A simple, inexpensive new technique to remove sulfur has been found which will remove an obstacle to wider use of fuel cells They use new materials: rare earth oxides, known to be stable and able to absorb hydrogen sulfide at high temperatures. And, instead of filtering gas through a thick sorbent bed, they pass it over the surface of a thin sorbent layer.
Rare earth oxides are inexpensive and easy to obtain. The system could be added to a SOFC using two small boxes — one for fresh sorbents, the other for spent ones. Sulfur-free gases generated by the fuel cell would sweep the spent sorbents clean, allowing the same sorbents to be used over and over. “You don’t need valves or pumps,” she says, because all gases would diffuse naturally through the system. She adds that her sorbents could also outperform those used for in low-temperature fuel cells.
Solid oxide and other fuel cell types are compared here SOFCs are expected to be around 50-60 percent efficient at converting fuel to electricity. In applications designed to capture and utilize the system’s waste heat (co-generation), overall fuel use efficiencies could top 80-85 percent.
The best applications for the fuel cells would be in cars and for back up power.