In the last decade, there has been a significant progress in several aspects that are related to the production of electric vehicles, and the use of new technologies as well as their sales. Similarly, the research efforts have also increased, which has caused a significant increase of new jobs and proposals that are related to electric vehicles. Within this section, a short compilation of the most relevant topics related to EVs, which have been addressed by previously available works in the literature, are introduced. In addition, the more notable differences with this survey are highlighted.
Some of the studies published to date deal with general aspects, such as the evolution of electrical vehicles throughout history, give diverse classifications according to the manner in which they have been designed and the characteristics of their engines, or analyze their impact on the electrical infrastructure. For instance, Yong et al. [9] review the history of EVs from their creation, in the middle of the nineteenth century, until present. Additionally, they carry out a classification of the vehicles according to their powertrain settings. Finally, their work analyzes the impact of charging electric vehicles on the electric grid. Likewise, Richardson [10] studies the effects that EVs can produce in the required productivity, efficiency, and capacity of the electric grid. Furthermore, he reviews the economical and environmental impact of electric vehicles. Habib et al. [11] present a review of charging methods for electric vehicles and analyze their impact in the power distribution systems. Additionally, the authors carry out an analysis of coordinated and non-coordinated charging methods, delayed loading, and intelligent planning of charges. Finally, they study the economic benefits of the vehicle-to-grid (V2G) technology according to the charging methods.
Another aspect also dealt with in diverse works has been the use of renewable energy sources (i.e., wind power, solar, and biomass) and their incorporation in the electric vehicles field. Liu et al. [12] present a general vision about electric vehicles and renewable energy sources. They specifically focus on solar and wind power, and present a set of works that are classified into three categories: (i) those works which study the interaction between EVs and the renewable energy sources for reducing the energy cost, (ii) those works focused on improving the energy efficiency, and (iii) the proposals that are mainly seeking to reduce emissions. On the other hand, Hawkins et al. [13] analyze the existing studies about the environmental impact of the Hybrid Electric Vehicles (HEVs) and the Battery Electric Vehicles (BEVs). For that purpose, they present a study of 51 environmental evaluations during the life span of the two kinds of vehicles (i.e., BEVs and HEVs). In their work, the authors take aspects, such as greenhouse gas emissions, the production, transmission, and distribution of electricity, as well as the production of vehicles, batteries, and their life span, into account. Vasant et al. [14] analyze the daily usage of PHEVs, and state that the appropriate deployment of daytime charging stations along with suitable charging control and management of this infrastructure can lead to a wider deployment of PHEVs.
Unlike the previous works, Shuai et al. [15] provide a general vision of the new economic model that is present in electric vehicles, bearing in mind the unidirectional and bidirectional flows of energy (in which the EVs themselves are capable of providing energy to the electric grid). To do this, they analyze different charging facilities for EVs, as well as different methods for unidirectional charging and bidirectional energy commercialization. Finally, they study the use of these vehicles as a feasible storage for the energy that is generated from renewable sources.
Other authors have focused on the different strategies that have been proposed for charging EVs. Tan et al. [16] revise the benefits and challenges of vehicle technology to the grid (V2G), in both the unidirectional and bidirectional charging. Besides advantages, they analyze the challenges, such as the battery deterioration and the high investment cost. Lastly, they complete a compilation of strategies for optimizing V2G, by grouping them according to the technique employed (e.g., genetic algorithms (GAs) and Particle Swarm Optimization (PSO)), as well as according to the objectives: (i) operation costs, (ii) carbon dioxide emissions, (iii) profit, (iv) support for renewable energy generation, (v) load curve, and (vi) power loss. Similar to the previous work, Hu et al. [17] present a revision and classification of methods for the intelligent charging of electric vehicles, but, in this case, focused on the fleet operators. In particular, they present works regarding battery modeling, charging and communications standards, as well as driving patterns. Lastly, they showcase a set of different control strategies to manage EV fleets, as well as mathematical algorithms for its modeling. Rahman et al. [18], present a set of employed methods for solving different problems that are related with the charging infrastructure of PHEVs and BEVs. Additionally, they assess the different charging systems in different environments, such as domestic garages, apartment complexes, and shopping centers.
Because the massive EV deployment will introduce negative impacts on the existing power grid, some works review the different issues and the potential opportunities that EV integration in the smart grid can bring. Yong et al. [9] study the impact of EV deployment from the perspective of vehicle-to-grid technology, and especially for mitigating the renewable energies intermittency. Mahmud et al. [19] discuss all of the aspects related to EV charging, energy transfer, and grid integration with distributed energy resources in the Internet of Energy (IoE). More recently, Das et al. [20] present an evaluation on how future connected EVs and autonomous driving would affect EV charging and grid integration.
Other important EV charging issues are those that are related to battery management, as well as battery health and lifetime estimations, since they are key factors in increasing the battery lifetime. Li et al. [21] review recent advancements in Big Data analytics to allow for data-driven battery health estimation. More specifically, they classify them in terms of feasibility and cost-effectiveness, and discuss their advantages and limitations. Liu et al. [22] go one step further and propose a machine learning-enabled system that is based on Gaussian process regression (GPR) to predict lithium-ion batteries aging. Finally, other approaches instead explore advanced fault diagnosis techniques, since battery faults can potentially cause performance degradation [23].
As previously shown, in general, most of the studies that deal with EVs have focused on: (i) the impact of EV charging in the electric demand, (ii) the use of renewable energy sources in the charging process, and (iii) the proposal of new methods for optimizing the charge of electric vehicles, including grid solutions. However, in this paper, we present the current situation of the market of electric vehicles, the main characteristics of the batteries, their technologies, and charging processes.
In particular, besides carrying out a comparison between the different standards, we display the different charging methods that are defined by these standards, and the connectors used by each of them. Finally, we also discuss the challenges that EVs have to face, and the research lines that we consider are left to explore yet.