EnergyPlus™ is a whole building energy simulation program that engineers, architects, and researchers use to model both energy consumption and water use in buildings.
For CO2 based proportional demand controlled ventilation, when tested with the EnergyPlus example “HeatPumpProportionalControl_DCV.idf”, the west zone indoor air CO2 concentration varies as shown in Figure 1 and the AHU ventilation flow rate varies proportionally to zone occupancy schedule as shown in Figure 2.
EnergyPlus issue #4216 revised this calculation so the ventilation air flow rate looks like in Figure 3. However, based on Figure 3, in the latest source code after bug fix, at each time step, the maximum ventilation rate and maximum zone CO2 level are re-calculated based on the actual zone occupancy level (design zone occupancy * zone occupancy schedule) at the specific time step. Then the zone required ventilation rate is calculated proportionally.
However, for practical applications, the zone controller usually does not have the real time occupancy information, and the maximum zone CO2 level and the maximum zone ventilation air flow rate for control is based on the design occupancy level. The result should look like shown in Figure 4.
Figure 1 Simulated Zone CO2 Concentration
Figure 2 AHU Outdoor Air Flow Rate before issue #4216 Revision
Figure 3 AHU Outdoor Air Flow Rate after Issue #4216 Revision
Figure 4 Desired Result of Outdoor Air Flow Rate
Description of proposed upgrade
To get the ventilation rate behave as shown in Figure 4, we suggest:
Adding an option to the “System Outdoor Air Method” field of the “Controller:MechanicalVentilation” object. The option should be named “ProportionalControl based on Design Occupancy”,
Change the name of the current proportional control to “ProportionalControl based on Occupancy Schedule” for clarity. This modification should be done in the IDD.
After the modification in IDD, there will be 6 options in the “System Outdoor Air Method” field.
VentilationRateProcedure
ZoneSum
IndoorAirQualityProcedure
ProportionalControlBasedOnDesignOccupancy
ProportionalControlBasedonOccupancySchedule
IndoorAirQualityProcedureGenericContaminant
Correspondingly in the source code, modify subroutine CalcOAController in MixedAir.f90 to accommodate the added option. Specific source code modifications will be proposed in the NFP.
The demand controlled ventilation section of Engineering Reference Manual, the Input/Output manual should also be modified to reflect this added feature.
mjwitte
commented
9 years ago
For CO2 based proportional demand controlled ventilation, when tested with the EnergyPlus example “HeatPumpProportionalControl_DCV.idf”, the west zone indoor air CO2 concentration varies as shown in Figure 1 and the AHU ventilation flow rate varies proportionally to zone occupancy schedule as shown in Figure 2. EnergyPlus issue #4216 revised this calculation so the ventilation air flow rate looks like in Figure 3. However, based on Figure 3, in the latest source code after bug fix, at each time step, the maximum ventilation rate and maximum zone CO2 level are re-calculated based on the actual zone occupancy level (design zone occupancy * zone occupancy schedule) at the specific time step. Then the zone required ventilation rate is calculated proportionally. However, for practical applications, the zone controller usually does not have the real time occupancy information, and the maximum zone CO2 level and the maximum zone ventilation air flow rate for control is based on the design occupancy level. The result should look like shown in Figure 4.
Description of proposed upgrade
To get the ventilation rate behave as shown in Figure 4, we suggest:
After the modification in IDD, there will be 6 options in the “System Outdoor Air Method” field.