modelPartialSolarCollector

Partial model for solar collectors

Extends from Buildings.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes), Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters (Parameters for flow resistance for models with two ports), Buildings.Fluid.Interfaces.PartialTwoPortInterface (Partial model with two ports and declaration of quantities that are used by many models).

Information

This component is a partial model of a solar thermal collector. It can be expanded to create solar collector models based on either ASHRAE93 or EN12975 ratings data.

References

EnergyPlus 23.2.0 Engineering Reference

Parameters

Type	Name	Default	Description
Boolean	homotopyInitialization	true	= true, use homotopy method
Integer	nSeg	3	Number of segments used to discretize the collector model
Modelica.Units.SI.Angle	azi		Surface azimuth (0 for south-facing; -90 degree for east-facing; +90 degree for west facing
Modelica.Units.SI.Angle	til		Surface tilt (0 for horizontally mounted collector)
Real	rho		Ground reflectance
Modelica.Units.SI.HeatCapacity	CTot	if per.CTyp == Buildings.Fluid.SolarCollectors.Types.HeatCapacity.TotalCapacity then per.C elseif per.CTyp == Buildings.Fluid.SolarCollectors.Types.HeatCapacity.DryCapacity then per.C + rho_defaultper.Vcp_default else 385per.mDry + rho_defaultper.V*cp_default	Heat capacity of solar collector with fluid
Buildings.Fluid.SolarCollectors.Data.GenericASHRAE93	per
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from LumpedVolumeDeclarations)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	substanceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of independent mass fraction balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	traceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of trace substance balance: dynamic (3 initialization options) or steady state
Advanced › Dynamics
Modelica.Fluid.Types.Dynamics	massDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state, must be steady state if energyDynamics is steady state
Initialization
Medium.AbsolutePressure	p_start (from LumpedVolumeDeclarations)	Medium.p_default	Start value of pressure
Medium.Temperature	T_start (from LumpedVolumeDeclarations)	Medium.T_default	Start value of temperature
Medium.MassFraction[Medium.nX]	X_start (from LumpedVolumeDeclarations)	Medium.X_default	Start value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]	C_start (from LumpedVolumeDeclarations)	fill(0, Medium.nC)	Start value of trace substances
Medium.ExtraProperty[Medium.nC]	C_nominal (from LumpedVolumeDeclarations)	fill(1E-2, Medium.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Dynamics
Real	mSenFac (from LumpedVolumeDeclarations)	1	Factor for scaling the sensible thermal mass of the volume
Flow resistance
Boolean	computeFlowResistance (from TwoPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp (from TwoPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n (from TwoPortFlowResistanceParameters)	2	Flow exponent, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance (from TwoPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM (from TwoPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Nominal condition
Modelica.Units.SI.PressureDifference	dp_nominal (from TwoPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.MassFlowRate	m_flow_nominal (from PartialTwoPortInterface)		Nominal mass flow rate
Assumptions
Boolean	allowFlowReversal (from PartialTwoPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
Modelica.Units.SI.MassFlowRate	m_flow_small (from PartialTwoPortInterface)	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Boolean	show_T (from PartialTwoPortInterface)	false	= true, if actual temperature at port is computed
Shading
Boolean	use_shaCoe_in	false	Enables an input connector for shaCoe
Real	shaCoe	0	Shading coefficient. 0.0: no shading, 1.0: full shading
Area declarations
Buildings.Fluid.SolarCollectors.Types.NumberSelection	nColType	Buildings.Fluid.SolarCollectors.Types.NumberSelection.Number	Selection of area specification format
Integer	nPanels	0	Desired number of panels in the simulation
Modelica.Units.SI.Area	totalArea	0	Total area of panels in the simulation
Configuration declarations
Buildings.Fluid.SolarCollectors.Types.SystemConfiguration	sysConfig	Buildings.Fluid.SolarCollectors.Types.SystemConfiguration.Series	Selection of system configuration
Integer	nPanelsPar	0	Number of array panels in parallel

Connectors

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_a (from PartialTwoPort)	Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_b (from PartialTwoPort)	Fluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Blocks.Interfaces.RealInput	shaCoe_in	Shading coefficient
Buildings.BoundaryConditions.WeatherData.Bus	weaBus	Weather data bus

Components

Type	Name	Default	Description
Modelica.Units.SI.MassFlowRate	m_flow (from PartialTwoPortInterface)	port_a.m_flow	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp (from PartialTwoPortInterface)	port_a.p - port_b.p	Pressure difference between port_a and port_b
Medium.ThermodynamicState	sta_a (from PartialTwoPortInterface)	if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow)))	Medium properties in port_a
Medium.ThermodynamicState	sta_b (from PartialTwoPortInterface)	if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow))	Medium properties in port_b
Buildings.BoundaryConditions.SolarIrradiation.DiffusePerez	HDifTilIso		Diffuse solar irradiation on a tilted surface
Buildings.BoundaryConditions.SolarIrradiation.DirectTiltedSurface	HDirTil		Direct solar irradiation on a tilted surface
Buildings.Fluid.Sensors.MassFlowRate	senMasFlo		Mass flow rate sensor
Buildings.Fluid.FixedResistances.PressureDrop	res		Flow resistance
Buildings.Fluid.MixingVolumes.MixingVolume[nSeg]	vol		Volume of fluid in one segment of the solar collector
Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor[nSeg]	temSen		Temperature sensor
Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow[nSeg]	QGai		Rate of solar heat gain
Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow[nSeg]	QLos		Rate of heat loss

Revisions

June 17, 2026, by Michael Wetter:
Updated implementation to allow a flow coefficient n that is different from 2. This allows use of the model for not fully turbulent flow.
This is for Buildings, #4620.
February 4, 2025, by Jelger Jansen:
Use nPanels_internal when calculating nPanelsPar_internal and nPanelsSer_internal. Only request nPanelsPar as an input for an array of collectors and add assert to check if the total collector area is an exact multitude of a single collector's area. This is for IBPSA, #1956.
February 27, 2024, by Jelger Jansen:
Refactor model.
This is for Buildings, #3604.
December 11, 2023, by Michael Wetter:
Corrected implementation of pressure drop calculation for the situation where the collectors are in parallel, e.g., if sysConfig == Buildings.Fluid.SolarCollectors.Types.SystemConfiguration.Parallel.
Changed assignment of computeFlowResistance to final based on dp_nominal.
This is for Buildings, #3597.
September 16, 2021, by Michael Wetter:
Changed lat from being a parameter to an input from weather bus.
This is for IBPSA, #1477.
April 14, 2020, by Michael Wetter:
Changed homotopyInitialization to a constant.
This is for IBPSA, #1341.
November 12, 2019, by Filip Jorissen:
Set prescribedHeatFlowRate=false to avoid a division by zero at zero flow when using SteadyState dynamics.
This is for Buildings, issue 1636.
April 27, 2018, by Michael Wetter:
Corrected displayUnit.
This is for Buildings, issue 912.
January 22, 2016, by Michael Wetter:
Corrected type declaration of pressure difference. This is for #404.
February 8, 2015, by Filip Jorissen:
Propagated multiple parameters from LumpedVolumeDeclarations, set prescribedHeatFlowRate = true in vol.
September 18, 2014, by Michael Wetter:
Removed the separate instance of Modelica.Thermal.HeatTransfer.Components.HeatCapacitor and added this capacity to the volume. This is in response to https://github.com/lbl-srg/modelica-buildings/issues/276.
June 25, 2014, by Michael Wetter:
Improved comments for tilt to address https://github.com/lbl-srg/modelica-buildings/issues/246.
October 8, 2013, by Michael Wetter:
Removed parameter show_V_flow in declaration of instance res.
January 4, 2013, by Peter Grant:
First implementation.