Hydrogen in Intelligent Energy Systems

At Fraunhofer IISB, we have established an extensive hydrogen infrastructure for research activities and services for our customers over the last ten years. ​

Here, several of our departments contribute their knowledge in various application scenarios. On the one hand, this applies to mobile applications in the fields of automotive, rail transport, aerospace as well as marine and underwater applications. On the other hand, our expertise also includes stationary applications such as grid stability, peak shaving or load shifting in industry, or intermediate storage and buffer applications for renewable energies. ​

Our technology and system competencies cover the classic hydrogen technologies such as hydrogen storage and hybrid storage systems, electrolyzers, fuel cells or exhaust gas utilization. The focus is also on functional safety, power electronics up to the megawatt range, and optimization through data analytics, operating strategies, monitoring and modeling. Central to this is our overall system and integration know-how, which in addition to multi-domain system integration also includes aspects such as testing, certification and approval. ​

An important basis for our holistic approach is our real-world laboratory for energy technology. The institute operates air-conditioned clean rooms and laboratories with large energy consumers in addition to offices. It is excellently suited as a real-world laboratory for energy system solutions for medium-sized companies and industrial operations. The optimization measures here are not only restricted to the individual energy sectors – heating, electricity and cooling – but also focus on the overall energy system by linking the various sectors.

Hydrogen storage systems are used for long-term energy storage, which provides the basis for optimization measures such as increasing the self-use of regeneratively generated and converted energy. In addition, low-loss long-term storage enables seasonal shifting of energy use over periods of several weeks and months. The self-production of hydrogen by means of electrolysis is also realized by stationary hydrogen systems and is relevant for industrial plants with their own hydrogen demand. Research activities at Fraunhofer IISB include system integration of electrolysers and fuel cells for both mobile and stationary applications. Parameters and boundary conditions of the underlying energy system strongly influence the development of operating strategies as well as automation technology.​

Hybrid storage systems include, in addition to hydrogen storage, electrical storage, e.g. batteries, and/or thermal energy storage in the form of heat or cold storage. Hybridization increases the dynamics and capacity of the hydrogen system by combining the respective system advantages. For example, hydrogen systems are integrated into storage systems because of the lower losses during long-term storage. If electric batteries are also added to the storage system, they contribute to the optimized storage dynamics due to their fast response time. Furthermore, the cross-sectoral consideration of storage systems opens up the possibility of holistic system optimization. Regardless of the type of storage system you already have, we support you in expanding it into a hybrid storage system.

Hybrid fuel cells are particularly well-suited in vehicles with high power requirements. They increase the long-distance capability of cars and commercial vehicles, while fuel cells enable emission-free operation of heavy vehicles such as trains or ships. By using hydrogen as an energy carrier, the vehicles can be refueled quickly, enabling high availability. In order to be able to use fuel cells in mobile applications in a reasonable way, we have developed a compact DC/DC converter. The converter is space-saving so that it can be installed in standard passenger cars (Power Electronics, see below). This makes us a suitable contact for vehicles of different sizes in the private as well as in the logistic sector. ​

Our experts support you in the system design and realization of your aircraft propulsion system through tailored components and a seamless system integration, taking into account the unique challenges specific to aviation. ​Possible fuel cell applications include DC/DC converters for coupling the fuel cell(s), high-speed drive converters and motors for air compressors, or galvanically isolated DC/DC converters for supplying the 28V and/or 400Hz grid from the fuel cell. We also use battery and fuel cell management systems to analyze on-board power system stability and redundancy concepts. Extensive infrastructure from innovative AVT to negative pressure climate chambers is available for this purpose in our joint aerospace laboratory.​ Due to the significantly higher gravimetric energy density of hydrogen compared to kerosene and batteries, we understand fuel cells as a key technology for emission-free aviation.​

In addition to hybrid vehicles and pure battery-electric solutions, the fuel cell represents a potential alternative for CO2 emission-free mobility, especially for commercial vehicles. Fuel cells show their best efficiency only under load-point-dependent current and voltage curves. Since electrical voltage sources such as batteries or fuel cells cannot simply be connected, the input voltages must be matched to the DC link voltage of the powertrain. Power electronics such as DC/DC converters with a wide input voltage range can optimally absorb the energy and increase it to the required voltage. High-frequency inverters and motor concepts for high-speed air compressors enable energy-efficient operation of central auxiliary units.​

In addition to cost and material usage, the focus is on energy conversion efficiency. In mobile applications such as transportation, racing or even aerospace, size and weight also play a decisive role. Therefore, technologies and prototypes are being developed at IISB demonstrate that high performance is also possible in very compact installation space with particularly high efficiency. We achieve this by using the latest materials, innovative packaging concepts, quasiresonant switching technologies, specially developed module-integrated power components and the utilization of parasitic elements for optimal switching operations. In this way, we achieve high switching frequencies, low switching losses, high power-densities and therefore advanced power electronics for hydrogen technologies. Our developments and range of services extend from individual technology investigations to complete, fully functional, reliable, mobile and stationary systems in prototype small series.​

A particular challenge is the integration and control of power electronics in the overall system and the assurance of system stability. Monitoring and system supervision, for example by impedance measurement, enable early fault detection and in this way the avoidance of downtimes. Consequently, the greatest possible efficiency is achieved through coordinated operation. We ensure this for you by integrating different plant subsystems. Here at Fraunhofer IISB, we benefit from our in-depth understanding of systems and the close cooperation between our departments.​

The purpose of an operating strategy is to determine the optimum operating point of a component or a constellation of different components (e.g. fuel cell, electrolyzer and hydrogen storage) for each point in time and to control the actuators accordingly. A wide variety of input variables and parameters are available as a basis for decision-making. These relevant boundary conditions and operating parameters must be taken into account when designing operating strategies. At Fraunhofer IISB, we develop intelligent control algorithms and operating strategies for the optimized use of the individual components. Our specialization here is the development of prototypes of functioning holistic systems. In doing so, we take into consideration the respective component characteristics as well as the higher-level system. In addition, forecasts, which are created with the help of our own algorithms and our simulation models, are incorporated into the operating strategies.​

As a foundation for simulation-based system design, we develop simulation models of the systems involved (e.g. fuel cells, hydrogen storage and battery) and validate them on the basis of measurement data from prototype plants. Intelligent operating strategies are devised for the optimal operation of the components, which include boundary conditions and parameters of the individual plants as well as the overall system. This enables the investigation and quantification of the effects of parameters, extensions and operating strategies before intervening in the real system. At Fraunhofer IISB, a wide-ranging model library for components from the entire energy sector is being developed for system simulations. The models are trained using historical measurement data and are partially self-optimizing. In addition, extensive measurement data is available, which is used for the development of component models, system simulations and intelligent operating strategies.​

The combination of sensor technology and monitoring electronics enables usable conclusions to be drawn about the condition of various components, for example the state-of-health (SoH) of fuel cells. In terms of cost efficiency in system design and operation, it is important to reduce the number of expensive and complex sensors while achieving comprehensive condition monitoring. ​Through its various demonstrators and test rigs, Fraunhofer IISB has extensive expertise in monitoring electrical and process parameters of hydrogen systems as well as the application of impedance spectroscopic techniques. In addition, the foxBMS-Plattform is a freely available and variably configurable electronic system for monitoring the voltage of fuel cells.

While condition monitoring captures the current state of a system, condition diagnosis analyzes the condition data in detail to understand the causes of the current system state. The analysis is performed automatically, usually using machine learning approaches or AI.​ With its work on "Cognitive Power Electronics 4.0", the linking of power electronic systems with AI, Fraunhofer IISB is laying the foundation for data- and AI-based state diagnosis and also offers the potential for state prediction, i.e. the estimation of the system state in the future.​

For prototype construction, we take particular account of the individual component characteristics as well as the higher-level system. At Fraunhofer IISB, we model complete systems, including generators, storage units and consumers. We also optimize the interaction between the various system components. A crucial aspect in the development of functional and transferable prototypes is optimized automation technology, including measurement and control technology. ​