Series of Articles: Interoperability – Evaluating interoperability in practice
Integrating controllable loads into the energy system is one of the current topics in the energy industry. The smart charging of electric vehicles is crucial in this context and at the same time poses new challenges. Interoperability plays a central role in enabling smart charging with different components. This was investigated at the FfE as part of the unIT-e² research project.
The first part of this series defined the concept of interoperability, identified existing challenges, and analyzed the potential benefits of its implementation. This second part focuses on an in-depth examination of methods for measuring interoperability. Assessing interoperability is crucial for determining the level of cooperation and integration between different systems. This helps enhance the efficiency and effectiveness of the technologies in use and ensures seamless integration.
In the third and final part of this series of articles, we look at how hardware and software components can work together seamlessly to enable smart charging of electric vehicles at different locations.
This three-part series of articles focuses on the central questions surrounding the theoretical foundations, the aim and purpose of interoperability, methods for measuring interoperability, and the evaluation of interoperability in practice.
- Interoperability – What is it, what challenges, and what benefits can be expected?
- Measuring Interoperability
- Evaluating interoperability in practice
Interoperability: evaluating interoperability in practice
To make smart charging of electric vehicles practical, it must function at various locations using diverse hardware and software components. This requires that the relevant components interact with each other independently of their specific combination, thereby achieving interoperability. The feasibility of this aspect was investigated as part of the unIT-e² research project. Expert interviews were conducted, and a so-called plugfest was organized. The results of these investigations indicate that, in many cases, a certain level of interoperability between systems already exists. However, it also became clear that there is still room for optimization to ensure seamless interaction of the components and thus provide a positive user experience. Such findings are crucial for identifying technological gaps and developing targeted measures to improve interoperability in the field of smart charging.
As part of the unIT-e² research project, the interoperability of the developed systems was examined in greater detail. A mixed methods approach was chosen for this, with the level of interoperability being assessed according to the LCIM model described in part two of this series.
The applied methodology for assessing interoperability varied according to the stages of the Levels of Conceptual Interoperability Model (LCIM). To collect data for levels 1 to 3, relevant information was gathered from experts at ten companies using a questionnaire. The primary objective was to determine whether manufacturers used standardized reference models or protocols for communication at the interfaces of their products.
The investigation of levels 4 and 5 was conducted through a practical plugfest. During this plugfest, various manufacturers had the opportunity to test the interoperability of their components under controlled laboratory conditions. The tests were carried out according to a structured test plan, with additional room provided for free testing to enable a more comprehensive analysis. The focus was on three use cases: power limitation, smart charging, and meter values acquisition.
The assessment of interoperability was performed by testing the components established in the project clusters and exchanging individual components between different clusters. This approach helped identify specific interfaces where problems occurred. The results provided valuable insights into existing challenges and formed the basis for further optimization of interoperability in practice.
Plugfest results
The results of the tests during the Plugfest show that interoperability exists to a high degree but is not yet fully functional. Systems are interoperable in a combination established in the clusters. The exchange of vehicles between clusters also works and therefore corresponds to dynamic interoperability. However, if components behind the EVSE are exchanged, errors sometimes occur and in no case did the exchange of EVSE and (H)EMS work.
In this respect, pragmatic interoperability (LCIM level 4) is given for the entire chain of effects within the established framework. However, the systems are only adaptable to new situations to a limited extent and therefore do not fulfill the conditions of dynamic interoperability (LCIM level 5). Dynamic interoperability can only be said to exist at the interface between EV and EVSE. In practice, experts are hoping for an improvement through the establishment of ISO 15118-20 at the interface between EV and EVSE. The ISO 15118-2 used to date is not yet mature enough for widespread use.
In the future cooperation between the various manufacturers will be crucial for the complete interoperability of e-mobility. The existing standards must be further developed together. EEBUS, OCPP 1.6, and Modbus TCP are particularly important here, as they are highly relevant for interoperability in some cases but are not yet fully developed.
Details of the results can be found in the Plugfest reports.
