**2. Background**

that advocate energy conservation for green buildings have been promoted, wherein the building energy efficiency upgrade program for reducing power consumption in buildings is one of the crucial contents outlined in the policy. Green building's three main pillars are environmental, economic, and social in aspect. Considered a paramount method to maintain quality of life, designed to replace use of environmentally harmful products, we could say that sustainable design is an important process involving science and arts from all fields [1]. In China, estimates indicate that more than 80% of annual new buildings and over 95% of existing buildings have high-energy consumption designs [2]. Low energy-efficiency buildings

of "green legislation" together with increased green building construction is forcing architects, planners, and builders to consider the environmental impact of buildings they design and construct [4]. Aside from the moderate amount of sunlight required for the health and comfort of occupants, solar radiation is particularly useful as an energy resource [5]. Apart from this, sunlight provides light more efficiently than electric light sources, while producing less heat for the same amount of light. With the development of sustainable design, researchers are attaching much more importance to energy savings related to sun exposure on buildings, an important component of sustainable development. One of the performance analyses done by architects is to predict how buildings are performing in terms of their luminous environment as a result of daylighting [6]. If energy savings from harvesting sunshine on buildings are considered in the building design stage, an optimal energy design can be selected. Demand for solar power has expanded in recent years for domestic and industrial needs. Solar power is produced by collecting sunlight and converting it into electricity, which is normally done by use of large, flat solar panels composed of many individual solar cells. Solar arrays are most often located remotely, although urban sitting is becoming more popular as well. As the cost of solar energy falls, more and more buildings are being outfitted with photovoltaic systems and some even generate more electricity than they use, which structures are called "energy positive," an impressive feat. In some areas, solar-enabled buildings actually turn a profit from surplus energy, which is sold to local utility companies and fed it onto the grid. In practice, photovoltaic materials (like solar panels) are normally used to replace conventional building materials in parts of the building envelope such as roofs, skylights, and facades. As a principle or ancillary source of electrical power, solar panels are increasingly incorporated into the construction of new buildings, although existing buildings may be retrofitted with similar technology. However, current analysis of solar energy extraction in comparison with the complexity of sunlight models needed for energy calculations clearly reflects the limited use of building information modeling, as well as the lack of effective visualization techniques. Sunlight analysis is performed by hand calculations or by computer simulation tools. In the process of hand calculation, the preparation of initial data can be a very lengthy and laborious, consisting as it does mostly of manual or semimanual translation from architectural model data to simulation data, which often results in numerous coding errors [7]. To solve the problem, graphic user interfaces have been created in simulation tools for defining model geometry. In addition, 3D digital technology, such as building information modeling (BIM), has been applied to sunlight simulation. BIM integrates all kinds of relevant information from construction projects, while related software enables energy consumption to be predicted and adjusted during the design

of urban buildings in China [3]. As well, the advent

account for 98% of more than 4 × 1010 m2

108 Emerging Solar Energy Materials

stage, thus providing great convenience for sustainable design.

#### **2.1. BIM and sustainable design**

With the importance of BIM becoming increasingly appreciated, BIM and sustainable design strategies in the building industry have drawn more and more attention. A number of published papers on BIM-related sustainable design have focused mostly on energy usage analysis alone [8]. Wang and Xuan [9] suggest a BIM-based parametric design method to establish the BKE (Bio-inspired Kinetic Envelop) system combined with utilization of solar radiation to make buildings acclimate to temperature swings, thus minimizing the energy needs. Wong and Fan [8] find two most significant benefits of BIM for sustainable building design: integrated project delivery (IPD) and design optimization. Hardin [10] established three main areas of sustainable design with a direct relationship to BIM, which are "material selection and use," "site selection and management," and "systems analysis." In addition, Azhar and Brown [11] investigate the development of a conceptual framework to illustrate the use of BIM for sustainability analyses throughout the project life-cycle.

In previous study on the integration BIM and building performance, it has been indicated that BIM can aid in the sunlight analysis [12]. BIM technologies offer new insights into the dynamic relationship and specificities of sunlight conditions and the individual building's use and properties, helping us identify the balancing points of solar gains and daylight conditions resulting from urban geometry [13]. Welle et al. [14] designed an automated product model decomposition and re-composition methodology for BIM-centric climate-based daylighting simulation called the BIM-Centric Daylight Profiler for Simulation (BDP4SIM). Joo et al. [15] developed a tool capable of analyzing various design schemes during the early stages of design by building a reasonable BIM data system for sustainability analysis and using the architectural BIM model to carry out sunshine and energy analysis in a Web environment. Generally, two main methods are used for sunlight analysis in building design. One method is the graphing method, which includes normal shadow-graph, pole shadow-graph, instantaneous shadow-graph, and hours shadow overlay. The other method is the modeling test, which performs analysis based on a scale-model of buildings and a sundial. Though the sun spacing coefficient table was widely used in China during the late 1990s, table's usefulness 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 can be saved on BIM database for property management and quality control.

technology's market penetration, while the current direct cost of photovoltaic solar panels is widely acknowledged to be much greater than fossil fuel generation or many other renewable energy sources. The initial cost of the solar panels may be expensive, but it is the only cost plus their installation provides potential complete relief from electric utility costs. Maintenance can be perceived as an added cost, but in reality, all the panels need is dusting and/or washing. Therefore, the cost analysis of solar panels is an important factor to be considered when making

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

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

111

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

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

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,

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.

decisions about solar systems in building design.

provided in regard to points, lines, surfaces, text, etc.

**3. Methodology**

**3.1. Analysis method**

executed (see **Figure 1**):

isohel map, shadow outlines, etc.

#### **2.2. Solar energy and buildings**

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

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 production volumes and greatly reduced costs.

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 technology's market penetration, while the current direct cost of photovoltaic solar panels is widely acknowledged to be much greater than fossil fuel generation or many other renewable energy sources. The initial cost of the solar panels may be expensive, but it is the only cost plus their installation provides potential complete relief from electric utility costs. Maintenance can be perceived as an added cost, but in reality, all the panels need is dusting and/or washing. Therefore, the cost analysis of solar panels is an important factor to be considered when making decisions about solar systems in building design.
