In 2021, the UK government published its hydrogen strategy with the target of developing 5GW of low carbon hydrogen production capacity in the UK by 2030. This ambition has since been revised to 10GW. So called “green” Hydrogen is produced from water electrolysis powered by renewable energy. This will provide an important energy vector that can directly replace fossil fuels and enable net-zero decarbonisation across challenging sectors of the economy such as heavy road transport, shipping, industrial and domestic heating, and industrial production such as chemicals, cement and steel.
In recent years the MTC, in partnership with the other High Value Manufacturing Catapult centres, has built a detailed understanding of the technological advancements required to support the future global hydrogen value chain. A huge amount of research effort is focused on reducing the levelised cost of hydrogen (LCOH) by increasing electrolyser efficiency and ramping up production rates in the coming years, but just as important is embedding a sustainable circular economy within the manufacturing supply chain to ensure the equipment itself has the lowest possible embodied carbon emissions.
In the RecHycle project, The MTC created a new net shape manufacturing method that has the potential to enable relatively low cost, and more sustainable scale-up in manufacture of Polymer Electrolyte Membrane (PEM) electrolysers, which are some of the most promising systems for the production of green hydrogen at present.
Consolidated titanium plate with integrated porous structure and dissolvable salt insert
The MTC, as a centre of excellence for net shape manufacturing and powder metallurgy, is very well placed to develop innovative processing methods that can dramatically reduce material waste and the embodied carbon emissions associated with traditional supply chains.
Net shape powder metallurgy processes are capable of forming components close to their final geometry by applying moderate pressures and heat, densifying powders into a solid part by bonding the particles together without melting them. Minimal material is wasted and very few finishing activities are needed to meet the final dimensional specification. In addition, components have excellent mechanical properties suitable for industries requiring high integrity products that operate in demanding operating environments.
Historically however, low-volume production and relatively high-cost tooling have limited the wider usage of powder metallurgy within high throughput and cost sensitive supply chains. In an attempt to address this the MTC has created an innovative solution that uses low-cost inserts made from dissolvable salt. These facilitate geometric complexity similar to investment castings, but enable the use of low cost tooling and the simple removal of finished components using regular water after the densification process is complete.
The MTC’s first application of this invention has been the production of multiple intricate titanium electrolyser plates with integrated porous surfaces through one, single, low energy processing step. This is not only a far more streamlined process compared to the cast and wrought titanium supply chains currently utilised, but also combines three conventionally separate components into one.
The huge opportunity presented by this increased design freedom at relatively low cost became very clear after discussion with experts in the field, who typically just look to purchase off-the-shelf sheet metal as their material starting stock. The MTC’s unique approach may, for example, have the potential to increase the operational efficiency of electrolysers and fuel cells, as reducing the number of components/ layers/ interfaces within the cell stack reduces overall electrical resistance. Additionally, tailored porous structures can easily be created that optimise fluid flow and proton exchange membrane performance.
NaCI salt granules and titanium sponge fines
Porous and solid sections created in-situ
The MTC initially identified Hot Isostatic Pressing (HIP) as a potential method to consolidate recycled or minimally processed titanium powders into electrolyser plates. After initial trials an alternative net shape process with fewer production steps called Spark Plasma Sintering (SPS), or alternatively Field Assisted Sintering Technology (FAST) was assessed. Like HIP, this is a solid state powder consolidation process achieving very high quality fine grain microstructures with uniform properties and extremely few defects.
After some feasibility trials, SPS was found to be just as capable as HIP for producing plate-like components with porous surface structures using The MTC’s dissolvable inserts technique. SPS has the added advantage of using reusable dies and having short consolidation cycles. When combined with automated die filling, the proposed solution may be capable of achieving relatively high throughput production at low-cost and with minimal material wastage or energy consumption.
The MTC worked in partnership with a team from the University of Sheffield to create a series of demonstrator parts. The Birmingham Energy Institute at the University of Birmingham supported the prototyping of bipolar plates intended to operate under the harsh acidic and high voltage environments found within an industrial PEM electrolyser.
To verify the proposed solution’s sustainability benefits, The MTC utilised its expertise in Life Cycle Assessment (LCA) to analyse the embodied carbon emissions of various supply chains and production processes. An approximation of the current commercial PEM electrolyser manufacturing route was used as a baseline, including conventional titanium sheet manufacturing and traditional electrolyser stack assembly routes. The findings confirmed that there is a great deal of environmental benefit to be gained from the unconventional powder production routes the MTC have developed through the RecHycle project.
Dissolvable inserts with intricate features demonstrated as metal powder consolidation space holders
The MTC has taken a truly innovative approach to this globally recognised challenge, building on existing expertise and applying unconventional techniques that challenge perceptions of “what’s possible”. The resulting demonstration components showcase a path towards not only streamlining end-to-end manufacture of hydrogen electrolysers, but also lower capital costs and improved operational performance.
The next step in the development of this project is to work with industrial partners to devise a high throughput automation process for net-shape consolidation of plates and porous structures for electrolyser and fuel cell applications. In addition, opportunities exist for metals suppliers to support in identifying the most suitable powder materials available to maximise the cost and sustainability benefits presented.
Going forwards, the MTC will continue to innovate in the hydrogen sector and seek to incorporate circular economy thinking into every aspect of manufacturing. To achieve this, the MTC will further develop the LCA capabilities used in this project, as this will play an integral role in providing a digital space to safely map the impact of technology and processes on the real-world environment in a time efficient and cost-effective manner.
The net shape manufacturing techniques developed in this project could be very easily applied to a wide range of applications outside of hydrogen electrolysis and fuel cells. The method can be used for metal or ceramic materials and is best applied at scales where additive manufacturing is either too slow or too costly for the required application, or where material melting cannot be tolerated. In particular, the use of dissolvable inserts to fabricate highly complex, high quality components from consolidated recycled waste streams is a very exciting prospect.
Innovative space holder technique allows freedom to re-imagine bipolar plate design