SOFC Performance at

Figure 8-14 SOFC Performance at 1000°C and 350 mA/cm, 85% Fuel Utilizatiou aud 25% Air Utilization (Fuel = Simulated Air-Blown Coal Gas Containing 5000 ppm NH3,...

Activation polarisation is the voltage drop due to the sluggishness of reactions occurring at the electrode-electrolyte interfaces. Several processes are necessary for electron transfer to take place, especially at the cathode. Because LSM has little ionic conductivity, these processes are localised at the TPBs. Recently, it has become common to use MIEC (composite or single-phase) cathodes to spread the TPB and extend the reaction zones this has had a beneficial effect on reducing the activation polarisation and allowed better SOFC performance at lower temperatures. 

Fig. 4.6 Single cell SOFC performance at redueed temperatures (Minh 2004)...

SOFCs, like PAFCs and MCFCs, show an enhanced performance by increasing cell pressure. The following equation approximates the effect of pressure on cell performance at 1000°C (1832°F) ... 

Figure 16. Propylene conversion and product-selectivity results for the membrane-reactor measurements performed at 723 K with pure propylene as the feed. The results in panel a were for the SOFC with a Cu—ceria—YSZ anode, and the results in panel b were for the Cu-molybdena-YSZ anode. In panel a, the points are the rate of CO2 production, and the line was calculated from the current density and eq 8. In panel b, the points show the production of acrolein, and the line was calculated from eq 9. (Reprinted with permission from ref 165. Copyright 2002 Elsevier.)...

The publicly-funded fuel cell research program started in 1985, with the main activities performed at the Energy research Centre ofthe Netherlands (ECN). Between 1985 and 2001, about 100 million was invested by mixed public-private funds in the development of fuel cell and hydrogen energy. The objectives ofthe Dutch fuel cell programs were initially oriented to the application of coal gas in MCFC based systems. The MCFC activities were terminated in 2001, after an evaluation failed to indicate its commercial viability with natural gas. Afterwards, the activities shifted to SOFC and PEM technology for high efficient conversion of natural gas in small-scale decentralised units. 

The material and structural design of the electrolyte, anode, and cathode is still the primary challenge for improving SOFC performance. The ultimate goal is to achieve high efficiency and a long performance lifetime, while operating at lower... 

Decreasing operation temperature of solid oxide fuel cells (SOFCs) and electrocatalytic reactors down to 800-1100 K requires developments of novel materials for electrodes and catalytic layers, applied onto the surface of solid electrolyte or mixed conducting membranes, with a high performance at reduced temperatures. Highly-dispersed active oxide powders can be prepared and deposited using various techniques, such as spray pyrolysis, sol-gel method, co-precipitation, electron beam deposition etc. However, most of these methods are relatively expensive or based on the use of complex equipment. This makes it necessary to search for alternative synthesis and porous-layer processing routes, enabling to decrease the costs of electrochemical cells. Recently, one synthesis technique based on the use... 

TABLE V Performance of a Single SOFC Evaluated at Different Scales, from Local to Global ... 

Hybridization of the SOFC witha GT significantly improves the system efficiency and can be beneficial for use in large (hundreds of KWs and higher) power plants. Table 33.4 compares the estimated performances of three SOFC power systems simple cycle, SOFC/GT hybrid, and SOFG/GT hybrid with anode and cathode gas recycle (AGR and CGR) [7]. The simple cycle system and hybrid systems (based on 800 °C planar SOFCs) operate at 1.3 and 4.6 atm, respectively and the fuel is methane. It can be seen that the hybrid system with gas recycle has an estimated efficiency of about 71%, about 26 points higher than the simple cycle system. 

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