Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

DC smart grids for production halls

02.06.2020

Most production plants today are still powered by alternating current. In the long term, however, research teams from the Fraunhofer Institutes for Manufacturing Engineering and Automation IPA and Integrated Systems and Device Technology IISB would like to see industrial manufacturing shift to operating with direct current. In the collaborative research project DC-INDUSTRIE 2, these teams have joined forces with more than 30 partners to develop new power supply systems for industry. The idea is to link all of a factory’s electrical systems to an intelligent DC grid (Direct Current) so as to make electrical supply more energy-efficient, stable and flexible.

Ever since the end of the 19th century, alternating current has been the standard means of power transmission and distribution. In Germany, for example, AC (Alternating Current) is what comes out of the power socket.


The DC Laboratory at Fraunhofer IPA tests components for converting production plants to direct current.

© Fraunhofer IPA/Rainer Bez

As far as industry is concerned, however, Fraunhofer researchers would now like to change this: “There’s a lot of good reasons why industry should change from alternating to direct current,” says Timm Kuhlmann, research associate at Fraunhofer IPA in Stuttgart. Kuhlmann and his project partners would like to bring about a paradigm shift in industrial power supply and, in the long term, convert entire factory halls from AC to DC.

“We’re already surrounded by DC devices,” he explains. “Computers, smartphones and LEDs all operate with DC and therefore need an adapter to convert AC power from the grid.” Yet on the supply front, the situation is also changing.

Whereas conventional power plants, such as coal-fired and nuclear, produce alternating current, locally installed and renewable energy resources such as photovoltaic plants – or, for that matter, electrochemical energy storage systems – only ever supply direct current.

Energy-saving alternatives to supply production machinery

In the DC-INDUSTRIE 2 project, researchers from Fraunhofer IPA and Fraunhofer IISB have teamed up with over 30 partners to develop and trial a concept for an intelligent, economic and efficient DC supply system for a production hall. The project is being funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) and is scheduled to run until the end of 2022.

The forerunner project, DC-INDUSTRIE, already gave reasons for optimism. Here, the partners were able to demonstrate the feasibility of local power flow control for a DC supply grid in a factory. Moreover, the shift from AC to DC voltage was shown to boost efficiency by between 5 and 10 percent – largely because with a DC network it is much easier to make use of regenerative braking, recuperation energy from variable-speed drives.

In all, four test systems equipped with DC components from various manufacturers underwent trials. Now that this concept has been shown to work for a group of machinery, the task is to implement it for an entire production hall. “In the follow-up project, DC-INDUSTRIE 2, we hope to increase energy efficiency even further and to cut CO2 emissions,” Kuhlmann explains.

“At the same time, we want to make the system more flexible so that it can accommodate an increasing use of climate-neutral technology. Having a local DC grid in the factory makes it easier to balance out any fluctuations in power supply resulting from weather-related variations in the amount of electricity generated by renewable energy sources and therefore increasingly common grid fluctuations.”

Moreover, most of the drives in production machinery are variable-speed motors. These are all equipped with frequency converters, which run on direct current. Therefore, in order to supply an electric motor with a variable voltage and frequency, the AC supply voltage must first be rectified.

By directly supplying the frequency converter with direct current, this conversion step is eliminated, thereby avoiding energy conversion losses and also facilitating simple recuperation of braking energy. Similarly, the rectification process subjects the AC network to a high harmonic load, which in turn necessitates the use of elaborate and costly filtering measures in order to ensure normative voltage quality. With a DC network, such measures are no longer required.

A DC smart grid ensures efficient energy supply

A further advantage here is that the load distribution between energy storage systems, grid feed and renewable sources of energy is managed locally on the basis of grid voltage as an indicator. “The big benefit of using direct current in production is that you can connect up all the factory’s electrical systems to one DC smart grid,” says Kuhlmann.

“This means you can improve the quality and availability of the power supply in your very own factory and thereby increase the reliability of production.” In the DC-INDUSTRIE 2 project, Kuhlmann and his team are responsible for the analysis of company requirements, the conversion process and network management.

Fellow researchers at Fraunhofer IISB are responsible for the equipment required for the conversion to DC. This includes supplying DC converters and protective equipment, inspecting the network for small-signal/large-signal stability, and local management of interconnected transformer systems.

“We’re establishing microgrid topologies – i.e., control clusters – which enable us to balance and coordinate energy storage, generation and consumption on the local factory level,” says Kuhlmann. “These can also be operated automatically.”

The new grid structure has one or a number of interfaces to the AC distribution grid. This provides production machinery with direct voltage via active or passive rectifiers. Every item of electrical equipment – e.g., variable-frequency drives, lighting, and process technology – is directly supplied with direct current and connected to a shared direct-voltage grid operating within a voltage band of ±10 percent of a nominal rating of 650 volts.

This enables a direct energy swap between the various drives that serve, for example, to accelerate or decelerate robots and machine tool spindles. Components such as brake resistors, which burn up surplus energy, are no longer required. It is the further development of power semiconductor devices that has enabled the creation of these new grid structures.

This is because the availability of these new power devices has substantially reduced the high cost otherwise required to cover DC switching components. “We also achieve energy savings of between 5 and 10 percent simply by using direct current,” Kuhlmann explains.

Further trials are already underway in test halls and at Factory 56, a production facility operated by project partner Daimler in Sindelfingen, Stuttgart. The Daimler plant is equipped with active infeed converters – active bidirectional rectifiers – that are connected directly to the grid and supply some items of plant machinery with direct current.

“Bidirectional means you can also supply the external AC grid with power, as a service, whenever you have excess generating capacity, so it’s not a one-way street,” says Kuhlmann. “And this in turn means that normal consumers also benefit from the transition to a new energy economy in the field of Industrie 4.0.”

Weitere Informationen:

https://www.fraunhofer.de/en/press/research-news/2020/june/dc-smart-grids-for-pr...

Joerg-Dieter Walz | Fraunhofer Forschung Kompakt

More articles from Power and Electrical Engineering:

nachricht Understanding the love-hate relationship of halide perovskites with the sun
13.07.2020 | Eindhoven University of Technology

nachricht Wanted: The best Storage Battery
13.07.2020 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron cryo-microscopy: Using inexpensive technology to produce high-resolution images

Biochemists at Martin Luther University Halle-Wittenberg (MLU) have used a standard electron cryo-microscope to achieve surprisingly good images that are on par with those taken by far more sophisticated equipment. They have succeeded in determining the structure of ferritin almost at the atomic level. Their results were published in the journal "PLOS ONE".

Electron cryo-microscopy has become increasingly important in recent years, especially in shedding light on protein structures. The developers of the new...

Im Focus: The spin state story: Observation of the quantum spin liquid state in novel material

New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices

Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...

Im Focus: Excitation of robust materials

Kiel physics team observed extremely fast electronic changes in real time in a special material class

In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...

Im Focus: Electrons in the fast lane

Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.

Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....

Im Focus: The lightest electromagnetic shielding material in the world

Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

International conference QuApps shows status quo of quantum technology

02.07.2020 | Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

 
Latest News

Shedding light on the brown color of algae

14.07.2020 | Life Sciences

Color barcode becomes ISO standard

14.07.2020 | Information Technology

New substance library to accelerate the search for active compounds

14.07.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>