EV charging evolution, the technology that’s coming

Technologies to make charging process easier and faster and to improve energy management, production and storage will be very important in the following years

EV charging is a sector in constant evolution and there are constantly new technologies in development. Some of the technologies being developed now are:

• Dynamic Load Management
• Integration between EV charging and existing payment systems
• OCPP 2.0: more security, more control, more information
• ISO 15118: EV identification through the power line
• Roaming 4.0: interoperability for EV charging
• Ultraquick charge in DC
• V2G and V2H: EV returns power from its battery to the grid
• Energy storage: in batteries inside and outside the EV
• Wireless load: magnetic induction charging

In this article we are going to analyse some of these technologies in detail.

ISO 15118: EV identification through the power line

This system simplifies the EV charging process through a complete elimination of RFID cards or mobile apps. The only required action to start the charge is to connect the charging cable to the vehicle. It’s based on international standard ISO 15118, that regulates automatic and safe data exchange between the vehicle and the charging infrastructure (energizes the charging stations through a digital certificate in the vehicle). ISO standard 15118 allows also other features, such as a future connection V2G (vehicle to grid), complying with safety requirements for the future charging infrastructure. Once the vehicle is connected to the charging station, driver’s authorized data is encrypted, transmitted and synchronized.

Ultraquick charge in DC

The implementation of quick charging in Europe began in 2010 with Japanese standard CHAdeMO. It consisted in a direct current (DC) to charge EV batteries quickly. The maximum power was 50kWcc, the maximum voltage was 500Vcc and the maximum current 125Acc. At that moment more popular EV batteries were: 16kWh (Mitsubishi iMiev) and 24kWh (Nissan Leaf). It allows to inject 12,5kWh in 15 minutes and 258kWh in 30 minutes. This was enough for the power of the existing batteries at that time.

Tesla appeared right after this with a massive deployment of its “super charger”, a system valid only for its own models which reached a load power if 120kWcc.

In 2012 CCS alliance was created and this was the beginning of DC quick charge in the EU and the USA. CCS standard was born with the clear idea of allowing more energy than CHAdeMO (reaching 350kW in the future). With CCS standard ultraquick charging concept was born and it consisted of increasing charging current and/or charging voltage to get a higher power (kW).

It is estimated that only 10-20% of E Vs will charge with ultraquick charge (DC), most of the charging will take place at home and at workplace using AC chargers. Nevertheless, it is crucial that electromobility achieves a technology with the following features:

• Simultaneous DC-DC charge (2 or more x DC).
• Dynamic power control DC-DC.
• Predefined power limitation in case of a grid restriction
• “Connect & Go” functionality: users do not have to wait until the previous user completes its session to start the charge in another plug.
•  Service mode function: the equipment should be able to keep working when a component not vital for the charge is not working properly.
• The most interesting option for quick charging stations is the combination between an AC/CC dynamic rectifier and a DC/DC converter.

V2G and V2H: EV returns power from its battery to the grid

Vehicle-to-Grid (V2G) is a system in which plug-in EVs (battery electric vehicles BEV, plug-in hybrids PHEV, Fuel Cell Electric Vehicle FCEV) communicate with the grid to sell services in response to the variation of power demand by giving power to the grid or through the limitation of its charging rate.

Vehicle-to-Home (V2H) is like V2G but instead of sending the storage energy to the grid, this energy is consumed only in the local installation.

In short, a V2G equipment can send power in two directions: from the VE to the grid, and from the grid to the EV. The stored energy comes from EV batteries or from backup batteries installed outside the EV. These batteries can be charge directly using DC (solar energy).

The following applications are foreseen:

The technology must evolve to obtain these V2G systems with an adequate power electronics at a reasonable cost.

Energy Storage in batteries inside and outside the VE

Energy storage is an opportunity to improve some aspects related to the load:

• The EV will charge faster when available local energy is low.
• The grid: avoid its collapse due to an excessive demand and reduce the demand curve.

The power to charge an EV can also come from renewable energy produced locally (for example through a domestic photovoltaic roof) or generated by larger hubs (for example, through solar or wind farms).

If we look at how power is produced, we’ll see how some countries such as Germany, United Kingdom, Netherlands, Denmark or Spain wind power is important (in Germany it represents a 35% of the annual power). This figure could be even more important, but wind farms are used for a rapid regulation of generation variations versus demand (a wind generation can be disconnected from the grid in seconds). It happens, then, that wind turbines do not produce energy whenever there is wind. Such a waste of natural resources is not logical when the infrastructure is available. A macro energetic vision shows that all this unused wind power could be used to charge EVs.

The energy produced by the sun or the wind can be stored increasing this way the available power in locations where this increase would be very expensive or non-feasible. This can be done by a small storage (15kWh batteries), a medium storage (100kWh) or a large storage (1MWh).

Another storage possibility is the EV itself. The energy stored inside it could be used to help the grid together with V2H or V2G as we’ve discussed before.

The most important technological challenges are, without any doubt, in batteries. The new battery generation should provide a better ratio between kWh versus dimensions, weight and cost.

Wireless load: magnetic induction charging

Wireless charging is defined as the transfer of electrical energy through magnetic waves between the grid and the EV to charge its battery.

This technology consists of bringing part of the DC charger on board of the car. The car receives AC power and rectifies it to charge its battery.

Article by;

Joan HInojo
Electrical Engineer
Circontrol’s General Manager