Page 118 - 00. Complete Version - Progress Report IPEN 2014-2016

118 Renewable Energies | Progress Report

Solid Oxide Fuel and tolerant to carbon deposits and sulphur
Cell (SOFC) contamination. The reduction of the operat-

ing temperature from 800-1000ºC down to
Solid Oxide Cells (SOCs) is a general classifica- 500-800ºC range, in order to minimize degra-
tion for Solid Oxide Fuel Cells (SOFCs) and Solid dation of components, improve design flexi-
Oxide Electrolysis Cells (SOECs) -SOFCs operat- bility, and lower material and manufacturing
ed in electrolysis mode- are solid-state devices costs, is also a key issue for disseminating SOCs.
that can be used to i) convert between chemi- Nevertheless, reducing the operating tempera-
cal and electrical energy and/or ii) drive chem- tures requires new materials for high-perfor-
ical reactions. These capabilities make them mance SOCs.
attractive for energy conversion, energy stor-
age, chemical sensing, chemical separation, The main activities of the SOFC research group
and chemical synthesis applications. Most of at IPEN have been the synthesis, processing,
the research focus has been given to the de- and characterization of the SOFC components,
velopment of reversible SOCs devices capa- along with single cell testing, aiming at direct
ble of operating in both modes (fuel cell and ethanol SOFCs. Ethanol is an available, efficient
electrolysis) for advanced application involv- and cost competitive renewable fuel. Different-
ing energy storage and generation in one de- ly from hydrogen, which still requires an infra-
vice. SOFCs are the most efficient electrochem- structure for widespread use, ethanol brings
ical devices to directly convert the chemical strategic advantages such as easy storage and
energy of fuels into electricity, thus they are good distribution. Moreover, it allows SOFCs
regarded as promising power sources for sev- to run in a carbon neutral cycle.
eral applications due to important character-
istics such as: i) wide range of power outputs Yttria-stabilized zirconia (YSZ) and nickel (Ni)
(from centralized power plants of MWatt to composite is the standard anode for solid ox-
auxiliary portable units of a few Watt); ii) fuel ide fuel cell. This composite is the best anodes
flexibility, SOFCs potentially run on different for hydrogen electrochemical oxidation, but
fuels such as hydrogen, natural gas, and eth- it lacks of stability when carbon containing
anol; and iii) high efficiency and carbon neu- fuels are used. In order to use available fuels
tral energy generation with rather low noise such as methane (natural gas) with the stan-
and harmful emissions. dard anodes, it is necessary to add an oxidant
agent, typically water. However, adding wa-
Basically, SOCs consist of two porous electrodes ter to the fuel stream adds complexity to the
separated by a dense electrolyte. Such a ceram- fuel cell system and decreases its efficiency.
ic cell requires complex fabrication technolo- Therefore, developing new concepts of SOFC
gies and each component must fulfill several anode remains a one of the challenges to ad-
criteria. Physical and chemical compatibili- vance SOFC technology to commercialization.
ty and stability at high temperature and ox- In this context, two main strategies can be
idizing/reducing environments along with identified. The first one is replacing the stan-
good electrochemical properties are important dard anode for more stable materials. Several
properties for materials used in these devic- compounds, mainly ceramic single-phase per-
es. Important goals in SOCs research include ovskites and alternative ceramic-metal com-
the development of fuel-flex anodes, capable posites, have been proposed, but so far none
of operating in different fuel, redox resistant, of them can reach the same performance of

Instituto de Pesquisas Energéticas e Nucleares