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Production Ready Heat Exchangers and Fuel Cell Stacks for Fuel Cell mCHP

Periodic Reporting for period 2 - HEATSTACK (Production Ready Heat Exchangers and Fuel Cell Stacks for Fuel Cell mCHP)

Période du rapport: 2017-12-01 au 2020-02-29

Micro-Combined heat and power (mCHP) generation holds great potential for lowering energy cost and CO2 emissions in the residential housing sector. Of the various mCHP technologies, fuel cells, show great promise due to their high electrical efficiency potential (electrical efficiency of up to 60% and a combined efficiency in cogeneration of more than 90%). Fuel cell technologies are still under development and the capital cost of units available today remains high, preventing mass-market exploitation. To become economically competitive, fuel cell mCHP system CAPEX costs must be reduced substantially. This can only be achieved with technological advancement and increased production volumes through the industrialisation of key component manufacturing.

Major components of the fuel cell systems include the fuel cell stack and heat exchangers. European FC mCHP technology pioneers, Vaillant Group, have developed a state-of-the-art mCHP system using a Solid Oxide Fuel Cell (SOFC) stack developed by Sunfire. To date, this system has undergone extensive field trials as part of European-wide residential fuel cell mCHP deployment initiatives and is one of the most promising SOFC mCHP technologies nearing commercial deployment. This system also utilises an innovative Cathode Air Preheater (CAPH) that is based on a novel gas to gas heat exchanger (recuperator) design developed by Senior Flexonics, responsible for recovering heat energy from the exhaust gas to heat air before it enters into the fuel cell. Together, the SOFC stack and CAPH represent the two most expensive components within the whole system for which the cost and supply will be key to future economic competitiveness and commercial uptake of SOFC mCHP appliances. Although Vaillant have withdrawn from FC mCHP development, Sunfire will now lead the development of the fuel cell module building on Vaillant’s original work.

HEATSTACK focuses on the industrialisation of these two components with the aim of achieving significant overall system cost reductions through volume production, ensuring that better total annual energy cost balance for the customer is provided:
1) Cathode Air Preheaters: HEATSTACK aims to develop a production ready CAPH for the residential (micro-)CHP market and associated manufacturing capacity for volume production
2) SOFC Stack: HEATSTACK will optimise the production process, and develop higher volume manufacturing capability, impacting the overall cost of fuel cell stack production.

HEATSTACK has successfully undertaken research, design, development and testing to achieve cost reductions and performance improvements to both the CAPH and the SOFC stack, with process innovation meaning that manufacturing of the full system is now more efficient and commencing (at low volumes initially) in 2020.
Senior Flexonics have developed a production-ready CAPH using AluChrom 318, which gives robustness, cost effectiveness and industry leading low levels of Cr leakage. Senior Flexonics have also invested in equipment and tooling for process efficiency – manufacturing of the CAPH using new processes proves that the cycle time is reduced by over two thirds. Senior Flexonics overcame manufacturing challenges presented by using AluChrom, including significantly modifying the form of the gas plate and improving laser welding consistency and quality. The new production equipment has been transferred, installed and recommissioned at their manufacturing facility in Czechia, with trials completed, ready for low-volume production.

Sunfire have proven printed glass seals as the best-value method for industrial production of fuel cell stacks, developed production processes and achieved process automation levels supported by a cost-benefit analysis. Sunfire have also undertaken intensive testing, including full units that integrate the new CAPH and optimised fuel cell stack, with performance tests showing these technologies are ready for use in series production.

UBHAM designed and used a Denuder technique to quantitatively analyse the chromium vaporisation from Inconel 625 and AluChrom 318. Cr evaporation rate for AluChrom 318 is approx. one order of magnitude lower than for Inconel 625. Their extensive materials research generated a number of key results, including: (i) low cost, low Cr evaporation and excellent high temperature corrosion resistance make AluChrom 318 highly suitable for CAPH application, (ii) AluChrom has improved Cr leakage rates when compared to all other materials after just 150 hours, (ii) AluChrom surface reduces Cr oxide content and increases Alumina thus offering a more robust surface material. UBHAM also investigated pre-heat treatment for material optimisation and found the best corrosion resistance was for samples pre-treated at 1100°C for 1 hour.

ICI Caldaie integrated the heat exchanger prototypes into their test rig and adapted it to test in the widest range of conditions possible and improve the quality of data collected. ICI Caldaie’s testing proves the Senior Flexonics CAPH performance levels and demonstrates their potential for other (larger) domestic/commercial CHP applications.

Field testing undertaken by Vaillant also generated positive results for HEATSTACK in terms of system performance and lifespan.

The exploitation of project outputs is supported by a techno-economic assessment including life cycle analysis, full business plan and exploitation strategy. Dissemination of project results includes featuring at the 2019 Bruges Workshop Series on Fuel Cell Systems, promotion at the Hannover Messe exhibition (2019, 2018), presentation at Fuel Cell and Hydrogen Joint Undertaking’s flagship event in 2018, and sponsoring the Joint European Summer School Fuel Cell, Electrolyser, and Battery Technologies. External publications include a blogpost and webinar, as well as via the project’s own website, social media and brochures.
Senior Flexonics developed new capital equipment and tooling with several process improvements and innovations, to reduce manufacturing speed and improve quality. The CAPH has a contra flow design, works up to 1000⁰C, proven effectiveness of over 90% and very low pressure drop for both fluids. This enhanced design has been modified to fit the requirements of Sunfire’s new mCHP system for use in different applications and functions at different temperatures, pressures and flow rates.

Sunfire have considerably improved the SOC stack manufacturing process with novel designs incorporating different levels of automation, which combined with new material formulations make stack manufacture less labour intensive and reduce material usage, thus reducing unit cost and production speed. Sunfire have also incorporated know-how and technology from Vaillant to design and build their own mCHP system.

UBHAM have generated extensive performance data for AluChrom, versus Inconel and other metals, demonstrating the viability of AluChrom for use in the high temperature and gas environment of an operational CAPH in a SOFC system, and have developed a novel pre-heat treatment process that optimises the CAPH for that application.

Socio-economic impacts and wider societal implications come from the fuel cell system developed, offering high efficiency and reduced environmental impact. From its capability to operate as a hybrid, the system will be able to operate using hydrogen (a clean fuel) when the infrastructure for this in Europe is ready.