, !- Rows to Skip at Top
    8760, !- Number of Hours of Data
    Comma; !- Column Separator

Schedule:File,
    EarthTubeWBSch, !- Name
    Any Number, !- ScheduleType
    W:\M\CALC\ETWB.csv, !- Name of File
    1, !- Column Number
    0, !- Rows to Skip at Top
    8760, !- Number of Hours of Data
    Comma; !- Column Separator


On Tue, Jul 5, 2011 at 1:53 PM, wasilqayyum <wasilqayyum@xxxxxxxxxxx> wrote:
 
Thanks for the detailed reply.

What I'm trying to achieve is that I want to know what energy can be saved by using earth tubes by pre-cooling.

For example, I've created a building and put an ideal loads air system (cooling set point at 22oC) and summed up all values of Zone Sys Sensible Cooling to determine the cooling demand.

Now with the earth tubes, I'm having issues since the earth tube outlet temperature is higher than the room temp so its "heating". What I want is to route the earth tube outlet air (since its a little cooler than ambient, but not cool enough for thermal comfort) into HVAC system. Thus, the energy required by HVAC system to maintain 22oC should be less.

Will the approach you mentioned help me achieve this? Please explain if you can.

Any help will be very much appreciated.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jason Kirkpatrick <jason.alan.kirkpatrick@...> wrote:
>
> I have found it easier to run two simulations.
> The first one simulates the earth-tube only and then outputs the hourly dry
> bulb and wet bulb temperatures to a .csv file
> The second simulation utilizes EMS routines to replace the dry bulb and wet
> bulb hourly temperatures in the weather file with those found in the .csv
> output file but only for the outdoor air intake node... See code below:
> (note this was done with v.5 so there may be some updating that you need to
> do for v6)
>
> EnergyManagementSystem:Sensor,
> Earth_Tube_DB_Sched, !Name
> EarthTubeDBSch, ! Output:Variable Index Key Name
> Schedule Value; ! Output:Variable or Output:Meter Name
>
> EnergyManagementSystem:Sensor,
> Earth_Tube_WB_Sched, !Name
> EarthTubeWBSch, ! Output:Variable Index Key Name
> Schedule Value; ! Output:Variable or Output:Meter Name
>
> EnergyManagementSystem:Actuator,
> ET_OADB_Override, ! Name
> DOAS Outside Air Inlet, ! Component Name
> Outdoor Air System Node, ! Component Type
> Drybulb Temperature; ! Control Variable
>
> EnergyManagementSystem:Actuator,
> ET_OAWB_Override, ! Name
> DOAS Outside Air Inlet, ! Component Name
> Outdoor Air System Node, ! Component Type
> Wetbulb Temperature; ! Control Variable
>
> EnergyManagementSystem:Program,
> SchedOA, ! Name
> SET ET_OADB_Override = Earth_Tube_DB_Sched,
> SET ET_OAWB_Override = Earth_Tube_WB_Sched;
>
> EnergyManagementSystem:ProgramCallingManager,
> Schedule OA, ! Name
> AfterPredictorBeforeHVACManagers, ! EnergyPlus Model Calling Point
> SchedOA; ! Program Name 1
>
> Output:EnergyManagementSystem,
> Verbose,
> Verbose,
> Verbose;
>
> Schedule:File,
> EarthTubeDBSch, !- Name
> Any Number, !- ScheduleType
> W:\M\CALC\ETDB.csv, !- Name of File
> 1, !- Column Number
> 0, !- Rows to Skip at Top
> 8760, !- Number of Hours of Data
> Comma; !- Column Separator
>
> Schedule:File,
> EarthTubeWBSch, !- Name
> Any Number, !- ScheduleType
> W:\M\CALC\ETWB.csv, !- Name of File
> 1, !- Column Number
> 0, !- Rows to Skip at Top
> 8760, !- Number of Hours of Data
> Comma; !- Column Separator
>
>
>
>
>
>
> On Sun, Jul 3, 2011 at 1:20 PM, YuanLu Li <yli006@...> wrote:
>
> > **
> >
> >
> > I think, you can feed the ET air to a small room (a separate zone) and
> > then exhaust or return it to the OA mixer, or a HVAC system..
> >
> > The HVAC system does not know whether the air is from the room or the OA
> > mixer.
> >
> > The OA mixer box is actually an air splitter, an air by-pass path, and an
> > air mixer. The releaf node air is fed to the inlet node via the
> > environment.
> >
> > If the inlet air volume low or zero, all the zone return air is directed
> > to the HVAC system.
> >
> > You need to decide which part of the building air is to be relieved with an
> > exhaust fan, so that the ET air is not relieved at the OA mixer.
> > =======================
> > There may be other ways. Think of an pratical real system installation and
> > then map it into the EPlus simulation system.
> >
> > The idea is similar to the domestic hot water system. The water from a
> > tank to the showers, etc. are thrown away and replaced by the main water
> > supply.
> >
> >
> >
> > Dr. Li
> >
> >
> > ------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > From: wasilqayyum@...

> > Date: Sun, 3 Jul 2011 14:31:11 +0000
> > Subject: [EnergyPlus_Support] Can HVAC system take air from earth tubes
> > instead of ambient?
> >
> >
> >
> > Hello all,
> >
> > I'm simulation earth tubes for pre-cooling.
> >
> > However, the issue im having is that earth tubes output air directly into a
> > zone (building). But can I have it output air to a HVAC system instead? or
> > have an HVAC accept air from the earth tubes?
> >
> > Thanks.
> >
> >
> >
> >
>






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