1. Concept, Definition, Enabling Technologies, and Challenges of Energy Integration in Whole Energy Systems To Create Integrated Energy Systems

In recent years, the vector coupling of energy systems is in progress by integrating different energy vectors such as power, heat, and gas and also integration of different sectors such as residential, transportation, commercial, and industry parts for efficient utilization of energy sources such as natural gas, coal, diesel, and renewable energy sources. The energy crisis, air pollution issues, increasing trend of energy consumption, reliability issues, and especially increasing the share of variable renewable energy sources are the major drivers of this transition. Interaction among energy systems is achieved through a real or physical node or even a virtual node so-called the energy hub or multi-energy node. Enabling technologies for integrating energy systems are energy conversion systems (such as cogeneration and trigeneration systems, heat pumps, diesel generator, and boilers), energy storage systems (such as battery, thermal, cold, and hydrogen storage), information and communication technologies, and particularly decarbonizing components. Demand-side management is also essential for energy integration since it contributes to energy conservation and flexibility of energy demands. In this chapter, the concept and definition of vector-coupling concept in the whole energy systems is discussed. In addition, enabling technologies and challenges associated with integrating energy vectors are discussed.