# Exploring the Benefits and Limitations of Digital Twin Technology in Building Energy
## 3 Background of BIM and Digital Twin
### Digital Twin  
The development of this technology can be traced back to the 1960s when NASA devised \"digital twins\" to assess failures in the Apollo missions. The same physical spacecraft was built to simulate and study the different conditions the spacecraft would face in space. Later, [PERSON] proposed the idea of Digital Twin technology in 1991. Subsequently, [PERSON] proposed the concept of Digital Twin Software in 2002; this was the first time to apply software to the manufacturing industry. In 2010, NASA defined the concept of the Digital Twin in detail, becoming an essential part of the aerospace field [4]. In 2002, NASA's [PERSON] and [PERSON] introduced the concept of digital twins for the product lifecycle management (PLM) [26]. Broadly defined as \"a digital twin is a dynamic, self-evolving digital/virtual model that represents the state of a real-life object and its physical twin. A digital twin is created by exchanging real-time data and preserving historical data realized\". However, for a long time, the 'digital twin' has been just a concept without any suitable technical means to support its application. With the advent of Industry 4.0, digital technologies are developing rapidly and promoting digital transformation in variousindustries. The transformation also promotes the development and application of digital twin technology. Digital twins are widely used in manufacturing, construction, medical care, urban planning, energy, agriculture, and other fields to optimize production, design, maintenance, and monitoring, improve efficiency and sustainability, and manage and optimize entities, processes and systems to achieve Increased efficiency, reduced costs and increased sustainability [27]. For the construction industry, a digital twin is defined as \"a real-time representation of a fully or partially completed and developed building or structure to represent the state and characteristics of the building or structure it reflects\" [28]. Thus, it enables seamless synchronization and monitoring of energy systems through computerized and virtual world simulations based on data, information, and consumer behavior. 3D modelling, digital prototyping, and system simulation are all products based on the digital twin concept [28]. As mentioned before, the digital twin (DT) aims to gain insight and predict the performance of a physical product, process, or infrastructure through a virtual model. A digital twin consists of a physical system, a virtual model, and the data network between the two [4]. Digital twins are used to improve physical entities' performance by using virtual models' computational tools. Real-time data from physical entities is used to inform the development of virtual model parameters, boundary conditions, and dynamics. This results in a more realistic representation of the actual entity being modelled [26]. The digital twin is a digital version of a physical entity with the principle of establishing a digital model by collecting data on physical entities, processes or systems, and interacting and collaborating with physical entities in real time to achieve optimization and improvement. Therefore, to make digital twin become practical, there is a need for an integrated analysis system [11]. Digital Twin can predict potential problems in real time by monitoring physical entities and providing feedback to aid decision-making and improvement, optimize design management processes, reduce costs, and promote sustainability [29]. Due to these characteristics, digital twins were introduced into the construction industry and combined with BIM based on CAD, SolidWorks, Revit, etc., to create an integrated construction management process covering the entire building life cycle [29]. Digital twin technology is at the heart of building energy efficiency. Electricity, heating, and air conditioning (HVAC systems) account for a large percentage of total building expenditures.