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Solar Collector Class Source Code

This is the source code for CollectorCls and CollectorECurveCls classes.

This is just to take a look at before you download -- if you want to download it, then download all the solar classes here:  Solar Tools Source

CollectorECurve Class:

This class models a solar collector based on its efficiency curve.  The efficiency of the collector and collector output are estimated as a function of inlet and ambient temperature, and solar radiation input.

'Solar Analysis Tools -
 'Copyright (C) 2005 Gary Reysa (gary@BuildItSolar.com)

 ' This program is free software; you can redistribute it and/or modify it
 ' under the terms of the GNU General Public License as published by the Free
 ' Software Foundation; either version 2 of the License, or (at your option)
 ' any later version.

 ' This program is distributed in the hope that it will be useful and encourage
 ' further development of solar tools, but   WITHOUT ANY WARRANTY; without even 
 ' the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 ' See the GNU General Public License   for more details.

' CollectorEcurveCls
' This class models a solar collector in which the efficiency 
' curve for the collector is known.
' It inherits from CollectorCls
' Adds Inputs:
'   YIntercept -- the Y intercept on the collector efficiency curve (ie max efic)
'   Slope      -- the slope of the collector curve in (BTU/hr-ft^2-F) (input as a negative number)
'   Ti      -- collector fluid inlet temperature (F)
'   Ta      -- ambient temperature (F)
' Adds Outputs:
'   ColEfic  -- collector efficiency (ratio of collector output/solar input
'   Qout     -- collector output in BTU/hr (defined as ColEfic * SolarInput)
'
' 11/08/05 
' Appears to be working OK -- gives general agreement with SRCC data -- should do more detailed checking.

Imports System.Math
Imports System.IO

Public Class CollectorEcurveCls
Inherits CollectorCls

Private mTi As Double ' collector inlet temp (F)
Private mTa As Double ' ambient temp (F)
Private mYIntercept As Double  ' Y intercept on efic curve (no units)
Private mSlope As Double  ' Slope of collector efficiency curve (BTU/hr-ft^2-F)

Private mEfic As Double ' collector efficiency
Private mQout As Double    ' power output of collector (BTU/hr)

' New input properties:
' Collector inlet temperature (F)
Public Property Ti() As Double
Get
    Return mTi
End Get
Set(ByVal Value As Double)
    mTi = Value
    ReCalcECurve()
End Set
End Property

' Ambient temperature (F)
Public Property Ta() As Double
Get
    Return mTa
End Get
Set(ByVal Value As Double)
    mTa = Value
    ReCalcECurve()
End Set
End Property

' Slope of the collector efficiency curve (BTU/hr-ft^2-F) -- this will normally be a negative number
Public Property Slope() As Double
Get
    Return mSlope
End Get
Set(ByVal Value As Double)
    mSlope = Value
    ReCalcECurve()
End Set
End Property

' Y (efficiency) intercept of the collector efficiency curve (no units)
' This is the efficiency of the collector when the parameter (Ti-Ta)/Isun = 0
Public Property YIntercept() As Double
Get
    Return mYIntercept
End Get
Set(ByVal Value As Double)
    mYIntercept = Value
    ReCalcECurve()
End Set
End Property

'New Output Properties:
' Efficiency of the collector
ReadOnly Property Efic() As Double
Get
    Return mEfic
End Get
End Property

' Output of the collector in (BTU/hr)
ReadOnly Property QOut() As Double
Get
    Return mQout
End Get
End Property

Sub New()
    ' how do I run parent constructor? -- seems to get run automatically
    mSlope = -1.0
    mYIntercept = 0.8
    mTi = 120.0
    mTa = 30.0
End Sub

Private Sub ReCalcECurve()
    ' call parent ReCalc
    ReCalc()
    ' now calc new parms
    Dim parm As Double
    If Icoltot < 0.1 Then
        parm = 100
    Else
         parm = (mTi - mTa) / mIcoltot
    End If

    mEfic = mYIntercept + parm * mSlope
    If mEfic < 0 Then mEfic = 0
    mQout = mEfic * mIcoltot * mArea

End Sub

Public Sub DumpEC()
    Dump()
    Console.WriteLine("  Eficiency              {0,6:F3}", mEfic)
    Console.WriteLine("  Qout                   {0,8:F0}", mQout)
    Console.WriteLine(" Yinter, Slope           {0,6:F3} {1,7:F3}", mYIntercept, mSlope)

End Sub

End Class

Collector Class:

This is the base class for the CollectorECurve Class listed above, and any future collector classes to model different types of collectors.

'Solar Analysis Tools -
 'Copyright (C) 2005 Gary Reysa (gary@BuildItSolar.com)

 ' This program is free software; you can redistribute it and/or modify it
 ' under the terms of the GNU General Public License as published by the Free
 ' Software Foundation; either version 2 of the License, or (at your option)
 ' any later version.

 ' This program is distributed in the hope that it will be useful and encourage
 ' further development of solar tools, but   WITHOUT ANY WARRANTY; without even 
 ' the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 ' See the GNU General Public License   for more details.

' Collector Class -- instances of this class represent a solar collector
' This is the base class for all other collector classes.

' When provided with Collector Area, Collector Orientation, Direction to Sun, 
' and incident solar radiation, objects of this class will provide the 
' incidence angle, and the direct, diffuse and total radiation on collector.
' Programs using this class must calculate collector gain and loss using 
' thier own logic.

' The collector updates itself every time any input is changed, so its
' always up-to-date with its inputs.  This causes some needless calculation,
' but the speed seems quite acceptable.  

' Inputs to define a CollectorCls object are:

'       Area        Net area of collector (ft^2)
'       Tilt        Tilt from horizontal Rad)
'       Azimuth     Direction collector is pointed -- measured from South, and + to east (Rad)
'       SunVec      Vector to sun -- used for performance calcs
'       Idn         Solar direct normal radiation (perpendicular to SunVec) (BTU/hr-ft^2)
'       Idif        Solar diffuse radiation   (BTU/hr-ft^2)

' Ouputs from objects of this class are:
'Outputs:
'       ColNor          A vector normal to the collector surface
'       IncidAngle      The angle of incidence for solar rays on collector (rad)
'       Icoldir         Direct solar radiation on collector surface (BTU/hr-ft^2)
'       Icoldif         Diffuse solar radiaition on collector surface (BTU/hr-ft^2)
'       Icoltot         Total solar radiation energy on collector = sum of Icoldir and Icoldif (BTU/hr-ft^2)
'
' Basic scheme to use Collector Class is:
'   1) Provide inputs that define collector geometry and performance 
'           (Area, orientation)
'   2) Provide solar Idn and Idif and solar direction 
'
'   Any change in inputs will trigger a recalc of the collector outputs.
'   So, in a simulation, 
'       You initialize collector with geom 
'       Then set a start time
'           Look up sun parms for current time and send to collector
'               (use TMY or SunTool for this)
'           Retrieve collector outputs and store/sum/plot
'           Increment time
'       Repeat from start

Imports System.Math
Imports System.IO

Public Class CollectorCls
Const DegPerRad As Single = 57.3

'Inputs:
'col - geometry/orientation
Protected mArea As Double             ' Area of collector (ft^2)
Protected mTilt As Double             ' Tilt angle of collector from horz (rad)
Protected mAzimuth As Double          ' Azimuth angle of collector (rad) -- South = 0, + to East, - to West

'sun
Protected mSunVec As New VectorCls    ' A unit vector pointing toward sun
Protected mIdn As Double              ' Direct component of radiation from sun (BTU/hr-ft^2)
Protected mIhorzdif As Double         ' Indirect component of radiation from sun (BTU/hr-ft^2)

'Outputs:
Protected mColNor As New VectorCls    ' A unit vector normal to the collector surface
Protected mIncidAngle As Double       ' The incidence angle that a ray from sun makes to collector surface (rad)
Protected mIcoltot As Double          ' radiation energy on collector = sum of mIcoldir and mIcoldif (BTU/hr-ft^2)
Protected mIcoldir As Double          ' direct radiation on collector surface (BTU/hr -ft^2)
Protected mIcoldif As Double          ' diffuse rediaition on collector surface (BTU/hr-ft^2)

'Inputs:
' Collect Area (sqft)
Public Property Area() As Double
Get
    Return mArea
End Get
Set(ByVal Value As Double)
    mArea = Value
    ReCalc()
End Set
End Property

'Tilt -- collector tilt -- horz to plane of collector (rad)
Public Property Tilt() As Double
Get
    Return mTilt
End Get
Set(ByVal Value As Double)
    mTilt = Value
    ReCalc()
End Set
End Property

'Azimuth -- collector Azimuth -- South is zero, + is toward East (rad)
Public Property Azimuth() As Double
Get
    Return mAzimuth
End Get
Set(ByVal Value As Double)
    mAzimuth = Value
    ReCalc()
End Set
End Property

'Sun Vector -- a unit vector from the sun 
Public Property SunVector() As VectorCls
Get
    Return mSunVec
End Get
Set(ByVal Value As VectorCls)
    mSunVec = Value
    ReCalc()
End Set
End Property

'Idn -- direct normal solar radiation (on surface Perp to sun direction)
Public Property Idn() As Double
Get
    Return mIdn
End Get
Set(ByVal Value As Double)
    mIdn = Value
    ReCalc()
End Set
End Property

'Ihorzdif -- diffuse solar radiation on horz surface
Public Property Idif() As Double
Get
    Return mIhorzdif
End Get
Set(ByVal Value As Double)
    mIhorzdif = Value
    ReCalc()
End Set
End Property

'Icoldir -- direct radiation on collector (= cos(IncidAng)*Idn)
ReadOnly Property Icoldir() As Double
Get
    Return mIcoldir
End Get
End Property

'Icoldif -- diffuse ratdiation on collector --  is a fractin of Ihorzdiffuse
ReadOnly Property Icoldif() As Double
Get
    Return mIcoldif
End Get
End Property

'Icoltot -- Radiation input into collector BTU/hr
ReadOnly Property Icoltot() As Double
Get
    Return mIcoltot
End Get
End Property

ReadOnly Property IncidAngle() As Double
Get
    Return mIncidAngle
End Get
End Property

''----------- Methods -------

' Constructor
' By default, construct a 1 ft^2, vertical collector facing south.
Sub New()
 mArea = 1.0
 mTilt = 90.0 / DegPerRad
 mAzimuth = 0.0

'sun
 mSunVec.X = 0.707
 mSunVec.Y = 0.0
 mSunVec.Z = 0.707
 mIdn = 400
 mIhorzdif = 20
 End Sub

Protected Sub ReCalc()
    ' calc solar output per the following method:

    ' update collector vector -- based on tilt and azimuth
    mColNor = VectorCls.AzElevVector(mAzimuth, 90 / DegPerRad - mTilt)

    ' update solar input to collector 
    Dim ColDotSun As Double
    ColDotSun = mColNor.Dot(mSunVec)
    mIncidAngle = Acos(ColDotSun)
    If ColDotSun < 0 Then     ' if sun vector is on back side of panel, made dot prod zero and incid 90
        ColDotSun = 0
        mIncidAngle = 90 / DegPerRad
    End If

    ' Update radiation on collector values
    mIcoldir = mIdn * ColDotSun
    mIcoldif = mIhorzdif * ((1 + Cos(mTilt)) / 2)
    mIcoltot = mIdn * ColDotSun + mIcoldif
End Sub ' Recalc

Public Sub Dump()
    Console.WriteLine()
    Console.WriteLine("Sun:")
    Console.WriteLine("  ToSunVector            {0,6:F3}  {1,6:F3} {2,6:F3} ", mSunVec.X, mSunVec.Y, mSunVec.Z)
    Console.WriteLine("  Sun: Idn, Ihorzdif     {0,8:F1}  {1,8:F1} ", Idn, Idif)

    Console.WriteLine("Collector:")
    Console.WriteLine("  Area                   {0,8:F1} ", Area)
    Console.WriteLine("  Azimuth, Tilt:         {0,6:F2} {1,6:F2} ", Azimuth * DegPerRad, Tilt * DegPerRad)
    Console.WriteLine("  Incid Angle            {0,8:F1}", IncidAngle * DegPerRad)
    Console.WriteLine("  Icoltot, Icoldir, Icoldif  {0,8:F1} {1,8:F1} {2,8:F1}", mIcoltot, mIcoldir, mIcoldif)         ' solar radiation on collector glazing
End Sub

End Class