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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - PRETZEL (Novel modular stack design for high pressure PEM water electrolyzer technology with wide operation range and reduced cost)

Teaser

Summary

Green hydrogen produced by electrolysis might become a key energy carrier for the implementation of renewable energy as a cross-sectional connection between the energy sector, industry and mobility. Proton exchange membrane (PEM) electrolysis is the preferred technology for this purpose, yet large facilities can hardly achieve FCH-JU key performance indicators (KPI) in terms of cost, efficiency, lifetime and operability. Consequently, a game changer in the technology is necessary. PRETZEL consortium will develop a 25 kW PEM electrolyzer system based on a patented innovative cell concept that is potentially capable of reaching 100 bar differential pressure. PEM electrolysis is highly dynamic and can fulfil the requirements for reserving power. Therefore the electrolyzer will dynamically operate between 4 and 6 A cm-2 and 90 Â°C achieving an unprecedented efficiency of 70%. Additionally, hydrogen enables the cross sectional use of renewable electrical energy sources such as wind or solar e.g. and can be used as fuel in the mobility sector, large scale energy storage in caverns or the gas grid, or builds up the basic chemical for the synthesis of alternative and conventional liquid energy carrier. The current state-of-the-art electrolyzer needs to become significantly cheaper (CAPEX), more efficient to reduce the operational cost, which are mainly related to electricity costs (OPEX), and need to avoid the use of the large amount of precious metals such as iridium and platinum and to reduce the amount of other expensive materials like titanium. Therefore the principal challenges in low temperature water electrolysis are the decrease CAPEX by reducing the use critical raw materials (precious metal catalysts and coatings), increase of the operating pressure for reducing mechanical compression requirements and so improving the energy performance of electrolyser-HRS or of power-to-gas systems injecting hydrogen into the highpressure gas transmission network. The overall goal of PRETZEL is to develop an innovative PEMEL that provides significant increases in efficiency and operability satisfying the market demands. Such electrolyzers are urgently needed in the context of the increased demands of the grid balancing market. PRETZEL is offering a break-through in becoming â€œGame Changerâ€ in the field of water electrolyzers. To reach this overall goal PRETZEL has the following objectives:
1.Develop and manufacture the components for the innovative high pressure PEMEL that operates at increased temperatures.
2.Develop and manufacture the high pressure PEMEL stack based on the novel principle of hydraulic compression.
3.Set-up and undertake continuous procedures to evaluate the development process through all phases against PRETZEL specifications.
4.Integrate the innovative PEMEL stack into a high pressure PEMEL test facility and validate the overall performance and operational criteria.
5.Disseminate and exploit the innovations in PRETZEL in order to prepare the market penetration of the new technology.

Work performed

Component specifications were established by defining the specifications and requirements for the components linking all cell components for the subsequent stack development. The objective was to identify, define and compile the cell parameters and requirements with the aim to reach the targets (performance, durability). The specifications are based on the relevant industrial areas for each electrolyzer component. The coating on the cupper polar plates were applied by VPS at DLR and corrosion measurements were performed at UPT. The PCDs with gradient porosity and Ir/Aerogel (30 wt%) catalysts were produced by optimized classical powder metallurgical technique and synthesized through sol gel process starting from alkoxide precursors, respectively. First PCDs made of expanded metal and fine powders were sent to partners (DLR, WHS) for further treatment and testing. The prepared and characterized catalyst support of Armines was sent to Ibercat for Iridium catalyst deposition. The synthesized catalysts were physicochemically and electrochemically characterized at CERTH while ADAMANT COMPOSITES and CERTH cooperated in small-scale MEA production. Performance assessment of the MEAs produced using typical commercial and specially designed test cells is ongoing. Preliminary results indicate the high potential of the iridium supported on ATO materials as anode PEM electrolysis materials mainly due to their high mass activity (current per electrocatalyst mass) and stability under PEM electrolysis conditions. Also the PCDs and coatings were physically and electrochemically characterized in a DLR in-house 4cm2 test cell as well as in the delivered ProH+ cell up to 4 and 6 A cm-2 at 75 and 90Â°C, respectively. Long term tests of 1000h were performed to investigate the durability behavior of the applied coatings for the PCDs. The computerized 3D model of the cell frame for the inner cell components is finalized as well as the CAD drawing of the HP electrolyzer stack. The two most crucial components are the cell frame for the inner cell components on the one hand, and the HP flange, which works as the base plate for the rest of the stack and contains the connections for media and electrical current, on the other hand. Therefore the design of the HP stack is completed and successfully reached.

Final results

Within this game changer project, major step improvements in terms of cost reduction, performance and efficiency will be delivered. It is actually expected to surpass perspectively the FCH JUâ€™s KPI targets in terms of cost, efficiency, lifetime and operability with further development based on this project by the year 2023. The improvements of the single components as well as the interaction of the innovations in a 25 kW scale high pressure system will be demonstrated. The hydraulically compressed cell design is a very new design with many advantages. A hydraulic medium which is closing and compressing the cells ensures an equal and homogeneous contact of the CCs against the electrode and is simultaneously cooling the cell. A homogeneous contact pressure is becoming the most important assembling issue at high current densities and leads to accelerated degradation if it is not fulfilled. The hydraulic medium is everywhere compressing with exactly the same force and additionally cooling the cell from outside which prevents even more the heating of the cell components. Additionally the hydraulic cell concept is able to counteract potential increase by degradation mechanism such as membrane or electrode thinning and prevent the loss of compression and electrical contact during operation. Furthermore the cell concept produces hydrogen at pressures above 100 bars and reduces additional compression steps. The development of the inner cell components will lead to a performance improvement of 20% which will reduce the cost significantly. Cost considerations and market analysis will be performed extrapolating from the project results to a megawatt range electrolyser in the following years. Due to the high amount of expected improvements, more markets can be addressed and more electrolysers can be commercially delivered than by continuous development based on todayâ€™s electrolysers.