Table 2 Protocols for vehicle grid integration (commonly used and under development) and their assessment on properties of openness, interoperability, maturity and market adoption

IEC 61851 (Front-end protocol)

Cross-cutting standard across charging topologies, safety and communication (Martinenas et al. 2017).

The International Electrotechnical Commission (IEC) is an international standards organisation that prepares and publishes international standards for all Electrotechnology.

High

High

High

Can be tested and certified at different test laboratories (Elaad 2016).

High

Every EV in Europe supports the standard.

Advanced data exchange (e.g. meter readings, tariff information, etc.) necessary for advanced smart charging strategies is not possible.

ISO 15118 (Front-end protocol)

Communication protocol allowing more advanced form of communication compared to IEC 61851 between EV and charging station. For example, ISO 15118 defines requirements for charging load management; metering and billing.

ISO 15118 includes wired (AC and DC) and wireless charging applications.

One main feature of ISO 15118 is using digital certificates to secure the communication. The protocol also allows automated authentication & authorization (ISO 2013; Elaad NL 2018; Mültin 2019a).

ISO 15118 is part of the Combined Charging System (CCS), which is a set of hardware and software standards for charging systems.

ISO, the International Organization for Standardisation, is an international standard-setting body composed of representatives from various national standards organisations.

High

High

Medium

No official certification is available yet.

Regular testing events (TS Testing Symposium 2019).

Open source implementation (Mültin 2019b).

Low

Research and development (R&D) implementations of smart charging and V2G functionality(Elaad 2019).

Received support from several major automotive companies (CharIN e.V. 2017).

Upcoming edition (ISO 15118-20) is likely to be published end 2020 and will define use cases for bidirectional power transfer. First market implementations expected in 2023/2024 (Mültin 2019a).

State of Charge information will remain optional but the car would communicate the energy amount necessary to fully charge (Mültin 2019a).

CHAdeMO (Front-end protocol)

Communication protocol maintained and developed by the CHAdeMO organisation. The protocol is used for DC charging and the v2.0 specification includes the possibility for bidirectional power transfer and the exchange of battery’s state of charge (CHAdeMO 2019a).

The protocol is available to paying members who can gain access to the source code needed to implement it but are not able to update/branch the code.

The CHAdeMO protocol adheres to IEC 61851–23 (DC EV charging station) and IEC 61851–24 (Digital communication between a DC EV charging station and an EV for control of DC charging) (Martinenas et al. 2017). But these do not provide sufficient detail to fully implement the protocol.

In 2019, CHAdeMO announced that it is co-developing the next generation ultra-fast EV charging standard called ChaoJi in collaboration with China Electricity Council (CEC) who is behind GB/T standard for EV charging in China (CHAdeMO 2019b)

Medium

Medium

High

High

R&D and market implementation of CHAdeMO in V2G projects in Japan, UK, Denmark(Christensen 2018; UK Government 2018; Andersen et al. 2019; Octopus EV 2019; OVO Energy 2019).

CHAdeMO lacks secure communication features (Martinenas et al. 2017).

Open Charge Point Protocol (OCPP)(back-end Protocol; EV-domain specific)

De-facto (as opposed to de-jure) standard for communications between an EV charge point and a central system operator (e.g. CPO).

Some of the features of include support for external smart charging control signals. OCPP 2.0 implements enhanced security features. OCPP is available from and maintained by the Open Charge Alliance (OCA), which is not an accredited standards organisation (Open Charge Alliance 2019a; de Leeuw 2019).

Medium/high

Medium because OCA is not accredited.

High

High

Testing tool and certification of OCPP 1.6 is possible (Open Charge Alliance 2019b).

High

Market implementations by many vendors in Europe and parts of the United States.

Lacks bidirectional power flow commands. On-going work to include it in upcoming versions of OCPP (de Leeuw 2019).

IEC 63110(back-end Protocol; EV-domain specific)

Protocol for management of EV Charging stations. It standardises the communication between charging station and a charging management system (IEC-TC69 2018; Bertrand 2020).

High

High

Low

Low

At an early stage of development. Might become the de-jure successor of OCPP.

Open ADR(back-end protocol, generic)

Open Automated Demand Response (ADR) allows demand response service providers to communicate signals directly to existing customers using a common language and existing communications such as the Internet. For example, communication between a third party operator and an EMS.

Open ADR allows manufacturer-independent and secure communication and it is available from and maintained by The Open ADR Alliance (Ghatikar and Bienert 2011; OpenADR Alliance 2019; Bienert 2019).

High

The IEC approved the Open ADR 2.0b Specification as a full IEC standard, to be known as IEC 62746–10-1 ED1(IEC 2019).

Medium

Generic description making it less interoperable

High

The OpenADR Alliance has partnered with several international test houses required for certification.

Medium/High

Increasingly being used on projects with EVs in R&D and market implementations. Open ADR mostly used in combination with OCPP (Ghatikar 2016; Hoekstra et al. 2016; Aylott 2019; Klein Koerkamp 2019).

Additional work required for alignment with complementary protocols (e.g. Open ADR- OCPP)

Program Guides required for EV use cases (this links to the protocol being generic).

IEEE 2030.5 (IEEE adoption of Smart Energy Profile SEP2) (Front-end; Back-end protocol, generic)

IP-based protocol with documentation available describing how it can be applied to EV smart charging (Elaad 2016; IEEE Standards Association 2018; Lum 2020).

Used for the communication between EV and EVSE (i.e. front-end) in some R&D projects in the US (Chhaya 2015).

Allow manufacturer-independent, secure communication between a third party operator and customer installed equipment such as EMSs, solar systems and EV charge points (IEEE Standards Association 2018).

The Institute of Electrical and Electronics Engineers (IEEE) is a professional association for electronic engineering and electrical engineering.

High

Medium

Generic description making it less interoperable

High

Test tools available and used in a conformance test program by nationally recognized testing laboratories in the US and Korea (Elaad 2016; International ZEV Alliance et al. 2019).

Low

Limited use with EVs outside R&D implementations.

Program Guides required for EV use cases.

If used as a front-end protocol, it lacks additional use cases such as automated authorisation &authentication.

EEBUS(Back-end Protocol; generic)

Allow manufacturer-independent, secure communication between a third party operator (e.g. DSO) and customer installed equipment such as EMSs, solar systems and EV charge points (EEBUS Initiative e.V. 2019)

EEBus is available and developed by the EEBus Initiative e.V.

Medium/high

The EEBus Initiative e.V. is not an accredited organisation, but “the working groups ensure that only what is necessary is standardized.”

Not able to assess.

Low

Low

Limited use with EVs outside R&D implementations. E.g. Global Grid Integration Project (Bienert 2019).

Program Guides required for EV use cases.

Several companies have developed their proprietary back-end communication protocols (for example, by extending on OCPP) (Christensen 2018; Astorg et al. 2019; Indra 2019; Octopus EV 2019; Nissan Energy 2019).

Low

Low

Low

Low

Diverse and proprietary protocols would lead to disjointed charging control strategies by managing different subsets of BEVs separately. This could risk losing or vastly under-utilising charging demand flexibility.