modelDirect

Direct heating ETS model for district energy systems with in-building pumping and deltaT control
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Extends from Buildings.DHC.ETS.BaseClasses.PartialDirect (Partial direct ETS model for district energy systems with in-building pumping and deltaT control).

Information

Direct heating energy transfer station (ETS) model with in-building pumping and deltaT control. The design is based on a typical district heating ETS described in ASHRAE's District Heating Guide. As shown in the figure below, the district and building piping are hydronically coupled. The control valve ensures that the return temperature to the district heating network is at or below the maximum specified value. This configuration naturally results in a fluctuating building supply tempearture.

DC ETS Direct

Reference

American Society of Heating, Refrigeration and Air-Conditioning Engineers. (2013). Chapter 5: Consumer Interconnection. In District Heating Guide.

Parameters

TypeNameDefaultDescription
Buildings.Fluid.Data.Fuels.Generic[nFue]fue (from PartialETS)Fuel type
Configuration
TypDisSystyp (from PartialETS)Buildings.DHC.Types.DistrictSystemType.CombinedGeneration2to4Type of district system
IntegernPorts_aHeaWat (from PartialETS)0Number of heating water return ports
IntegernPorts_bHeaWat (from PartialETS)0Number of heating water supply ports
IntegernPorts_aChiWat (from PartialETS)0Number of chilled water return ports
IntegernPorts_bChiWat (from PartialETS)0Number of chilled water supply ports
Booleanhave_heaWat (from PartialETS)falseSet to true if the ETS supplies heating water
Booleanhave_hotWat (from PartialETS)falseSet to true if the ETS supplies hot water
Booleanhave_chiWat (from PartialETS)falseSet to true if the ETS supplies chilled water
Booleanhave_fan (from PartialETS)falseSet to true if fan power is computed
Booleanhave_pum (from PartialETS)falseSet to true if pump power is computed
Booleanhave_eleHea (from PartialETS)falseSet to true if the ETS has electric heating system
IntegernFue (from PartialETS)0Number of fuel types (0 means no combustion system)
Booleanhave_eleCoo (from PartialETS)falseSet to true if the ETS has electric cooling system
Booleanhave_weaBus (from PartialETS)falseSet to true to use a weather bus
Assumptions
BooleanallowFlowReversalSer (from PartialETS)falseSet to true to allow flow reversal on service side
BooleanallowFlowReversalBui (from PartialETS)falseSet to true to allow flow reversal on building side
Nominal condition
Modelica.Units.SI.HeatFlowRateQHeaWat_flow_nominal (from PartialETS)0Nominal capacity of heating system (>=0)
Modelica.Units.SI.HeatFlowRateQHotWat_flow_nominal (from PartialETS)0Nominal capacity of hot water production system (>=0)
Modelica.Units.SI.HeatFlowRateQChiWat_flow_nominal (from PartialETS)0Nominal capacity of cooling system (<=0)
Modelica.Units.SI.MassFlowRatemBui_flow_nominal (from PartialDirect)Nominal mass flow rate of building side
Modelica.Units.SI.PressureDifferencedpConVal_nominal (from PartialDirect)50Nominal pressure drop in the control valve
Modelica.Units.SI.PressureDifferencedpCheVal_nominal (from PartialDirect)6000Nominal pressure drop in the check valve
PID controller
Modelica.Blocks.Types.SimpleControllercontrollerType (from PartialDirect)Modelica.Blocks.Types.SimpleController.PIType of controller
Realk (from PartialDirect)0.1Gain of controller
Modelica.Units.SI.TimeTi (from PartialDirect)60Time constant of integrator block
Modelica.Units.SI.TimeTd (from PartialDirect)0.1Time constant of derivative block
RealyMax (from PartialDirect)1Upper limit of output
RealyMin (from PartialDirect)0Lower limit of output
Advanced
Modelica.Fluid.Types.DynamicsenergyDynamics (from PartialDirect)Modelica.Fluid.Types.Dynamics.FixedInitialType of energy balance: dynamic (3 initialization options) or steady state
Realbandwidth (from PartialDirect)0.2Bandwidth around reference signal for on/off controller

Connectors

TypeNameDefaultDescription
Modelica.Fluid.Interfaces.FluidPorts_a[nPorts_aHeaWat]ports_aHeaWat (from PartialETS)Fluid connectors for heating water return (from building)
Modelica.Fluid.Interfaces.FluidPorts_b[nPorts_bHeaWat]ports_bHeaWat (from PartialETS)Fluid connectors for heating water supply (to building)
Modelica.Fluid.Interfaces.FluidPorts_a[nPorts_aChiWat]ports_aChiWat (from PartialETS)Fluid connectors for chilled water return (from building)
Modelica.Fluid.Interfaces.FluidPorts_b[nPorts_bChiWat]ports_bChiWat (from PartialETS)Fluid connectors for chilled water supply (to building)
Modelica.Fluid.Interfaces.FluidPort_aport_aSerAmb (from PartialETS)Fluid connector for ambient water service supply line
Modelica.Fluid.Interfaces.FluidPort_bport_bSerAmb (from PartialETS)Fluid connector for ambient water service return line
Modelica.Fluid.Interfaces.FluidPort_aport_aSerHea (from PartialETS)Fluid connector for heating service supply line
Modelica.Fluid.Interfaces.FluidPort_bport_bSerHea (from PartialETS)Fluid connector for heating service return line
Modelica.Fluid.Interfaces.FluidPort_aport_aSerCoo (from PartialETS)Fluid connector for cooling service supply line
Modelica.Fluid.Interfaces.FluidPort_bport_bSerCoo (from PartialETS)Fluid connector for cooling service return line
Buildings.Controls.OBC.CDL.Interfaces.RealOutputPHea (from PartialETS)Power drawn by heating system
Buildings.Controls.OBC.CDL.Interfaces.RealOutputPCoo (from PartialETS)Power drawn by cooling system
Buildings.Controls.OBC.CDL.Interfaces.RealOutputPFan (from PartialETS)Power drawn by fan motors
Buildings.Controls.OBC.CDL.Interfaces.RealOutputPPum (from PartialETS)Power drawn by pump motors
Buildings.Controls.OBC.CDL.Interfaces.RealOutput[nFue]QFue_flow (from PartialETS)Fuel energy input rate
BoundaryConditions.WeatherData.BusweaBus (from PartialETS)Weather data bus
Modelica.Blocks.Interfaces.RealInputTDisRetSet (from PartialDirect)Setpoint for the district return temperature (min for cooling, max for heating)
Modelica.Blocks.Interfaces.RealOutputQ_flow (from PartialDirect)Measured heating demand at the ETS
Modelica.Blocks.Interfaces.RealOutputQ (from PartialDirect)Measured energy consumption at the ETS

Components

TypeNameDefaultDescription
Buildings.Fluid.Sensors.TemperatureTwoPortsenTDisSup (from PartialDirect)District supply temperature sensor
Buildings.Fluid.Sensors.MassFlowRatesenMasFlo (from PartialDirect)District supply mass flow rate sensor
Buildings.Fluid.FixedResistances.Junctionjun (from PartialDirect)Bypass junction
Buildings.Fluid.Sensors.TemperatureTwoPortsenTDisRet (from PartialDirect)District return temperature sensor
Buildings.Fluid.FixedResistances.Junctionspl (from PartialDirect)Bypass junction, splitter
Buildings.Fluid.Actuators.Valves.TwoWayEqualPercentageconVal (from PartialDirect)Control valve
Buildings.Fluid.Sensors.TemperatureTwoPortsenTBuiRet (from PartialDirect)Building return temperature sensor
Fluid.FixedResistances.CheckValvecheVal (from PartialDirect)Check valve (backflow preventer)
Modelica.Blocks.Math.AdddTDis (from PartialDirect)Temperature difference on the district side
Modelica.Blocks.Math.Productpro (from PartialDirect)Product
Modelica.Blocks.Math.Gaincp (from PartialDirect)Specific heat multiplier to calculate heat flow rate
Modelica.Blocks.Continuous.Integratorint (from PartialDirect)Integration
Controls.OBC.CDL.Reals.PIDcon (from PartialDirect)District return temperature controller
Buildings.Fluid.Sensors.TemperatureTwoPortsenTBuiSup (from PartialDirect)Building supply temperature sensor

Revisions

  • March 27, 2024, by David Blum:
    Update icon and fix port orientation to align with convention.
    This is for issue #3606.
  • January 8, 2024, by David Blum:
    Correct documentation to describe heating. This is for issue 3628.
  • April 7, 2023, by David Blum:
    First implementation.