Environmental Engineering Reference
In-Depth Information
High-temperature FC also provide heat, which can be converted into electricity using
conventional technologies, such as gas turbines (GT) or steam turbines, resulting in
even more efficient energy systems. Moreover, biomass conversion is carbon
neutral and offers decentralized energy generation. Although the MCFC is suitable
for biosyngas conversion, in this chapter, we will focus on the SOFC as this
type of FC has a higher resistance to gas contaminants, which is important when using
biosyngas as fuel.
16.2 SOLID OXIDE FUEL CELLS
16.2.1 Principle of an SOFC
SOFCs typically work at temperatures in the range of 600
1000
C. The operation of
an SOFC is presented schematically in Figure 16.1. In an SOFC with an oxide ion-
conducting electrolyte, the fuel enters the anode chamber and is electrochemically
oxidized. Oxygen enters the cathode chamber and is ionized and transported through
the solid electrolyte to the anode. The porous anode disperses the fuel gas over its
interphase with the electrolyte, allowing the reaction products to diffuse through the
interphase to become mixed with the anode flow. The anode catalyzes the chemical
and electrochemical reactions and conducts the electrons that are freed. These
electrons flow through an external circuit to the cathode, delivering electrical power.
The cathode distributes the oxygen at its interphase with the electrolyte and conducts
the electrons from the external circuit so that oxygen molecules are reduced into
oxide ions. Oxide ions are conducted through the electrolyte to the anode. The
electrolyte contains many oxygen vacancies that allow oxygen ions to hop through.
The electrolyte mainly prevents the two electrodes from coming into electronic
-
Electrical energy
Fuel
outlet
Air
outlet
e
-
H
2
O, CO
2
,
unconverted
fuel
O
2
O
2-
H
2
, CO, CH
4
O
2
Anode Cathode
Electrolyte
Fuel
inlet
Air
inlet
FIGURE 16.1
Schematic diagram of an SOFC.
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