Direct Fuel Cell Materials Experience

Abstract

The Direct Fuel Cell® (DFC®) power plant is an emerging high efficiency, ultra-clean electric power generation system. The power-producing block is the carbonate fuel cell, which uses alkali carbonate electrolyte and operates at ~550-650{degree sign}C. Its internal reforming process results in a simpler, more efficient and cost-effective energy conversion system. Since 2000, FCE has placed around the world approximately 85 units ranging from 250kW to 2.4 MW, accumulating extensive materials experience (up to >30,000h). Consistent DFC stack durability and performance improvement, and substantial cost reduction have been demonstrated. This paper describes status of DFC field products, stack material durability, power output increase, and cost reduction.

Status of Carbonate Fuel Cell Materials

“…It has been demonstrated by FCE that for atmospheric-pressure DFC systems with a proper operational control (e.g., a lower CO 2 partial pressure) and improved cell design the cathode stability and nickel shorting are controllable to achieve desired useful life. Post-test analysis of the NiO cathode after long-term (∼40,000h) field operation showed that the agglomerated dual-porosity morphology and surface area remained sufficiently stable (13). Also, Ni-shorting free operation has been achieved in numerous long-term stacks.…”

“…Material development status for carbonate fuel cell has been reviewed extensively (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Material properties such as creep, sintering, compaction, resistance to oxidation, hot corrosion, and carburization, etc.…”

Molten Carbonate Fuel Cells

“…As alternative anodes, Cu-Al alloy and LiFeO 2 were tested, but they had insufficient creep strengths [2].…”

“…The NiO-MgO-LiFeO 2 is a solid solution, and the material has lower NiO solubility due to the stable structure [32]. Industrially, thickening the matrix and reducing the CO 2 partial pressure were attempted, and FCE Co. reported that it could ensure a cell life of 5 years using these methods [2].…”

“…The primary developer is FCE (FuelCell Energy Co.) in the USA, which has developed an internal reforming type MCFC unit stack of up to 350 kW and provides up to 2.5 MW MCFC systems by combination of the unit stacks. It also reported that a combination of an MCFC and a gas turbine recorded 56% electrical efficiency (based on the lower heating value (LHV) of natural gas) [2]. MTU, a German company, has designed a 250 kW class system, "Hot Module," by adapting FCE's stack.…”