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# Water pump consumption in Graywater and RainWater harvesting

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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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: ExteriorEnergyUse.cc#L316[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.

Exterior:Lights,
RainWaterPump,
[...],
Rain Water Pump; !- End Use Subcategory

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

WaterUse:Storage,
RainWaterTank, !- Name
[....]

EnergyManagementSystem:Sensor,
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

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

EnergyManagementSystem:Program,
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
ELSE,
SET RainWaterPump_ElecPower_Override = 0.0,
ENDIF;

more

It goes without saying, but if your pump is small enough, perhaps you can just ignore it or model a rough, constant value...

( 2017-12-06 05:29:08 -0500 )edit

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Last updated: Dec 06 '17