Metal supported SOFC technology for stationary and mobile applications
Key Objectives of the project
Most SOFC demonstrations with ceramic cells in real system operation have until now revealed problems regarding reliability issues. Attention to reliability and robustness has especially been paid in connection with SOFC technology for mobile application. Modelling studies as well as recent practical experience has proved how up-scaling of cells and stacks to larger more industrially relevant sizes generally leads to lower reliability in real system operation and intolerance towards system abuse and operation failures. The aim of the METSAPP project is to develop novel cells and stacks based on a robust and reliable up-scale-able metal supported technology for stationary as well as mobile applications with the following primary objectives:
- Robust metal-supported cell design, ASRcell < 0.5 _cm2, 650ºC
- Cell optimized and up-scaled to > 300 cm2 footprint
- Improved durability for stationary applications, degradation < 0.25%/kh
- Modular, up-scaled stack design, stack ASRstack < 0.6 _cm2, 650ºC
- Robustness of 1-3 kW stack verified
- Cost effectiveness, industrially relevance, up-scale-ability illustrated.
Degradation tests have revealed that the SoA metal supported stack technology such as METSOFC has a potential for 5.000-10.000 operation hours at 650-750 oC stack temperature fulfilling the well known requirements for APU applications. However, the knowledge gained from the METSOFC project as well as from other parallel projects on metal supported cells (see state of the art below) highlighted the need for further improvements of the cell components in order to fulfil durability requirements in stationary applications (such as: Distributed generation, and CHP) where lifetime of 20.000 to 60.000 hours is mandatory. The established experience indicates that long term durability requires a further reduction of the operation temperature to 600 – 700 ºC further electrode development and further improvements of materials regarding high temperature stability. For commercial breakthrough of the SOFC technology it is vital that the materials cost in case of large scale cell and stack production is reduced.
The project is dealing with key parameters limiting the long term stability of current metal supported cells. For the metal support layers and cermet layers the type and amount of metal and ceramic components will be optimized. Improved nano-structured electrodes adapted to the metal-supported cell concept will be developed and tailored for high performance aiming at 40.000 hours lifetime operated on natural gas. To ensure high cell and stack component robustness physical models for the different governing failure modes and mathematical models for related random processes, accelerated test procedures will be validated. The electro-chemical model of the repeatable stack elements will be used for optimising the cell size and flow patterns of the interconnects. CFD & FEM modelling will be used for minimising pressure drop across the cells and contact resistance between cells and interconnects. Small stacks with larger cells will be developed and tested with respect to electrochemical performance and mechanical robustness.
Expected socio and economic impact
The impact in the society is expected to be seen in a faster and solid opening of the market of SOFC systems for many applications, such as micro-CHP in single houses, distributed generation of power and heat in apartment houses, hospitals, banks and office buildings, and APU for the transport sector (trucks and ships). This will result in much more efficient and clean means of utilizing our fuel resources for the production of electricity and heat, and hence have a tremendous impact on the future. Successful integration of SOFCs on the market will thus bring EU one step closer in achieving the targets for 2020 (20% cut in greenhouse gases, 20% increase in energy efficiency and 20% energy from renewable sources). The robust, reliable (and cheaper) SOFC systems of these European players will create important high-tech, clean-tech jobs in Europe with sales on the global market. The potential market for micro-CHP units is a significant part of the approx. 5 million boilers that are sold in the EU (Germany: 800 000) every year.