**4. Results and discussion**

**Figure 7.** Area analysis map.

120 Emerging Solar Energy Materials

**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

#### **4.1. The assumption of energy calculation**

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


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, ground reflected, and diffused radiations are neglected under the assumption that they will be equal for all shapes. Additionally, effects of the other factors, like shading and type of building material, are assumed to be equal for all situations. These assumptions do not change the main results of this study.

#### **4.2. Energy consumption calculation and cost analysis**

In this study, each surface of the building was first analyzed separately, and then all systems were discussed. Surfaces of the building were encoded by using abbreviations ("South," "East/ West"), as seen in **Table 5**. Instant and hourly solar energy from the surface of a building depend upon some parameters, like the time of day, day of year, effective area of the wall, sunshine duration, etc. According to the BIM model of the Civil Building described above, the total area and effective area of walls on each floor can be summarized in **Table 5**. Note that the northfacing surface is not taken into consideration because its sunshine duration is less than 5 h. As well, the sunshine duration of different surfaces in each solar term is shown in **Table 6**, where the surfaces labeled in italics are the vertical walls with a sunshine duration of less than 5 hours.

In this part of the study, sunshine striking a given surface between sunrise and sunset is of concern. First, the total amount of annual solar energy striking surface for more than 5 h was


calculated for each solar term over a whole year, which calculation was performed for every surface of the building. The related and required parameters for cost calculation were then assigned. According to the sustainable design plan of the Civil Building, polycrystalline silicon solar panel at 240 W and 18% conversion efficiency (1.65 m long, 0.991 m wide, and 0.04 m light) are suitable components for a larger photovoltaic energy generation and supply system. The installed photovoltaic system will receive 3 RMB per watt capacity in construction subsi-

dies, thus each solar panel 240 W will yield 720 RMB in subsidy.

**Floor Surface The spring** 

**equinox**

**The summer solstice**

*West 3.3 4.5 3.3 2.4*

West 3.6 4.5 3.6 2.6

*West 4 3 4 3*

*West 4.75 6 4.75 3.5*

Roof 12 14 12 10 2376 1 South 5.4 4.8 5.4 3 920.7

2 South 6 4.8 6 4 594

3 South 7 4.7 7 4.5 1148.4

4-5 South 8.6 6.5 8.6 6.5 1470.15 East 6 7 6 5 1188

6-10 South 12 6 12 10 1980

11-14 South 12 4 12 10 1881

East 6 7 6 5 1188 West 6 7 6 4.8 1178.1

East 6 7 6 5 1188 West 6 7 6 5 1188 15 South 12 1.5 12 10 1757.25

East 6 6.5 6 5 1163.25 West 6 6.5 6 5 1163.25

16 South 6.8 0.5 6.8 9 1143.45

*East 3.4 3.6 3.4 3.5 West 4.3 4.5 4.3 4*

**Table 6.** Sunshine duration of different surfaces (unit: h).

East 6 7 6 4.5 1163.25

East 6 7 6 5 1188

East 6 5 6 5 1188

**The autumnal equinox**

**The winter solstice**

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

**Effective sunshine duration in a year (h)** 123

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

**Table 5.** The area of the wall.

A BIM-Based Study on the Sunlight Simulation in Order to Calculate Solar Energy… http://dx.doi.org/10.5772/intechopen.74161 123


**Table 6.** Sunshine duration of different surfaces (unit: h).

ground reflected, and diffused radiations are neglected under the assumption that they will be equal for all shapes. Additionally, effects of the other factors, like shading and type of building material, are assumed to be equal for all situations. These assumptions do not change

In this study, each surface of the building was first analyzed separately, and then all systems were discussed. Surfaces of the building were encoded by using abbreviations ("South," "East/ West"), as seen in **Table 5**. Instant and hourly solar energy from the surface of a building depend upon some parameters, like the time of day, day of year, effective area of the wall, sunshine duration, etc. According to the BIM model of the Civil Building described above, the total area and effective area of walls on each floor can be summarized in **Table 5**. Note that the northfacing surface is not taken into consideration because its sunshine duration is less than 5 h. As well, the sunshine duration of different surfaces in each solar term is shown in **Table 6**, where the surfaces labeled in italics are the vertical walls with a sunshine duration of less than 5 hours. In this part of the study, sunshine striking a given surface between sunrise and sunset is of concern. First, the total amount of annual solar energy striking surface for more than 5 h was

**) Windows area (m2**

Roof 867.8 0 867.8 1 South 255.78 89.64 166.14

2 South 219.24 77.76 141.48

3 South 219.24 67.2 152.04

4-5 South 219.24 89.6 129.64

6-10 South 219.24 89.6 129.64

11-14 South 219.24 89.6 129.64

15 South 219.24 89.6 129.64

16 South 216 64 152

East/west 66.78 6.3 60.48

East/west 57.24 5.67 51.57

East/west 57.24 4.2 53.04

East/west 57.24 5.67 51.57

East/west 57.24 5.67 51.57

East/west 57.24 5.67 51.57

East/west 57.24 5.67 51.57

East/west 56.16 5.67 50.49

**) Effective area (m<sup>2</sup>**

**)**

the main results of this study.

122 Emerging Solar Energy Materials

**Floor Surface Total area (m2**

**Table 5.** The area of the wall.

**4.2. Energy consumption calculation and cost analysis**

calculated for each solar term over a whole year, which calculation was performed for every surface of the building. The related and required parameters for cost calculation were then assigned. According to the sustainable design plan of the Civil Building, polycrystalline silicon solar panel at 240 W and 18% conversion efficiency (1.65 m long, 0.991 m wide, and 0.04 m light) are suitable components for a larger photovoltaic energy generation and supply system. The installed photovoltaic system will receive 3 RMB per watt capacity in construction subsidies, thus each solar panel 240 W will yield 720 RMB in subsidy.

The total number of solar panels n that can be installed on the surface is given in Eq. (1), where Ai is the combined effective area of the facade and rooftop of the Civil Building, while S is the cross-sectional area of the solar panel.

$$m\_i = \left\lfloor \frac{\mathcal{A}\_i}{S} \right\rfloor \tag{1}$$

visualizations, the sunshine duration and energy consumption of buildings can be calculated with a fair level of accuracy. As a widely used tool in construction sector, BIM has great prospects. With a three-dimensional digital technology, the concept of BIM integrates various kinds of relevant information from construction projects, aiding in complex building performance analyses to ensure an optimized sustainable building design. As well, related software enables energy consumption to be predicted and adjusted during the design stage, thus pro-

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

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

125

This case study presents both method and technology for integration of building energy simulation and cost calculation with building information modeling (BIM). The early feasibility study stage included sunlight simulation using Revit and THS-WARE, after which the solar energy production was investigated based on the application of solar panels. Initial sunlight analysis and energy use calculations by BIM software were generated based on a number of building specifications and environmental data. According to analysis of solar energy as absorbed by facades, the expense saved by electricity generated from the solar energy can be calculated. Taking the cost of solar panels and project feasibility into consideration, the study shows that application of the studied solar panels contributes greatly to social, economic, and environmental benefits. The

Though application of building information modeling (BIM) technology assists effective decisions-making as related to sustainable building design in the early stages, BIM is still developing and limited by software compatibility. If the following aspects can be improved while applying sunshine simulation to real projects through BIM, the long-term benefits of a sustainable design will be realized. (1) Strengthen software analysis area. In order to provide a more comprehensive analysis, apart from the analysis of sunlight condition of the building, indoor lighting, ventilation, and air conditioning should be taken into consideration. (2) The result of calculation on solar energy converted to electricity has effect on the development of solar panels. Optimizing the utilization of solar panels contributes to energy saving. (3) A new plug-in is needed to combine solar energy analysis with sunshine simulation, which can solve

The authors' special thanks go to the National Science Council of P. R. C. for financially supporting this research (NSFC-71302138), and fund by the National Key Research and

energy-saving proposal is feasible in this case and realizes the sustainable design.

viding great convenience for sustainable design.

related practical problem more efficiently.

Development Program of China (2016YFC0702001-06).

Address all correspondence to: bernardos@163.com

Department of Civil Engineering, Southeast University, Nanjing, China

**Acknowledgements**

**Author details**

Zhao Xu and Jingfeng Yuan

The total electrical energy Q generated by solar panels installed on the Civil Building can be calculated by Eq. (2), where η is the conversion efficiency of the solar panel, w is the power output of solar panels, and Ti is the effective sunshine duration per year of each surface.

$$\underline{Q} = \eta \sum\_{t=1}^{d/2} n\_t \le T\_i = \eta \sum\_{t=1}^{d/2} \left\lfloor \frac{A\_t}{S} \right\rfloor \nu T\_i \tag{2}$$

The amount of the electricity converted by solar panels can be calculated in Eq. (3).

$$\underline{Q} = 18\% \times 240 \times 2600 \times \sum n\_i T\_i = 6\\$ 1860789.2\,\text{kJ} \tag{3}$$

As is shown in Eq. (3), the solar panels yield more than 60 billion joules of savings in electricity, which shows that the solar panels installed on "Civil Building" reduce traditional energy consumption and in turn contribute to the overall energy efficiency. To assess economic benefit of solar panels, the payback period for solar panel cost can be calculated using Eq. (4).

$$C = \sum\_{i}^{42} \left\lfloor \frac{\mathcal{A}\_i}{S} \right\rfloor \times p = 2.544 \times 720 = 1831680 \, RMB \tag{4}$$

In this case, p is the price of each solar panel and C is the operating cost of solar panels. Considering an average electricity price 0.88 RMB per kilowatt-hour in Nanjing, the daily saving on electricity rates P and the recovery period T can be calculated as follows.

*P* = 0.88 × (651860789.2/3600) = 159343.7485*RMB*

*T* = *C*/*P* = 1831680/159343.7485 = 11.5 *years*

Through the cost analysis, after year 11, the investment status solar panels become positive, which means that after 11.5 years, the solar panel system will operate as a positive cash flow source. Based on the 30-year estimated lifespan of the solar panels, there will be more years benefitting from the solar panel installation than years paying for it. After fully analyzing all the results, the investment is definitely cost-beneficial.

#### **5. Conclusions**

The switch to alternative energy sources of electricity is increasing, especially solar energy. The installation of solar panels is advertised throughout the world including China by use of information technologies. Based on the application of building energy modeling and sunlight simulation by BIM technology, and taking advantage of information modeling with 3D visualizations, the sunshine duration and energy consumption of buildings can be calculated with a fair level of accuracy. As a widely used tool in construction sector, BIM has great prospects. With a three-dimensional digital technology, the concept of BIM integrates various kinds of relevant information from construction projects, aiding in complex building performance analyses to ensure an optimized sustainable building design. As well, related software enables energy consumption to be predicted and adjusted during the design stage, thus providing great convenience for sustainable design.

This case study presents both method and technology for integration of building energy simulation and cost calculation with building information modeling (BIM). The early feasibility study stage included sunlight simulation using Revit and THS-WARE, after which the solar energy production was investigated based on the application of solar panels. Initial sunlight analysis and energy use calculations by BIM software were generated based on a number of building specifications and environmental data. According to analysis of solar energy as absorbed by facades, the expense saved by electricity generated from the solar energy can be calculated. Taking the cost of solar panels and project feasibility into consideration, the study shows that application of the studied solar panels contributes greatly to social, economic, and environmental benefits. The energy-saving proposal is feasible in this case and realizes the sustainable design.

Though application of building information modeling (BIM) technology assists effective decisions-making as related to sustainable building design in the early stages, BIM is still developing and limited by software compatibility. If the following aspects can be improved while applying sunshine simulation to real projects through BIM, the long-term benefits of a sustainable design will be realized. (1) Strengthen software analysis area. In order to provide a more comprehensive analysis, apart from the analysis of sunlight condition of the building, indoor lighting, ventilation, and air conditioning should be taken into consideration. (2) The result of calculation on solar energy converted to electricity has effect on the development of solar panels. Optimizing the utilization of solar panels contributes to energy saving. (3) A new plug-in is needed to combine solar energy analysis with sunshine simulation, which can solve related practical problem more efficiently.
