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mitchute merged 3 commits into from
Jul 6, 2026
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ZoneHVAC:HybridUnitaryHVAC - Check for ventilation setting before defaulting to standby #11642

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9178b72
#11568 - Find the best available ventilation-only setting instead of …
kevin-moos Jun 16, 2026
a6eaf1b
Make adjustments to unit tests
kevin-moos Jun 17, 2026
4aa67c0
Add standby for partial setting
kevin-moos Jun 17, 2026
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80 changes: 45 additions & 35 deletions src/EnergyPlus/HybridEvapCoolingModel.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1078,30 +1078,28 @@ namespace HybridEvapCoolingModel {
Real64 PLHumidRatio, PLDehumidRatio, PLVentRatio, PLSensibleCoolingRatio, PLSensibleHeatingRatio, PartRuntimeFraction;
PLHumidRatio = PLDehumidRatio = PLVentRatio = PLSensibleCoolingRatio = PLSensibleHeatingRatio = 0;

if (Mvent > 0) {
if (VentilationRequested && Mvent > 0) {
PLVentRatio = MinOA_Msa / Mvent;

@rraustad rraustad Jun 19, 2026

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  1. is this redundant?, 2) is Mvent > 0 possible if StepIns.MinimumOA = 0? and 3) does it hurt to calculate PLVentRatio each time step?

     if (StepIns.MinimumOA > 0) {
     VentilationRequested = true;
 }

@kevin-moos kevin-moos Jun 19, 2026

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I don't think it will be common, but yes, Mvent > 0 is possible when StepIns.MinimumOA is 0. Checking for VentilationRequested might be a little redundant, but I figured it was better to skip a division when we know the result is 0.

@mitchute mitchute Jun 23, 2026

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Anything else on this point @rraustad?

@rraustad rraustad Jun 23, 2026

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Nothing else. I think this meets the objective.

}
PartRuntimeFraction = PLVentRatio;

if (SensibleRoomORZone > 0) {
if (CoolingRequested && SensibleRoomORZone > 0) {

@mitchute mitchute Jun 23, 2026

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This seems like a reasonable guard.

PLSensibleCoolingRatio = std::abs(RequestedCoolingLoad) / std::abs(SensibleRoomORZone);
}
if (PLSensibleCoolingRatio > PartRuntimeFraction) {
PartRuntimeFraction = PLSensibleCoolingRatio;
}

if (SensibleRoomORZone < 0) {
if (HeatingRequested && SensibleRoomORZone < 0) {

@mitchute mitchute Jun 23, 2026

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Same here.

PLSensibleHeatingRatio = std::abs(RequestedHeatingLoad) / std::abs(SensibleRoomORZone);
}

if (PLSensibleHeatingRatio > PartRuntimeFraction) {
PartRuntimeFraction = PLSensibleHeatingRatio;
}

if (RequestedDehumidificationLoad > 0) {
PLDehumidRatio = std::abs(RequestedDehumidificationLoad) / std::abs(LatentRoomORZone);
}

if (PLDehumidRatio > PartRuntimeFraction) {
PartRuntimeFraction = PLDehumidRatio;
}
Expand Down Expand Up @@ -1193,13 +1191,15 @@ namespace HybridEvapCoolingModel {
bool DidWeMeetLoad = false;
bool DidWeMeetHumidification = false;
bool DidWePartlyMeetLoad = false;
bool DidWeMeetVentilation = false;
Real64 OptimalSetting_RunFractionTotalFuel = IMPLAUSIBLE_POWER;
Real64 Tma;
Real64 Wma;
Real64 Hsa;
Real64 Hma;
Real64 PreviousMaxiumConditioningOutput = 0;

@mitchute mitchute Jun 23, 2026

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Spelling correction. OK.

Real64 PreviousMaxiumHumidOrDehumidOutput = 0;
Real64 PreviousMaximumConditioningOutput = 0;
Real64 PreviousMaximumHumidOrDehumidOutput = 0;
Real64 PreviousMaximumSupplyFanElectricPower = IMPLAUSIBLE_POWER;
std::string ObjectID = Name.c_str();
if (StepIns.RHosa > 1) {
ShowSevereError(
Expand Down Expand Up @@ -1328,11 +1328,8 @@ namespace HybridEvapCoolingModel {
CandidateSetting.Unscaled_Supply_Air_Mass_Flow_Rate = UnscaledMsa;
CandidateSetting.ScaledSupply_Air_Mass_Flow_Rate = ScaledMsa;

// If no load is requested but ventilation is required, set the supply air mass flow rate to the minimum of the
// required ventilation flow rate and the maximum supply air flow rate
if (!CoolingRequested && !HeatingRequested && !DehumidificationRequested && !HumidificationRequested) {
CandidateSetting.ScaledSupply_Air_Mass_Flow_Rate =
min(MinOA_Msa, CandidateSetting.ScaledSupply_Air_Mass_Flow_Rate);
// If no load is requested but ventilation is required, set the supply air temp to the outside air temp
// add fan heat if not included in lookup tables for supply air stream
Tsa = StepIns.Tosa + FanHeatTemp;
}
Expand Down Expand Up @@ -1453,33 +1450,32 @@ namespace HybridEvapCoolingModel {
thisSetting.oMode.CalculateCurveVal(state, StepIns.Tosa, Wosa, StepIns.Tra, Wra, UnscaledMsa, OSAF, WATER_USE);

// Calculate partload fraction required to meet all requirements
// Fraction can be above 1 meaning its not able to do it completely in a time step
Real64 PartRuntimeFraction = CalculatePartRuntimeFraction(MinOA_Msa,
thisSetting.Supply_Air_Ventilation_Volume * state.dataEnvrn->StdRhoAir,
StepIns.RequestedCoolingLoad,
StepIns.RequestedHeatingLoad,
SensibleRoomORZone,
StepIns.ZoneDehumidificationLoad,
StepIns.ZoneMoistureLoad,
latentRoomORZone);
thisSetting.Runtime_Fraction = CalculatePartRuntimeFraction(MinOA_Msa,
thisSetting.Supply_Air_Ventilation_Volume * state.dataEnvrn->StdRhoAir,
StepIns.RequestedCoolingLoad,
StepIns.RequestedHeatingLoad,
SensibleRoomORZone,
StepIns.ZoneDehumidificationLoad,
StepIns.ZoneMoistureLoad,
latentRoomORZone);

Real64 RunFractionTotalFuel;
switch (ObjectiveFunction) {
default:
case ObjectiveFunctionType::ElectricityUse:
RunFractionTotalFuel = thisSetting.ElectricalPower * PartRuntimeFraction;
RunFractionTotalFuel = (thisSetting.ElectricalPower * thisSetting.Runtime_Fraction) +
(thisSetting.SupplyFanElectricPower * thisSetting.Runtime_Fraction);
Comment on lines +1466 to +1467

@mitchute mitchute Jun 23, 2026

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I like that these are tied to the actual settings now.

break;
case ObjectiveFunctionType::SecondFuelUse:
RunFractionTotalFuel = thisSetting.SecondaryFuelConsumptionRate * PartRuntimeFraction;
RunFractionTotalFuel = thisSetting.SecondaryFuelConsumptionRate * thisSetting.Runtime_Fraction;
break;
case ObjectiveFunctionType::ThirdFuelUse:
RunFractionTotalFuel = thisSetting.ThirdFuelConsumptionRate * PartRuntimeFraction;
RunFractionTotalFuel = thisSetting.ThirdFuelConsumptionRate * thisSetting.Runtime_Fraction;
break;
case ObjectiveFunctionType::WaterUse:
RunFractionTotalFuel = thisSetting.WaterConsumptionRate * PartRuntimeFraction;
RunFractionTotalFuel = thisSetting.WaterConsumptionRate * thisSetting.Runtime_Fraction;
break;
}
thisSetting.Runtime_Fraction = PartRuntimeFraction; //

@mitchute mitchute Jun 23, 2026

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I guess we don't need to assert(false) here since these are the only four valid options?


if (Conditioning_load_met && Humidification_load_met) {
// store best performing mode
Expand All @@ -1495,24 +1491,33 @@ namespace HybridEvapCoolingModel {

if (Conditioning_load_met) {
DidWeMeetLoad = true;
if (HumidificationRequested && (latentRoomORZone < PreviousMaxiumHumidOrDehumidOutput)) {
if (HumidificationRequested && (latentRoomORZone < PreviousMaximumHumidOrDehumidOutput)) {
store_best_attempt = true;
}
if (DehumidificationRequested && (latentRoomORZone > PreviousMaxiumHumidOrDehumidOutput)) {
if (DehumidificationRequested && (latentRoomORZone > PreviousMaximumHumidOrDehumidOutput)) {
store_best_attempt = true;
}
if (store_best_attempt) {
PreviousMaxiumHumidOrDehumidOutput = latentRoomORZone;
PreviousMaximumHumidOrDehumidOutput = latentRoomORZone;
}
} else {
if (CoolingRequested && (SensibleRoomORZone > PreviousMaxiumConditioningOutput)) {
if (CoolingRequested && (SensibleRoomORZone > PreviousMaximumConditioningOutput)) {
store_best_attempt = true;
}
if (HeatingRequested && (SensibleRoomORZone < PreviousMaxiumConditioningOutput)) {
if (HeatingRequested && (SensibleRoomORZone < PreviousMaximumConditioningOutput)) {
store_best_attempt = true;
}
if (store_best_attempt) {
PreviousMaxiumConditioningOutput = SensibleRoomORZone;
PreviousMaximumConditioningOutput = SensibleRoomORZone;
} else if (VentilationRequested && !DidWePartlyMeetLoad) {
// If no load is requested but ventilation is required, find the setting that uses the least supply fan power.
// Note that settings that meet partial load still take priority, so use logic separate from store_best_attempt.
Real64 RunFractionSupplyFanElectricPower = thisSetting.SupplyFanElectricPower * thisSetting.Runtime_Fraction;
if (RunFractionSupplyFanElectricPower < PreviousMaximumSupplyFanElectricPower) {
PreviousMaximumSupplyFanElectricPower = RunFractionSupplyFanElectricPower;
OptimalSetting = thisSetting;
DidWeMeetVentilation = true;
}
}
Comment on lines +1512 to 1521

@mitchute mitchute Jun 23, 2026

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I guess the reasoning is that if we're only requiring ventilation, we should minimize the fan power, and not necessarily the specified objective function, which could be fuel or water. Is that correct? I think I can agree with that, if true.

@kevin-moos kevin-moos Jun 23, 2026

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Correct, that was the reasoning.

}
if (store_best_attempt) {
Expand Down Expand Up @@ -1542,25 +1547,30 @@ namespace HybridEvapCoolingModel {
ErrorCode = 0;
// save the optimal setting in the
CurrentOperatingSettings[0] = OptimalSetting;
PrimaryMode = OptimalSetting.Mode;
PrimaryModeRuntimeFraction = OptimalSetting.Runtime_Fraction;
oStandBy.Runtime_Fraction = (1 - PrimaryModeRuntimeFraction);
if (oStandBy.Runtime_Fraction < 0) {
oStandBy.Runtime_Fraction = 0;
}
CurrentOperatingSettings[1] = oStandBy;
} else {
// if we partly met the load then do the best we can and run full out in that optimal setting.
if (DidWePartlyMeetLoad) {
// if we partly met the load or met the ventilation then do the best we can
if (DidWePartlyMeetLoad || DidWeMeetVentilation) {
ErrorCode = 0;
count_DidWeNotMeetLoad++;
if (OptimalSetting.ElectricalPower == IMPLAUSIBLE_POWER) {
ShowWarningError(state, "Model was not able to provide cooling for a time step, called in HybridEvapCooling:dostep");
OptimalSetting.ElectricalPower = 0;
}
OptimalSetting.Runtime_Fraction = 1;
CurrentOperatingSettings[0] = OptimalSetting;
PrimaryMode = OptimalSetting.Mode;
PrimaryModeRuntimeFraction = 1;
PrimaryModeRuntimeFraction = OptimalSetting.Runtime_Fraction;
oStandBy.Runtime_Fraction = (1 - PrimaryModeRuntimeFraction);
if (oStandBy.Runtime_Fraction < 0) {
oStandBy.Runtime_Fraction = 0;
}
CurrentOperatingSettings[1] = oStandBy;
}
Comment on lines +1568 to 1574

@mitchute mitchute Jun 23, 2026

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Looks OK to me.

// if we didn't even partially meet the load make sure the operational settings are just the standby mode.
else {
Expand Down
2 changes: 1 addition & 1 deletion tst/EnergyPlus/unit/Resources/UnitaryHybridUnitTest_DOSA.idf
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Expand Up @@ -748,7 +748,7 @@
1, !- Mode 4 Minimum Outdoor Air Fraction
1, !- Mode 4 Maximum Outdoor Air Fraction
0.7039, !- Mode 4 Minimum Supply Air Mass Flow Rate Ratio
0.957, !- Mode 4 Maximum Supply Air Mass Flow Rate Ratio
1, !- Mode 4 Maximum Supply Air Mass Flow Rate Ratio

@mitchute mitchute Jun 23, 2026

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Not sure why the change, but I assume it's fine.

@kevin-moos kevin-moos Jun 23, 2026

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One of the unit tests was failing to find this mode because the ventilation ratio wasn't high enough. This small change seemed to fix it without breaking anything else and I didn't have to rework that section of the unit test.

Mode5_Heat, !- Mode 5 Name
Mode5_TSA_lookup, !- Mode 5 Supply Air Temperature Lookup Table Name
Mode5_wSA_lookup, !- Mode 5 Supply Air Humidity Ratio Lookup Table Name
Expand Down
4 changes: 2 additions & 2 deletions tst/EnergyPlus/unit/UnitaryHybridAirConditioner.unit.cc
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Expand Up @@ -313,8 +313,8 @@ TEST_F(EnergyPlusFixture, Test_UnitaryHybridAirConditioner_Unittest)
EXPECT_EQ(modenumber, 4); // Ventilation Mode
EXPECT_NEAR(Tsa, Tosa, 1.0);
EXPECT_NEAR(Msa, DesignMinVR, 0.001);
EXPECT_GT(Electricpower, 4000 / NormalizationDivisor * MinFlowFraction);
EXPECT_LT(Electricpower, 5000 / NormalizationDivisor);
EXPECT_GT(Electricpower, 3000 / NormalizationDivisor * MinFlowFraction);
EXPECT_LT(Electricpower, 4000 / NormalizationDivisor);

// check fan heat calculation in supply air stream if not included in lookup tables
thisUnitary.FanHeatGain = true;
Expand Down
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