The safe and efficient operation of modern engineering systems requires a deep understanding of internal processes as well as reliable condition monitoring. Digital twins—virtual representations of physical systems—provide a powerful solution by combining physics-based models with measurement data and advanced control methods. They enable accurate prediction of system behavior and support optimized operation in real time.

The Christian Doppler Laboratory for Digital Twins for Distributed Parameter Systems focuses on systems in which key processes are spatially distributed. In such systems, variables like temperature, pressure, or chemical reactions vary across space and time—for example in district heating networks, chemical reactors, or industrial production processes. These so-called distributed parameter systems pose significant challenges for monitoring and control, as internal states are often only partially measurable.

Our research develops advanced digital twin methodologies that reconstruct these internal states with high accuracy. This enables improved efficiency, increased system lifetime, and enhanced operational safety. Application areas include fuel cells, electrolyzers, battery systems, and elastomer extrusion processes—contributing to sustainable energy technologies and high-quality industrial production.

Application Areas

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Modern battery systems rely on complex electrochemical processes that vary spatially within the cell. Local differences in current density, temperature, and lithium concentration significantly affect performance, aging, and safety.

We develop reduced-order, physics-based models that retain high accuracy while enabling real-time implementation in battery management systems. These models support advanced state estimation and diagnostics, including reliable predictions of critical operating conditions during fast charging.

By enabling robust estimation of key indicators such as State of Charge (SOC) and State of Health (SOH), digital twins facilitate intelligent charging strategies, improved monitoring, and extended battery lifetime.

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Fuel Cell in an electrical vehicle

Fuel cells and electrolysers are key technologies for future energy systems. Their performance and lifetime are strongly influenced by degradation mechanisms that depend on local operating conditions within the cell.

Since internal measurements are typically not feasible, our approach combines external sensor data with high-resolution models to reconstruct internal states using model-based observers. This allows for accurate assessment of system health and degradation processes.

The resulting digital twins enable adaptive operating strategies that improve energy efficiency and significantly extend system lifetime - even under dynamic conditions.

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Schematic diagram of an extrusion process, a shaping method used in manufacturing technology.

Alongside injection moulding and calendering, extrusion is one of the most important shaping processes in the elastomer industry. It enables the manufacture of a wide range of products, such as industrial hoses, seals and handrails. Product quality depends largely on the internal conditions within the extruder, particularly on the development of the melt temperature along the screw. However, these internal conditions are generally not directly measurable during extrusion; mathematical models of the process are therefore required to make them accessible.

The strong coupling of the rheological, thermal and fluid dynamic processes means that high-resolution simulations of the extrusion process involve considerable computational effort and are therefore usually not suitable for real-time applications. However, by using suitable model reduction methods, real-time-capable surrogate models can be derived from these complex models.

When combined with process measurement data available online, these reduced models form the basis for a digital twin of the extrusion process. By combining these models with real-time measurement data, deviations in the simulated variables can be continuously corrected by using differences between measured and modelled variables to update states and parameters. The digital twin thus enables not only the reconstruction of internal states that cannot be measured directly, but also predictive analyses, state-based process control and the early detection of deviations or faults.

Extrusion is a key manufacturing process in the elastomer industry, where product quality strongly depends on internal process conditions such as melt temperature distribution. Because these internal states cannot be directly measured, we develop reduced-order models derived from high-fidelity simulations. These models enable real-time capable digital twins that integrate live process data.

This approach allows continuous correction of model predictions, early detection of deviations, and implementation of predictive and condition-based process control—leading to improved product quality and process stability.

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Research Questions & Methodological Approach

Distributed parameter systems share a common difficulty: the states that decide performance, ageing and safety – local current density, membrane humidity, melt temperature – vary in space, change in time, and cannot be measured where they matter most. High-fidelity PDE models capture this behaviour but are far too computationally expensive for real-time use. This project closes this gap along three connected research lines, applied across the application areas.

Table with methodological approaches and indurstiral impact

1. State observers for distributed parameter systems

How can spatially resolved internal states be reconstructed in real time from a handful of external or in-situ sensors?

We develop observer architectures for PDE-governed systems – addressing early- versus late-lumping, optimal sensor placement, local versus global observability, and the interaction of multiple distributed observers – to turn measurement-poor processes into fully observable digital twins.

2. Diagnosis, virtual sensing and prognosis

How can local degradation be detected, localised and predicted before it compromises the whole system?

Building on the observers above, we develop virtual sensors and stressor identification methods that quantify ageing mechanisms, separate coupled degradation effects, and predict remaining useful lifetime under realistic dynamic operation.

3. Real-time models for spatially distributed processes

How can high-fidelity PDE models be systematically reduced to real-time-capable representations that preserve physical interpretability and remain valid across components, units and full systems?

We combine reduced-basis methods, dynamic mode decomposition and hybrid physics-plus-machine-learning models, with structured parameter identification and design of experiments tailored to spatial sensitivity.

News

Joint Workshop on Fuel Cells, Electrolyzers and Batteries at AVL

A group of people are standing on the AVL premises

How do we turn complementary expertise from multiple research groups into shared progress on digital twins for distributed parameter systems? Stepping out of the usual environment and meeting in person is an essential ingredient.

In early May 2026, we came together for a joint workshop hosted by AVL List GmbH in Graz. Researchers from Vienna, Ljubljana, and Jülich travelled in to present, discuss, and inspire ongoing and future research directions. Across eight presentations, participants shared recent results on model order reduction, state estimation, knowledge transfer and degradation analysis for fuel cells, electrolyzers, and battery systems – reflecting on current activities, brainstorming new ideas, and setting the course for the next years of the CDL, in both research and industry.

Local aging effects inside the cell

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What happens locally inside a fuel cell plays a decisive role in determining its service life—but this is difficult to observe experimentally and requires extensive testing. In a recent publication, a simulation methodology was employed that efficiently visualizes aging processes in fuel cell membranes over their entire service life. Instead of computationally intensive, detailed models, the approach uses a network of simplified models to precisely map local aging effects on the sensitive membrane. This allows long-term aging effects to be simulated under realistic operating conditions in a fraction of the lifespan. The results show that dynamic operation particularly promotes locally occurring wear. The methodology aims to enable efficient monitoring of fuel cells—an important step toward climate-friendly mobility and energy supply.

Discover the local aging effects inside the cell:

https://doi.org/10.1016/j.ijhydene.2026.154672, opens an external URL in a new window

Advancing Fuel Cell Understanding

Mole fractions of H₂O in different areas of a PEM fuel cell model

A key research highlight is the development of advanced models for PEM fuel cells that simultaneously capture temperature distribution and two-phase water transport in a computationally efficient way. 

These models enable detailed analysis of critical phenomena such as local overheating and water accumulation—major causes of performance loss and degradation. Despite their high physical fidelity, they remain suitable for dynamic simulations and real-time applications in diagnostics and control.

Take a look inside the fuel cell with us: https://doi.org/10.1016/j.ecmx.2026.101584, opens an external URL in a new window

 

Selected Publications

<< full list of publications

Team

Ao.Univ.Prof. Dipl.-Ing. Dr.techn.Martin Kozek

Head of Laboratory

Send email to Martin Kozek

Rene Hofmann, opens an external URL in a new window (TUW): Expert in digital twin technologies and model-based optimisation of complex energy systems, Head of the Institute of Energy Technology and Thermodynamics

Michael Eikerling, opens an external URL in a new window (FZJ): Expert in physics-based modelling of PEM fuel cells and electrochemical energy systems

Christoph Hametner, opens an external URL in a new window (TUW): Expert in model-based control, state estimation and optimisation of complex dynamic and energy systems

Thomas Kadyk, opens an external URL in a new window (FZJ): Expert in modelling and techno-economic assessment of electrochemical energy systems

Tomaž Katrašnik, opens an external URL in a new window (UL): Expert in multiphysics modelling and the optimisation of electrochemical energy and propulsion systems

Andraž Kravos, opens an external URL in a new window (UL): Expert in multiphysical modelling of electrochemical energy systems and fuel cells

Matteas Jelovic, opens an external URL in a new window (TUW): How can parametrically distributed electrochemical battery models be simplified so that they can be used in real-time in battery management systems?

Johanna Bartlechner, opens an external URL in a new window (TUW): What information can be obtained about the properties within the cell by taking measurements during operation?

Benjamin Fuchs, opens an external URL in a new window (TUW): How can local damage effects in fuel cells and electrolysers be detected and influenced?

Jernej Gašperšič, opens an external URL in a new window (UL): How can models that describe different effects at different levels be systematically integrated?

Andrej Leber, opens an external URL in a new window (FZJ): What quantitative influence do material and operating parameters have on the ageing of individual cell components?

Patrick Frentzel-Pfaller, opens an external URL in a new window (TUW): How can model-based control and optimisation methods be developed to operate complex energy systems efficiently?

Johannes Lichtenegger, opens an external URL in a new window (TUW): How can different modelling approaches be combined to develop real-time dynamic process models?