## 2 Concepts Review
### Smart City Model
In being competitive, cities seek to attract greater investments and offer a higher level of quality of life to its inhabitants, and they will be able to get the best out of human capabilities, thus in turn making them increasingly competitive [38]. To reach these goals, the working sectors of smart cities can be classified into \"hard\" and \"soft\" domains, depending on the importance of ICT systems operating within them [26]. According to this classification, the Hard domain includes the sectors in which ICT help to configure cities at a technical level. These are energy grids; public lighting; natural resources and water management; waste management; environment; transport, mobility, and logistics; office and residential buildings; healthcare and public security. As for the Soft domains, the presence of ICT is limited since they are sectors that do not necessarily require real-time information, processing, and integration. These sectors include education and culture, social inclusion and welfare, public administration and (e-)government and economy. The inclusion of ICT in the systems and technological elements makes them smart technologies [42], and examples of these are sensors, electric meters, and other elements interconnected via the Internet under the concept of the Internet of Things (IOT) [43; 44]. These technologies allow interoperability between components that capture and demand signals and provide a continuous response to service management. In this sense, since the energy service is a transversal element in the efficient provision of the services of cities, the smart cities are found within the framework of the urban energy transition. Figure 4 summarizes this approach in the sense that the integration of ICT in cities allows the application of smart technologies to provide the services demanded by the urban population with the aim of improving the city's quality of life, competitiveness, and sustainability. It should be noted that other authors pose different positions or approaches to study. Authors such as [45; 46] go one step further and consider the potential of smart technologies as a solution to the problems of environmental unsustainability, which is determined by the size of the carbon footprint and the environmental and energy impact that these technologies will cause during the improvement of other processes. In addition, according to [47], cities can be made sustainable without the use of smart ICT, and smart technologies can be used in cities without contributing to sustainable development; and, these technologies can also be used for sustainable development in locations other than cities. The energy dimension of smart cities is called the smart energy system. Technically, this is a system in which the technological elements of the energy system and the economic agents of the market (consumers, producers, system and market operators, etc.) are combined to identify synergies between them in order to achieve an optimal solution for each individual sector as well as for the overall energy system [10]. Through these synergies, the smart energy systems can reduce the primary energy consumption of cities and cover the remaining demand by taking advantage of the local renewable energy resources, depending on the climatic characteristics of each city and the profitability of the energy vectors [48]. As seen above, the increase in efficiency (however, work on finding a way to increase efficiency is not new for the electricity sector, and, as a result of an industrial process, the electric sector has always been looking for increased efficiency in order to avoid economic losses) is an objective of the flexibilization of the electricity supply value chain through empowering consumers in power generation and management of demand [49]. The main technological components of a flexible electrical system are smart meters, storage systems, distributed generation (DG) systems and smart grids in order to link all of these components together.