Wide availability of public electric vehicle charging stations (EVCS) would alleviate the range anxiety of potential consumers, thus accelerating electric vehicle (EV) growth. According to estimates, government investments in the installation of public EVCS facilitates four times higher adoption of EVs than subsidising their demand.
EVCS technologies have several sub-components, including grid type, charging level, battery swapping ability and type of charging method. The extent and efficiency of these technological developments will shape the trajectory of global EV adoption.
Types of chargers
EV chargers can broadly be classified into wired/conductive chargers and non-conductive/wireless chargers. Wired chargers mostly use cables, while wireless chargers utilise inductive charging. Needless to say, wireless charging is at a nascent stage and is expected to take off in the coming decade, depending on viability.
Meanwhile, conductive charging has three variants – cable-based charging, battery swapping and pantograph-based charging. Battery swapping involves replacing exhausted batteries at an EVCS with charged ones. Pantograph chargers are useful for heavy duty, long distance vehicles such as e-trucks and e-buses, as they can supply a large amount of current for fast charging. Cable-based charging accounts for the majority of charging systems and is likely to continue growing rapidly, as EVCSs based on this technology have been proven to be commercially viable and technologically feasible.
Broadly speaking, EVCSs are classified on the basis of the charging current. AC chargers are a simple and affordable way of charging EVs. However, these chargers take six to eight hours to fully charge a vehicle, making them more suitable for deployment in households than in commercial settings. On the other hand, DC chargers are high capacity chargers that charge EVs more rapidly, given that they bypass the AC-DC conversion process.
Cable-based charging stations are further classified on the basis of their charging speed, with different standards in different countries. These include:
- Type-2 chargers, which are based on both AC and DC. These chargers operate on single-phase or three-phase input power systems, depending on the charger rating. They can provide a current of 3.3 kW to 43 kW, with around 400 Volts of electricity. They are ideally deployed in households, as they are affordable and very modular in design.
- GB/T chargers, which are DC chargers with a current output of 10-15 kW for low power EVs and 27-250 kW of output for heavy duty vehicles. These chargers do not utilise control protocols based on power line communications, rendering it harder for an EVCS to incorporate internet of things in payment mechanisms, or automation.
- Charge de Move (CHAdeMO) chargers, which are DC chargers that can provide currents of up to 62.5 kW. However, newer EVs are switching to combined charging systems (CCSs) because of their modularity.
- CCSs utilise DC charging, allowing them to provide power of up to 350 kW and voltage of 200-1,000 V. These are used in charging stations and commercial areas, as well as to charge buses and heavy duty vehicles due to their rapid charging speed.
- An alternative battery recharging method that is receiving global attention is battery swapping, whereby a depleted EV battery is removed from the vehicle and replaced with a fully charged one. Battery swapping allows drivers to replace depleted packs quickly with fully charged ones, rather than plugging the vehicle into a charger.
Role of smart chargers
EVCS based on traditional grid systems that are unidirectional by nature procure electricity from the grid to charge EVs. Meanwhile, EVCSs based on bidirectional grids have specific captive capacities (such as rooftop solar) for charging EVs during peak hours, while exporting surplus electricity back to the grid. In off-peak hours, these EVCSs procure electricity from the grid.
Currently, most EVCSs operate on traditional grids. However, such uncoordinated charging with sudden peaks and troughs in demand can potentially cause fluctuations, leading to outages and deterioration of the grid. Hence, in the upcoming years, the growth of EVCS will be accompanied by the growth of smart grids and captive sources of power. It makes more business sense for an EVCS to have captive capacity, as this reduces the operational overheads related to power procurement.
In a coordinated charging system with a reliable communication network, the whole operation is controlled directly by a third-party controller or aggregator. The aggregators and controllers are responsible for achieving objectives such as cost minimisation, power loss minimisation and others. In this case, EV users, and private and public charging station operators, are involved in charging management by selling or buying electric power.
Smart charging entails the use of smart energy management software, which determines the best time to charge and the best energy source to use for charging vehicles. Such software uses advanced algorithms and demand-side response to provide near-real-time load balancing that dynamically distributes energy to and from the grid, helping prevent the demand from exceeding the grid capacity during peak usage times. In essence, smart energy management adds another dimension to EV smart charging. It optimises energy consumption based on grid constraints, energy pricing, renewable energy availability, locally stored energy, preconfigured EV owner preferences and driver needs. Smart energy management optimises the charging infrastructure by efficiently delivering the available power to EVs, and shifting charging loads across energy sources to safely deliver electricity without interfering with the power needs of buildings, homes or other power consumers.
Another radical smart charging technology is vehicle-to-grid technology, which proposes pushing electricity from an EV battery to the grid during off-peak hours. This can also create an extra power source when weather-dependent renewable energy sources are not available. For example, a home that uses solar power cannot generate electricity at night, but an EV could provide a secondary source of power if needed. This technology could potentially elevate the business proposition and commercial viability of EVs and EVCSs.
Issues and challenges
High EV integration into the distribution grid will create challenges and concerns such as increased peak demand, harmonic distortions and frequency; and unpredictable, dynamic behaviour. Moreover, EVs require a considerable amount of electric energy from the power grid, which is mostly delivered by the grid from fossil fuel-based power plants. Thus, EVs may contribute to carbon emissions, depending on the source of energy used to charge the battery. There may be substantial problems springing from differing charging standards. Hence, it is increasingly essential that charging stations, chargers and other equipment, batteries, AC-DC power converters, etc., adopt uniform standards. Delays in land acquisition and reception of regulatory permits may in turn delay the deployment and installation of EVCSs, thus lowering the adoption of EVs.
EVs utilise IoT to relay sensitive data such as charging levels and travel routes to aggregators and EVCS companies, so that they may reserve parking slots in advance. However, such communications require confidentiality.
The way forward
The growth of EVs is directly tied to increasing the number of EVCSs, as demonstrated by several studies. It is thus important to account for the type of charger used, the nature of an EVCSs’ connection with the grid (bidirectional or unidirectional). These factors will determine the success of EVCS and, by extension, the future trajectory of EVs.