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Water pump consumption in Graywater and RainWater harvesting

asked 2017-11-25 08:45:26 -0600

Avi gravatar image

updated 2017-12-06 05:28:01 -0600

I wrote both Rainwater and Greywater harvesting E+ measures but both of them don't take into account the power consumption of the water pump that delivers the water from the collecting water tank. I am looking at modeling the power consumption at the relevant times ( when water demand is presented to the water tank). I am aware of that question. Did anyone figured out how to do that?

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answered 2017-12-06 05:02:00 -0600

updated 2017-12-06 07:13:00 -0600

You should be able to use EnergyManagementSystem to do this:

  • Create an exterior equipment. I think you'll need to use Exterior:Lights here, because it has an actuator called "Electric Power", Exterior:FuelEquipment doesn't look it has one. See source:[1] . Set the Exterior:Lights End-Use Subcategory to "Water Pump" or whatever you want in order to have the right reporting in your eplustbl.htm.

  • Add an EMS Sensor for your flow rate, probably capturing the WaterUse:Storage's output variable Water System Storage Tank Inlet Volume Flow Rate [m3/s] (ref here)

  • Declare an EMS Actuator for your chosen Exterior equipment's Electric Power.
  • Write an EMS program that will compute the power used by the pump based on the flow rate given by the EMS Sensor.

Debug, look at outputs.

I hope it helps.

[1] You could make sure: try with Exterior:FuelEquipment, request the EMS actuator dictionary (see here), check if there is indeed an actuator for this object or not.

Here's a completely untested, written on the fly and manually (problems/typos expected), EMS snippet. I think the calling point should be about right, but you may have to change it.

  Rain Water Pump; !- End Use Subcategory

  RainWaterPump_ElecPower_Override,     !- Name
  RainWaterPump,                        !- Actuated Component Unique Name
  Exterior:Lights,                      ! Actuated Component Type
  Electric Power;                       ! Actuated Component Control Type

   RainWaterTank, !- Name

  RainWaterTank_OutletFlowRate_Sensor, !- Name
  RainWaterTank,                       !- Output:Variable or Output:Meter Index Key Name
  Water System Storage Tank Inlet Volume Flow Rate; !- Output:Variable or Output:Meter Name

  Model_RainWaterPump_CallingManager,                         !- Name
  AfterPredictorAfterHVACManagers ,       !- EnergyPlus Model Calling Point
  Model_RainWaterPump;                        !- Program Name 1

  Model_RainWaterPump ,         ! Name
  IF RainWaterTank_OutletFlowRate_Sensor > 0,
    ! ### IMPLEMENT PUMP POWER CALC HERE, assuming 30 ft of head and 0.5 total pump eff ###
    SET RainWaterPump_ElecPower_Override =  RainWaterTank_OutletFlowRate_Sensor * 89,672 / 0.5,
  ! This IF/ELSE statement is useless here (if flow is zero, power is zero), but I wanted to show the syntax
     SET RainWaterPump_ElecPower_Override = 0.0,
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It goes without saying, but if your pump is small enough, perhaps you can just ignore it or model a rough, constant value...

Julien Marrec gravatar imageJulien Marrec ( 2017-12-06 05:29:08 -0600 )edit

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Asked: 2017-11-25 08:45:26 -0600

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Last updated: Dec 06