Lowering the operating temperature of high-temperature fuel cells has historically been motivated by stack and system cost reduction and durability considerations towards making fuel cells a more attractive distributed generation technology. Protonic ceramic fuel cells (PCFCs) operating beneath 600^oC have emerged as a promising technology candidate for developing power generation systems. Recent progress in PCFC development has solved the challenges of poor cathodes and cell fabrication thereby, enabling them to achieve high power density at intermediate temperatures (450-600^oC) while demonstrating remarkable fuel flexibility (hydrogen, hydrocarbon gases, alcohols, ammonia) without external fuel processing measures [1]. This ARPA-E funded project focuses on PCFC cells made by solid-state reactive sintering (SSRS) fabrication processes for cells comprised of a thin BaZr_0.8Y_0.2O_3-δ (BZY20) electrolyte screen-printed onto a BZY20/Ni porous anode support, with a triple conducting cathode material based on BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ (BCFZY0.1). In this paper, we present an economic manufacturing model that was developed to estimate the overall expected cost of a PCFC stack and compare the results with solid oxide fuel cell (SOFC) technology for hydrogen and methane fuels. The comparative analysis is based on similar cell and stack SOFC manufacturing processes and cost data for small-scale stacks (5-10 kW) at production volumes of about 10,000 units/year. Relying on previous SOFC stack cost manufacturing studies [2, 3] a competitive stack capital cost for PCFCs operating at intermediate temperature is projected. Specifically, operating on methane fuel, the costs of PCFC stacks at 500^oC (0.155 W/cm²) and 550^oC (0.240 W/cm²) are estimated to be 5-10% lower and ~35% lower, respectively, than SOFC stacks running at 800^oC (~0.300 W/cm²). To eliminate any uncertainties using methane fuel gas supply (such as extent of reforming, fuel utilization, steam content, etc.), the PCFC and SOFC stack cost estimates were also benchmarked on 97% hydrogen / 3% water vapor fuel gas where an impressive 29% lower stack cost was estimated for PCFC technology (at 500^oC). This potential cost advantage of PCFC vs. SOFC stacks is found despite the 20-50% lower power density of PCFCs and is driven by fewer firing steps and the use of lower lower-grade materials. Improvements to further decrease PCFC stack cost consist of replacing nickel oxide precursor, reducing the anode thickness and merging the two-firing steps into a one-firing step SSRS. Overall, as PCFC power density performance is expected to increase with further development, this work demonstrates that if PCFC technology scale-up to larger platforms is successful, they have excellent potential for filling the technology gap of low-cost, high efficiency distributed generation for small- and intermediate-scale commercial combined heat and power systems.

References:

[1] C. Duan, J. Tong, M. Shang, S. Nikodemski, M. Sanders, S. Ricote, a. Almansoori, R. O’Hayre, Readily processed protonic ceramic fuel cells with high performance at low temperatures, Science (80-. ). 349 (2015) 1321–1326. doi:10.1126/science.aab3987.

[2] B.D. James, D.A. Desantis, Manufacturing Cost and Installed Price Analysis of Stationary Fuel Cell Systems, (2015).

[3] Battelle, Manufacturing Cost Analysis of 1 KW and 5 KW Solid Oxide Fuel Cell (SOFC) for Auxilliary Power Applications, Columbus OH, 2014.