modelChillerBorefield

ETS model for 5GDHC systems with heat recovery chiller and optional borefield

Extends from Buildings.Obsolete.DHC.ETS.Combined.BaseClasses.PartialParallel.

Information

This model represents an energy transfer station as illustrated in the schematics below.

  • The heating and cooling functions are provided by a heat recovery chiller, see Buildings.Obsolete.DHC.ETS.Combined.Subsystems.Chiller for the operating principles and modeling assumptions. The condenser and evaporator loops are equipped with constant speed pumps.
  • The supervisory controller ensures the load balancing between the condenser side and the evaporator side of the chiller by controlling in sequence an optional geothermal borefield (priority system), the district heat exchanger (second priority system), and ultimately the chiller, by resetting down the chilled water supply temperature, see Buildings.Obsolete.DHC.ETS.Combined.Controls.Supervisory for a detailed description. The borefield and district heat exchanger loops are equipped with variable speed pumps modulated by the supervisory controller.

Note that the heating and cooling enable signals (uHea and uCoo) connected to this model should be switched to false when the building has no corresponding demand (e.g., based on the requests yielded by the terminal unit controllers, in conjunction with a schedule). This will significantly improve the system performance as it is a necessary condition for the chiller to be operated at a lower lift, see Buildings.DHC.ETS.Combined.Controls.Reset.

System schematics

Parameters

TypeNameDefaultDescription
Booleanhave_borFiefalseSet to true in case a borefield is used in addition of the district HX
Booleanhave_WSEfalseSet to true in case a waterside economizer is used
Buildings.Fluid.Geothermal.Borefields.Data.Borefield.ExampledatBorFie
Chiller
Modelica.Units.SI.PressureDifferencedpCon_nominalNominal pressure drop accross condenser
Modelica.Units.SI.PressureDifferencedpEva_nominalNominal pressure drop accross evaporator
Buildings.Fluid.Chillers.Data.ElectricEIR.GenericdatChiChiller performance data
Waterside economizer
Modelica.Units.SI.PressureDifferencedp1WSE_nominal40E3Nominal pressure drop across heat exchanger on district side
Modelica.Units.SI.PressureDifferencedp2WSE_nominal40E3Nominal pressure drop across heat exchanger on building side
Modelica.Units.SI.HeatFlowRateQWSE_flow_nominal0Nominal heat flow rate through heat exchanger (<=0)
Modelica.Units.SI.TemperatureT_a1WSE_nominal279.15Nominal water inlet temperature on district side
Modelica.Units.SI.TemperatureT_b1WSE_nominal284.15Nominal water outlet temperature on district side
Modelica.Units.SI.TemperatureT_a2WSE_nominal288.15Nominal water inlet temperature on building side
Modelica.Units.SI.TemperatureT_b2WSE_nominal281.15Nominal water outlet temperature on building side
Realy1WSEMin0.05Minimum pump flow rate or valve opening for temperature measurement (fractional)
Modelica.Units.SI.MassFlowRatem1WSE_flow_nominalabs(QWSE_flow_nominal/4200/(T_b1WSE_nominal - T_a1WSE_nominal))WSE primary mass flow rate
Borefield
Modelica.Units.SI.TemperatureTBorWatEntMax313.15Maximum value of borefield water entering temperature
RealspePumBorMin0.1Borefield pump minimum speed
Modelica.Units.SI.PressuredpBorFie_nominal5E4Pressure losses for the entire borefield (control valve excluded)
Supervisory controller
Buildings.Controls.OBC.CDL.Types.SimpleControllercontrollerTypeBuildings.Controls.OBC.CDL.Types.SimpleController.PIType of controller
RealkHot0.05Gain of controller on hot side
RealkCol0.1Gain of controller on cold side
Modelica.Units.SI.TimeTiHot300Time constant of integrator block on hot side
Modelica.Units.SI.TimeTiCol120Time constant of integrator block on cold side
Modelica.Units.SI.TemperatureTHeaWatSupSetMindatChi.TConEntMin + 5Minimum value of heating water supply temperature set point
Modelica.Units.SI.TemperatureTChiWatSupSetMindatChi.TEvaLvgMinMinimum value of chilled water supply temperature set point
Modelica.Units.SI.TemperatureTChiWatSupSetMaxdatChi.TEvaLvgMaxMinimum value of chilled water supply temperature set point

Components

TypeNameDefaultDescription
Buildings.Obsolete.DHC.ETS.Combined.Subsystems.ChillerchiChiller
Buildings.Obsolete.DHC.ETS.Combined.Subsystems.BorefieldborFieBorefield
Buildings.Controls.OBC.CDL.Reals.Sources.ConstantzerPPumZero power
Buildings.Controls.OBC.CDL.Reals.Sources.ConstantzerPHeaZero power
Buildings.DHC.Networks.BaseClasses.DifferenceEnthalpyFlowRatedHFloHeaWatVariation of enthalpy flow rate
Buildings.Controls.OBC.CDL.Interfaces.RealOutputdHHeaWat_flowHeating water distributed energy flow rate
Buildings.Controls.OBC.CDL.Interfaces.RealOutputdHChiWat_flowChilled water distributed energy flow rate
Buildings.DHC.Networks.BaseClasses.DifferenceEnthalpyFlowRatedHFloChiWatVariation of enthalpy flow rate
Buildings.DHC.ETS.Combined.Subsystems.WatersideEconomizerWSEWaterside economizer
Buildings.DHC.ETS.BaseClasses.JunctionsplWSEFlow splitter for WSE
Buildings.DHC.ETS.BaseClasses.JunctionmixWSEFlow mixer for WSE

Revisions

  • November 3, 2025, by Michael Wetter:
    Moved to Buildings.Obsolete.
    This is for #4354.
  • March 6, 2025, by Hongxiang Fu:
    Added parameters to support chilled water temperature reset.
    This is for #4133.
  • November 22, 2024, by Michael Wetter:
    Reduced number of time events by replacing zero order hold with true and false hold, and increasing the minimum cycle time.
    This is for #4058.
  • March 27, 2024, by David Blum:
    Update icon.
    This is for issue #3606.
  • April 30, 2021, by Michael Wetter:
    Reformulated replaceable class to avoid access of components that are not in the constraining type.
    This is for issue #2471.
  • July 31, 2020, by Antoine Gautier:
    First implementation.