THE CHALLENGE

Fuel cells and Hydrogen are technologies of key importance for the successful transformation to low carbon economy. The report of the International Energy Association from January 2013 stressed on the importance of hydrogen as energy carrier which ensures zero emissions, as well as on its production from water with electricity from Renewable Energy Sources (RES). Therefore, fuel cells and hydrogen are essential part of the technologies included in the European Strategic Plan for Energy Technologies (SЕT Plan), which reflects also in the Bulgarian engagements presented in the National Scientific Research Strategy and in the Innovation Strategy for Smart Specialization. An important role is given to energy conservation and energy production from RES as the two key measures for overcoming the problems of climate changes and energy security. For our country which is rich on RES, the introduction of “new and innovative technologies for energy production from renewables will ensure the utilization of only national resources. In this aspect the development of reversible devices which may work both in fuel cell and in electrolyzer mode, is marked as one of the technological challenges. The possibilities for reversibility make such systems very attractive for energy storage/generation from RES and for balancing services in smart grids. Thus IMOOD entirely covers both the European and national priorities, being focused on an innovative concept for reversible fuel cell/electrolyzer.

Overview

The main objective of the proposed project is the development of a concept for intermediate temperature fuel cell (600-700oC) which can work as electrolyzer in reverse mode. It is based on a new design of solid oxide fuel cell (dual membrane fuel cell - dmFC) confirmed in a previous (FP7) project, which eliminates the basic disadvantages of the existing designs in respect to water formation and evacuation through the electrodes. The kernel of the present proposal is a deeper insight in some new phenomena: (i) mixed ionic (proton and oxide ion) conductivity in the proton conducting electrolyte BaCe0.85Y0.15O2.925 (BCY15) and (ii) tendency for hydroxylation. Those recently discovered properties of the material need profound fundamental understanding combined with laboratory proof for controlled and targeted applications in direction increase of the dmFC efficiency, durability and operation in reversible mode.

The team members are selected according to their multidisciplinary expertize (functional ceramics, electrochemical methods, catalysis, neutron diffraction) which will be used for investigation of the water formation, transport, evacuation, splitting and conductivity mechanisms in the dmFC architecture based on the newly discovered properties of BCY15. An advanced approach is the combination of macroscopic electrochemical methods (impedance spectroscopy) with structural atomic level studies by neutron diffraction and experimental verification of the basic conclusions by electrochemical testing of laboratory cells (“button type”) at operating conditions. The planned key activities can be classified as basic and breakthrough research which should overcome technology readiness levels 2-3. After reaching level 4, the topic can be further supported by Fuel Cells and Hydrogen Joint Undertaking in Horizon 2020. Those provisory activities will be a prerogative of ARMINES (France) – the foreign participant in this proposal. In addition the team will apply its expertise in amorphous solid state electrolytes for the development of proton-conducting materials for operation in the temperature gap between SOFC and Polymer electrolyte fuel cell, covering the range 200-350oC.


IMPLEMENTATION

For IMOOD implementation advanced techniques and methods have been applied: impedance spectroscopy with new designs of testing cells; pioneer studies of water behavior in the ceramic matrix by neutron diffraction; a series of advanced physical methods for material characterization. Some of them were especially developed for the needs of IMOOD: (i) simple method and equipment for evaluation of gases permeability in porous ceramic media; (ii) technology for impregnation of the BCY anode matrix with metal (Ni and Ni/Co) catalyst which eliminates technological hurdles of the classical procedures; (iii) electrochemical analysis - “Differential Resistance Analysis” which for a first time offers a solution for quantitative evaluation of the cell operation in both FC and EL mode.

The project was successfully terminated, obtaining important results and achievements in combination with intensive knowledge dissemination:

• Optimization of the CM microstructure in respect to conductivity and water vapor permeability. It is found that the applied material BCY15 has good mixed ionic conductivity for porosity 25-35 vol. % in the operating temperature range (700-800oC).This result has positive technological impact.

• Optimization of the CM thickness in reverse mode operation. Central membrane with 200-250 µm thickness in planar configuration works well which is beneficial from technological point of view. The pathway towards decrease of the cell operating resistance concerns the decrease of the dense electrolyte layers, which is a routine procedure.

• Instantaneous switch between the two modes is obtained due to the permanent presence of water in the CM.

• The operational parameters in FC mode reach those of a commercial cell (after recalculations in respect to the cell thickness).

• The electrolyzer mode efficiency is higher than the fuel cell one, which eliminates the main disadvantage of classical SOFC and rSOC.

• The presence of catalyst in the CM increases the operational efficiency in both regimes.

• The first attempts for development of amorphous electrolyte materials for operation in the range of 300-500oC (still unreached in global scale), show that the selected approach gives results. Presence of protonic and/or mixed ionic conductivity is registered. The future attempts will be concentrated in direction further stabilization of the structures and increase of the conductivity.

• Strong knowledge dissemination activity is realized between the partners, as well as outside the project. (http://imood.iees.bas.bg)

• A Post project plan is developed on the basis of IMOOD achievements. In summary the next activities swill bring to further development overcoming TRL 4.