Direct current is gaining importance in industrial and building applications due to its greater stability and efficiency compared to traditional AC grids. Battery energy storage systems (BESS) enhance these benefits in DC grids. Phoenix Contact (Blomberg) and Voltfang (Aachen) have successfully implemented such systems in practice.
DC-coupled battery storage systems as an aid to the success of DC technology
DC grids are gaining attention for their advantages, especially in industrial settings. As a result, DC-coupled storage solutions are crucial for the widespread adoption of this technology. Already, photovoltaic systems, production facilities, and the transport sector are seamlessly integrated into DC infrastructures.
According to Tobias Lüke, DC expert at Phoenix Contact, these systems are forward-looking because DC grids optimize the entire energy chain from generation through distribution to consumption. Moreover, energy storage systems play a vital role in this process.
One major benefit of DC-coupled BESSs is their higher efficiency compared to traditional AC systems. By eliminating the need to convert DC to AC and back, conversion losses are avoided. Consequently, stored energy is used more effectively, and available power is maximized. Additionally, smaller cable cross-sections reduce material usage and costs. Therefore, battery storage systems in DC grids offer a cost-effective solution, with lower investment and operating expenses enhancing their profitability and competitiveness.
Industrial companies as early adopters and innovation drivers
For industrial companies like Phoenix Contact, generating affordable electricity from renewable sources is essential. It allows them to strategically manage energy use, reduce long-term costs, and ensure reliable supply. By using in-house energy storage systems, electricity can be bought at low prices and used when needed.
Furthermore, battery storage systems offer high flexibility, delivering and storing energy with millisecond-level response times. Their modular design allows easy scaling for various applications, from small units to large industrial systems. In addition, advanced analysis tools enable accurate monitoring and control of battery performance and energy levels.
As a result, the collected data supports smart grids by optimizing energy feed-in, storage, and usage. This improves grid stability and enhances the integration of renewable energy into existing systems.
Cooperation as the basis for the development of new technologies
Voltfang is focused on developing efficient methods for repurposing e-mobility batteries. Second-life and surplus batteries, originally designed for electric vehicles, often offer higher load capacity than those made for stationary use. Voltfang leverages this by using high-performance batteries with strong cycle stability. Through smart energy management and optimized operations, these systems achieve long service life and reliable efficiency for stationary applications.
Its energy management system (EMS) supports key functions like peak shaving, self-consumption optimization, dynamic tariffs, and flexibility marketing, helping users run their energy systems more cost-effectively. This highlights the role of intelligent systems in driving a sustainable and economical energy transition.
Additionally, Voltfang has long worked on integrating battery storage into DC grids, focusing on Phoenix Contact’s Charx power modules as interfaces for DC microgrids. Their collaboration has steadily evolved over time.
From the outset, Phoenix Contact aimed to build the All Electric Society Factory—an advanced industrial facility with a full DC infrastructure. This vision strengthened its collaboration with Voltfang to develop a DC-coupled battery energy storage system. The result is a cutting-edge 300 kWh solution.
“This project shows how cooperation and innovation can create sustainable, efficient energy systems,” says Dr. Rüdiger Meyer of Phoenix Contact. Roman Alberti, CSO of Voltfang, adds, “We’re committed to optimizing energy systems, and Phoenix Contact’s DC concept immediately inspired us to contribute our expertise.”
From the idea to operation in practice
Voltfang used re-qualified electric vehicle batteries for the energy storage system installed at the All-Electric Society Factory. This stationary application extends their lifespan before recycling. Charx DC power modules supply 270 kW bidirectional power and serve as the interface between the DC grid and the battery.
The project leveraged strong synergies between both companies’ product ranges, combining existing solutions into an optimized, efficient system. Control cabinet components such as terminal blocks, safety devices, relays, and fuse links were installed alongside Phoenix Contact’s 24 V DC Quint series with UPS, powered directly by the battery. This enables blackstart capability for the All Electric Society Factory’s DC microgrid and provides backup power. The system, housed in a 20-foot container, is reliably protected against surge voltages by Phoenix Contact’s VAL MB series.
The DC BESS is connected to the All Electric Society Factory’s DC grid via Phoenix Contact’s PLCnext Technology. Voltfang’s EMS uses droop control based solely on system voltage to manage charging and discharging, stabilizing the grid by compensating for voltage fluctuations. The higher-level energy management system defines the control curve based on the application. In normal operation, the BESS stabilizes the grid. This architecture ensures efficient, scalable, and fault-tolerant performance with minimal subsystem communication.
This pilot project by Phoenix Contact and Voltfang resulted in a modular, scalable, sustainable, and efficient energy storage system, now used in similar-scale industrial DC microgrids thanks to its higher efficiency and reduced material use compared to AC coupling.
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