# Review of Renewable Energy-Based Charging Infrastructure for Electric Vehicles
## 1 Introduction  
The remarkable increase in the use of electric vehicles (EVs) has resulted in a massive rise in demand for electric energy across the globe. The global electric vehicle market has grown significantly. The number of EVs on the road in 2010 was a few hundred; this number rose to approximately three million in 2017 and approximately six million in early 2019 [1]. Electric vehicles are exciting alternatives to conventional vehicles (CVs). With zero carbon emissions during operation, the EV has the ability to reduce total climate effect and pollutant emissions significantly. As fossil fuels are phased out to a greater degree, the need for biofuels would also be reduced. Electric motors have an efficiency of 80-95% [2], making them a more appealing choice than CVs, which have an efficiency of less than 20% [3]. EVs are also a critical element of modern transportation, because they incorporate a variety of new industrial technologies (e.g., an electric motor, a battery, and a charging facility). However, the adoption of electric vehicles is not going as well as predicted. The limited range and slow charging time of EVs are widely regarded as the most serious barriers to promotion [4, 5]. Although electric vehicles have a high purchase price, they have low maintenance costs and use substantially less energy than conventional vehicles. According to the rapid increase of EV demand and EV charging, many research centers, and energy supplying companies began thinking seriously about reducing the pressure on local electricity networks because of the increasing number of electric vehicle charging points. Renewable energy sources such as wind and solar are some of the most effective solutions to bridge this deficit faced by local electricity networks, potentially supporting the EV charging infrastructure [6]. After the announcement of the rapid development of the EV at the turn of the millennium, renewable energy-based charging infrastructure (RCI) research began with the effortof wind and solar charging infrastructure [7; 8; 9; 10; 11; 12]. It envisioned a charging facility that could match EV demand with renewables and direct current (DC) to improve shortcomings of conventional charging infrastructure. The traditional charging stations affect the grid's stability with issues such as harmonics, fluctuations, and voltage outages [8; 9; 12]. By contrast, the RCI has several advantages, such as high efficiency [13], low system cost [14], and simple arrangement [15; 16]. Besides, it requires less power conversion levels than those in alternating current (AC)-based facilities [17; 18]. The RCI can contribute significantly to reducing carbon emissions and expanding the energy domain's penetration of renewable energy sources. Moreover, RCI has the potential to lower the cost of EV charging [19]. However, uncertainties of the renewable sources (e.g., seasonal variations in wind speed and sun irradiance and daily randomness in cloud coverage for solar panels) and load characteristics of EVs (e.g., battery capacity, number and types of EVs, stop time, charging start time, and the initial state of charge) are serious challenges in implementing the RCI [20]. Currently, there is an ongoing considerable research work on the aforementioned topics. At the same time, other researchers are working on various aspects of implementation and operation of RCI, such as optimal planning, controlling and sizing, pricing approaches, and examination of the key factors influencing the linking of EV load directly with the RCI. For instance, few studies reviewed EV charging infrastructure research; however, they considered general technical aspects and did not concentrate on renewable energy sources (e.g., [1; 21]). Another study reviewed the RCI studies but with the focus on the consumer preferences and interactions with EVs [22]. To our knowledge, no study has reviewed RCI studies extensively by discussing all related research areas. This study examines recent advances in RCI technology and the latest research progress in this critical field.