Buildings.DHC.ETS.Combined.BaseClasses

Package with base classes

Information

This package contains base classes that are used to construct the classes in Buildings.DHC.ETS.Combined.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
PartialHeatPumpHeatExchanger	Partial model of a substation with heat pump and compressor-less cooling
PartialParallel	Partial ETS model with district heat exchanger and parallel connection of production systems

Buildings.DHC.ETS.Combined.BaseClasses.PartialHeatPumpHeatExchanger

Partial model of a substation with heat pump and compressor-less cooling

Buildings.DHC.ETS.Combined.BaseClasses.PartialHeatPumpHeatExchanger

Information

This model represents an energy transfer station based on that described in Sommer (2020), with some additioinal details:

The cooling function is provided in a compressor-less mode by a heat exchanger connected to the district supply line.

The cooling heat exchanger primary pump is modulated based on a PI control loop tracking the chilled water supply temperature at the outlet of the heat exchanger secondary side.
The chilled water is typically produced at high temperature and distributed to radiant cooling systems, for instance at 19°C.

The space heating heating function is provided by a water-to-water heat pump Buildings.DHC.ETS.Combined.Subsystems.HeatPump.

By default, the condenser loop is operated with a variable mass flow rate to maintain a difference between supply and return water of dT_nominal, with a lower limit of mass flow specified by the ratio ratFloMin. The control logic is implemented and described in Buildings.DHC.ETS.Combined.Controls.PrimaryVariableFlow. The model can also represent a constant flow condenser loop by setting have_varFloCon to false.
The evaporator loop is controlled according to the documentation in Buildings.DHC.ETS.Combined.Subsystems.HeatPump. Evaporator water is supplied by mixing flow directly from the district line with flow leaving the district side of the cooling heat exchanger. The hydronic arrangement modeled in Buildings.DHC.ETS.Combined.Subsystems.SwitchBox ensures that the resulting fluid stream in the district line always flows in the same direction.
The space heating hot water is typically produced at low temperature, for instance 40°C.

Space Heating and Cooling Enable/Disable

Heating (resp. cooling) is enabled based on the input signal uHea (resp. uCoo) which is held for 15 minutes, meaning that, when enabled, the mode remains active for at least 15 minutes and, when disabled, the mode cannot be enabled again for at least 15 minutes. The heating and cooling enable signals should be computed externally based on a schedule (to lock out the system during off-hours), ideally in conjunction with the number of requests yielded by the terminal unit controllers, or any other signal representative of the load.

Modeling considerations

There is a control volume at each of the two fluid ports that serve as inlet and outlet of the heating and cooling systems. These approximate the dynamics of the substation, and they also generally avoid nonlinear systems of equations if multiple substations are connected to each other.

References

Sommer T., Sulzer M., Wetter M., Sotnikov A., Mennel S., Stettler C. The reservoir network: A new network topology for district heating and cooling. Energy, Volume 199, 15 May 2020, 117418.

Extends from Buildings.DHC.ETS.BaseClasses.PartialETS (Partial class for modeling an energy transfer station).

Parameters

Type	Name	Default	Description
replaceable package MediumSer		Water	Service side medium
replaceable package MediumSerHea_a		Water	Service side medium at heating inlet
replaceable package MediumBui		Water	Building side medium
Generic	fue[nFue]		Fuel type
Boolean	have_varFloCon	true	Set to true for heat pumps with variable condenser flow
Boolean	have_varFloEva	true	Set to true for heat pumps with variable evaporator flow
Real	ratFloMin	0.3	Minimum condenser mass flow rate (ratio to nominal) [1]
Configuration
DistrictSystemType	typ	Buildings.DHC.Types.District...	Type of district system
Boolean	have_heaWat	true	Set to true if the ETS supplies heating water
Boolean	have_hotWat	false	Set to true if the ETS supplies hot water
Boolean	have_chiWat	true	Set to true if the ETS supplies chilled water
Boolean	have_fan	false	Set to true if fan power is computed
Boolean	have_pum	true	Set to true if pump power is computed
Boolean	have_eleHea	true	Set to true if the ETS has electric heating system
Integer	nFue	0	Number of fuel types (0 means no combustion system)
Boolean	have_eleCoo	false	Set to true if the ETS has electric cooling system
Boolean	have_weaBus	false	Set to true to use a weather bus
Nominal condition
HeatFlowRate	QHeaWat_flow_nominal	0	Nominal capacity of heating system (>=0) [W]
HeatFlowRate	QHotWat_flow_nominal	0	Nominal capacity of hot water production system (>=0) [W]
HeatFlowRate	QChiWat_flow_nominal	0	Nominal capacity of cooling system (<=0) [W]
TemperatureDifference	dT_nominal	5	Water temperature drop/increase accross load and source-side HX (always positive) [K]
Temperature	THeaWatSup_nominal	313.15	Heating water supply temperature [K]
Temperature	THotWatSup_nominal	336.15	Domestic hot water supply temperature to fixtures [K]
Temperature	TColWat_nominal	288.15	Cold water temperature (for hot water production) [K]
Pressure	dp_nominal	50000	Pressure difference at nominal flow rate (for each flow leg) [Pa]
Real	COPHeaWat_nominal		COP of heat pump for heating water production [1]
Real	COPHotWat_nominal		COP of heat pump for hot water production [1]
DHC system
Temperature	TDisWatMin		District water minimum temperature [K]
Temperature	TDisWatMax		District water maximum temperature [K]
Nominal conditions
Temperature	TChiWatSup_nominal	291.15	Chilled water supply temperature [K]
Assumptions
Boolean	allowFlowReversalSer	false	Set to true to allow flow reversal on service side
Boolean	allowFlowReversalBui	false	Set to true to allow flow reversal on building side
Dynamics
Dynamics	mixingVolumeEnergyDynamics	Modelica.Fluid.Types.Dynamic...	Formulation of energy balance for mixing volume at inlet and outlet

Connectors

Type	Name	Description
FluidPorts_a	ports_aHeaWat[nPorts_aHeaWat]	Fluid connectors for heating water return (from building)
FluidPorts_b	ports_bHeaWat[nPorts_bHeaWat]	Fluid connectors for heating water supply (to building)
FluidPorts_a	ports_aChiWat[nPorts_aChiWat]	Fluid connectors for chilled water return (from building)
FluidPorts_b	ports_bChiWat[nPorts_bChiWat]	Fluid connectors for chilled water supply (to building)
FluidPort_a	port_aSerAmb	Fluid connector for ambient water service supply line
FluidPort_b	port_bSerAmb	Fluid connector for ambient water service return line
FluidPort_a	port_aSerHea	Fluid connector for heating service supply line
FluidPort_b	port_bSerHea	Fluid connector for heating service return line
FluidPort_a	port_aSerCoo	Fluid connector for cooling service supply line
FluidPort_b	port_bSerCoo	Fluid connector for cooling service return line
output RealOutput	PHea	Power drawn by heating system [W]
output RealOutput	PCoo	Power drawn by cooling system [W]
output RealOutput	PFan	Power drawn by fan motors [W]
output RealOutput	PPum	Power drawn by pump motors [W]
output RealOutput	QFue_flow[nFue]	Fuel energy input rate [W]
Bus	weaBus	Weather data bus
input BooleanInput	uCoo	Cooling enable signal
input BooleanInput	uHea	Heating enable signal
input BooleanInput	uSHW	SHW production enable signal
input RealInput	THeaWatSupSet	Heating water supply temperature set point [K]
input RealInput	THotWatSupSet	Domestic hot water temperature set point for supply to fixtures [K]
input RealInput	TColWat	Cold water temperature [K]
input RealInput	QReqHotWat_flow	Service hot water load [W]
input RealInput	TChiWatSupSet	Chilled water supply temperature set point [K]
output RealOutput	mHea_flow	District water mass flow rate used for heating service [kg/s]
output RealOutput	mCoo_flow	District water mass flow rate used for cooling service [kg/s]

Modelica definition

model PartialHeatPumpHeatExchanger "Partial model of a substation with heat pump and compressor-less cooling" extends Buildings.DHC.ETS.BaseClasses.PartialETS( final typ=Buildings.DHC.Types.DistrictSystemType.CombinedGeneration5, final have_weaBus=false, final have_chiWat=true, final have_heaWat=true, have_hotWat=false, final have_eleHea=true, final nFue=0, final have_eleCoo=false, final have_pum=true, final have_fan=false, nPorts_aHeaWat=1, nPorts_aChiWat=1); // SYSTEM GENERAL parameter Boolean have_varFloCon = true "Set to true for heat pumps with variable condenser flow"; parameter Boolean have_varFloEva = true "Set to true for heat pumps with variable evaporator flow"; parameter Real ratFloMin( final unit="1", final min=0, final max=1)=0.3 "Minimum condenser mass flow rate (ratio to nominal)"; parameter Modelica.Units.SI.Temperature TDisWatMin "District water minimum temperature"; parameter Modelica.Units.SI.Temperature TDisWatMax "District water maximum temperature"; parameter Modelica.Units.SI.TemperatureDifference dT_nominal(min=0) = 5 "Water temperature drop/increase accross load and source-side HX (always positive)"; parameter Modelica.Units.SI.Temperature TChiWatSup_nominal=291.15 "Chilled water supply temperature"; final parameter Modelica.Units.SI.Temperature TChiWatRet_nominal= TChiWatSup_nominal + dT_nominal "Chilled water return temperature"; parameter Modelica.Units.SI.Temperature THeaWatSup_nominal=313.15 "Heating water supply temperature"; final parameter Modelica.Units.SI.Temperature THeaWatRet_nominal= THeaWatSup_nominal - dT_nominal "Heating water return temperature"; parameter Modelica.Units.SI.Temperature THotWatSup_nominal=336.15 "Domestic hot water supply temperature to fixtures"; parameter Modelica.Units.SI.Temperature TColWat_nominal=288.15 "Cold water temperature (for hot water production)"; parameter Modelica.Units.SI.Pressure dp_nominal(displayUnit="Pa") = 50000 "Pressure difference at nominal flow rate (for each flow leg)"; final parameter Modelica.Units.SI.MassFlowRate mHeaWat_flow_nominal(min=0)= abs(QHeaWat_flow_nominal/cpBui_default/(THeaWatSup_nominal - THeaWatRet_nominal)) "Heating water mass flow rate"; final parameter Modelica.Units.SI.MassFlowRate mChiWat_flow_nominal(min=0)= abs(QChiWat_flow_nominal/cpBui_default/(TChiWatSup_nominal - TChiWatRet_nominal)) "Chilled water mass flow rate"; final parameter Modelica.Units.SI.MassFlowRate mEvaHotWat_flow_nominal(min=0)= QHotWat_flow_nominal*(COPHotWat_nominal - 1)/COPHotWat_nominal/cpSer_default/dT_nominal "Evaporator water mass flow rate of heat pump for hot water production"; final parameter Modelica.Units.SI.MassFlowRate mSerWat_flow_nominal(min=0)= max(proHeaWat.mCon_flow_nominal + mEvaHotWat_flow_nominal, hexChi.m1_flow_nominal) "Service water mass flow rate"; constant Modelica.Units.SI.SpecificHeatCapacity cpBui_default= MediumBui.specificHeatCapacityCp(MediumBui.setState_pTX( p=MediumBui.p_default, T=MediumBui.T_default)) "Specific heat capacity of the fluid"; constant Modelica.Units.SI.SpecificHeatCapacity cpSer_default= MediumBui.specificHeatCapacityCp(MediumSer.setState_pTX( p=MediumSer.p_default, T=MediumSer.T_default)) "Specific heat capacity of the fluid"; // Heat pump for heating water production parameter Real COPHeaWat_nominal(final unit="1") "COP of heat pump for heating water production"; // Heat pump for hot water production parameter Real COPHotWat_nominal(final unit="1") "COP of heat pump for hot water production"; // District HX final parameter Modelica.Units.SI.MassFlowRate m1HexChi_flow_nominal(min=0)= abs(QChiWat_flow_nominal/cpSer_default/dT_nominal) "CHW HX primary mass flow rate"; final parameter Modelica.Units.SI.MassFlowRate m2HexChi_flow_nominal(min=0)= abs(QChiWat_flow_nominal/cpSer_default/(THeaWatSup_nominal - THeaWatRet_nominal)) "CHW HX secondary mass flow rate"; // Dynamics parameter Modelica.Fluid.Types.Dynamics mixingVolumeEnergyDynamics= Modelica.Fluid.Types.Dynamics.FixedInitial "Formulation of energy balance for mixing volume at inlet and outlet"; // IO CONNECTORS Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uCoo "Cooling enable signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHea "Heating enable signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uSHW if have_hotWat "SHW production enable signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput THeaWatSupSet( final unit="K", displayUnit="degC") "Heating water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.RealInput THotWatSupSet( final unit="K", displayUnit="degC") if have_hotWat "Domestic hot water temperature set point for supply to fixtures"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TColWat( final unit="K", displayUnit="degC") if have_hotWat "Cold water temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput QReqHotWat_flow( final unit="W") if have_hotWat "Service hot water load"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TChiWatSupSet(final unit="K", displayUnit="degC") "Chilled water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput mHea_flow(final unit="kg/s") "District water mass flow rate used for heating service"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput mCoo_flow(final unit="kg/s") "District water mass flow rate used for cooling service"; // COMPONENTS Buildings.Fluid.Delays.DelayFirstOrder volMix_a( redeclare final package Medium = MediumSer, final m_flow_nominal=mSerWat_flow_nominal, tau=600, final energyDynamics=mixingVolumeEnergyDynamics) "Mixing volume to break algebraic loops and to emulate the delay of the substation"; Buildings.Fluid.Delays.DelayFirstOrder volMix_b( redeclare final package Medium = MediumSer, final m_flow_nominal=mSerWat_flow_nominal, tau=600, final energyDynamics=mixingVolumeEnergyDynamics) "Mixing volume to break algebraic loops and to emulate the delay of the substation"; Buildings.DHC.ETS.BaseClasses.Pump_m_flow pum1HexChi( redeclare final package Medium = MediumSer, final m_flow_nominal=m1HexChi_flow_nominal, final allowFlowReversal=allowFlowReversalSer, dp_nominal=dp_nominal) "Chilled water HX primary pump"; Buildings.Fluid.HeatExchangers.DryCoilEffectivenessNTU hexChi( redeclare final package Medium1 = MediumSer, redeclare final package Medium2 = MediumBui, final m1_flow_nominal=m1HexChi_flow_nominal, final m2_flow_nominal=m2HexChi_flow_nominal, final dp1_nominal=dp_nominal/2, final dp2_nominal=dp_nominal/2, configuration=Buildings.Fluid.Types.HeatExchangerConfiguration.CounterFlow, final Q_flow_nominal=QChiWat_flow_nominal, final T_a1_nominal=TDisWatMax, final T_a2_nominal=TChiWatRet_nominal, final allowFlowReversal1=allowFlowReversalSer, final allowFlowReversal2=allowFlowReversalBui) "Chilled water HX"; Buildings.Fluid.Delays.DelayFirstOrder volHeaWatRet( redeclare final package Medium = MediumBui, final m_flow_nominal=proHeaWat.mCon_flow_nominal, tau=60, final energyDynamics=mixingVolumeEnergyDynamics, T_start=THeaWatSup_nominal, nPorts=3) "Mixing volume representing building HHW primary"; Buildings.Fluid.Sensors.MassFlowRate senMasFloHeaWat( redeclare final package Medium = MediumBui, final allowFlowReversal=allowFlowReversalBui) "Heating water mass flow rate"; Buildings.Fluid.Delays.DelayFirstOrder volChiWat( redeclare final package Medium = MediumBui, final m_flow_nominal=m1HexChi_flow_nominal, tau=60, final energyDynamics=mixingVolumeEnergyDynamics, T_start=TChiWatSup_nominal, nPorts=3) "Mixing volume representing building CHW primary"; Buildings.Fluid.Sensors.MassFlowRate senMasFloChiWat( redeclare final package Medium = MediumBui, final allowFlowReversal=allowFlowReversalBui) "Chilled water mass flow rate"; Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai2(final k= m1HexChi_flow_nominal); Buildings.DHC.ETS.Combined.Controls.PIDWithEnable conTChiWat( k=0.05, Ti=120, yMax=1, controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI, reverseActing=false, yMin=0) "PI controller for district HX primary side"; Buildings.Controls.OBC.CDL.Reals.MultiSum PPumHeaTot(nin=2) "Total pump power for heating applications"; Buildings.Fluid.Sources.Boundary_pT bouHeaWat( redeclare final package Medium = MediumBui, nPorts=1) "Pressure boundary condition representing the expansion vessel"; Buildings.Fluid.Sources.Boundary_pT bouChiWat( redeclare final package Medium = MediumBui, nPorts=1) "Pressure boundary condition representing the expansion vessel"; Buildings.Controls.OBC.CDL.Reals.MultiSum PPumCooTot(nin=1) "Total pump power for space cooling"; Buildings.Controls.OBC.CDL.Reals.MultiSum PPumTot(nin=2) "Total pump power"; Buildings.Fluid.Sensors.TemperatureTwoPort senTHeaWatSup( redeclare final package Medium=MediumBui, final allowFlowReversal=allowFlowReversalBui, final m_flow_nominal=mHeaWat_flow_nominal) "Heating water supply temperature"; Buildings.Fluid.Sensors.TemperatureTwoPort senTChiWatSup( redeclare final package Medium=MediumBui, final allowFlowReversal=allowFlowReversalBui, final m_flow_nominal=mChiWat_flow_nominal) "Chilled water supply temperature"; Buildings.DHC.ETS.Combined.Subsystems.SwitchBox swiFlo( redeclare final package Medium = MediumSer, final m_flow_nominal=mSerWat_flow_nominal, dpValve_nominal=1e-4) "Flow switch box"; Buildings.DHC.ETS.BaseClasses.Junction bypHeaWatSup( redeclare final package Medium = MediumBui, final m_flow_nominal=proHeaWat.mCon_flow_nominal *{1,-1,-1}) "Bypass heating water (supply)"; Buildings.DHC.ETS.BaseClasses.Junction bypHeaWatRet( redeclare final package Medium = MediumBui, final m_flow_nominal=proHeaWat.mCon_flow_nominal *{1,-1,1}) "Bypass heating water (return)"; Buildings.Controls.OBC.CDL.Logical.TrueFalseHold enaHea( trueHoldDuration=15*60) "Enable heating"; Buildings.DHC.ETS.Combined.Subsystems.HeatPump proHeaWat( redeclare final package Medium1 = MediumBui, redeclare final package Medium2 = MediumSer, dT_nominal=dT_nominal, final have_varFloCon=have_varFloCon, final COP_nominal=COPHeaWat_nominal, final TCon_nominal=THeaWatSup_nominal, final TEva_nominal=TDisWatMin - dT_nominal, final Q1_flow_nominal=QHeaWat_flow_nominal, final allowFlowReversal1=allowFlowReversalBui, final allowFlowReversal2=allowFlowReversalSer, final dp1_nominal=dp_nominal, final dp2_nominal=dp_nominal) "Subsystem for heating water production"; Buildings.Controls.OBC.CDL.Reals.MultiSum masFloHeaTot(nin=2) "Compute district water mass flow rate used for heating service"; Modelica.Blocks.Sources.Constant zer(final k=0) if not have_hotWat "Replacement variable"; Buildings.Fluid.Sensors.TemperatureTwoPort senTHeaWatRet( redeclare final package Medium = MediumBui, final allowFlowReversal=allowFlowReversalBui, final m_flow_nominal=mHeaWat_flow_nominal) "Heating water return temperature"; Buildings.Fluid.Sensors.TemperatureTwoPort senTChiWatRet( redeclare final package Medium = MediumBui, final allowFlowReversal=allowFlowReversalBui, final m_flow_nominal=mChiWat_flow_nominal) "Chilled water return temperature"; Buildings.Fluid.Sensors.MassFlowRate senMasFloHeaWatPri(redeclare final package Medium = MediumBui, final allowFlowReversal=allowFlowReversalBui) "Primary heating water mass flow rate"; Buildings.Controls.OBC.CDL.Logical.TrueFalseHold enaSHW( trueHoldDuration=15*60) if have_hotWat "Enable SHW production"; Modelica.Blocks.Sources.Constant zer1(k=0) if not have_hotWat "Replacement variable"; Buildings.Controls.OBC.CDL.Reals.Add masFloHea "Service water mass flow rate for heating applications"; Buildings.Controls.OBC.CDL.Reals.MultiSum PHeaTot(nin=2) "Total power used for heating and hot water production"; Buildings.Controls.OBC.CDL.Reals.Subtract dTHHW "Heating hot water DeltaT"; Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter capFloHHW( final k=cpBui_default) if have_varFloEva or have_varFloCon "Capacity flow rate"; Buildings.DHC.ETS.Combined.Controls.PrimaryVariableFlow conFloConHHW( final Q_flow_nominal=QHeaWat_flow_nominal, final dT_nominal=dT_nominal, final ratFloMin=ratFloMin, final cp=cpBui_default) if have_varFloCon "Mass flow rate control"; Buildings.Controls.OBC.CDL.Reals.Max priOve if have_varFloCon "Ensure primary overflow"; Buildings.Controls.OBC.CDL.Reals.Multiply loaHHW if have_varFloEva or have_varFloCon "Heating load"; equation connect(TChiWatSupSet, conTChiWat.u_s); connect(pum1HexChi.P, PPumCooTot.u[1]); connect(PPumHeaTot.y, PPumTot.u[1]); connect(PPumCooTot.y, PPumTot.u[2]); connect(pum1HexChi.port_b, hexChi.port_a1); connect(pum1HexChi.m_flow_actual, mCoo_flow); connect(volMix_a.ports[1], swiFlo.port_bSup); connect(swiFlo.port_aRet, volMix_b.ports[1]); connect(volMix_b.ports[2], pum1HexChi.port_a); connect(hexChi.port_b1, volMix_a.ports[2]); connect(pum1HexChi.m_flow_actual, swiFlo.mRev_flow); connect(gai2.y, pum1HexChi.m_flow_in); connect(PPumTot.y, PPum); connect(ports_aHeaWat[1], senMasFloHeaWat.port_a); connect(bypHeaWatSup.port_2, senTHeaWatSup.port_a); connect(senTHeaWatSup.port_b, ports_bHeaWat[1]); connect(bypHeaWatRet.port_2, volHeaWatRet.ports[1]); connect(bouHeaWat.ports[1], volHeaWatRet.ports[2]); connect(ports_aChiWat[1], senMasFloChiWat.port_a); connect(senTChiWatSup.port_b, ports_bChiWat[1]); connect(bypHeaWatRet.port_3, bypHeaWatSup.port_3); connect(volHeaWatRet.ports[3], proHeaWat.port_a1); connect(proHeaWat.port_b2, volMix_b.ports[3]); connect(volMix_a.ports[3], proHeaWat.port_a2); connect(enaHea.y, proHeaWat.uEna); connect(THeaWatSupSet, proHeaWat.TSupSet); connect(proHeaWat.PPum, PPumHeaTot.u[1]); connect(masFloHeaTot.y, mHea_flow); connect(zer.y, masFloHeaTot.u[2]); connect(proHeaWat.mEva_flow, masFloHeaTot.u[1]); connect(zer.y, PPumHeaTot.u[2]); connect(senMasFloHeaWat.port_b, senTHeaWatRet.port_a); connect(senTHeaWatRet.port_b, bypHeaWatRet.port_1); connect(senMasFloChiWat.port_b, senTChiWatRet.port_a); connect(proHeaWat.port_b1, senMasFloHeaWatPri.port_a); connect(senMasFloHeaWatPri.port_b, bypHeaWatSup.port_1); connect(port_aSerAmb, swiFlo.port_aSup); connect(swiFlo.port_bRet, port_bSerAmb); connect(uHea, enaHea.u); connect(conTChiWat.y, gai2.u); connect(uCoo, conTChiWat.uEna); connect(uSHW, enaSHW.u); connect(senTChiWatRet.port_b, volChiWat.ports[1]); connect(volChiWat.ports[2], hexChi.port_a2); connect(hexChi.port_b2, senTChiWatSup.port_a); connect(bouChiWat.ports[1], volChiWat.ports[3]); connect(senTChiWatSup.T, conTChiWat.u_m); connect(zer1.y, masFloHea.u2); connect(proHeaWat.mEva_flow, masFloHea.u1); connect(masFloHea.y, swiFlo.mPos_flow); connect(proHeaWat.PHea, PHeaTot.u[1]); connect(zer.y, PHeaTot.u[2]); connect(PHeaTot.y, PHea); connect(senTHeaWatRet.T, dTHHW.u2); connect(senTHeaWatSup.T, dTHHW.u1); connect(senMasFloHeaWat.m_flow, capFloHHW.u); connect(senMasFloHeaWat.m_flow, priOve.u1); connect(conFloConHHW.m_flow, priOve.u2); connect(priOve.y, proHeaWat.m1_flow); connect(capFloHHW.y, loaHHW.u2); connect(dTHHW.y, loaHHW.u1); connect(loaHHW.y, conFloConHHW.loa); end PartialHeatPumpHeatExchanger;

Buildings.DHC.ETS.Combined.BaseClasses.PartialParallel

Partial ETS model with district heat exchanger and parallel connection of production systems

Buildings.DHC.ETS.Combined.BaseClasses.PartialParallel

Information

This is a base model providing the hydronic configuration for an energy transfer station as described in the schematics below. It is typically used to integrate systems providing both heating water and chilled water, such as heat recovery chillers. Furthermore, it can be connected to an adjustable number (nSouAmb) of systems serving as ambient sources (including the district heat exchanger).

The connection to the district loop is realized with a heat exchanger, according to the operating principles described in Buildings.DHC.ETS.Combined.Subsystems.HeatExchanger.
The connection of the heating water and chilled water production systems to the systems serving as ambient sources is realized in parallel.
A replaceable partial class is used to represent a supervisory controller, which must be replaced by a control block providing at least the control signals listed in Buildings.DHC.ETS.Combined.Controls.BaseClasses.PartialSupervisory.

Models that extend this base class must

specify the number of systems serving as ambient sources nSouAmb, the number of heating water production systems nSysHea, and the number of chilled water production systems nSysCoo (by default nSysCoo=nSysHea which corresponds to a configuration where both productions are ensured by the same system, such as a heat recovery chiller),
modify the parameter binding with the nominal mass flow rate of each connection to each collector/distributor model, namely the parameter mCon_flow_nominal (array) of the components colChiWat, colHeaWat and colAmbWat. The connection index 1 for the components colChiWat and colHeaWat is reserved for the connection with the ambient source circuit. It increases with the distance from the buffer tank. The connection index 1 for the component colAmbWat is reserved for the connection with the district heat exchanger. Note that the order of the connections has no impact on the flow distribution as the connections are in parallel.

Note that the model includes a pressure boundary condition which is shared between the hot water and chilled water circuits, the two circuits being hydronically connected.

Sequence chart

Extends from Buildings.DHC.ETS.BaseClasses.PartialETS (Partial class for modeling an energy transfer station).

Parameters

Type	Name	Default	Description
replaceable package MediumSer		Water	Service side medium
replaceable package MediumSerHea_a		Water	Service side medium at heating inlet
replaceable package MediumBui		Water	Building side medium
Generic	fue[nFue]		Fuel type
ConnectionConfiguration	conCon	Buildings.DHC.ETS.Types.Conn...	District connection configuration
Integer	nSysHea		Number of heating systems
Integer	nSysCoo	nSysHea	Number of cooling systems
Integer	nSouAmb	1	Number of ambient sources
PartialSupervisory	conSup	redeclare Buildings.DHC.ETS....	Supervisory controller
Configuration
DistrictSystemType	typ	Buildings.DHC.Types.District...	Type of district system
Boolean	have_heaWat	true	Set to true if the ETS supplies heating water
Boolean	have_hotWat	false	Set to true if the ETS supplies hot water
Boolean	have_chiWat	true	Set to true if the ETS supplies chilled water
Boolean	have_fan	false	Set to true if fan power is computed
Boolean	have_pum	true	Set to true if pump power is computed
Boolean	have_eleHea	false	Set to true if the ETS has electric heating system
Integer	nFue	0	Number of fuel types (0 means no combustion system)
Boolean	have_eleCoo	false	Set to true if the ETS has electric cooling system
Boolean	have_weaBus	false	Set to true to use a weather bus
Nominal condition
HeatFlowRate	QHeaWat_flow_nominal	0	Nominal capacity of heating system (>=0) [W]
HeatFlowRate	QHotWat_flow_nominal	0	Nominal capacity of hot water production system (>=0) [W]
HeatFlowRate	QChiWat_flow_nominal	0	Nominal capacity of cooling system (<=0) [W]
PressureDifference	dpValIso_nominal	2E3	Nominal pressure drop of ambient circuit isolation valves [Pa]
District heat exchanger
PressureDifference	dp1Hex_nominal		Nominal pressure drop across heat exchanger on district side [Pa]
PressureDifference	dp2Hex_nominal		Nominal pressure drop across heat exchanger on building side [Pa]
HeatFlowRate	QHex_flow_nominal		Nominal heat flow rate through heat exchanger (from district to building) [W]
Temperature	T_a1Hex_nominal		Nominal water inlet temperature on district side [K]
Temperature	T_b1Hex_nominal		Nominal water outlet temperature on district side [K]
Temperature	T_a2Hex_nominal		Nominal water inlet temperature on building side [K]
Temperature	T_b2Hex_nominal		Nominal water outlet temperature on building side [K]
Real	spePum1HexMin	0.1	Heat exchanger primary pump minimum speed (fractional) [1]
Real	spePum2HexMin	0.1	Heat exchanger secondary pump minimum speed (fractional) [1]
Buffer Tank
Volume	VTanHeaWat		Heating water tank volume [m3]
Length	hTanHeaWat	(VTanHeaWat*16/Modelica.Cons...	Heating water tank height (assuming twice the diameter) [m]
Length	dInsTanHeaWat	0.1	Heating water tank insulation thickness [m]
Volume	VTanChiWat		Chilled water tank volume [m3]
Length	hTanChiWat	(VTanChiWat*16/Modelica.Cons...	Chilled water tank height (without insulation) [m]
Length	dInsTanChiWat	0.1	Chilled water tank insulation thickness [m]
Integer	nSegTan	3	Number of volume segments for tanks
Assumptions
Boolean	allowFlowReversalSer	false	Set to true to allow flow reversal on service side
Boolean	allowFlowReversalBui	false	Set to true to allow flow reversal on building side

Connectors

Type	Name	Description
FluidPorts_a	ports_aHeaWat[nPorts_aHeaWat]	Fluid connectors for heating water return (from building)
FluidPorts_b	ports_bHeaWat[nPorts_bHeaWat]	Fluid connectors for heating water supply (to building)
FluidPorts_a	ports_aChiWat[nPorts_aChiWat]	Fluid connectors for chilled water return (from building)
FluidPorts_b	ports_bChiWat[nPorts_bChiWat]	Fluid connectors for chilled water supply (to building)
FluidPort_a	port_aSerAmb	Fluid connector for ambient water service supply line
FluidPort_b	port_bSerAmb	Fluid connector for ambient water service return line
FluidPort_a	port_aSerHea	Fluid connector for heating service supply line
FluidPort_b	port_bSerHea	Fluid connector for heating service return line
FluidPort_a	port_aSerCoo	Fluid connector for cooling service supply line
FluidPort_b	port_bSerCoo	Fluid connector for cooling service return line
output RealOutput	PHea	Power drawn by heating system [W]
output RealOutput	PCoo	Power drawn by cooling system [W]
output RealOutput	PFan	Power drawn by fan motors [W]
output RealOutput	PPum	Power drawn by pump motors [W]
output RealOutput	QFue_flow[nFue]	Fuel energy input rate [W]
Bus	weaBus	Weather data bus
input BooleanInput	uHea	Heating enable signal
input BooleanInput	uCoo	Cooling enable signal
input RealInput	THeaWatSupSet	Heating water supply temperature set point [K]
input RealInput	TChiWatSupSet	Chilled water supply temperature set point [K]

Modelica definition

model PartialParallel "Partial ETS model with district heat exchanger and parallel connection of production systems" extends Buildings.DHC.ETS.BaseClasses.PartialETS( final typ=Buildings.DHC.Types.DistrictSystemType.CombinedGeneration5, final have_heaWat=true, final have_chiWat=true, final have_pum=true, have_hotWat=false, have_eleHea=false, have_weaBus=false); parameter Buildings.DHC.ETS.Types.ConnectionConfiguration conCon= Buildings.DHC.ETS.Types.ConnectionConfiguration.Pump "District connection configuration"; parameter Integer nSysHea "Number of heating systems"; parameter Integer nSysCoo=nSysHea "Number of cooling systems"; parameter Integer nSouAmb=1 "Number of ambient sources"; parameter Modelica.Units.SI.PressureDifference dpValIso_nominal(displayUnit= "Pa") = 2E3 "Nominal pressure drop of ambient circuit isolation valves"; parameter Modelica.Units.SI.PressureDifference dp1Hex_nominal(displayUnit= "Pa") "Nominal pressure drop across heat exchanger on district side"; parameter Modelica.Units.SI.PressureDifference dp2Hex_nominal(displayUnit= "Pa") "Nominal pressure drop across heat exchanger on building side"; parameter Modelica.Units.SI.HeatFlowRate QHex_flow_nominal "Nominal heat flow rate through heat exchanger (from district to building)"; parameter Modelica.Units.SI.Temperature T_a1Hex_nominal "Nominal water inlet temperature on district side"; parameter Modelica.Units.SI.Temperature T_b1Hex_nominal "Nominal water outlet temperature on district side"; parameter Modelica.Units.SI.Temperature T_a2Hex_nominal "Nominal water inlet temperature on building side"; parameter Modelica.Units.SI.Temperature T_b2Hex_nominal "Nominal water outlet temperature on building side"; parameter Real spePum1HexMin( final unit="1", min=0)=0.1 "Heat exchanger primary pump minimum speed (fractional)"; parameter Real spePum2HexMin( final unit="1", min=0.01)=0.1 "Heat exchanger secondary pump minimum speed (fractional)"; parameter Modelica.Units.SI.Volume VTanHeaWat "Heating water tank volume"; parameter Modelica.Units.SI.Length hTanHeaWat=(VTanHeaWat*16/Modelica.Constants.pi) ^(1/3) "Heating water tank height (assuming twice the diameter)"; parameter Modelica.Units.SI.Length dInsTanHeaWat=0.1 "Heating water tank insulation thickness"; parameter Modelica.Units.SI.Volume VTanChiWat "Chilled water tank volume"; parameter Modelica.Units.SI.Length hTanChiWat=(VTanChiWat*16/Modelica.Constants.pi) ^(1/3) "Chilled water tank height (without insulation)"; parameter Modelica.Units.SI.Length dInsTanChiWat=0.1 "Chilled water tank insulation thickness"; parameter Integer nSegTan=3 "Number of volume segments for tanks"; // IO VARIABLES Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHea "Heating enable signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uCoo "Cooling enable signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput THeaWatSupSet( final unit="K", displayUnit="degC") "Heating water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TChiWatSupSet( final unit="K", displayUnit="degC") "Chilled water supply temperature set point"; // COMPONENTS replaceable Buildings.DHC.ETS.Combined.Controls.BaseClasses.PartialSupervisory conSup constrainedby Buildings.DHC.ETS.Combined.Controls.BaseClasses.PartialSupervisory ( final nSouAmb=nSouAmb) "Supervisory controller"; Buildings.Fluid.Actuators.Valves.TwoWayLinear valIsoEva( redeclare final package Medium = MediumBui, final dpValve_nominal=dpValIso_nominal, final m_flow_nominal=colAmbWat.mDis_flow_nominal, use_inputFilter=false) "Evaporator to ambient loop isolation valve"; Buildings.Fluid.Actuators.Valves.TwoWayLinear valIsoCon( redeclare final package Medium = MediumBui, final dpValve_nominal=dpValIso_nominal, final m_flow_nominal=colAmbWat.mDis_flow_nominal, use_inputFilter=false) "Condenser to ambient loop isolation valve"; Buildings.DHC.ETS.Combined.Subsystems.HeatExchanger hex( redeclare final package Medium1=MediumSer, redeclare final package Medium2=MediumBui, final allowFlowReversal1=allowFlowReversalSer, final allowFlowReversal2=allowFlowReversalBui, final conCon=conCon, final dp1Hex_nominal=dp1Hex_nominal, final dp2Hex_nominal=dp2Hex_nominal, final Q_flow_nominal=QHex_flow_nominal, final T_a1_nominal=T_a1Hex_nominal, final T_b1_nominal=T_b1Hex_nominal, final T_a2_nominal=T_a2Hex_nominal, final T_b2_nominal=T_b2Hex_nominal, final spePum1Min=spePum1HexMin, final spePum2Min=spePum2HexMin) "District heat exchanger"; Buildings.DHC.ETS.BaseClasses.StratifiedTank tanChiWat( redeclare final package Medium = MediumBui, final m_flow_nominal=colChiWat.mDis_flow_nominal, final VTan=VTanChiWat, final hTan=hTanChiWat, final dIns=dInsTanChiWat, final nSeg=nSegTan) "Chilled water tank"; Buildings.DHC.ETS.BaseClasses.StratifiedTank tanHeaWat( redeclare final package Medium = MediumBui, final m_flow_nominal=colHeaWat.mDis_flow_nominal, final VTan=VTanHeaWat, final hTan=hTanHeaWat, final dIns=dInsTanHeaWat, final nSeg=nSegTan) "Heating water tank"; Buildings.DHC.ETS.BaseClasses.CollectorDistributor colChiWat( redeclare final package Medium = MediumBui, final nCon=1 + nSysCoo, mCon_flow_nominal={colAmbWat.mDis_flow_nominal}) "Collector/distributor for chilled water"; Buildings.DHC.ETS.BaseClasses.CollectorDistributor colHeaWat( redeclare final package Medium = MediumBui, final nCon=1 + nSysHea, mCon_flow_nominal={colAmbWat.mDis_flow_nominal}) "Collector/distributor for heating water"; Buildings.DHC.ETS.BaseClasses.CollectorDistributor colAmbWat( redeclare final package Medium = MediumBui, final nCon=nSouAmb, mCon_flow_nominal={hex.m2_flow_nominal}) "Collector/distributor for ambient water"; Buildings.Controls.OBC.CDL.Reals.MultiSum totPPum( nin=1) "Total pump power"; Buildings.Controls.OBC.CDL.Reals.MultiSum totPHea( nin=1) "Total power drawn by heating system"; Buildings.Controls.OBC.CDL.Reals.MultiSum totPCoo( nin=1) "Total power drawn by cooling system"; Buildings.Fluid.Sources.Boundary_pT bou(redeclare final package Medium = MediumBui, nPorts=1) "Pressure boundary condition representing expansion vessel (common to HHW and CHW)"; protected parameter Boolean have_val1Hex= conCon == DHC.ETS.Types.ConnectionConfiguration.TwoWayValve "True in case of control valve on district side, false in case of a pump"; equation connect(hex.PPum,totPPum.u[1]); connect(THeaWatSupSet,conSup.THeaWatSupPreSet); connect(tanHeaWat.TTop,conSup.THeaWatTop); connect(tanChiWat.TBot,conSup.TChiWatBot); connect(hex.port_b2,colAmbWat.ports_aCon[1]); connect(hex.port_a2,colAmbWat.ports_bCon[1]); connect(totPPum.y,PPum); connect(hex.yValIso_actual[1],valIsoCon.y_actual); connect(hex.yValIso_actual[2],valIsoEva.y_actual); connect(valIsoEva.port_b,colAmbWat.port_bDisSup); connect(valIsoCon.port_b,colAmbWat.port_aDisSup); connect(TChiWatSupSet,conSup.TChiWatSupPreSet); connect(uCoo,conSup.uCoo); connect(uHea,conSup.uHea); connect(valIsoEva.port_a,colChiWat.ports_aCon[1]); connect(colAmbWat.port_aDisRet,colChiWat.ports_bCon[1]); connect(conSup.yValIsoEva,valIsoEva.y); connect(conSup.yValIsoCon,valIsoCon.y); connect(conSup.yAmb[nSouAmb],hex.u); connect(colChiWat.port_bDisRet,tanChiWat.port_aBot); connect(colChiWat.port_aDisSup,tanChiWat.port_bTop); connect(colHeaWat.port_bDisRet,tanHeaWat.port_aTop); connect(tanHeaWat.port_bBot,colHeaWat.port_aDisSup); connect(valIsoCon.port_a,colHeaWat.ports_aCon[1]); connect(colAmbWat.port_bDisRet,colHeaWat.ports_bCon[1]); connect(totPHea.y,PHea); connect(totPCoo.y,PCoo); connect(bou.ports[1], colChiWat.port_aDisSup); end PartialParallel;