EV-ROAMING BASICS 102: Know about different roaming protocols – OCPI, OICP, OCHP & eMIP

Currently, there are several roaming protocols in use in the European Union (EU), of which the Open Clearing House Protocol (OCHP), the Open InterCharge Protocol (OICP), the eMobility Inter-Operation Protocol (eMIP) and the Open Charge Point Interface (OPCI) are the most widely adopted.

The roaming protocols differ in functionality, adopters, geographical area usage, ownership and organization structure. Furthermore, there are several roaming protocols developed and used internally by specific countries (e.g. Portugal) or companies (e.g. Plugsurfing), and furthermore, the International standards setting body - IEC has also started developing a standard for EV roaming under IEC 63119.

This article may share a quick overview of each of these protocols.

What is Open Clearing House Protocol (OCHP):

OCHP is managed and developed by Smartlab Innovationsgesellschaft GmbH and ElaadNL, which are organizations founded by German and Dutch utilities respectively. OCHP is used by the roaming hub e-clearing.net which is operated by Smartlab and owned by Smartlab and ElaadNL. As a not-for-profit platform, the main interest of e-clearing.net is to develop the e-mobility market.

What is OCHPDirect ?

OCHP can be used for communication via a roaming hub, and there is also an extension named OCHPDirect which can be used for peer-to-peer connectivity.

How does OCHP work ?

OCHP is based on the SOAP computer protocol. It mainly relies on asynchronous communication (opposed to real-time communications).

It creates, for instance ‘white lists’ of users which are allowed to authenticate, instead of having an actual real-time authentication of users using the information present at the MSP. This choice seems to reflect a design strategy, where a single point of failure (SPOF) is avoided: should the roaming hub ever go down, charge sessions still work. e-clearing.net does not store transaction data.

How to download OCHP protocol ?

OCHP are made available for free and do not require registration. The latest release is Open Clearing House Protocol v1.4 . Anyone can download from the link: http://www.ochp.eu/downloads/

What is Open InterCharge Protocol (OICP)

OICP was created by Hubject in 2013. Hubject’s stakeholders are the BMW Group, Daimler, Bosch, EnBW, Enel X, Siemens, Volkswagen, and Innogy – mostly around German OEMs. OICP can be used to communicate within Hubject’s platform, enabling communication between MSPs and CPOs.

Unlike the other roaming platforms, Hubject does not only offer a technical connection between parties but also a contractual framework for roaming. The protocol consists of two parts: the MSP and the CPO each use a part of the protocol especially designed for them. According to Hubject, it is the most widely implemented communication standard between European EMSP and CPO systems.

How does OICP work?

OICP is based on SOAP (similar to OCHP explained above) and uses an objectbased approach. It is a real-time protocol, although asynchronous operation is also possible. Hubject does have a database as back-up, but they are not actively supporting downloads from their database to the charging station. Hubject’s platform keeps track of the transaction data.

How to download OICP protocol ?

OICP is publicly available at no cost and without registration. Here are the links to the OICP specifications download pages.

What is eMobility Inter-Operation Protocol (eMIP)

The eMIP specification is designed and managed by GIREVE. The core business of GIREVE is to offer a roaming platform for MSPs and CPOs. GIREVE was founded by EDF, Renault, CNR and Caisse des Dépôts (so, mostly French companies) and its main objective is to provide open access to vehicle charging stations.

The eMIP protocol enables roaming via a data clearing house, provide access to charging point databases, and provide smart charging features.

How does eMIP work?

eMIP is based on SOAP (like both previous protocols we described). It is designed as a real-time protocol and advised to be used as such, but it does also support asynchronous operations. eMIP has an architecture that makes the protocol quite flexible. 

New types of data messages, but for example also new identification methods, can easily be added, by means of definition tables. This means that not even a standard update is required to do so. So, in a sense, the standard is less ‘hard-wired’, and the developers have not yet felt a need to update the current version, which is from 2015, as explained above.

How to download OICP protocol ?

eMIP is available for free, but registration is required. GIREVE also offers certification services, and such certification is in fact required to connect to GIREVE’s platform.

The most recent version, eMIP 0.7.4, was released in 2015. This version is also the first official release of the protocol, can be downloaded from https://www.gireve.com/en/download

What is Open Charge Point Interface (OCPI)

The first OCPI protocol was originally developed by eViolin, a collaboration of several Dutch CPOs and EMSPs, in cooperation with ElaadNL, a collaboration of all major Dutch grid operators. OCPI is currently managed by the Netherlands Knowledge Platform for Public Charging Infrastructure (NKL), which is a collaboration of trade organizations, governmental bodies and research institutes.

OCPI supports roaming hub operation, but NKL itself is not a roaming hub. Recently, an interim Advisory Board was established to govern OCPI, and in the future, an elected, final Advisory Board will govern the protocol. Any party can join its OCPI development community and contribute to its development via the online developer’s platform Slack.

How does OCPI work ?

OCPI is based on JSON/rest and is real-time protocol (in contrast to previous three protocols we discussed, which were all based on SOAP). It supports synchronous as well as asynchronous operations.

How to download OCPI Specifications ?

OCPI is publicly available at no cost and without registration. The first official version was released in 2015, and the most recent version (v2.2) was released on Oct-2019, can be downloaded from official OCPI link here.

OCPI has a modular set-up, meaning that parties can choose the modules they incorporate. It also includes a version check, which is crucial for peer-to-peer connections as there is no central actor enforcing updates or stopping to support older protocols versions.

What is the best EV roaming standard: OCPI vs OICP vs OHCP vs eMIP

All the above mentioned four the protocols are open and share many basic functionalities. The differences are mostly at their governance structure and supported business models. 

For example:
➤ On protocol governance: OCPI development is community-based, and where the managing organization is not at the same time operating the associated roaming hub. This is different from other protocols such as OICP, OHCP and eMIP – which are developed and managed by a roaming hub operator.

➤ On the supported business models: OCHP and OCPI support roaming both via hub as well as peer-to-peer. eMIP is also kind of supporting both the business models (in practice is mainly used to connect to GIREVE’s hub). OICP only supports roaming via Hubject’s platform, and this protocol is thus linked to a single business model by a specific party. 

Overall: All the roaming protocols fulfill the current minimal market demands, but the market is still developing and new functionalities such as German Eichrecht, Plug&Charge are yet to be incorporated in any of the protocols. So it may be too early to look for the best protocol to coverage to.

Further read: A detailed comparative analysis on all these EV protocols are done by the Eindhoven University of Technology (TU/e) in the Netherlands and created this report, as part of the evRoaming4EU project. Anyone who’s interested to know more about these protocols should read it. Highly recommended!

This report not only presents a comparison of the major existing EV roaming protocols in Europe, but also offers detailed insights on how to achieve interoperability from a standardization perspective, through a combination of desk research and stakeholder interviews.