Diagnostics and Control of SOE

Several previous monitoring, diagnostic and control projects were performed in the field of SOFC in the last years e.g. DESIGN, DIAMOND and INSIGHT [53]. They developed and validated monitoring and diagnostic techniques ranging from processing conventional signals to advanced techniques like Electrochemical Impedance Spectroscopy (EIS), with both conventional sinewave excitation and PRBS (pseudorandom binary sequence signal) and Total Harmonic Distortion (THD), and diagnostic algorithms for Detection and Isolation of faults (FDI). In order to embed in a real SOFC system, the developed monitoring, diagnostic and lifetime tools described above, specific hardware has been developed.

The topic aims at developing the same approach on SOE (possibly including co-SOE) and/or rSOC stacks and systems, with the aim to increase lifetime of stack and availability of systems operated dynamically. To establish the ranges of dynamic operation (frequency, amplitude and occurrence of reactant, power and heat ratios involved) the most promising process chains should be considered, as determined e.g. in the H2020 project BALANCE [54] or motivated by recorded industrial assessment.

The project should cover the following:

• Enhance the understanding of (co-)SOE and/or rSOC stack degradation mechanisms in representative operating conditions of intermittent electricity supply and/or rSOC cycles using both experimental and modelling approaches;
• Assess system capabilities:
  • For rSOC operation to switch from one mode to the other with the appropriate dynamics (time scale, hydrogen or syngas production volume, electricity - and possibly heat) production, etc.);
  • For (co-)SOE operation to cope with fluctuating electricity input in terms of thermal management (time scale, hydrogen or syngas production volume, down-stream processes, etc.);
• Identify suitable stack and system level monitoring parameters which indicate a possible critical state of the (co-)SOE and/or rSOC stack/module within the system, using advanced monitoring techniques like EIS (electrochemical impedance spectroscopy) and using both sinusoidal and PRBS (pseudo random binary signal) stimuli) complemented by THD (total harmonic distortion) and/or DRT (distribution of relaxation time) analysis in addition to conventional signals (temperature, pressure, flow rate etc.);
• Develop the algorithms able to perform the diagnostics and to determine the remaining useful lifetime depending on the state of health of the stack/module;
• Develop the hardware for the implementation of these advanced Monitoring, Diagnostic and Lifetime tools, able to interact with the power electronics of the system to apply counteractions;
• Develop control devices and strategies to keep performance, and improve durability and availability of stacks and systems;
• Demonstrate the diagnostic approach and the developed hardware for monitoring and lifetime prediction, and to validate the control strategy and devices in a relevant environment with (co-SOE) and/or rSOC stacks or stack modules;
• Develop a physical product, embedding the software tools, evaluate the TCO (total cost of ownership) of this product and propose routes for exploitation of the solutions developed.

Taking advantage of previous SOFC projects in this research area, the project should start with TRL 4 and conclude at TRL 6.

Any safety-related event that may occur during execution of the project shall be reported to the European Commission's Joint Research Centre (JRC) dedicated mailbox JRC-PTT-H2SAFETY@ec.europa.eu , which manages the European hydrogen safety reference database, HIAD and the Hydrogen Event and Lessons LEarNed database, HELLEN.

Activities developing test protocols and procedures for the performance and durability assessment of fuel cell or electrolyser components should foresee a collaboration mechanism with JRC (see section 3.2.B ""Collaboration with JRC""), in order to support EU-wide harmonisation. Test activities should adopt the already published FCH 2 JU harmonized testing protocols to benchmark performance and quantify progress at programme level.

The FCH 2 JU considers that proposals requesting a contribution of EUR 2.5 million would allow the specific challenges to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts.

Expected duration: 3 years.

[53] https://www.fch.europa.eu/page/fch-ju-projects

[54] https://cordis.europa.eu/project/rcn/206760/factsheet/en

High temperature Solid Oxide Electrolysers (SOE) are the most promising solution for efficient and cost-effective hydrogen production and storage/re-use of intermittent electricity from renewable sources. The integration of SOE stacks with balance of plant components proved the successful use of these systems, however, coupling with real intermittent renewable energy sources (RES) is still a big challenge. Due to the intermittent nature of RES, using them to power SOE systems is expected to require substantial transient operation capability from the SOEs, which can induce high stress onto the stack and system as compared to steady state operation, resulting in thermal issues and degradation worsening.

As compared to other electrolysis technologies, SOE offers two specificities. The first one is the reversible operation (rSOC), meaning the possibility to operate in electrolysis mode to produce hydrogen when an excess of intermittent renewable energy is available, and in fuel cell mode to produce electricity from hydrogen previously produced when electricity available stands below the demand. Depending on the use case, a large number of cycles between electrolysis and fuel cell mode will have to be performed over the lifetime of the rSOC system (at least one per day). The time to switch from one mode to the other can be in the range of 20 minutes or below. It has been found recently in ongoing EU/FCH 2 JU projects that such an operation can induce accelerated degradation compared to stationary SOFC or SOE operation. So far, the exact mechanism behind this acceleration is not well understood. The second specificity of SOE is its ability to electrolyse not only steam but also CO2, and as a consequence the possibility to co-electrolyse steam and CO2 to produce syngas (H2+CO mixture), which can subsequently be used for the production of synthesis molecules (gaseous or liquid). As compared to pure SOE operation, the co-electrolysis (so-called co-SOE) can induce additional degradation due to the presence of carbon, in addition to the dynamic and transient operation also needed for this technology.

Consequently, careful and coordinated control actions during transient manoeuvres, which may occur when coupling (co-)SOEs with RES or rSOC operation are therefore needed. It is key to first identify the specific consequences of dynamic operation at stack and system level, and then to develop methods to detect and finally counteract related issues with simple and cost-efficient methods. Subsequently, BoP control actions are to be developed to i) guarantee smooth transient operations during mode shift operations and ii) select proper working points to optimize performance, keeping durability and availability in the planned maintenance timeframe.

Development of a monitoring and diagnostic tool, also able to evaluate remaining useful lifetime and to propose counteractions to the (co-)SOEC or rSOC stack/system. This will contribute to improve the durability, reliability and availability of those systems, thus reducing their TCO and accelerating their market penetration. The most relevant degradation mechanisms in (co-)SOE or rSOC stacks/systems for specific market segments will be identified and analysed with respect to impact on lifetime, such as fatal impact or slow decrease of performances.

Monitoring parameters will be determined that reveal the State-of-Health of (co-)SOE and/or rSOC stacks regarding those identified critical mechanisms.

Counter measures to prevent fatal (co-)SOE or rSOC stack failure should be proposed, including possible regular treatments that prevent or slow-down long-term degradation, with a target of (co-) SOE and/or rSOC stack lifetime increase by 5%, allowing to reach a production loss rate of 1.2%/1,000h and an availability increase by 3% to reach a value of 98% (in agreement with the MAWP target in 2024 [55]).

It should be demonstrated that the added cost of this monitoring/diagnostics approach does not increase the overall system manufacturing costs by more than 3%, and contribute to achieve the reduction of the operation and maintenance cost by 10%, to reach a value of €120/(kg/d)/y in agreement with the MAWP target in 2024.

A physical product, embedding the software tools should be developed. An evaluation of the TCO (total cost of ownership) should be done, to assess the benefit of installing such a tool in SOE systems, with a target to improve the TCO of a SOE of 15%, thanks to the increase of the maintenance interval and the minimization of the stack replacement as compared to a system not equipped with this tool. Accordingly, an exploitation roadmap should be defined at the end of the project.

[55] https://www.fch.europa.eu/page/multi-annual-work-plan

The conditions related to this topic are provided in the chapter 3.3 of the FCH2 JU 2020 Annual Work Plan and in the General Annexes to the Horizon 2020 Work Programme 2018– 2020 which apply mutatis mutandis.