Car manufacturer saves energy with direct current

Cables and wires Car manufacturer saves energy with direct current

2024-03-22 From Lapp | Translated by AI 4 min Reading Time

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In our alternating current world, direct current in factories is still a rarity. However, DC supply systems are on the rise thanks to fewer voltage conversions. Lapp has equipped a test facility for body construction with direct current at a Bavarian car manufacturer.

Many robots are required for body construction at the BMW plant in Dingolfing. They are all powered by direct current, saving energy.(Image: Lapp) — Many robots are required for body construction at the BMW plant in Dingolfing. They are all powered by direct current, saving energy.
(Image: Lapp)

Stamping, welding, riveting, gluing: Body construction in the automotive industry is highly automated – and very energy-intensive. Robots, in particular, require a lot of energy. "In the future, this energy will probably be supplied more and more by direct current," predicts Alois Heimler, Strategic Marketing Manager Intralogistics & Automotive at Lapp. "The magic word is fewer voltage conversions." In the BMW Group plant in Dingolfing, Lapp, a provider of cable and connection technology, has equipped a facility with DC solutions.

Direct current network: Brake energy recovery saves energy

Machines and robots consume the majority of electricity in industrial plants, and therefore, they offer significant potential for savings. This is particularly effective in highly dynamic processes, such as those found in industrial robots. The production lines move on programmed paths to assemble the individual parts of a body into a vehicle, momentarily accelerating and then decelerating. This means a robot temporarily draws a lot of energy to initiate a motion or to convert it into kinetic energy. However, during deceleration or lowering operation, the kinetic energy is converted back into electrical energy. The drive is now in generator mode. This kinetic energy is usually not stored in alternating current (AC) systems and is lost as thermal energy. Brake resistors have been used so far to dissipate the excess energy.

Gallery

Close-up of the connection solutions of the DC test facility at the BMW plant in Dingolfing.(Image: Lapp)

The entire DC portfolio of Lapp is used in the BMW Group plant in Dingolfing.(Image: Lapp)

The DC test facility at the BMW Group plant in Dingolfing. It is part of the DC Industrie2 project, of which Lapp and BMW are members.(Image: Lapp)

Close-up of DC cables from Lapp.(Image: Lapp)

Gallery with 17 images

In a direct current (DC) network, things are different: "Here, the energy is fed into the DC link circuit, other DC consumers or energy storage. Thus, the energy released during braking processes can be sent back to the grid without significant conversion losses, centrally for all consumers," explains Alois Heimler about brake energy regeneration. This allows direct energy exchange between all drives, such as those found in robots.

Only one central energy conversion

Instead of many decentralized conversions from AC to DC, there is now only one central energy conversion that supplies all systems with direct current. A bonus point: If the electricity comes from renewable sources such as photovoltaics, it is already in the form of direct voltage, especially as consumers are increasingly designed for direct current. "DC is therefore a core element of the energy transition," Heimler is confident. The exact savings from switching to DC vary depending on the facility and its usage. However, results between 15 and 20 percent are realistic.

Direct current for the automotive industry

Lapp is the first manufacturer to develop a cable portfolio for various DC applications in the low-voltage range. These cables are used in body production in Dingolfing. Among them is the connection and control cable Ölflex DC 100. With its maximum voltage of 0.75 / 1.5 kV, it forms the basis for energy-efficient DC networks in industrial facilities. Also installed is the Ölflex DC Grid 100. As a DC power cable for direct current networks, it offers a flexible, fine-stranded design that can be used even in dry, damp, and wet environments, making it suitable for control systems, motors, and frequency converters.

The Ölflex DC Robot is used on the seventh axis of the robots in the facility. The cable's flexibility allows the robots to move precisely while remaining resistant to rotations and bends. Its compact design also saves space. Movable applications are essential for the production line. For this, Lapp offers the Ölflex DC Chain 800. The cable can be used in cable carriers with long travel paths or high accelerations. Its short wire stranding allows for the smallest bending radii. Its outer sheath, made of specially designed thermoplastic polymer, is chemically resistant and enhanced oil-resistant.

Less copper is required with direct current

While alternating current (AC) requires five-wire cables, direct current (DC) uses one to two fewer conductors. The lower number of conductors results in less material usage. Thus, DC cables require far less copper than their AC counterparts. This makes them more space-saving and particularly interesting for applications with limited space or in switchgear cabinets. The potential for material savings is about 40 percent.

Testing DC technology in practice

The body construction facility at the BMW Group plant in Dingolfing is an application pilot currently testing DC technology in practice. It was initiated as part of the DC-Industrie2 project. The German research project explores the opportunities and challenges of direct current technology in industrial production facilities. In the long term, researchers plan to convert entire factory halls to direct current. The results of DC-Industrie2 are pioneering in creating energy-efficient solutions and standards. Lapp is also a project partner. The Ölflex DC 100, which emerged from the project, is now available as a serial product.

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However, it is not only the research project that connects BMW and Lapp, but also a long-standing partnership. DC cables with special cross-sections were specially and quickly manufactured by Lapp as prototypes for the automaker. "We believe that in the future, more and more production facilities will be supplied with direct current," summarizes Alois Heimler.