modelSolarThermal

Model of a solar thermal panel

Extends from AixLib.Fluid.BoilerCHP.BaseClasses.PartialHeatGenerator.

Information

Overview

Model of a solar thermal collector. Inputs are outdoor air temperature and solar irradiation. Based on these values and the collector properties from database, this model creates a heat flow to the fluid circuit.

Concept

The model maps solar collector efficiency based on the equation

eta = eta_o - c_1 * deltaT / G - c_2 * deltaT^2/ G

Known Limitations

  • Connected directly with Sources.TempAndRad, this model only represents a horizontal collector. There is no calculation for radiation on tilted surfaces.
  • With the standard BaseParameters, this model uses water as working fluid

Example Results

AixLib.HVAC.HeatGeneration.Examples.SolarThermalCollector

Parameters

Furbo1996 (Optimum solar collector fluid flow rates) suggests a default volume flow rate of approx. 0.2 l/(min.m2) to 0.4 l/(min.m2). Taken from a panel manufacturer's manual (SunMaxx Technical Manual.pdf) the standard volume flow rate seems to be around 1.5 l/(min.m2). This is 3 l/min for collectors of size 0.93 m2 up to 2.79 m2.

"Volume flow rate suggestions according to Furbo1996 and SunMaxx" cellspacing="0" cellpadding="2" border="1" width="50%">

unit

SunMaxx

Furbo1996

l/(min.m2)

1.5

0.3

m3/(h.m2)

0.091

0.018

m3/(s.m2)

2.5e-5

5.0e-6

gpm/m2

0.40

0.079


Assuming a default size for a unit of 2 m2 we get pressure losses for a module as in the following table (vfr=0.79 gpm):

"Pressure drop of two flat collector modules" cellspacing="0" cellpadding="2" border="1" width="50%">

Collector

pressure drop in psi

pressure drop in Pa

Titan Power Plus SU2

0.28

1900

SunMaxx-VHP 30 (40 % Glycol)

0.43

3000


The pressureloss factor should therefore be around 2500 Pa / (2*2.5e-5 m3/s)^2 = 1e12.

  • Febraury 7, 2018  by Peter Matthes:
    Rename "gain" block into "convertRelHeatFlow2absHeatFlow" to make clearer what it does.
    Remove redundant connect(solarThermalEfficiency.Q_flow, convertRelHeatFlow2absHeatFlow.u)
    Change default pressure drop coefficient from 1e6 to 2500 Pa / (2*2.5e-5 m3/s)^2 = 1e12 Pa.s2/m6.
    Change default collector area to 2 m2.
    Extend documentation with some default parameters from references.
    Grid-align the RealInputs.
  • Febraury 1, 2018  by Philipp Mehrfeld:
    Delete max block as it is now implemented in the efficiency model
  • October 25, 2017 by Philipp Mehrfeld:
    Extend now from AixLib.Fluid.BoilerCHP.BaseClasses.PartialHeatGenerator.
    Use mean temperature.
    Limiter moved in equation section of efficiency model.
  • December 15, 2016 by Moritz Lauster:
    Moved
  • November 2014  by Marcus Fuchs:
    Changed model to use Annex 60 base class
  • November 19, 2013  by Marcus Fuchs:
    Implemented

Parameters

TypeNameDefaultDescription
RealpressureDropCoeff2500/(A*2.5e-5)^2Pressure drop coefficient, delta_p[Pa] = PD * Q_flow[m^3/s]^2
Construction measures
Modelica.Units.SI.AreaA2Area of solar thermal collector
Modelica.Units.SI.VolumevolPipWater volume of piping
Efficienc
AixLib.DataBase.SolarThermal.SolarThermalBaseDataDefinitionCollectorAixLib.DataBase.SolarThermal.SimpleAbsorber()Properties of Solar Thermal Collector

Components

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealInputT_airOutdoor air temperature in K
Modelica.Blocks.Interfaces.RealInputIrradiationSolar irradiation on a horizontal plane in W/m2
AixLib.Fluid.Solar.Thermal.BaseClasses.SolarThermalEfficiencysolarThermalEfficiency
Modelica.Blocks.Math.GainconvertRelHeatFlow2absHeatFlow
Modelica.Blocks.Math.AddcalcTempMean