Periodic Reporting for period 2 - REACTT (REliable Advanced Diagnostics and Control Tools for increased lifetime of solid oxide cell Technology)
Berichtszeitraum: 2022-07-01 bis 2023-12-31
The exploitation of renewable energy sources such as wind, water, and solar energy has become one of the priorities of the modern energy sector across the globe. However, renewable sources cannot solely be used due to their intermittent nature, meaning that there are periods when supply exceeds demand and vice versa. Solid Oxide Electrolysis Cell (SOEC) systems are electrochemical energy conversion devices capable of converting electrical energy into carbon-free hydrogen. Hydrogen can be stored and potentially re-used as fuel for fuel cells to be re-converted into electrical energy. SOEC systems operate at high temperatures and have a unique property that the same device can operate in the reverse mode, i.e. as a Solid Oxide Fuel Cell (the the so-called rSOC).
Despite their attractive features, SOC systems (a common term for SOEC, SOFC, and rSOC) are still not massively present in in-field applications. To ensure that SOC systems operate reliably, and efficiently and deliver hydrogen or electric power when required, an accurate assessment of their performance, health, and life span is necessary. That is the topic at the heart of the REACTT project.
REACTT aims at designing, engineering, and testing a platform that integrates monitoring, diagnostics, prognostics, and control (MDPC) for the emerging generation of SOC systems for massive production of hydrogen at low cost from renewable energy sources. Such platforms will ensure maximal efficiency of operation, reliability, durability, and reduction of operational and maintenance costs. Consequently, SOC systems cope more efficiently with the non-stationary operational regimes at the stack and system level, thanks to the optimally tailored control actions across the dynamic transients and switching between different modes of operation. Taking advantage of previous SOFC projects in this research area, REACTT project starts at TRL 4. After the engineering design process, validation and testing of the MDPC tool on stacks will be performed and the final TRL of 6 is expected to be achieved (Figure 1).
The overall objectives of the REACTT project are the following:
1. Improve durability, reliability, and maintainability of SOEC and rSOC stacks by developing innovative algorithms for diagnostics and prognostics of lifetime;
2. Develop the advanced control strategy with self-optimizing and fault-tolerant features;
3. Develop the hardware module for implementation of the monitoring, diagnostics, prognostics, and control functions; and
4. Perform characterization of stacks and systems in SOE and rSOC nominal and faulty conditions and validation of the product prototype.
Despite their attractive features, SOC systems (a common term for SOEC, SOFC, and rSOC) are still not massively present in in-field applications. To ensure that SOC systems operate reliably, and efficiently and deliver hydrogen or electric power when required, an accurate assessment of their performance, health, and life span is necessary. That is the topic at the heart of the REACTT project.
REACTT aims at designing, engineering, and testing a platform that integrates monitoring, diagnostics, prognostics, and control (MDPC) for the emerging generation of SOC systems for massive production of hydrogen at low cost from renewable energy sources. Such platforms will ensure maximal efficiency of operation, reliability, durability, and reduction of operational and maintenance costs. Consequently, SOC systems cope more efficiently with the non-stationary operational regimes at the stack and system level, thanks to the optimally tailored control actions across the dynamic transients and switching between different modes of operation. Taking advantage of previous SOFC projects in this research area, REACTT project starts at TRL 4. After the engineering design process, validation and testing of the MDPC tool on stacks will be performed and the final TRL of 6 is expected to be achieved (Figure 1).
The overall objectives of the REACTT project are the following:
1. Improve durability, reliability, and maintainability of SOEC and rSOC stacks by developing innovative algorithms for diagnostics and prognostics of lifetime;
2. Develop the advanced control strategy with self-optimizing and fault-tolerant features;
3. Develop the hardware module for implementation of the monitoring, diagnostics, prognostics, and control functions; and
4. Perform characterization of stacks and systems in SOE and rSOC nominal and faulty conditions and validation of the product prototype.
The main accomplishments of REACTT by the end of the second reporting period are summarized as follows:
• Test protocols that include fingerprint tests under non-faulty operation, as well as tests that would emulate faulty operation, all to better understand how stacks would respond to faults and how easily they recover once the normal operation is restored;
• 4 short stacks (6 cells each) and 3 full stacks with 70 repeating elements were delivered by the manufacturer SolydEra (Figure 2);
• An extensive experimental campaign was conducted by CEA and EPFL on SOEC short stack (Figure 4) and segmented cell stack at EPFL (Figure 3). Over 11.000h and 2100h of operating hours for the short stacks and the full stack respectively. Several fault regimes were included: (i) high steam conversion, (ii) H2 inlet starvation, (iii) humidity in O2 electrode. Over 1.000 EIS measurements have been performed with sinusoidal and discrete random binary signal (DRBS) excitation. An excerpt is given in Figure 4.
• The second (upgraded) release of the MDPC HW platform (Figure 5). It hosts and executes the monitoring, diagnosis, prognosis, and control algorithms. The overall concept of this HW and of the firmware running on it is shown in Figure 5. The platform is low-cost, yet with high computational performance, thanks to the carefully selected components and optimized HW and SW design.
• Firmware for the MDPC platform including the algorithms running on the MDPC board, the database for the data exchange among the MDPC algorithms, and the communication with external control units (Figure 5).
• An innovative excitation module (EM) for stack perturbation with conventional sinusoidal and non-conventional discrete random binary signal (DRBS) has been developed (Figure 6).
• A real-time optimization (RTO) algorithm scaled up for operating the 5kW solid-oxide electrolyzer (SOE) system at optimal efficiency has been designed. The RTO problem is formulated as a constrained nonlinear optimization problem and, at this stage, Constraint Adaptation with input filtering has been selected as the RTO solution approach. First simulation results were obtained on a simulated SOEC system. The proposed RTO scheme effectively pushes the system to higher levels of efficiency and maintains the system there despite perturbations by tracking active constraints (Figure 7).
• A consistent diagnostic framework comprising a set of tools supporting two kinds of diagnostic approaches:
- the passive one utilizing conventional process and data-driven models of the stack and system (Figure 8) and
- the active one based on additional stack perturbation to get the stack dynamics in terms of the electrochemical impedance spectra (EIS). The diagnosis is pursued by interpreting the spectra by using e.g. Equivalent Circuit Models (c.f. Figure 9).
• A supervisory module that coordinates the operation of the MDPC modules (Figure 10).
• Test protocols that include fingerprint tests under non-faulty operation, as well as tests that would emulate faulty operation, all to better understand how stacks would respond to faults and how easily they recover once the normal operation is restored;
• 4 short stacks (6 cells each) and 3 full stacks with 70 repeating elements were delivered by the manufacturer SolydEra (Figure 2);
• An extensive experimental campaign was conducted by CEA and EPFL on SOEC short stack (Figure 4) and segmented cell stack at EPFL (Figure 3). Over 11.000h and 2100h of operating hours for the short stacks and the full stack respectively. Several fault regimes were included: (i) high steam conversion, (ii) H2 inlet starvation, (iii) humidity in O2 electrode. Over 1.000 EIS measurements have been performed with sinusoidal and discrete random binary signal (DRBS) excitation. An excerpt is given in Figure 4.
• The second (upgraded) release of the MDPC HW platform (Figure 5). It hosts and executes the monitoring, diagnosis, prognosis, and control algorithms. The overall concept of this HW and of the firmware running on it is shown in Figure 5. The platform is low-cost, yet with high computational performance, thanks to the carefully selected components and optimized HW and SW design.
• Firmware for the MDPC platform including the algorithms running on the MDPC board, the database for the data exchange among the MDPC algorithms, and the communication with external control units (Figure 5).
• An innovative excitation module (EM) for stack perturbation with conventional sinusoidal and non-conventional discrete random binary signal (DRBS) has been developed (Figure 6).
• A real-time optimization (RTO) algorithm scaled up for operating the 5kW solid-oxide electrolyzer (SOE) system at optimal efficiency has been designed. The RTO problem is formulated as a constrained nonlinear optimization problem and, at this stage, Constraint Adaptation with input filtering has been selected as the RTO solution approach. First simulation results were obtained on a simulated SOEC system. The proposed RTO scheme effectively pushes the system to higher levels of efficiency and maintains the system there despite perturbations by tracking active constraints (Figure 7).
• A consistent diagnostic framework comprising a set of tools supporting two kinds of diagnostic approaches:
- the passive one utilizing conventional process and data-driven models of the stack and system (Figure 8) and
- the active one based on additional stack perturbation to get the stack dynamics in terms of the electrochemical impedance spectra (EIS). The diagnosis is pursued by interpreting the spectra by using e.g. Equivalent Circuit Models (c.f. Figure 9).
• A supervisory module that coordinates the operation of the MDPC modules (Figure 10).
Some of the developments in REACTT go beyond the state of the art. The Bitron Board as low-cost embedded hardware is definitely a new versatile tool for SOC systems operation. It allows the execution of monitoring diagnostics, prognostics, and control techniques to enhance the lifetime while keeping the efficiency at a feasible maximum.
The essential feature of the excitation module is that it can inject practically deliberately chosen waveform on the frequency range up to 18kHz while able to provide 200 A maximum direct current to the stack. The excitation module can be applied directly to a broad range of stacks and on top of the existing power supplies. That discards any need for expensive re-design of the existing power converter and greatly saves efforts in the development stage of the monitoring and control technologies for SOC systems.
The initial achievements of the REACTT project indicate their potential to lead to marketable solutions that ensure more effective and versatile asset monitoring and optimized operation in the context of in-field applications of the SOC technology. REACTT relates to the FCH-2-JU- Multi-Annual Work Plan -2014-2020 - Innovation Pillar 2 (MAWP). The goals are in agreement with those set by the Energy Pillar for the area and, in particular, its strategic objective to “implement an optimal research and innovation program at EU level to develop a portfolio of clean and efficient solutions that exploit the properties of hydrogen as an energy carrier and fuel cells as energy converters”.
The essential feature of the excitation module is that it can inject practically deliberately chosen waveform on the frequency range up to 18kHz while able to provide 200 A maximum direct current to the stack. The excitation module can be applied directly to a broad range of stacks and on top of the existing power supplies. That discards any need for expensive re-design of the existing power converter and greatly saves efforts in the development stage of the monitoring and control technologies for SOC systems.
The initial achievements of the REACTT project indicate their potential to lead to marketable solutions that ensure more effective and versatile asset monitoring and optimized operation in the context of in-field applications of the SOC technology. REACTT relates to the FCH-2-JU- Multi-Annual Work Plan -2014-2020 - Innovation Pillar 2 (MAWP). The goals are in agreement with those set by the Energy Pillar for the area and, in particular, its strategic objective to “implement an optimal research and innovation program at EU level to develop a portfolio of clean and efficient solutions that exploit the properties of hydrogen as an energy carrier and fuel cells as energy converters”.