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EVOLVE Sintesi della relazione

Project ID: 303429
Finanziato nell'ambito di: FP7-JTI
Paese: Germany

Periodic Report Summary 3 - EVOLVE (Evolved materials and innovative design for high-performance, durable and reliable SOFC cell and stack)

Project Context and Objectives:
Emission of greenhouse gases (GHG) from industry, transportation and agriculture has played a major role in the recently observed global warming. In order to reduce the impact on environment, zero or near-zero emission energy systems, converting fuel efficiently into useful energy are increasingly investigated. Unprecedented rise in the fossil fuel prices has led to a growing economic concern towards the need of such energy systems. Additionally, geopolitical priority of reducing the dependence on foreign energy resources emphasizes the development of systems that may work with a variety of fuels and eventually with renewable energy resources such as hydrogen or bio-fuels.
Solid Oxide Fuel Cells (SOFCs) are one of the most attractive energy conversion devices, owing to the potential of operating at high efficiency of about 60% in standalone condition and over 80% (net) if waste heat is used for cogeneration. SOFCs do not require noble metals for catalysis in electrodes and may use a variety of fuels including hydrocarbons, CO and bio-fuels, besides hydrogen. These low-noise convertors thus offer very high potential in stationary application and combined heat and power units (CHP) for decentralized energy and in Auxiliary Power Units (APU) as well for mobile applications. Despite all the promising advantages and the unparalleled progress in its power output, SOFC faces critical challenges in term of its poor reliability, low durability and higher cost. Unless addressed meticulously, these obstacles will impede large-scale commercialization of fuel cells. Reliability and durability are adversely affected by a number of factors of which the following two can be considered as the route cause: 1) high operating temperatures (800-1000°C) of SOFC and 2) the need to use materials that provide multiple functionalities. This includes structural support, electrochemical activity, and electrical or ionic conduction, as well as at the same time compatibility with neighbouring components during the manufacturing process and fuel cell operation.

Looking back to the cell architectures which have been investigated in the last decades, one can point out three main cell designs: the oldest one or the first cell generation is the so called Electrolyte Supported Cell (ESC). The second cell generation which can be named as Anode Supported Cell (ASC) and finally the third architecture, called the Metal Supported Cell (MSC) have been then successively developed, targeting for each of them improved performance and reliability in comparison to the former one.

Beyond the state of the art, the EVOLVE cell concept will assist in combining the beneficial characteristics of the previous cell generations, the so called ASC and MSC and will address further key challenge like sulfur poisoning, of these two competing technologies linked with presence of Nickel as catalyst and structural component in the nickel / zirconia standard anodic cermet. The innovation of the EVOLVE cell concept remains in its anode compartment without having nickel as structural component. The anode compartment is based on a metal alloy forming a protective alumina layer enhancing stability during re-oxidation cycles and an electronic conducting perovskite for the current collection. An European consortium including academics and industrial partners with complementary backgrounds and expertise has been build up, and has been granted a financial support in 2011 by the Fuel Cells and Hydrogen Joint Understanding under the Grant Agreement n° 303429, for the development of the EVOLVE cell concept. The consortium EVOLVE includes: the German Aerospace Center (Germany) assuming the leadership and the coordination, Alantum Europe GmbH (Germany), ARMINES (France), Ceramic Powder Technology AS (Norway), Consiglio Nazionale delle Ricerche (Italy), Institut Polytechnique de Grenoble (France), Saan Energi AB (Sweden) and Ceraco Ceramic Coating GmbH (Germany).

Project Results:
A first prototype has been developed by means of Plasma Spraying using as reference material La0,1Sr0,9TiO3-α (LST) for the anode and cermet NiCrAl / LST with or without addition of Nickel.
Without addition of Nickel in the substrate and/or the anode materials, the performances remain low ie. power density < 100 at 750 °C and 0.7 V in average. Enhanced performances were recorded when infiltrating Ni in both substrate and anode functional layer (100 < power density < 150 at 750 °C and 0.7 V). This corresponds to an increased catalytic activity for the H2 oxidation. The best performances were recorded when anode and substrate materials were infiltrated by Ni and by loading the substrate material with a LST + NiO composite (power density > 350 at 750 °C and 0.7 V). This confirms that the electronic percolation is still an issue and must be improved when perovskite materials are considered as anode or current collector.
It was evidenced that based on this architecture, the EVOLVE cell can withstand at least 10 redox cycles without significant degradation, showing a significant improvement compared to main streams anode supported cells. Nonetheless degradation rate observed during galvanostatic aging for more than 500 hours remain significantly larger (between 15% and 30%) than target value.

Potential Impact:
The development of the EVOLVE cell is actually scheduled until end of October 2016. Causes of degradation are still under investigation and will be addressed further during the next twelve months in order to implement mitigation solution. Cell architecture is being up-scaled to a 90 mm x 100 mm footprint for stack integration and assessment of potential against main stream SOFC technologies.

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