Monthly Archives: November 2024

Modular AC/DC converters increase the availability of electrolyzers

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Green electricity from wind and solar power can be abundant or scarce. Power-to-X technologies store this energy as electrochemically produced hydrogen, which is converted back into electricity in fuel cells. A modular solution with AC/DC converters supports various topologies for supplying electrolysis cells with direct current, simplifying maintenance and enhancing the availability and service life of electrolysis stacks.

The vision of an All Electric Society relies on affordable, renewable electricity. Wind and solar power are crucial but volatile, necessitating storage solutions. Future power grids will use pumped storage plants and battery storage systems to balance generation and consumption, though these aren’t suitable for long-term storage of large quantities of surplus electricity.

Power-to-X technologies can be used to store surplus electricity long-term by splitting water into hydrogen and oxygen via electrolysis. These can be converted into chemicals or fuels, or the hydrogen produced can be stored and later converted back into electricity in gas-fired power plants or fuel cells. Direct current through an electrolysis cell produces hydrogen at the cathode and oxygen at the anode, separated by a membrane to prevent reaction. The gases are vented off separately.

Modular concepts for electrolysis cells and power supply

Today’s electrolyzers are modular, with cells arranged in stacks, achieving powers from 10 kW to several MW. Larger plants, up to gigawatt scale, interconnect dozens or hundreds of electrolyzers. This modularity allows easy scalability and simplifies mass production. Designing a modular power supply for electrolyzers is ideal.

Scalable alternative to monolithic large-scale converters

All electrolyzers need direct current, so AC from the power grid must be converted by AC/DC converters. The cell voltage (1.6 to 2 V) must be maintained for the electrolytic process. Often, large monolithic converters are used, but a modular supply concept like the CHARX power system from Phoenix Contact offers an alternative. CHARX AC/DC converters convert AC to DC with the required voltage, ensuring high-quality electrical energy by reducing grid-side harmonics and the DC ripple is a maximum of just 1.5%. They also prevent short-term voltage dips and peaks.

Megawatt electrolyzer manufacturers impressed by modular supply concept

Phoenix Contact has implemented this concept in several electrolysis projects, equipping containerized units with modular rectifier units based on AC/DC converters. This modularized approach allows for standardized control cabinets that are adaptable to the power needs of each electrolysis module. Manufacturers were impressed by the technical details, such as integrated condition monitoring, long service life, easy maintenance, and high efficiency of the converters.

High-level efficiency and easy-to-integrate condition monitoring

Charx AC/DC converters, typically using IGBT technology with a 30 kW output, are highly efficient (up to 96%) and superior to monolithic converters. They offer a controllable DC output voltage range of 30 to 1,000 V, adaptable to various electrolysis stacks. Both voltage and current can be ramped up slowly. These converters provide internal electrical isolation between AC and DC grids, crucial for many electrolyzers. Charx converters with 20 kW output using SiC power semiconductors can achieve 97% efficiency, further reducing waste heat.

PLCnext Control devices from Phoenix Contact are ideal for control applications, offering library elements for simplified programming, flexible voltage and current control, and easy data integration for condition monitoring. Charx converters feature an openly accessible bus system. The modular power supply approach benefits electrolyzer manufacturers, allowing scalable green hydrogen production from pilot to megawatt plants.

Higher availability of converters and electrolyzer

Charx rectifiers optimize partial load operation by allowing parallel converters to be partially switched off, ensuring the remaining ones operate at optimal efficiency. This extends the service life by evenly reducing operating hours. Alternating the operation of converters also aids maintenance planning and prevents uneven loading

The concept benefits maintenance and servicing. Small-format modules can be easily kept as spares, and integrated condition monitoring alerts operators when replacements are needed. Modules can be replaced with standard tools while others continue to supply the electrolyzer, increasing system availability. Only during full-load operation is a slight reduction in supply noticeable when a module is replaced.

If a large monolithic converter fails, the entire electrolysis plant it supplies will stop. Replacement converters must be custom-made, causing the plant to be down for weeks and resulting in high yield losses.

Large megawatt converters supply multiple electrolysis stacks with the same voltage, but variations in stacks can cause issues. If one stack has a problem, it can affect the entire system. In contrast, using Charx modules allows individual stacks to be isolated and checked without shutting down the whole system, ensuring the remaining stacks continue to operate.

Using 19-inch modules may require more space and higher initial investment than large-scale converters. However, their advantages—higher availability, lower maintenance costs, and efficiency gains, especially in partial load operation—quickly offset these drawbacks.

Read more about AC/DC converters.

Sensor technology of tomorrow for end-to-end communication

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Single Pair Ethernet: Lean communication through to the field level of automation

Single Pair Ethernet (SPE) enables smarter, more sustainable connections, making it ideal for long-distance communication. Sensor manufacturer Jumo trusts SPE for its measurement technology, using connection solutions from Phoenix Contact, developed through close project collaboration.

“Single Pair Ethernet (SPE) enhances the use of intelligent sensors by transmitting more data, enabling profitable insights,” says Manfred Walter, product manager at Jumo. He highlights the seamless distribution of sensor information across system levels and the consistency it brings. SPE also saves cables by routing data and power via Power over Data Line (PoDL), allowing end-to-end communication from ERP to field level without media disruptions.

OEE as a basis for investment

Jumo and Phoenix Contact emphasize Ethernet’s consistency as crucial for sustainable production. It simplifies troubleshooting, facilitate condition-based maintenance, and improves Overall Equipment Effectiveness (OEE) by enhancing system availability. Additionally, it facilitates easier connections to cloud-based services.

Using SPE to combat media discontinuity in industrial communication could influence sensor-level connection technology choices. However, Manfred Walter notes that customer expectations in machine building and systems manufacturing are primarily price-driven, with limited budgets for measurement chains. The additional cost of SPE connections and the benefits of an end-to-end Ethernet architecture are difficult to present, especially in standardized tenders. Positive impacts on OEE are crucial for investment decisions and are best be argued directly.

Convergent networks are in demand

Martin Müller, a fieldbus expert at Phoenix Contact, views SPE as an important step towards convergent networks. TSN is designed for time-critical tasks like functional safety and motion control, while 5G is used for cellular communication needs. Similarly, WLAN 6 and 7 are used for license-free, wireless transmission.

“Single Pair Ethernet is ideal for communication at the field level,” says Martin Müller. The convergent Ethernet network is the common standard for industrial communication. If stakeholders in automation, electrical engineering, machine building, and systems manufacturing agree on this path, industry-specific fieldbus wars will end.

1,000 meters with 10 Mbit

The chances are favorable, supported by the transmission performance of standard consumer communication. SPE achieves a transmission rate of 10 Mbps over 1,000 meters, while I/O-Link delivers 230.4 kbps over 20 meters. Despite I/O-Link simplifying sensor connections, Manfred Walter believes its data rate won’t suffice for future tasks in coupled sectors.

Phoenix Contact and Jumo foresee a trend towards convergent Ethernet networks, particularly among younger specialists. “Digital natives are less tolerant of multiple systems in industrial automation,” says Martin Müller. The focus should be on maximizing sensor capabilities for efficient, resource-saving operations. “We see enormous potential for the future,” emphasizes Manfred Walter.

Hygienically clean IP67 connector solution

Install, connect, and you’re done: With SPE connectivity, installing a Jumo sensor is easy. The Ethernet layer eliminates the need for gateways or complex interface programming. Phoenix Contact’s M12 connector supports Single Pair Ethernet transmission up to 1,000 meters without limiting attenuation. “The M8 format wouldn’t fit a two-wire AWG 18 data cable for 1,000 meters,” explains Manfred Walter. The connection design ensures robustness and hygiene. Jumo’s “flowTRANS MAG H20” and “DELOS S02” sensors are popular in the pharmaceutical and food industries. High operational safety over long distances is achieved with connections that withstand demanding production processes or CiP cleaning. Phoenix Contact’s solution meets hygienic design standards and provides IP67 protection.

Read more about Sensor technology.