The aim of the research. This article discusses the use of the Digital Twin in automation and its impact on the resulting solution. The research aims to illuminate the Digital Twin concept explanation and systematise the knowledge base and fulfill information gaps. Research results. The paper overviews the history of the concept and determines the main phases of Digital Twin development. The significant attention was paid to the classification issue to show the huge variation depending on Digital Twin‘s purpose, lifecycle phase, the scale of the physical twins and data amount in order to explain the twin‘s relation and the hierarchy of complex system. The defined capabilities and values of the concept identify the possible use cases and explain the potential benefits of Digital Twin implementation. Also, this paper takes a look at the use of Digital Twin in the area of building automation. This concept potentially may act as the integration platform for building management systems (BMS) and building information modelling (BIM) technologies with IoT solutions. The discussion of Digital Twin implementation for the building automation complex is presented. We conclude that the Digital Twin can integrate human factor to the control system by using the indexes of climate satisfaction, the feedback functionality and human-machine interfaces. As a result, the improvement of system efficiency depends on the coordination and orchestration of equipment operating mode. Conclusion. The Digital Twin has a high potential for energy efficiency improvements, as it considers many factors, integrates a huge amount of data and continuously improves themselves with real-world data.

Fan coils are widely used in heating and air conditioning systems in both residential buildings and commercial areas. This article deals with the creation of a mathematical model of the fan coil for use in control systems, building digital twins, etc. The development of models of components of building engineering systems contributes to the introduction of more sophisticated control algorithms and analytics to coordinate the operation of equipment and as a result improve the energy efficiency of systems, the ability to investigate the dynamics of systems, etc. In this paper, a system of heat balance equations for the water, air and walls of the heat exchanger was used, which allows for simulating the operation of the system in transient modes. Considerable attention was paid to the calculation of the coolant and air parameters, including specific heat capacity, heat transfer coefficients, water and air thermal conductivity, kinematic viscosity coefficients, density, etc. The use of dynamic calculation of the coolant and air characteristics was proposed, an algorithm using the Python programming language and the CoolProp, SciPy, and NumPy libraries were implemented, and simulation results were presented. To assess the effectiveness of the proposed solutions, an analysis of the simulation results for the system with constant values of the coolant and air parameters, determined from the averaged initial values of the input and output parameters of the model, compared to the system with dynamic calculation, was performed. Finally, we investigated the dynamics of the external factor influence on the simulation results and presented an analysis of the influence of the model input variables on the output temperature values due to implicit relationships in the calculation of the parameters characterizing the heat transfer fluid and the air in the fan coil. According to the results of the comparison, the deviations in the simulation results of the models under study were estimated for the calculated value of heat output on the air side in absolute and relative units.