**3. Methodology**

is restricted by some limitations that require compliance during early building layout design, where the sun spacing factor is applied in parallel with layer settings for the building. Shadow graphs created for software applications offer a new detailed representation of shadow constraints. Overall, the solar analysis model using BIM has advantage of being importable to related software, generating shadow animations for target periods and simulation results that

Solar energy is the portion of the sun's energy available at the earth's surface for useful applications, such as exciting electrons in a photovoltaic cell and indoor illumination. Solar energy system is currently the most widely installed renewable energy system in the building sector in an effort to reduce the energy consumption of buildings [16]. Developing the calculation model for solar energy in buildings is helpful to describe the mathematical relations between the solar energy and building attributes such as orientation, location, height, area, etc. An important aspect in calculating solar energy is the accuracy of the developed model, which is evaluated using initial data input [17]. The large volume of residential building construction in recent years and the deficit of conventional energy sources justify any initiatives conducive to the construction of self-sustainable residential buildings that are capable of producing their

The design of alternative energy devices is a predictable way to develop a wide range of new technologies for a more sustainable future. To achieve energy sustainability, the installation of building-integrated solar panels is a viable option. Solar panels are a type of semiconductor device that converts the energy from sunlight into electric energy. Solar panels do not use chemical reactions to produce electric power, and they have no moving parts. Rooftop and vertical surfaces on buildings are convenient installation position to supply solar energy to meet growing energy demands. Depending on material, solar panels can be classified into different kinds: silicon solar cell, compound solar cells, polymer solar cell, nanocrystal solar cell, organic solar cell, and plastic solar cell. Many of factors play part in determining the practicality of a given solar installation and the selection of solar panels. One major factor is the available sunlight. Considering the sun is what combines with the photovoltaic panels to produce the energy, an area rich in sunlight is highly desirable [19]. Glasnovic and Margeta [19] performed an analysis of photovoltaic pumps versus diesel pumps and concluded that photovoltaic pumps were more efficient than diesel pump. Photovoltaic solar cells are thin silicon disks that convert sunlight into electricity. These disks act as energy sources for a wide variety of uses, such as rooftop panels on buildings. The past decade has seen a remarkable evolution in mainstream silicon solar cell technology, documented by greatly increased pro-

By using solar panels, electricity costs from outside sources are negated by the electricity produced by the building's surface installations. Additionally, emissions that are the environmental cost of burning coal to produce electricity are significantly reduced. Although solar energy is renewable, more efficient than fossil fuel and environmentally friendly, it is costly. According to Borenstein [20], the high cost of power from solar panels has been a major deterrent to the

can be saved on BIM database for property management and quality control.

own energy for illumination, HVAC, electrical appliances, etc. [18].

duction volumes and greatly reduced costs.

**2.2. Solar energy and buildings**

110 Emerging Solar Energy Materials

### **3.1. Analysis method**

The importance of developing an integrated approach for potential solar energy analysis of buildings using BIM technology has been established above. Integration of quantitative results for energy consumption by building objects and 3D visualization of spatial modeling requires a well-managed framework that combines sunlight simulation and the calculation of solar energy. Such a framework should be designed to transmit data in the basic steps used for developing an effective building sunshine model. Our research aims to estimate the solar energy consumption and cost analysis of photovoltaic solar energy systems that could be installed on the rooftops and vertical walls of buildings with the use of BIM for building performance simulation and sunlight analysis. In order to estimate total harvestable solar energy and to analyze cost of photovoltaic systems, the following four-level research framework was executed (see **Figure 1**):

Level 0: CAD drawing. The building object selected in this study was described according to construction drawings made on AutoCAD Architecture. Original 2D image information is provided in regard to points, lines, surfaces, text, etc.

Level 1: 3D modeling. In the course of preparing 3D building models, the virtual data are exported from the CAD system to a suitable CAD exchange format (e.g., DWG), then processed to re-build the plan in a 3D environment with the aid of BIM software system (e.g., Revit). The BIM 3D model is used to generate traditional building abstractions: plans, sections, details, and elevations. 3D models produced using BIM also possess interactive viewing properties.

Level 2: Sunlight simulation. Building environment analysis (like energy analysis and sunhour analysis) is normally carried out as part of BIM based design. In this step, the representative rooftop and surface area of the sample building are selected. Sunlight simulation is made by input of the Industrial Foundation Classes (IFC) model into the sunlight analysis program, followed by additional related analysis on occlusion relationship, sunshine duration sheet, isohel map, shadow outlines, etc.

Level 3: Solar energy analysis. The main objective of Level 3 is to assess the geometric characteristics under sunlight models in solar energy analysis. This step obtains dimensions of the useful rooftop and vertical surfaces, where photovoltaic solar panels could be installed, from which the solar energy generation potential and the energy costs are calculated for the sample building.

study, the technology for systematic sustainable design modeling that enabled sunlight simulation and analysis is driven by a Revit platform, which is able to design all of the required processes and components from a 2D building digital drawing to a 3D model. This platform uses an attribute driven modeling engine to simulate overall building design and create the network of building element relationships (inferred by the software and/or set by the user). The relationship network is the basis by which to achieve information exchange and to later

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In this study, Autodesk Revit is applied to simulate the sample building in 3D with 2D drafting elements and export building data from the model database, as a BIM solution to plan and track various stages in the building's lifecycle from the concept to construction for architectural, structural and MEP design. The modeling process refers to generation of completed 3D models and related building information database. In general, the modeling process begins by analyzing initial data in 2D CAD environment followed by creation of Revit-parametric families, and then establishment of the Revit 3D model based on which the IFC file is trans-

Initial data acquisition is a process of selecting, extracting, and transforming information from the source systems. In BIM modeling, initial data are normally prepared using AutoCAD drawing, which stores layers, floors, rooms, and footprints of the buildings in 2D environment on dwg and dxf formats. The boundaries of building elements need to be determined carefully in the AutoCAD process. The optimized AutoCAD drawing will be imported into

A key understanding is that both standard and custom-building elements can be added in Revit model by using a predefined family that is composed of elements with common parameters, allowing users to make design changes easily and to manage projects more

Family classification and building component attribute setting are key phrases of the modeling stage. In Revit, basic building components/elements like walls, windows, doors, and so on are created using the responding category including families and family types. The building component or model element which is defined in terms of family contains a broad array of information in addition to dimensional aspects. At this stage, the initial parameters are set to define family attributes. The initial settings will affect the project environment and include types for levels, grids, drawing sheets, and viewports. The project model can be established using the generic families in Revit. After identifying the position of the building components inserted on an axis, the defined family types can be load one by one from top down, and the

generate sunlight analysis results.

**3.3. Building modeling process**

formed and exported.

*3.3.1. Initial data analysis*

*3.3.2. Revit model establishment*

efficiently.

Revit in terms of creating a geometric model.

attributes of the model elements can be modified separately.

**Figure 1.** Overview of four-level research framework for solar energy analysis.

#### **3.2. Simulation models and settings**

The study case in this paper refers to the Civil Building located on the Jiulonghu Campus of Southeast University in Nanjing, China. The Civil Building is designed to be a 16-storey, technology-rich learning environment, hosting over 1000 classroom seats in-state-of-the-laboratory classrooms, with conference rooms and professors' offices. The building will be home to undergraduate and graduate students in Department of Civil Engineering and all staffs in that department. Surrounded by the newly-built Traffic Building, Laboratory Building (Building B) and Lecture Hall (Building A3), the sample building is sheltered from the sun in this sunlight simulation and analysis. The sample building's structure information is listed in **Table 1**.

In order to achieve the objective stated above, a schema converter is proposed in this paper to facilitate the information exchange between BIM tools and sunlight modeling tools. In this


**Table 1.** Information of civil building, traffic building, building A3 and B.

study, the technology for systematic sustainable design modeling that enabled sunlight simulation and analysis is driven by a Revit platform, which is able to design all of the required processes and components from a 2D building digital drawing to a 3D model. This platform uses an attribute driven modeling engine to simulate overall building design and create the network of building element relationships (inferred by the software and/or set by the user). The relationship network is the basis by which to achieve information exchange and to later generate sunlight analysis results.

### **3.3. Building modeling process**

In this study, Autodesk Revit is applied to simulate the sample building in 3D with 2D drafting elements and export building data from the model database, as a BIM solution to plan and track various stages in the building's lifecycle from the concept to construction for architectural, structural and MEP design. The modeling process refers to generation of completed 3D models and related building information database. In general, the modeling process begins by analyzing initial data in 2D CAD environment followed by creation of Revit-parametric families, and then establishment of the Revit 3D model based on which the IFC file is transformed and exported.

### *3.3.1. Initial data analysis*

**3.2. Simulation models and settings**

112 Emerging Solar Energy Materials

**Name Status Height** 

**(M)**

**Figure 1.** Overview of four-level research framework for solar energy analysis.

**Table 1.** Information of civil building, traffic building, building A3 and B.

Civil Building Proposed 61.89 16559.05 South by east4° Teaching

Traffic Building Built 54.67 20419.2 South by east 4° Academic Building B Built 25.6 13210.18 South by east 4° Teaching

Building A3 Built 18.44 3747.08 South by east4° Lecture and conference

The study case in this paper refers to the Civil Building located on the Jiulonghu Campus of Southeast University in Nanjing, China. The Civil Building is designed to be a 16-storey, technology-rich learning environment, hosting over 1000 classroom seats in-state-of-the-laboratory classrooms, with conference rooms and professors' offices. The building will be home to undergraduate and graduate students in Department of Civil Engineering and all staffs in that department. Surrounded by the newly-built Traffic Building, Laboratory Building (Building B) and Lecture Hall (Building A3), the sample building is sheltered from the sun in this sunlight simulation and analysis. The sample building's structure information is listed in **Table 1**.

In order to achieve the objective stated above, a schema converter is proposed in this paper to facilitate the information exchange between BIM tools and sunlight modeling tools. In this

**Floor areas (M2) Orientations Use**

Initial data acquisition is a process of selecting, extracting, and transforming information from the source systems. In BIM modeling, initial data are normally prepared using AutoCAD drawing, which stores layers, floors, rooms, and footprints of the buildings in 2D environment on dwg and dxf formats. The boundaries of building elements need to be determined carefully in the AutoCAD process. The optimized AutoCAD drawing will be imported into Revit in terms of creating a geometric model.

#### *3.3.2. Revit model establishment*

A key understanding is that both standard and custom-building elements can be added in Revit model by using a predefined family that is composed of elements with common parameters, allowing users to make design changes easily and to manage projects more efficiently.

Family classification and building component attribute setting are key phrases of the modeling stage. In Revit, basic building components/elements like walls, windows, doors, and so on are created using the responding category including families and family types. The building component or model element which is defined in terms of family contains a broad array of information in addition to dimensional aspects. At this stage, the initial parameters are set to define family attributes. The initial settings will affect the project environment and include types for levels, grids, drawing sheets, and viewports. The project model can be established using the generic families in Revit. After identifying the position of the building components inserted on an axis, the defined family types can be load one by one from top down, and the attributes of the model elements can be modified separately.

#### *3.3.3. IFC transformation*

Using the Revit model requires transformed of data into the IFC format for compatibility with THSWARE software, based on which sunlight would be simulated in this study. The IFC file format is designed to provide interoperability between different BIM-related software applications. Enabling importing and exporting of building objects and their properties, the IFC format covers core project information such as building elements, geometric and material properties of building products, etc. The major computer-aided design (CAD) systems, such as THSWARE, can transfer imported IFC data directly to the database elements, using a parsing subsystem described by Revit families of building elements.

A city with a population of one-half million people can be defined as a metropolis. Reaching that population standard, together with high level of economy, politics and culture, Nanjing qualifies as a metropolis that belongs to climatic region III, and its sunlight standard is therefore no less than 2 h of sunshine on the Great Cold day. The sunlight standard in Nanjing Technical Codes of Sunlight Analysis Management for High-Rise Building (Nanjing codes for sunlight in buildings) is adopted in this study, of which the Clause 4 (sunlight analysis object)

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The Civil Building with 16 stories is a high-rise building, whose planned design and blueprints are considered to conform to the prescribed regulations. Here, the sunlight simulation and analysis standard is defined in Clause 6 (technical parameter) of Nanjing Technical Codes of Sunlight Analysis Management for High-Rise Building. The start and ending times for sunlight analysis are 8 a.m. and 4 p.m. on Great Cold day, 9 a.m. and 3 p.m. on Winter Solstice day, while the calculating point is 32.04 north latitude (Nanjing), the sampling distance is 1.0 m, the time interval is 10 minutes, and the sill height is 0.9 m. The finalized start and ending time of the sunlight simulation are 8 a.m. and 4 p.m. on the Great Cold day, while

The Sunlight-analysis function module of THSWARE which has an AutoCAD-oriented user interface focus on parameter setting and shelter influences. Before sunlight analysis begins, the THSWARE model is required to set some parameters including sunshine duration, win-

For analysis of a building's window-accessible sunlight, a precondition is to identify occlusion by neighboring structures that prevents penetration of light into living space. In **Table 3**, building occlusion relationships focus on occasions when objects block sunlight (in **Figure 2**). By overlaying the sun occlusion path of a particular sample building, the area of sun blockage could be determined by projecting lines out from this point to each surrounding object. Since the shading diagram will be constructed with all buildings, the result is always a hard-edged

The sunshine duration sheet on THSWARE is designed to measure the length of time which

standard for access to sunlight should be no less than 2 h on that day.

dow exposure, sunshine standards, simulation accuracy, etc.

shading block with the observation window shaded or not.

**Occluded building Occlusion building** Civil building A3, B, Traffic building

is used for the planning of high-rise buildings.

**3.5. Sunlight simulation**

*3.5.1. Occlusion between buildings*

*3.5.2. Sunshine duration sheet*

**Table 3.** Occlusion between buildings.

the sun shines through a given window.

### **3.4. Sunlight simulation settings**

The Ministry of Construction for China has published a series of national codes, such as Code of Urban Residential Areas Planning and Design (GB 50180-93), Standard for Daylighting Design of Buildings (GB/T 50033-2001), Residential Building Code (GB 50368-2005), and others. With these codes, the Ministry of Construction for China has clearly prescribed requirements for the standard of available sunlight for buildings design and placement. On the basis of Code for Planning and Design on Urban Residential Areas (GB 50180-93) (2002), there is a code for sunlight standard in clause 5.0.2.1. Therefore, the sunlight simulation and analysis in this study conform to clause 5.0.2.1: The sunlight standard of buildings should accord with the regulations in **Table 2** and conform to the prescribed regulations listed below under particular conditions:



**Table 2.** Sunlight standard of civil building.

A city with a population of one-half million people can be defined as a metropolis. Reaching that population standard, together with high level of economy, politics and culture, Nanjing qualifies as a metropolis that belongs to climatic region III, and its sunlight standard is therefore no less than 2 h of sunshine on the Great Cold day. The sunlight standard in Nanjing Technical Codes of Sunlight Analysis Management for High-Rise Building (Nanjing codes for sunlight in buildings) is adopted in this study, of which the Clause 4 (sunlight analysis object) is used for the planning of high-rise buildings.

The Civil Building with 16 stories is a high-rise building, whose planned design and blueprints are considered to conform to the prescribed regulations. Here, the sunlight simulation and analysis standard is defined in Clause 6 (technical parameter) of Nanjing Technical Codes of Sunlight Analysis Management for High-Rise Building. The start and ending times for sunlight analysis are 8 a.m. and 4 p.m. on Great Cold day, 9 a.m. and 3 p.m. on Winter Solstice day, while the calculating point is 32.04 north latitude (Nanjing), the sampling distance is 1.0 m, the time interval is 10 minutes, and the sill height is 0.9 m. The finalized start and ending time of the sunlight simulation are 8 a.m. and 4 p.m. on the Great Cold day, while standard for access to sunlight should be no less than 2 h on that day.

### **3.5. Sunlight simulation**

*3.3.3. IFC transformation*

114 Emerging Solar Energy Materials

**3.4. Sunlight simulation settings**

ticular conditions:

be no less than 2 h;

Cold day (Jan 20/21).

**Architectural climate zone**

Day for sunlight standard

Effective sunlight

hour

standard of adjacent residence;

Great Cold day

**Table 2.** Sunlight standard of civil building.

Either 20 or 21 January depending on the year

Sunlight hour (h) ≥2 ≥3 ≥1

Using the Revit model requires transformed of data into the IFC format for compatibility with THSWARE software, based on which sunlight would be simulated in this study. The IFC file format is designed to provide interoperability between different BIM-related software applications. Enabling importing and exporting of building objects and their properties, the IFC format covers core project information such as building elements, geometric and material properties of building products, etc. The major computer-aided design (CAD) systems, such as THSWARE, can transfer imported IFC data directly to the database elements, using a pars-

The Ministry of Construction for China has published a series of national codes, such as Code of Urban Residential Areas Planning and Design (GB 50180-93), Standard for Daylighting Design of Buildings (GB/T 50033-2001), Residential Building Code (GB 50368-2005), and others. With these codes, the Ministry of Construction for China has clearly prescribed requirements for the standard of available sunlight for buildings design and placement. On the basis of Code for Planning and Design on Urban Residential Areas (GB 50180-93) (2002), there is a code for sunlight standard in clause 5.0.2.1. Therefore, the sunlight simulation and analysis in this study conform to clause 5.0.2.1: The sunlight standard of buildings should accord with the regulations in **Table 2** and conform to the prescribed regulations listed below under par-

**1.** The sunlight on the Winter Solstice day in residential buildings for elderly people should

**2.** Increasing of facilities outside the original design should not lower the original sunlight

**3.** In terms of reconstruction of old dwellings, the sunlight standard of new residential buildings could be reduced conditionally but should not be reduced to less than 1 h on the Great

8 am~4 pm 9 am~3 pm

**I, II, III, VII Climate zone IV Climate zone V, VI** 

**zone Large city Medium/small city Large** 

**city**

**Climate** 

**Medium/small city**

Winter Solstice day Either 21 or 22 December depending on the year

ing subsystem described by Revit families of building elements.

The Sunlight-analysis function module of THSWARE which has an AutoCAD-oriented user interface focus on parameter setting and shelter influences. Before sunlight analysis begins, the THSWARE model is required to set some parameters including sunshine duration, window exposure, sunshine standards, simulation accuracy, etc.

#### *3.5.1. Occlusion between buildings*

For analysis of a building's window-accessible sunlight, a precondition is to identify occlusion by neighboring structures that prevents penetration of light into living space. In **Table 3**, building occlusion relationships focus on occasions when objects block sunlight (in **Figure 2**). By overlaying the sun occlusion path of a particular sample building, the area of sun blockage could be determined by projecting lines out from this point to each surrounding object. Since the shading diagram will be constructed with all buildings, the result is always a hard-edged shading block with the observation window shaded or not.

#### *3.5.2. Sunshine duration sheet*

The sunshine duration sheet on THSWARE is designed to measure the length of time which the sun shines through a given window.


**Table 3.** Occlusion between buildings.

**Figure 2.** The occlusion between sample buildings.

**Table 4** shows the simulation results of sunshine duration on the first floor of the Civil Building 8:00 AM–4:00 PM on Great Cold day, which is the last solar term in 24 solar terms and comes around January 20th or 21st each year. According to Code for Planning and Design on Urban Residential Areas (GB 50180-93) and Nanjing Technical Codes of Sunlight Analysis Management for High-rise Building, sunshine duration on Great Cold day cannot be less than 2 h. In **Table 4**, a red figure represents a window exposed to sunshine less than 2 h sunshine a day, while blue represents a window with 2 h sunshine on that day.

Analysis results are configured in the BIM model by marking the windows' positions as in **Figure 3**, where the blue line on the south face of the Civil Building represents the boundary of windows receiving less than 2 h of sunshine on Great Cold day. The serial number of the windows are 1/33-1/34, 2/36-2/38, 3/36-3/38 (windows no. 33-34 on the first floor, windows no.36-38 on the second floor, and windows no.36-38 on the third floor). On the North face of the Civil Building, the red line identifies windows areas, where the sunshine duration is zero on Great Cold day. The serial number of the windows are 1/4-1/13, 1/36-1/41 (windows no. 4–13 and No. 36–41 on the first floor).

#### *3.5.3. Isohel map*

An isohel is a line on a solar map which connects points that receive equal amounts of sunshine. In this study, two types of isohel map were produced to measure sunshine intensity: an isohel map for building elevation and an isohel map for the building plan.

#### *3.5.4. Isohel map of building elevation*

In this step, isohel maps were produced from average values of light intensity at measuring points for the area between the isohels on the building elevation including all four cardinal points, as shown in **Figures** 4 and **5**, wherein a, b represents the serial number of window located in ath floor is b.

**Figure 4** shows the isohel map for the 6th–9th windows on the 10th–12th floor of the South elevation of the Civil Building. The white figures calculated in the isohel map indicate areas that will receive approximately 8 h of sunshine on Great Cold day.

**Figure 5** shows the isohel map for 18th windows in 16th floor on east elevation of Civil Building. The blue figures calculated on the isohel map indicate areas that will receive more than 4 h of sunshine on Great Cold day, while green figures indicate areas receiving more

**Floor Window position Window height (m) Sunshine duration**

15 0.50 09:11–09:15

16 0.50 09:19–09:21

**Table 4.** Sunshine duration sheet of first floor.

1st 1 0.50 12:01–14:15 02:14 2 0.50 08:55–08:59

3 0.50 09:55–14:23 04:28 4–13 0.50 0 00:00 14 0.50 09:57–14:29 04:32

 0.50 10:07–14:45 04:38 0.50 10:11–14:49 04:38 0.50 10:13–14:53 04:40 0.50 10:15–14:59 04:44 0.50 10:15–15:01 04:46 0.50 10:15–15:05 04:50 0.50 10:23–15:09 04:46 0.50 10:39–15:13 04:34 0.50 10:53–15:15 04:22 0.50 11:07–15:19 04:12 0.50 11:15–15:21 04:06 0.50 11:35–15:25 03:50 0.50 11:51–15:27 03:36 0.50 12:21–15:29 03:08 0.50 12:45–15:31 02:46 0.50 13:35–15:35 02:00 0.50 14:13–15:35 01:22 0.50 15:07–15:41 00:34 0.50 08:00–12:01 04:01 36–41 0.00–0.50 0 00:00

**Time Effective time duration (hour)**

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04:32

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04:40

04:38

09:51–14:19

09:59–14:35

10:05–14:41


**Table 4.** Sunshine duration sheet of first floor.

**Figure 2.** The occlusion between sample buildings.

116 Emerging Solar Energy Materials

4–13 and No. 36–41 on the first floor).

*3.5.4. Isohel map of building elevation*

located in ath floor is b.

*3.5.3. Isohel map*

**Table 4** shows the simulation results of sunshine duration on the first floor of the Civil Building 8:00 AM–4:00 PM on Great Cold day, which is the last solar term in 24 solar terms and comes around January 20th or 21st each year. According to Code for Planning and Design on Urban Residential Areas (GB 50180-93) and Nanjing Technical Codes of Sunlight Analysis Management for High-rise Building, sunshine duration on Great Cold day cannot be less than 2 h. In **Table 4**, a red figure represents a window exposed to sunshine less than 2 h sunshine

Analysis results are configured in the BIM model by marking the windows' positions as in **Figure 3**, where the blue line on the south face of the Civil Building represents the boundary of windows receiving less than 2 h of sunshine on Great Cold day. The serial number of the windows are 1/33-1/34, 2/36-2/38, 3/36-3/38 (windows no. 33-34 on the first floor, windows no.36-38 on the second floor, and windows no.36-38 on the third floor). On the North face of the Civil Building, the red line identifies windows areas, where the sunshine duration is zero on Great Cold day. The serial number of the windows are 1/4-1/13, 1/36-1/41 (windows no.

An isohel is a line on a solar map which connects points that receive equal amounts of sunshine. In this study, two types of isohel map were produced to measure sunshine intensity: an

In this step, isohel maps were produced from average values of light intensity at measuring points for the area between the isohels on the building elevation including all four cardinal points, as shown in **Figures** 4 and **5**, wherein a, b represents the serial number of window

**Figure 4** shows the isohel map for the 6th–9th windows on the 10th–12th floor of the South elevation of the Civil Building. The white figures calculated in the isohel map indicate areas

isohel map for building elevation and an isohel map for the building plan.

that will receive approximately 8 h of sunshine on Great Cold day.

a day, while blue represents a window with 2 h sunshine on that day.

**Figure 5** shows the isohel map for 18th windows in 16th floor on east elevation of Civil Building. The blue figures calculated on the isohel map indicate areas that will receive more than 4 h of sunshine on Great Cold day, while green figures indicate areas receiving more

**Figure 6** above shows division on the basis of sunshine duration of a given building plane. The image shows analysis of sunshine duration on the first floor, in which dark blue represents areas receiving sunshine for more than 4 h, light blue represents more than 3 h of light, green represents more than 2 h, yellow represents more than 1 hour, and red represents less than 1 h of light. Results indicate very little sunshine on the North plane, and the windows no. 33-34 have a sunshine duration of zero, due to occlusion by the Traffic Building (Building T)

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Area analysis (in **Figure 7**) yields sunshine duration values for different areas within the same plane of a building. Theoretically, analysis of isohel lines is in accordance with area analysis, which facilitates cross-confirmation. The object of sunlight analysis in the image above is the first floor, from which the obtained data represent the length of time that area receives sunshine. The results accord with actual conditions, where N represents sunshine duration greater than or equal to N, but less than N + 0.5 and N+ represents sunshine duration greater

**Figure 8** clearly shows the shadow size at 11:00 of each building in this study. Three windows of the South side on floors 1-3 of the Civil Building are shaded by the Traffic Building

**Figure 9** shows shadow range of Civil Building and its continuous shadow envelope on the

This research section examines sunshine of the Civil Building 8:00–16:00 h (in **Figure 10**). The shadow area is relatively large around 8:00, while most windows on the North side can

(Building T), falling it far from the insolation standards on Great Cold day of 2 h.

from the south, which is in accordance with the analysis above.

than or equal to N + 0.5 but less than N + 1.

**1.** Occlusion of and by the Civil Building

**2.** Shadow range of the Civil Building

*3.5.8. Screenshot of sunshine simulation*

ground on Great Cold day.

**Figure 6.** Isohel map of building plane.

*3.5.7. Shadow outline and shadow range of building*

*3.5.6. Area analysis*

**Figure 3.** The windows which do not reach the sunshine requirement. (a) South face, (b) North face.

**Figure 4.** Isohel map for windows in 10th–12th floor on south elevation of civil building.

**Figure 5.** Isohel map for the 18th window on 16th floor of the East elevation of the building.

than 2 h of sunshine and yellow figures indicate areas with more than 1 h of sunshine. Note that the area of red figures that receives less than 1 h of sunshine is mainly the result of shadowing by the building roof.

#### *3.5.5. Isohel map of building plane*

The isohel maps of building planes, which is similar to the map of building elevation, apply plane partition according to sunshine duration. The isohel lines shown in building plane mode indicate clearly those areas receiving equal amounts of sunshine.

**Figure 6** above shows division on the basis of sunshine duration of a given building plane. The image shows analysis of sunshine duration on the first floor, in which dark blue represents areas receiving sunshine for more than 4 h, light blue represents more than 3 h of light, green represents more than 2 h, yellow represents more than 1 hour, and red represents less than 1 h of light. Results indicate very little sunshine on the North plane, and the windows no. 33-34 have a sunshine duration of zero, due to occlusion by the Traffic Building (Building T) from the south, which is in accordance with the analysis above.

#### *3.5.6. Area analysis*

**Figure 3.** The windows which do not reach the sunshine requirement. (a) South face, (b) North face.

**Figure 4.** Isohel map for windows in 10th–12th floor on south elevation of civil building.

owing by the building roof.

118 Emerging Solar Energy Materials

*3.5.5. Isohel map of building plane*

than 2 h of sunshine and yellow figures indicate areas with more than 1 h of sunshine. Note that the area of red figures that receives less than 1 h of sunshine is mainly the result of shad-

The isohel maps of building planes, which is similar to the map of building elevation, apply plane partition according to sunshine duration. The isohel lines shown in building plane

mode indicate clearly those areas receiving equal amounts of sunshine.

**Figure 5.** Isohel map for the 18th window on 16th floor of the East elevation of the building.

Area analysis (in **Figure 7**) yields sunshine duration values for different areas within the same plane of a building. Theoretically, analysis of isohel lines is in accordance with area analysis, which facilitates cross-confirmation. The object of sunlight analysis in the image above is the first floor, from which the obtained data represent the length of time that area receives sunshine. The results accord with actual conditions, where N represents sunshine duration greater than or equal to N, but less than N + 0.5 and N+ represents sunshine duration greater than or equal to N + 0.5 but less than N + 1.

#### *3.5.7. Shadow outline and shadow range of building*

**1.** Occlusion of and by the Civil Building

**Figure 8** clearly shows the shadow size at 11:00 of each building in this study. Three windows of the South side on floors 1-3 of the Civil Building are shaded by the Traffic Building (Building T), falling it far from the insolation standards on Great Cold day of 2 h.

**2.** Shadow range of the Civil Building

**Figure 9** shows shadow range of Civil Building and its continuous shadow envelope on the ground on Great Cold day.

### *3.5.8. Screenshot of sunshine simulation*

This research section examines sunshine of the Civil Building 8:00–16:00 h (in **Figure 10**). The shadow area is relatively large around 8:00, while most windows on the North side can


**Figure 6.** Isohel map of building plane.


Cold day, and the shadow is accordingly stretches. According to the three images above, no windows on the nightside can receive sunshine at any time of the day, which is in accordance

A BIM-Based Study on the Sunlight Simulation in Order to Calculate Solar Energy…

http://dx.doi.org/10.5772/intechopen.74161

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In this study, the analyzed building is treated as one system, where the amount of solar energy gained by any facade of building is the main research target. Related data used to calculate solar energy are generated in the sunlight simulation by BIM modeling, which shows the sunshine duration on facades of a selected building. For solar energy calculation in this

**1.** Solar panels can be installed on the rooftop and vertical walls with a sunshine duration

**2.** In order to satisfy required cost savings, the solar panels will not be installed on the northfacing vertical wall of the building because of its insufficient sunshine all year around. **3.** Every solar panel is made up of the same material, and the absorbed sunlight can be con-

**5.** The analysis period for energy cost is classified into Vernal Equinox, Summer Solstice, Autumn Equinox, and Winter Solstice. The duration time is assumed to be the average of

**6.** According to the weather statistics over the last 3 years, the average number of sunny days

**7.** The duration of the sunshine period on the facade of the building is considered to be the average length of the period as estimated by sunlight simulation on THESWARE.

The assumptions mentioned above are made in order to facilitate investigation easy and to make the comparison more realistic. In this study, direct solar radiation was calculated,

study, it is assumed that Civil Building meets the following conditions:

verted into electricity to attain efficiency in stable networks.

**8.** The rate paid for electricity is 0.88 RMB per kilowatt-hour.

**4.** The energy cost analysis mainly considers the cost of solar panels.

with the sunshine analysis of windows as shown above.

**Figure 10.** Sunshine simulation at (a) 8:00 A.M., (b) 12:00 P.M., and (c) 16:00 P.M.

**4. Results and discussion**

more than 5 h.

each solar term.

each year accounted for 55%.

**4.1. The assumption of energy calculation**

**Figure 7.** Area analysis map.

**Figure 8.** Shadow outline of civil building.

**Figure 9.** Shadow range of civil building.

receive sunshine. The shadow area at 12:00 is much less than any other time of the day, which means that windows receiving sunshine increase and sunshine duration is much longer. 16:00 is the latest time point used for analyzing sunshine duration on the Civil Building on Great

**Figure 10.** Sunshine simulation at (a) 8:00 A.M., (b) 12:00 P.M., and (c) 16:00 P.M.

Cold day, and the shadow is accordingly stretches. According to the three images above, no windows on the nightside can receive sunshine at any time of the day, which is in accordance with the sunshine analysis of windows as shown above.
