**3. Building simulation modelling in TRNSYS**

*Recent Advances in Numerical Simulations*

energy consumption of buildings.

*Schematic diagram of the BIPV-DSF.*

**Figure 1.**

energy consumption of buildings.

summer, while the openings are closed to reduce heat loss in winter, hence delivers a comfortable indoor thermal condition [2]. Moreover, the energy production (electric power generated by PV panel and thermal energy from the heated air in the cavity) can be obtained from the BIPV-DSF, which contributes to the reduction of the

Numerical simulation modelling of buildings and building systems has been developing and carrying out for over 30 years, during which time the accuracy, depth and speed of the simulation have been widely verified and significantly improved for the design and analysis of new buildings [3]. It has been proved that numerical simulation modelling is much more cost-effective and less time consuming than experimental study, especially for those inaccessibly experimental conditions in real life [4]. In this context, the proposed chapter presents a comprehensive method of numerical simulation modelling of the novel BIPV-DSF system in buildings. The proposed numerical BIPV-DSF model can be used to investigate the advantages of double-skin façades and building-integrated photovoltaic technology in terms of thermal and electrical performances of the entire BIPV-DSF integrated onto buildings, which are related to indoor thermal condition and

**2. Overview of the proposed numerical simulation modelling**

TRNSYS and TRNFlow programmes are selected for carrying out the proposed

numerical modelling, which are able to predict the effects of the implementation of the BIPV-DSF on building performance such as energy consumption and indoor thermal condition, based on the capabilities of the software. TRNSYS is a graphically based software, which has been validated and widely used in the BIPV and building related research activities [5–8]. In addition, TRNSYS output data files are in a (human) readable and editable plain text format, which allows users to convert dataset simulation results to Excel spreadsheet; hence, they precisely present the result plots and effectively observe the errors of simulations. Energy consumption of thermal building models and electricity productions of the BIPV

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TRNSYS was initially developed by the University of Wisconsin and the latest programme and external plugins of the software are the outcomes of international collaboration of the US, France and Germany [10]. TRNSYS and its plugins can be used for functions, such as electric power simulation, solar design, building thermal performance analysis, HVAC system sizing as well as airflow analysis [10]. TRNSYS provides a modular structure for simulating the transient systems, especially energy systems, such as solar systems (PV systems) and HVAC systems [11]. The simulation activities in this chapter are demonstrated by using the version of TRNSYS 17. The main programmes of TRNSYS 17 [11] include:


In general, TRNSYS Simulation Studio in association with TRNBuild are used to assess energy performance of the proposed BIPV-DSF building model. In addition, as mentioned earlier, an external plugin, namely TRNFlow (as shown in **Figure 4**), is chosen for the integration with the TRNSYS thermal building model, in order to assess the performance of ventilation (for example, natural ventilation) within the DSF.

In the Simulation Studio interface (as shown in **Figure 5**), Type 56-TRNFlow (the green "Building" icon) contains the specific numerical information of the multi-zone building model, which is not only including building geometry, load profiles, construction and window glazing properties, but also including the airflow input and output values for the purpose of the simulation of ventilation.

The functionalities of those programmes of TRNSYS are implemented by using the common computer programming languages for instance "Fortran", which establishes mathematical models for the components and types (in TRNSYS) of the proposed systems in terms of their ordinary differential or algebraic Equations [12]. The general procedures of the simulation modelling in TRNSYS are as follows, in sequence:

**Figure 2.** *Simulation studio user interface in TRNSYS 17.*

**Figure 3.** *TRNBuild user interface in TRNSYS 17.*

First, the user needs to identify if the available system component and the type of models of the proposed system in TRNSYS will satisfy the specific needs of the real system [11].

The simulation modelling can proceed in TRNSYS if the proposed real system can be designed by the available components and types; otherwise, the missing components and types must be created by writing the corresponding programming language such as Fortran and C++. The "type" normally consists of inputs (variables such as input temperature or airflow rate), parameters (the fixed values such as the area of solar PV panel, dimension of buildings, and so on) and outputs (the resultant values such as output temperature or airflow rate). Moreover, the "type" in TRNSYS can also include external files (for example, weather file) and derivatives which specify the initial values (for example, initial room air temperature in a building) for the "type" [11]. For the proposed BIPV-DSF building model, all the

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*Numerical Simulation Modelling of Building-Integrated Photovoltaic Double-Skin Facades*

required system components and types are available in TRNSYS 17, so the additional

All the non-geometry information of the TRNSYS building model are then created and edited in TRNBuild (see **Figure 3**). The user can flexibly edit the material properties of building envelope, create ventilation and infiltration profiles, add internal gain and position occupants for the indoor comfort calculations [13].

As mentioned earlier, TRNFlow is used for the calculation of ventilation for the proposed BIPV-DSF building model. TRNFlow will work as a plug-in of TRNSYS, which can be accessed through the user interface in TRNBuild (see **Figure 7**). Basically, an airflow network of the ventilated building model needs to be created in terms of the selected airlinks (for example, the DSF and outdoor air) in TRNFlow. In detail, the model of airflow between the selected airlinks must be

Once the components and types that represent the proposed real system are fully prepared, the system modelling can proceed in the visual interface – TRNSYS Simulation Studio. All the selected system components and types need to be connected to each other in the Simulation Studio, then the simulation parameters are defined accordingly by the user [11]. For the proposed simulation modelling (the BIPV-DSF), the building geometry information are created in TRNSYS 3D (**Figure 6**). TRNSYS 3D is a plugin for SketchUp (a 3D modelling software developed by Google) to draw 3D multi-zone buildings and export the building geometry information directly from the SketchUp interface into the

*DOI: http://dx.doi.org/10.5772/intechopen.97171*

programming procedures are left out.

*Type56-TRNFlow in TRNSYS model.*

**Figure 4.**

**Figure 5.**

*TRNFlow user interface.*

visual interface of TRNBuild [13].

*Numerical Simulation Modelling of Building-Integrated Photovoltaic Double-Skin Facades DOI: http://dx.doi.org/10.5772/intechopen.97171*

**Figure 4.** *TRNFlow user interface.*

*Recent Advances in Numerical Simulations*

*Simulation studio user interface in TRNSYS 17.*

First, the user needs to identify if the available system component and the type of models of the proposed system in TRNSYS will satisfy the specific needs of the

The simulation modelling can proceed in TRNSYS if the proposed real system can be designed by the available components and types; otherwise, the missing components and types must be created by writing the corresponding programming language such as Fortran and C++. The "type" normally consists of inputs (variables such as input temperature or airflow rate), parameters (the fixed values such as the area of solar PV panel, dimension of buildings, and so on) and outputs (the resultant values such as output temperature or airflow rate). Moreover, the "type" in TRNSYS can also include external files (for example, weather file) and derivatives which specify the initial values (for example, initial room air temperature in a building) for the "type" [11]. For the proposed BIPV-DSF building model, all the

**64**

real system [11].

*TRNBuild user interface in TRNSYS 17.*

**Figure 3.**

**Figure 2.**

**Figure 5.** *Type56-TRNFlow in TRNSYS model.*

required system components and types are available in TRNSYS 17, so the additional programming procedures are left out.

Once the components and types that represent the proposed real system are fully prepared, the system modelling can proceed in the visual interface – TRNSYS Simulation Studio. All the selected system components and types need to be connected to each other in the Simulation Studio, then the simulation parameters are defined accordingly by the user [11]. For the proposed simulation modelling (the BIPV-DSF), the building geometry information are created in TRNSYS 3D (**Figure 6**). TRNSYS 3D is a plugin for SketchUp (a 3D modelling software developed by Google) to draw 3D multi-zone buildings and export the building geometry information directly from the SketchUp interface into the visual interface of TRNBuild [13].

All the non-geometry information of the TRNSYS building model are then created and edited in TRNBuild (see **Figure 3**). The user can flexibly edit the material properties of building envelope, create ventilation and infiltration profiles, add internal gain and position occupants for the indoor comfort calculations [13].

As mentioned earlier, TRNFlow is used for the calculation of ventilation for the proposed BIPV-DSF building model. TRNFlow will work as a plug-in of TRNSYS, which can be accessed through the user interface in TRNBuild (see **Figure 7**). Basically, an airflow network of the ventilated building model needs to be created in terms of the selected airlinks (for example, the DSF and outdoor air) in TRNFlow. In detail, the model of airflow between the selected airlinks must be

#### **Figure 6.**


#### **Figure 7.** *TRNFlow interface in TRNBuild.*

modified accordingly. For the modelling of the BIPV-DSF, both the external air and DSF are linked together, in which the ventilation openings (for example, ventilation louvres) are modelled as large opening through the Link Type Manager (see **Figure 8**). There are 6-category of "links" in the selected version of TRNFlow (version 1.4) as follows:

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**Figure 9.**

*The printer that loads the external files.*

*Numerical Simulation Modelling of Building-Integrated Photovoltaic Double-Skin Facades*

According to the TRNFlow user manual [14], "large opening" is the most fit type

The simulation can then be performed when all the inputs, parameters, and outputs are completely edited. The TRNSYS Simulation Studio will report errors if the connections among different components and types are not correct or logically functionable. It will also report errors if any non-geometry information is not correctly created and edited in TRNBuild. The simulation results will be printed in external files through a printer component (see **Figure 9**) or visualised in an online plotter (implemented by TRNEXE, as shown in **Figure 10**, reporting the value of solar radiation as an example) in the Simulation Studio interface [11]. In the proposed simulations of the BIPV-DSF, the online plotter (**Figure 11**) is used to view the output variables during and after the simulations for ensuring the simulations run properly, while a .OUT formatted file (**Figure 12**) as an external text file is used to print the numerical simulation results. The various numerical results can be directly copied from the .OUT file and pasted in an Excel sheet, which are then plotted as viewable graphs accordingly to simplify the analysis of the results.

*DOI: http://dx.doi.org/10.5772/intechopen.97171*

of link for modelling the ventilation openings.

*The link type manager of "large opening" in TRNFlow.*

**Figure 8.**


*Numerical Simulation Modelling of Building-Integrated Photovoltaic Double-Skin Facades DOI: http://dx.doi.org/10.5772/intechopen.97171*


#### **Figure 8.**

*Recent Advances in Numerical Simulations*

*TRNSYS 3D user interface – A 3D BIPV-DSF model sample.*

modified accordingly. For the modelling of the BIPV-DSF, both the external air and DSF are linked together, in which the ventilation openings (for example, ventilation louvres) are modelled as large opening through the Link Type Manager (see **Figure 8**). There are 6-category of "links" in the selected version of TRNFlow

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(version 1.4) as follows:

*TRNFlow interface in TRNBuild.*

c.Straight duct

d.Flow controller

e.Large opening

f. Test data

a.Crack

**Figure 7.**

**Figure 6.**

b.Fan

*The link type manager of "large opening" in TRNFlow.*

According to the TRNFlow user manual [14], "large opening" is the most fit type of link for modelling the ventilation openings.

The simulation can then be performed when all the inputs, parameters, and outputs are completely edited. The TRNSYS Simulation Studio will report errors if the connections among different components and types are not correct or logically functionable. It will also report errors if any non-geometry information is not correctly created and edited in TRNBuild. The simulation results will be printed in external files through a printer component (see **Figure 9**) or visualised in an online plotter (implemented by TRNEXE, as shown in **Figure 10**, reporting the value of solar radiation as an example) in the Simulation Studio interface [11]. In the proposed simulations of the BIPV-DSF, the online plotter (**Figure 11**) is used to view the output variables during and after the simulations for ensuring the simulations run properly, while a .OUT formatted file (**Figure 12**) as an external text file is used to print the numerical simulation results. The various numerical results can be directly copied from the .OUT file and pasted in an Excel sheet, which are then plotted as viewable graphs accordingly to simplify the analysis of the results.

**Figure 9.** *The printer that loads the external files.*

#### **Figure 10.**

*The online plotter is implemented by TRNEXE.*

**Figure 11.** *The online plotter as part of the simulation model.*
