Humidity produced by the plants (green houses)

ladybug-tools
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1

Hello dear @chris and @mostapha

I am planning to measure humidity which is produced by the plants in the greenhouses. So I was wondering if we could be able to edit people gain battery in the ladybug tools to just have humidity and remove the produced heat from its script and make a new battery for plants role in the space. I will also be able to edit the plant’s produced humidity based on the literature.
Could you please help me with this case?

2

Hi @Pourya ,

That’s a clever way of going about it. You can set the latent_fraction of people using a line or two of Python inside a GHPython component. You can see here on the SDK docs that the People object has a property to hard-set the latent fraction:

https://www.ladybug.tools/honeybee-energy/docs/honeybee_energy.load.people.html

Setting this to 1 will mean that effectively all of the hear from people will be turned into humidity so you can match things with the literature.

FYI, I have also found that trying to model irrigated beds of plants is not all that dissimilar from modeling indoor swimming pools if you wanted to try adding this object to your IDF using additional strings:

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3

@chris I know this has been an old topic but has there been any better way at modelling indoor plants other than as people loads with a 1.0 fraction of latent?

4

Hi @Mo, energyplus doesnt have a direct way to model plants other that Material:RoofVegetation, and that unfortunately wont help with modeling indoor plants.
You can however use an ems routine like the following (I just checked it ran simulation without throwing any errors):
just copy, paste to a panel and add to the _add_str input on the simulation component and edit zone name etc as needed.


! Always-on schedule used by the equipment
Schedule:Constant,
  AlwaysOn,            !- Name
  Fraction,            !- Schedule Type Limits Name
  1.0;                 !- Hourly value

! Latent-only “plant transpiration” load controlled by EMS
OtherEquipment,
  Plants_Latent,       !- Name
  None,                !- Fuel Type  (valid choices include None, Electricity, NaturalGas, ... )
  Zone One,            !- Zone or ZoneList or Space or SpaceList Name
  AlwaysOn,            !- Schedule Name
  EquipmentLevel,      !- Design Level Calculation Method
  0,                   !- Design Level {W}  (overwritten by EMS)
  ,                    !- Power per Floor Area {W/m2}
  ,                    !- Power per Person {W/person}
  1.0,                 !- Fraction Latent
  0.0,                 !- Fraction Radiant
  0.0,                 !- Fraction Lost
  ,                    !- Carbon Dioxide Generation Rate {m3/s-W} (leave blank)
  Plants;              !- End-Use Subcategory

EnergyManagementSystem:Sensor,
  ZAT,                       !- Name
  Zone One,                  !- Key Name
  Zone Mean Air Temperature; !- Output:Variable Name

EnergyManagementSystem:Sensor,
  ZW,                        !- Name
  Zone One,
  Zone Air Humidity Ratio;

EnergyManagementSystem:Actuator,
  PlantLatentAct,            !- Name
  Plants_Latent,             !- Actuated Component Unique Name
  OtherEquipment,            !- Actuated Component Type
  Power Level;               !- Actuated Component Control Type

EnergyManagementSystem:Program,
  Plants_ET_Control,
  SET Tdb = ZAT,                                      ! degC
  SET w   = ZW,                                       ! kg/kg
  SET RH  = @RhFnTdbWPb Tdb w 101325,                 ! [-]
  SET Psat_Pa = @PsyPsatFnTdb Tdb,                    ! Pa
  SET VPD_kPa = (1.0 - RH) * Psat_Pa / 1000.0,        ! kPa
  ! --- Cal model: ET [kg/s] = k * LeafArea[m2] * VPD[kPa]
  ! Tune k and LeafArea for your case:
  SET LeafArea_m2 = 5.0,
  SET k = 1.0e-6,                                     ! kg/s per m2 per kPa
  SET ET_kgps = k * LeafArea_m2 * VPD_kPa,
  SET Q_lat_W = ET_kgps * 2450000.0,                  ! W (h_fg ~ 2.45e6 J/kg)
  SET PlantLatentAct = Q_lat_W;

EnergyManagementSystem:ProgramCallingManager,
  PlantControlManager,
  AfterPredictorAfterHVACManagers,
  Plants_ET_Control;

best trevor

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