modelThermalCollector
Extends from BuildingSystems.Fluid.Interfaces.PartialTwoPortInterface, BuildingSystems.Fluid.Interfaces.LumpedVolumeDeclarations.
Information
This model is a general solar thermal collector.
Main equations
Calculation of the total incident solar radiation, Itot, is defined as follows.
Itot = Idir *(1-GSC)*IAM+Idif
where Idir and Idif are the total direct and diffuse irradiation on the absorption surface in W/m2 respectively. GSC is the geometrical shading coefficient for the direct irradiation and IAM the incidence angle modifier.
Calculation of incidence angle modifier,
IAM = 1 + (IAMC-1)/0.5557*(1/cos(θ)-1)
where θ is the angle between the normal to the collector surface and the incident irradiation.
IAMC is the incidence angle modifier evaluated at θ=50 deg.
Typical use and important parameters
nEle. The use of the preset value of 10 nodes pro solar thermal collector is recommended.
angleDegAzi and angleDegTil. The parameters are used by external models such as
radiation.
C_0, C_1 and C_2 are referenced to the absoerber area. In case
of flat plate collectors this is the total exposed are of the solar absorber and for evacuated tube collectors, the
diameter of the round absorber, or flat area of the absorber for evacuated tubes with absorber fins inside.
Options
The heat capacity of the solid part of the collector can be lumped into the volume heat capacity via defining a heat capacity per square meter of absorber area.
It is possible to take into account the shadings on the solar panels via the use of the geometrical shading coefficient GSC.
For that purpose it is necessary to set to true the parameter use_GSC_in found in the advanced tab. The GSC
stands for the ratio between shaded and total receiver plane area, its value should be thus between 0 and 1. Notice that the GSC factor is applied
just to the direct irradiation but not to the diffuse portion.
Assumption and limitations
A single incidence angle modifier, IAM, for direct radiation is calculated. Furthermore the model does not distinguish between transverse and logitudional IAM. This assumption is valid for flat solar thermal collectors but innapropiaite for evacuated tub collectors, ETC, and concentrating solar panels,CPC. For those type of collectors the incidence angle modifier should be evaluated for more than one direction (longitudinal and transversal) and at different angles (20 deg, 40 deg, ...).
The efficiency of the collector does not take into account explicitly the wind speed.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nEle | 10 | Number of elements used in the discretization |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Boolean | AColData | true | = true, use A from collector data; false A = height * width |
| Modelica.Units.SI.Volume | V | collectorData.V_A*A | Volume of the fluid |
| Modelica.Units.SI.HeatCapacity | C | collectorData.C_A*A | |
| Real | GSC_constant | 0.0 | Constant shading coefficient (if use_GSC_in = true) |
| Modelica.Units.SI.Area | A | if AColData then collectorData.A else width*height | Absorber area of the collector |
| General › Geometry | |||
| Modelica.Units.SI.Length | width | 1.0 | Width of the collector |
| Modelica.Units.SI.Length | height | 1.0 | Height of the collector |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal | Nominal mass flow rate at nominal conditions | |
| Modelica.Units.SI.Pressure | dp_nominal | Pressure drop at nominal mass flow rate | |
| Advanced | |||
| Boolean | use_GSC_in | false | = true, use input for geometric shading coefficient GSC |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| BuildingSystems.Fluid.MixingVolumes.MixingVolume | vol | Volume for fluid stream | |
| Modelica.Thermal.HeatTransfer.Components.HeatCapacitor[nEle] | cp_solid | Heat capacity of the solid part of the solar collector to be lumped into the fluid volume | |
| BuildingSystems.Interfaces.Angle_degOutput | angleDegTil | Tilt angle of the solar collector | |
| BuildingSystems.Interfaces.Angle_degOutput | angleDegAzi | Azimuth angle of the solar collector: South=0 deg West=90 deg East=-90 deg | |
| BuildingSystems.Interfaces.RadiationPort | radiationPort | ||
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | heatPortCon | Heat port for convective heat transfer | |
| Modelica.Thermal.HeatTransfer.Components.ThermalCollector | thermalCollectorCon | Sum of the convective heat flows | |
| Modelica.Blocks.Routing.Replicator | replicatorQrad | replicate Qrad value | |
| BuildingSystems.Technologies.SolarThermal.Data.Collectors.CollectorPartial | collectorData | Data about the thermal solar collector | |
| BuildingSystems.Fluid.FixedResistances.PressureDrop | res | ||
| Real | IAM | IncidenceAngleModifier | |
| Modelica.Units.SI.RadiantEnergyFluenceRate | IrrTot | Total solar radiation on collector's absorber surfcace | |
| Modelica.Blocks.Sources.RealExpression[nEle] | QCon | Convective heat flow rate | |
| Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow[nEle] | preSumCon | Heat input into volum element due to convective heat transfer | |
| Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow | preConRad | Heat input into volume element from convective and radiative heat | |
| Modelica.Blocks.Sources.RealExpression | QRad | Radiative heat flow rate | |
| Modelica.Blocks.Math.Sum[nEle] | sumConRad | Sum of convective and radiative heat flow rate | |
| Modelica.Blocks.Interfaces.RealInput | GSC_in | ||
| BuildingSystems.Interfaces.Temp_KOutput[nEle] | TSeg | vol.T | Temperature of each collector element |