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Real operation pem fuel cells HEALTH-state monitoring and diagnosis based on dc-dc COnverter embeddeD Eis

Periodic Reporting for period 2 - HEALTH-CODE (Real operation pem fuel cells HEALTH-state monitoring and diagnosis based on dc-dc COnverter embeddeD Eis)

Période du rapport: 2017-05-01 au 2018-12-31

HEALTH-CODE aimed at improving and validating an advanced Monitoring and Diagnostic Tool (MDT) capable of evaluating the State-of-Health (SoH) of Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems for micro-Combined Heat and Power (µ-CHP) and Backup applications. The tool is based on the use of suitable data derived from Electrochemical Impedance Spectroscopy (EIS) measurements performed during system operation. In the literature, EIS has been widely recognized as an effective technique to extract valuable information through one single measurement. HEALTH-CODE solutions leverage EIS advantages through the proper HW design and on-board implementation, bridging laboratory and on-field applications.

The purpose of the diagnosis is to promptly detect and isolate specific faults within the FCs, to avoid any performance reduction or at least to hinder the irreversible degradation of the system and the consequent failure. As a result, the overall performance of the FC will improve, thus enhancing the deployment of these systems with a reduction of their operational costs.

HEALTH-CODE achieved the following main objectives:

1. Enhancement of PEMFC diagnosis for residential μ-CHP and backup:
An EIS board was designed and prototyped along with power electronics for µ-CHP application and the reengineering of the backup system’s power electronics. Optimal functionalities were proposed as trade-off between tool reliability and easiness of use.

2. Development of a diagnostic tool:
The second objective dealt with the design and implementation of diagnostic algorithms used for PEMFC stack monitoring and diagnosis to detect and isolate six faults, related components degradation and non-optimal operations. The algorithms were designed to support system status and durability estimation.

3. Innovative scaling-up methodology able to reduce testing efforts:
The proposed scaling-up approach is able to estimate full stack impedance data from single cell/short stack measurements. This technique allows reducing equipment, costs and investigation time.
The advancements achieved within HEALTH-CODE proved the capability of performing on-board impedance measurements, moving this technique from laboratory uses to product applications. It can be stated that the diagnostic tool along with its on-board implementation was successfully validated in terms of efficacy, reliability, cost and easy HW/SW integration.
The main project results are related to three main areas:

Hardware and power electronics
For the design and manufacturing of the EIS board and power electronics, great attention was given to current and voltage signals acquisition. The tool is suitable for stand-alone use and potentially for lab applications. This latter option was explored during Support Services for Exploitation of Research Results (SSERR) workshop held during the project. The HW related to µ-CHP was designed and manufactured to reach a maximum efficiency up to 94% when connected to the grid. The backup system power electronics required small modifications for the correct interfacing with the EIS board. By the end of the project, the prototypes are: 2 EIS board (proto 1), 4 EIS board (proto 2) and 1 DC/DC converter.

Experimental analysis
The experimental activity in HEALTH-CODE project was performed on PEMFC stacks on dedicated test bench and in operative configuration as commercial product. In total, more than 2300 impedance measurements were acquired at laboratory premises. About 25% of the measurements refers to nominal conditions, whereas the remaining 75% to faulty conditions, and all measurements exhibit high data quality. For µ-CHP system, the measurement features scaled consistently with the laboratory reference and the diagnostic tool requires only minimal tuning once installed. For backup system the result confirms the potentiality of scaling-up methodology to derive full stack impedance from single-cell measurements.

Monitoring and diagnostic algorithm
The proposed diagnostic tool was validated under operations similar to real field uses. The tool was able to perform on-board impedance measurements and process the data in a short time (few minutes) compatible with on-field applications. Moreover, the diagnostic tool was embedded with a user-friendly hardware interface – out of the scope of the project – for testing procedures and future exploitable applications. Through a touch-monitor, the operator can easily set the impedance measurement, initialize the diagnostic tool and, finally, analyse the results. The interface could be used for on-site checking and maintenance purposes. The indications derived from the measurements were used to follow the evolution of the stack status, inferring on its durability
Before HEALTH-CODE, the diagnosis of fuel cells was performed making use of measures taken with conventional sensors. Traditional diagnostic approaches require massive use of data analysis as well as modelling techniques to compensate for the lack of direct information on the electrochemical process occurring inside the cells. EIS brings more meaningful information than any other conventional measurement, thus enhancing the capability of diagnostic algorithms to detect and isolate faults. HEALTH-CODE introduces innovative solutions enhancing FC competitiveness thanks to the increase of reliability, leading to an impact on lifetime and performance. Therefore, a larger diffusion of FC systems will be gained with a further impact on energy savings and emissions reduction. Moreover, market growth is expected, enhancing the creation of new and innovative industries with new employment opportunities.

The proposed methodology will be exploited by the project partners towards the tested market products (backup & µ-CHP). The industry partners plan to integrate in their systems the EIS board developed during the HEALTH-CODE project. Initially, the new feature could be provided upon client requests and then, after gaining on-field experience, implemented on all FCs products available on companies’ catalog.

Moreover, during the project an exploitation analysis was conducted to evaluate the feasibility of applying the proposed solutions for further uses, such as mobile systems (automotive, buses, trains). Further exploitation will be pursued by academic partners to investigate the use of EIS-based diagnosis for other electrochemical devices, extending the potentiality of the diagnostic tool towards electrolysers (low and high temperature) and batteries. The above exploitations will come with enhanced features of the power electronics, which will benefit from the experience gained while designing, building and testing the DC/DC converters along with new functions.

The outcomes of HEALTH-CODE pave the way towards the implementation of monitoring and diagnostics through impedance measurements on commercial product after customization engineering activities. The availability of impedance measurements acquired while the system runs on field will facilitate the use of such a technique for lifetime, prognostics and advanced control of PEMFC. Additionally, perspective exploitation of advanced monitoring and diagnostics will lead to the improvement of maintenance actions and full integration within new energy paradigms such as smart building/grid as well as a useful implementation of Virtual Power Plant management concept.
Fig. 11 - EIS board - MDT interface
Fig. 10 - MDT off/on line results
Fig. 07 - BPSE Micro-CHP - EPS Backup Systems
Fig. 06 - EIS Board
Fig. 01 – Schematic representation of grid connected fuel cell system
Fig. 03 – Low voltage converter and EIS board at test bench being tested for EIS
Fig. 12 - Scaling up
Fig. 09 - EIS Stack Acquisition
Fig. 08 - Diag. Algorithm Tool
Fig. 04 - Examples of EIS spectra in nominal and faulty operations
Fig. 05 - Overall Schematization
Fig. 02 – Box with EIS board and analog fronte end communication board