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Solar power storage system consisting of salt-battery technology from innovenergy. Photo Credit: Wittmann Battenfeld

After debuting the concept of an injection molding machine running off renewably sourced direct current (DC) at K 2022, Wittmann Battenfeld once again promoted the technology and a battery collaboration partner at Fakuma 2023. At the show, an EcoPower B8X series, powered via a solar power storage battery, molded a polypropylene drainage body from a single-cavity tool supplied by Kunststofftechnik Grabher GmbH. The part was removed by a modified Wittmann WX142 robot also equipped to utilize DC energy.

At the live Fakuma presentation, the machine was disconnected from the exhibition hall’s grid, but was instead powered independently via Innovenergy’s solar power storage salt battery. To balance the brief load peaks of the injection molding machine, additional electrochemical capacitors, known as super-caps, were used to complement the sodium-nickel storage batteries. The battery has a total capacity of more than 45 kWh, which was more than sufficient for continuous machine operation throughout the 8-hour trade fair day.

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Wittmann said that since it first presented the technology, it has taken further developmental steps, including finding a partner specializing in DC infrastructure: Swiss firm Innovenergy. That company has been developing and operating energy storage systems with salt batteries for almost 10 years, originally creating sodium-nickel technology for e-mobility, but more recently entering the stationary storage battery sector. The Innovenergy batteries range in storage capacity from 9 to 999 kWh, with inverter capacities from 3 to 300 kVA. Focused on the industrial sector, the company has installed roughly 1,000 salt-battery storage systems to date. Innovenergy says key factors in the industrial space include energy efficiency, connected load limitations of AC infrastructures, independence and the potential for failure safety in cases of power interruption.

To address these, Innovenergy markets its DConnect system featuring renewable energy generators, powered by photovoltaics or wind, and energy storage batteries that are linked with each other in a separate DC network. The company says this enables direct use of the generated energy with greatly reduced conversion loss, and only surplus electricity returns to the power network. Overall, Innovenergy says DC/AC/DC conversion losses between the solar power station and the machine can be lowered by up to 15%.

In addition to lowering energy costs and helping preserve the environment, Wittmann notes that using a machine that applies energy generated by an in-house solar power station enables molders to store direct current in batteries, avoiding expensive current peaks and improving power supply reliability.

The company says its all-electric EcoPower, equipped with highly dynamic servo motors, is well suited for use in a DC power network. The machine comes with the patented KERS — kinetic energy recovery system — as standard, enabling it to convert kinetic energy from machine movement into electric energy during deceleration processes and further reducing energy consumption.

Wittmann says that also applies to a DC-compatible robot powered directly via the DC voltage interim circuit of the EcoPower. The robot returns any surplus energy to the interim circuit whenever its axes are decelerated. If the machine operates in a DC network, the deceleration energy can also be fed back into the network, enabling other connected machines to be powered by this energy or to store it in batteries.

This “super caps” system was used to cover brief load peaks. Photo Credit: Wittmann Battenfeld