Ddck repository

Pytrnsys enhances system simulations by making use of component modularization. This is done by separating the dck file to single components of an energy system simulation, which are defined by ddck files. In a pytrnsys run, these ddck files will then be merged together in order to build the full system dck. Pytrnsys comes with a default repository of ddck files that is installed alongside the main package.

Repository content

The repository contains the following subfolders:

pytrnsys_ddck
+-- air_source_heat_pump
+-- battery
+-- boiler
+-- brine_source_heat_pump
+-- brine_source_heat_pump_two_hex
+-- building
+-- control
+-- demands
+-- dlls
+-- generic
+-- ground_heat_exchanger
+-- heat_exchanger
+-- building
+-- ice_storage
+-- pv
+-- solar_collector
+-- weather
+-- __init__.py
+-- example.ddck
+-- generalVariables.ddck
+-- NOMENCLATURE.txt

Each subfolder represents one component, that is supported by default in the pytrnsys GUI. A lot of the components - but not all of them - are used in the pytrnsys example systems. Each component subfolder has the following structure. Not all folders and files are present in all components:

pytrnsys_ddck
+-- component subfolder
    +-- typeX subfolder1
        +-- typeX.ddck
        +-- database
    +-- typeY subfolder2
        +-- typeY.ddck
        +-- database
    +-- non type related ddcks
    +-- profiles

Some components can be represented by different TRNSYS types. Usually a more basic one of the standard library and a advanced custom model that allow for detailed parametrization. Each TRNSYS type is represented by its own subfolder in the component folder. In the type subfolder, the main ddck of the type is stored. This ddck contains both the TRNSYS type parameter and input section, the type output section, as well as some equations for parameter and input scaling or output processing. The parametrization of the model is outsourced in the database folder where a specific version - for example parameters of a specific collector curve - can be specified.

Ddck file structure

The file sctructure of the ddck files is shown in the example.ddck file in the pytrnsys_ddck repository root. Each ddck should contain the following parts. Some parts can be empty if not used.

Inputs from hydraulics solver

The pytrnsys ddcks are designed to be used in combination with the hydraulic solver type 935. In each timestep the hydraulic solver computes all mass flows and component input temperatures starting depending on the component output temperatures, the pump powers and the valve positions. Therefore, the mass flows and component input temperatures are outputs of the hydraulic solver that have to be connected to the component ddcks as inputs:

***********************************
** inputs from hydraulic solver
***********************************

** tIn from hydraulic
** mIn from hydraulic

Outputs to the hydraulic solver

Similar to the inputs, the output temperatures of the component should be stated here, such that they are easily accessible to be connected to the hydraulics file:

***********************************
** outputs to hydraulic solver
***********************************

** which outputs will be used to connect the hydraulic solver
** typically tOutType will be defined here to be used in the hydraulic ddck

Outputs to the energy balance

In the processing, pytrnsys automatically computes the systems heat and electricity energy balance. All variables that should be collected for the energy balance have to be specified in this section according to the right nomenclature:

******************************************************************************************
** outputs to energy balance in kWh and ABSOLUTE value
** Following this naming standard : qSysIn_name, qSysOut_name, elSysIn_name, elSysOut_name
******************************************************************************************

** Add here those variables that will go into the overall energy balance of the system
** These values will be used to automatically generate the energy balance

Dependencies with other ddck files

In order to enhance modularization, dependencies with other ddcks should be kept minimal. Dependencies that cannot be avoided and are neither part of the component-database relation or the general variables should be declarated and reassigned to an internally used variable in this part:

***********************************
** Dependencies with other ddck
***********************************

** Re-assing here the variables necessary from other types
** variableInternal = variableExternal
** Exception: those from general variables

Outputs to other ddck files

Variables that are designated to be used in other ddck files should be added here:

***********************************
** outputs to other ddck
***********************************

** Add here the outputs of the TYPE or TYPES that will be used in other types
** Exception: those for printers and so on dont need to be here.

Type section

TRNSYS has its own syntax that calls the type dll files. This core part of the ddck goes here:

***********************************
** Begin TYPE
***********************************

Component printers

Each component should have a monthly as well as an hourly printer. This helps to simplify the setup and the processing of the simulation. In addition, an online plotter is a nice tool for the debugging of the system:

***********************************
** Monthly printer
***********************************

***********************************
** Hourly printer
***********************************

***********************************
** Online plotter
***********************************

Hydraulics files

The hydraulics file represents the systems hydraulics layout. Each pytrnsys example system except the pv battery system has its own hydraulic layout file. In order to create your own hydraulic files that represent the hydraulics of your choice you need access to the pytrnsys GUI. The hydraulics file are not part of the ddck repository. The hydraulic files of the example systems are located in the example system folder of pytrnsys_examples.

Examples

The following example shows the ddck file of the solar collector type 1 used in the solar domestic hot water system:

*******************************
**BEGIN Type1.ddck
*******************************

*****************************************
** Contact person : Dani Carbonell
** Creation date  : 10.01.2010
** Last changes   : 03.2020 Jeremias Schmidli
*****************************************

***************************************************************************
** Description:
** Collector model using efficiency curve efficiency
***************************************************************************

***********************************
** inputs from hydraulic solver
***********************************

EQUATIONS 2
TCollIn = TPiColIn
MfrColl = ABS(MfrPiColIn)

***********************************
** outputs to hydraulic solver
***********************************

EQUATIONS 1
TCollOut = [28,1]

***********************************
** outputs to other ddck
***********************************

******************************************************************************************
** outputs to energy balance in kWh and ABSOLUTE value
** Following this naming standard : qSysIn_name, qSysOut_name, elSysIn_name, elSysOut_name
******************************************************************************************

EQUATIONS 1
qSysIn_Collector = PColl_kW

***********************************
** Dependencies with other ddck
***********************************

EQUATIONS 1
pumpColOn = puColOn

CONSTANTS 2
C_tilt = slopeSurfUser_1  ! @dependencyDdck Collector tilt angle / slope [°]
C_azim = aziSurfUSer_1    ! @dependencyDdck Collector azimuth  (0:s, 90:w, 270: e) [°]

EQUATIONS 4
**surface-8
IT_Coll_kJhm2 = IT_surfUser_1  ! Incident total radiation on collector plane, kJ/hm2
IB_Coll_kJhm2 = IB_surfUser_1  ! incident beam radiation on collector plane, kJ/hm2
ID_Coll_kJhm2 = ID_surfUser_1  ! diffuse and ground reflected irradiance on collector tilt
AI_Coll = AI_surfUser_1  ! incident angle on collector plane, °

EQUATIONS 5
IT_Coll_kW = IT_Coll_kJhm2/3600     ! Incident total radiation on collector plane, kW/m2
IB_Coll_kW = IB_Coll_kJhm2/3600     ! incident beam radiation on collector plane, kW/m2
ID_Coll_kW = ID_Coll_kJhm2/3600     ! diffuse and ground reflected irradiance on collector tilt (kW/m2)
IT_Coll_Wm2 = IT_surfUser_1/3.6
IT_Coll_kWm2 = IT_surfUser_1/3600

***********************************
** Begin CONSTANTS
***********************************

CONSTANTS 3
MfrCPriSpec = 15  ! Coll. Prim. loop spec. mass flow [kg/hm2]
AcollAp=5         ! Collector area
MfrCPriNom = MfrCPriSpec*AcollAp !

***********************************
** Begin TYPE
***********************************

UNIT 28 TYPE 1
PARAMETERS 11
nSeries       ! number in series
AcollAp       ! collector area
cpBri          ! fluid specific heat kj(kgK
efficiencyMode ! efficiency mode
testedMfr      ! tested flow rate kg/(hm2)
Eta0          ! intercept efficiency
a1            ! efficiency slope kJ/hm^2K
a2            ! efficiency curvature kJ/hm^2K^2
2             ! optical mode
FirstOrderIAM  ! 1st order IAM
SecondOrderIAM ! 2nd order IAM
INPUTS 9
TCollIn
MfrColl
Tamb
IT_Coll_kJhm2
IT_H
ID_Coll_kJhm2
0,0
AI_Coll !Flo check ! JS: This was defined wrong before (C_azim, even though it is incident angle input). Now it should be correct.
C_tilt !Flo check  ! JS: This should be correct
*** INITIAL INPUT VALUES
20 0 10 0 0 0 GroundReflectance 45 0

EQUATIONS 4
**MfrCout = [700,2]
Pcoll = [28,3] !kJ/h
PColl_kW = Pcoll/3600
PColl_kWm2 = PColl_kW/(AcollAp+1e-30)
PColl_Wm2  = PColl_kWm2*1000


***********************************
** Monthly printer
***********************************

CONSTANTS 1
unitPrintSol = 31

ASSIGN temp\SOLAR_MO.Prt unitPrintSol

UNIT 32 TYPE 46
PARAMETERS 6
unitPrintSol ! 1: Logical unit number, -
-1           ! 2: Logical unit for monthly summaries, -
1            ! 3: Relative or absolute start time. 0: print at time intervals relative to the simulation start time. 1: print at absolute time intervals. No effect for monthly integrations
-1           ! 4: Printing & integrating interval, h. -1 for monthly integration
1            ! 5: Number of inputs to avoid integration, -
1            ! 6: Output number to avoid integration
INPUTS 4
Time  Pcoll_kW  PColl_kWm2  IT_Coll_kWm2
**
Time  Pcoll_kW  PColl_kWm2  IT_Coll_kWm2

***********************************
** Hourly printer
***********************************

CONSTANTS 1
unitHourlyCol = 33

ASSIGN    temp\SOLAR_HR.Prt    unitHourlyCol

UNIT 34 TYPE 46     ! Printegrator Monthly Values for System
PARAMETERS 7
unitHourlyCol ! 1: Logical unit number, -
-1            ! 2: Logical unit for monthly summaries, -
1             ! 3: Relative or absolute start time. 0: print at time intervals relative to the simulation start time. 1: print at absolute time intervals. No effect for monthly integrations
1             ! 4: Printing & integrating interval, h. -1 for monthly integration
2             ! 5: Number of inputs to avoid integration, -
4             ! 6: Output number to avoid integration
5             ! 7: Output number to avoid integration
INPUTS 6
Pcoll_kW  PColl_kWm2  IT_Coll_kWm2 TCollOut TCollIn MfrColl
**
Pcoll_kW  PColl_kWm2  IT_Coll_kWm2 TCollOut TCollIn MfrColl

A specific parametrization can be added by using a ddck from the database for example the type1_CONSTANTS_cOBRAak2_8v.ddck:

******************************
**BEGIN Type1_Constants_CobraAK2_8V.ddck
*******************************

*****************************************
** Solar Thermal Data for covered collector.
** Very well performing collector Cobra AK 2.8V
** Version : v0.0
** Last Changes: Jeremias Schmidli
** Date: 10.03.2020
******************************************

CONSTANTS 11

Eta0= 0.857     ! Eta0 (a0) of collector (zero heat loss efficiency)
a1 = 4.16*3.6    ! linear heat loss coefficient of collector [kJ/hm^2K] ![W/m2K]*3.6
a2 = 0.0089*3.6   ! quadratic heat loss coefficient of collector [kJ/hm^2K^2] ![W/m2K2]*3.6

AbsorberArea = 2.435 !m2
TotArea = 2.768 !m2

nSeries = 1
efficiencyMode = 1
testedMfr = 200/AbsorberArea !l/hm2

GroundReflectance = 0.2

FirstOrderIAM = 0.108
SecondOrderIAM = 0
*******************************
**END Type1_Constants_Test.ddck
*******************************