Periodic Reporting for period 2 - PRETZEL (Novel modular stack design for high pressure PEM water electrolyzer technology with wide operation range and reduced cost)
Okres sprawozdawczy: 2019-07-01 do 2021-06-30
The main challenges in PEMEL design are the CAPEX-reduction by minimizing the use of critical raw materials (precious metal catalysts and coatings and titanium structures) and the increase of the operating pressure to reduce mechanical compression requirements, reducing system complexity and increasing system efficiency.
The central target of the PRETZEL project has been to design and manufacture a 25 kW PEMEL stack that reaches an operation temperature of 90°C, pressure of 100 bar and current density of 4 A cm-2 (6 A cm-2 in overload mode), while maintaining above 70 % efficiency and fast system response times. This has been demonstrated by reaching the main objectives of developing and evaluating optimized PEMEL components and a stack design based on hydraulic compression. Following the objective to disseminate and exploit the PRETZEL archivements impactfully, results have been published in scientific journals and several novel components designed during PRETZEL have been commercialized.
The central target of the PRETZEL project has been to design and manufacture a 25 kW PEMEL stack that reaches an operation temperature of 90°C, pressure of 100 bar and current density of 4 A cm-2 (6 A cm-2 in overload mode), while maintaining above 70 % efficiency and fast system response times. This has been demonstrated by reaching the main objectives of developing and evaluating optimized PEMEL components and a stack design based on hydraulic compression. Following the objective to disseminate and exploit the PRETZEL archivements impactfully, results have been published in scientific journals and several novel components designed during PRETZEL have been commercialized.
High activity antimony doped tin oxide (ATO) supported iridium catalysts were synthesised at IBERCAT exploring several synthesis routes, iridium loadings and ATO support types. The highest mass activity, measured in RDE at CERTH, up to eight times and three times higher than commercial iridium oxide and iridium metal, respectively, was achieved by synthesising a commercial ATO supported 30 wt.-% iridium catalyst via the Lettenmeier synthesis route. Research results were published in ACS catalysis.
ADAMANT and CERTH prepared MEAs exploring different catalyst types, catalyst loadings, coating procedures and pressing procedures. Small scale PEMEL cell characterisations at CERTH and DLR identified the developed doctor blade coating and roll-to-roll pressing, which could enable low cost and continuous mass production, as a promising technique. After comparison of different manufacturing techniques for CCM production, spraying was selected as a suitable technique especially for large-scale double CCM manufacture in the framework of the project. The work performed was presented in the Patras IQ exhibition through PRETZEL’s brochure and poster created by ADAMANT. The double-CCMs and their developed manufacturing process will be exploited for using in further research activities, developing products, and providing service to stakeholders.
GKN manufactured novel porous current distributors (PCDs) by sintering a titanium powder micro porous layer onto titanium expanded metal sheets. Selective laser melting was identified as a rapid, low-cost technique, but additional optimisation and testing is needed to perfect and upscale this approach. Tests at DLR have shown that the developed Ti-GKN PCDs increase PEMEL efficiency very significantly by over 20% at 4 A cm-2 compared to state-of-the-art mesh type PCDs. This innovation was publicized in the high impact scientific journal Advanced Energy Materials. The Ti-GKN PCD component was commercialised and is now available as a product, sparking the interest of several potential customers.
DLR manufactured novel, low-cost corrosion resistant PCDs, by coating commercial stainless-steel mesh PCDs with thin layers of titanium and niobium via VPS. 1000-hour accelerated stress test have shown, that this layer is effective in preventing catastrophic surface corrosion and MEA poisoning completely and reduces mass transport limitations significantly (12% efficiency increase at 2 A cm-2). This novel approach was published in the journal Energy & Environmental Science and has led to additional industry cooperation developing new and optimised coated PCD structures.
DLR and WHS produced the PRETZEL pole plates by coating high conductivity copper plates with corrosion resistant titanium or niobium via VPS. Corrosion test performed by UPT showed, that both coatings are totally effective in protecting the copper plate from corrosion at harsh anodic conditions. Interfacial contact resistance tests showed that the niobium coating provides better electrical contact than titanium. The research results were published in the International Journal of Electrochemical Science.
While iGas carried out the extensive retrofitting of the PRETZEL PEMEL system, WHS designed, optimised, and successfully manufactured the hydraulically compressed, modular, low-cost, high-performance PRETZEL stack. The design approach was presented in the International Journal of Hydrogen Energy and the concept is licenced to a WHS spin-off company offering a commercial product.
Bringing together all individual performance and durability optimisations on the PEMEL components of the PRETZEL project, the long-term 2000-hour electrochemical characterisation of the PRETZEL stack will be carried out by iGas and WHS. Tests with a prototype stack at near target conditions demonstrated the successful stack design. Characterisation of the final 25 kW stack is ongoing, and results will be shared subsequently.
Physical characterisations at CERTH, UPT and DLR of catalysts, MEAs and PPs provided valuable insight and enabled the connection of observed phenomena and trends to their physical cause.
IBERCAT managed and planned the dissemination and exploitation actions of the relevant PRETZEL results. A website (http://pretzel-electrolyzer.eu/) and social media presence was established. Among many other successful communication and dissemination activities, a NEPTUNE-PRETZEL joint workshop was organised.
ADAMANT and CERTH prepared MEAs exploring different catalyst types, catalyst loadings, coating procedures and pressing procedures. Small scale PEMEL cell characterisations at CERTH and DLR identified the developed doctor blade coating and roll-to-roll pressing, which could enable low cost and continuous mass production, as a promising technique. After comparison of different manufacturing techniques for CCM production, spraying was selected as a suitable technique especially for large-scale double CCM manufacture in the framework of the project. The work performed was presented in the Patras IQ exhibition through PRETZEL’s brochure and poster created by ADAMANT. The double-CCMs and their developed manufacturing process will be exploited for using in further research activities, developing products, and providing service to stakeholders.
GKN manufactured novel porous current distributors (PCDs) by sintering a titanium powder micro porous layer onto titanium expanded metal sheets. Selective laser melting was identified as a rapid, low-cost technique, but additional optimisation and testing is needed to perfect and upscale this approach. Tests at DLR have shown that the developed Ti-GKN PCDs increase PEMEL efficiency very significantly by over 20% at 4 A cm-2 compared to state-of-the-art mesh type PCDs. This innovation was publicized in the high impact scientific journal Advanced Energy Materials. The Ti-GKN PCD component was commercialised and is now available as a product, sparking the interest of several potential customers.
DLR manufactured novel, low-cost corrosion resistant PCDs, by coating commercial stainless-steel mesh PCDs with thin layers of titanium and niobium via VPS. 1000-hour accelerated stress test have shown, that this layer is effective in preventing catastrophic surface corrosion and MEA poisoning completely and reduces mass transport limitations significantly (12% efficiency increase at 2 A cm-2). This novel approach was published in the journal Energy & Environmental Science and has led to additional industry cooperation developing new and optimised coated PCD structures.
DLR and WHS produced the PRETZEL pole plates by coating high conductivity copper plates with corrosion resistant titanium or niobium via VPS. Corrosion test performed by UPT showed, that both coatings are totally effective in protecting the copper plate from corrosion at harsh anodic conditions. Interfacial contact resistance tests showed that the niobium coating provides better electrical contact than titanium. The research results were published in the International Journal of Electrochemical Science.
While iGas carried out the extensive retrofitting of the PRETZEL PEMEL system, WHS designed, optimised, and successfully manufactured the hydraulically compressed, modular, low-cost, high-performance PRETZEL stack. The design approach was presented in the International Journal of Hydrogen Energy and the concept is licenced to a WHS spin-off company offering a commercial product.
Bringing together all individual performance and durability optimisations on the PEMEL components of the PRETZEL project, the long-term 2000-hour electrochemical characterisation of the PRETZEL stack will be carried out by iGas and WHS. Tests with a prototype stack at near target conditions demonstrated the successful stack design. Characterisation of the final 25 kW stack is ongoing, and results will be shared subsequently.
Physical characterisations at CERTH, UPT and DLR of catalysts, MEAs and PPs provided valuable insight and enabled the connection of observed phenomena and trends to their physical cause.
IBERCAT managed and planned the dissemination and exploitation actions of the relevant PRETZEL results. A website (http://pretzel-electrolyzer.eu/) and social media presence was established. Among many other successful communication and dissemination activities, a NEPTUNE-PRETZEL joint workshop was organised.
The hydraulically compressed design has proven itself as an innovative design with several advantages. The large heat exchange surface area that is attained in this design, in combination with the high thermal conductivity developed pole plates, minimizes lateral temperature gradients and hot-spots, reducing thermal stress and prolonging stack lifetime. Furthermore, the inevitable long term dimensional change of the membrane electrode assembly caused by membrane or electrode thinning is compensated by the hydraulic compression preventing the loss of electrical contact. The PRETZEL-developed pore graded porous current distributor increases electrical efficiency of the electrolysis process by over 20 % at the target current densities, reducing operational cost significantly. The highly corrosion resistant niobium, titanium and gold coated copper polar plates designed and manufactured in the PRETZEL project provide two distinct improvements. Firstly, the material costs are significantly lower than state-of-the-art high-grade titanium and secondly the high conductivity copper ensures low electrical and heat transport resistance.
The PRETZEL innovations, commericalized stack design and components will directly enable the additional commerical roll-out of PEMEL systems in the future. Furthermore, new knowledge with respect to operating PEMEL systems at high pressure, current density and temperature as well as on all developments of the PRETZEL components was gained and shared with the scientific community, presenting the lessons learned. This will accelerate further technological advancements. In this, the PRETZEL results will have a signficant impact on both a scientific as well as on an economic level.
The PRETZEL achievements will, together with the numerous impactful innovations realized in the scientific community, drive the large-scale commercial PEM electrolysis adaptation forward, accelerating the green revolution that is direly needed to combat a catastrophic climate change.
The PRETZEL innovations, commericalized stack design and components will directly enable the additional commerical roll-out of PEMEL systems in the future. Furthermore, new knowledge with respect to operating PEMEL systems at high pressure, current density and temperature as well as on all developments of the PRETZEL components was gained and shared with the scientific community, presenting the lessons learned. This will accelerate further technological advancements. In this, the PRETZEL results will have a signficant impact on both a scientific as well as on an economic level.
The PRETZEL achievements will, together with the numerous impactful innovations realized in the scientific community, drive the large-scale commercial PEM electrolysis adaptation forward, accelerating the green revolution that is direly needed to combat a catastrophic climate change.