Powered by direct current

It’s an idea that puts a glint in the eye of technicians and engineers alike – instead of drawing alternating current from the grid, why not run all production systems and equipment on electricity supplied by an energy-saving, direct-current in-house network? This would be fed by on-site solar and wind power, with any surpluses, such as braking energy from robots, recovered and temporarily stored along with the short-term surpluses that renewables generate. Switching industrial production systems from alternating current to direct current offers companies clear benefits.

To start with, it boosts energy efficiency. Smart production operations based on direct current can put green energy from solar or wind power straight to use, incurring none of the losses that would otherwise come from converting the DC generated by renewables into the AC required by conventional consumers.

What’s more, running production operations directly on green electricity makes an important contribution to the energy revolution and therefore to climate protection, which is an international task. Not only that, but companies that generate their own power from renewables are less exposed to current fluctuations in the public grid, which can potentially cause rejects during production.

The automotive industry – by far the biggest user of industrial robots – has grasped the opportunities that come with using direct current and is spearheading this process. The first step in developing energy-saving and energy-efficient automobile manufacturing came from researchers and engineers working on the European AREUS (Automation and Robotics for European Sustainable Manufacturing) project and its follow-up project DC-INDUSTRIE at Daimler’s TecFactory in Sindelfingen, Germany.

Staff at this innovation and development centre for production technology are researching energy-saving production processes in a ‘Smart DC Grid’ and testing them out under realistic conditions. Involved in this work are a number of German universities, the Fraunhofer Institute and companies such as Daimler, Siemens and Bosch-Rexroth – Rittal is acting as a technology partner for various aspects.

AREUS experts developed the prototype for a completely new robot cell based on the premise that production would run on an efficient direct current grid. Four robots work in a square measuring nine by nine metres – a complete production plant in miniature format. Rittal Blue e+ cooling units are being run on a DC voltage of up to 650 volts for the first time as part of this pilot plant.

Their job is to provide the cooling output needed to ensure the production sequence runs smoothly. Steffen Wagner, Director Product Management Climate Control at Rittal, says: “We have developed the world’s first cooling unit for these special needs. We’re also using the patented hybrid process for the pilot plant.” This means that the compressor is only used when passive cooling is no longer sufficient. That detail already helps Blue e+ units to be 75 per cent more efficient on average than conventional cooling technology.

“Innovations and new technologies like those we have seen in the TecFactory also call for new, cutting-edge infrastructure solutions,” points out Markus Schäfer, Member of the Divisional Board of Mercedes-Benz Cars, Production and Supply Chain Management.

An environment under control

It won’t just be robots and devices running on direct current that will come to the fore in efforts to boost energy efficiency by up to 20 per cent – automatic control and monitoring systems will also play an increasingly important role. The Rittal IoT interface, for instance, can be used to monitor ambient temperature and atmospheric humidity and to measure and analyse energy data.

The power consumed in the TecFactory is generated by a photovoltaic system, and there are storage devices for temporary energy surpluses. When these storage devices are full, excess solar power can be fed into the public AC power grid and, conversely, the public grid can safeguard production in the DC smart grid when a shortfall in the power supply needs to be made up.

Daimler is hoping to get successful product developments from the TecFactory into production as soon as possible. “Our Mercedes-Benz plants in Germany are going to be running on a carbon-neutral basis from 2022,” declares Schäfer, adding: “New factories in Europe are already being planned with carbon-neutral power supplies. To achieve these ambitious targets, Mercedes intends to digitalize its power grids and switch its production sites to smart DC grids in a step-by-step process. Michael Scholl, Key Account Manager Automotive International at Rittal, sees the endeavours of the automotive industry as a key “driver for new technology”.

The market potential is huge – with more than two million cooling units in operation throughout the whole of Europe. If all these were replaced by Blue e+ units running on direct current, the CO2 savings would amount to more than three million metric tons. All the same, a lot of work remains to be done before that is achieved.

• AC/DC in data centers

  Frankfurt’s data centers now use more electricity than the city’s airport. And that power consumption is still growing. The use of direct current could harness brand new potential for energy and cost efficiency. First and foremost – OCP. 

  What is OCP? The Open Compute Project (OCP) was launched by Facebook in 2011 in an effort to find cheaper, more efficient and fully standardised ways to run data centers. Rittal has supported the initiative from the start and helped to develop the innovative IT architecture for large data centers. Servers and storage systems in enclosures no longer require their own, dedicated mains adapters. Instead, they are powered by direct current supplied via bus bars integrated into the racks themselves.

  Who needs it? Companies running large data centers that collate data from millions of users on thousands of servers and colocation suppliers. Besides service giants like Amazon, Facebook and Google, the solution is also useful for telecommunications suppliers and large digitalized industrial production sites.

  What does Rittal offer? Rittal now supplies standard OCP V2.0 racks. Special OCP servers are used in the racks, operating on an electrical supply voltage of 12 V / 48 V direct current (DC). The average efficiency gain is around 5 per cent of total current load. Thanks to the 21” standard dimensions, full use can be made of the interior, and the design is based on the flexible modular model.