After seven years, the DC-Industry2 research project came to an end at the end of March. What are the concrete results?

Dr. Hartwig Stammberger, Chair ODCA and Eaton Industries. © ZVEI/Eaton

Dr. Hartwig Stammberger: We have brought DC "into the factory" in nine model plants and tested it very successfully. Together with the project's 39 partner companies and institutes, we were able to show that the entire braking energy of moving masses such as robots is used instead of being literally burned up in braking resistors. In addition, the peak power that has to be drawn from the supply grid has been reduced by around 40 %, depending on the type of system. This leads to lower energy costs, which are linked to the peak power, and to lower investment costs, for example for transformers and energy distribution in the factory.

Furthermore, the results show that by supplying DC voltage, only around 50% of the copper in the cables is required and at the same time the power loss in the cables is reduced by around 45%, as no reactive power has to be transmitted. And the whole thing can be used directly, the first systems are already running safely and stably!

One aspect of DC Industry was to create synergies with electromobility. What advantage does the industry see in this and how satisfied are you with the results in this context?

Stammberger: One part of the DC industry is the connection of battery storage systems to the local DC grid in the factory. These storage systems can be stand-alone batteries - such as those used in electric vehicles - or batteries in electric vehicles that are connected via bidirectional charging. This balances out load peaks. Resistance spot welding, for example, requires high power for short periods - this is now provided by the storage system and no longer by the AC supply grid.

The Open Direct Current Alliance, ODCA for short, emerged from the research projects. Its aim is to disseminate the findings and solutions of DC technology internationally. How exactly are you going about this?

Dr. Jan Stefan Michels, Vice-Chair ODCA and Weidmüller. © ZVEI/Weidmüller

Dr. Jan Stefan Michels: Now that we have created the technological foundations for industrial DC applications in our DC Industry project and validated them in the model systems just mentioned, we want to transfer them to a wide range of series systems in order to make broad use of the potential of DC technology. That is why we are already working intensively with the more than 40 members of the ODCA in three working groups on the topics of "Open Technology", "Use Cases" and "Communication".

Even though we have focused on industrial applications so far, DC technology is of course also suitable for other applications beyond actual production. We are particularly concerned with making it easy for users, planners and installers to take advantage of the benefits of DC voltage in DC microgrids.

What influence do the current climate discussions and the trend towards greater sustainability have on your project?

Michels: We see this as confirmation of our approach. After all, one of the drivers of DC technology is the direct connection of photovoltaics to the production process. Photovoltaics generate direct current, which can be fed directly into the drives in the factory using the DC industry approach. For the most part, these drives are operated with frequency converters that already have a DC link. The local DC grid in the factory eliminates many conversion stages from DC to AC and back. This requires fewer resources and saves losses in the converters that are not required.

Do you see comparable projects for office buildings in the future, for example for the operation of server systems and the like?

Michels: Yes, absolutely - although the DC industry concept was developed with a focus on production facilities, it is transferable to many other sectors. That's exactly what the ODCA is all about: we want to consistently use the potential of DC technology to achieve climate neutrality and raise energy efficiency to a new level. That is why we have also set ourselves the goal with the ODCA of preparing and supporting the transfer to new areas of application. If the technology needs to be developed further or standards need to be defined, we also want to tackle this together with our partners in the ODCA.