The Pacific Northwest National Laboratory has developed a new solid oxide fuel cell system for distributed generation. The system is based on small cells that operate at the highest efficiency rate yet -- 57 percent versus 30 to 50 percent efficiencies previously reported -- for solid oxide fuel cell systems of the same size.
A key advantage of the new system is its potential role in local, distributed generation. Smaller systems based on these fuel cells can be placed closer to the homes and businesses that would use the power. In contrast, the larger systems would be comparable to traditional power plants and electricity would need to be sent over transmission lines, which introduces some loss.
A single cell from the lab generates 2 kilowatts of electricity, and the lab says it can scale a system to 250 kilowatts. This total capacity is very unusual. “Until now, most people have focused on larger systems that produce 1 megawatt of power or more and can replace traditional power plants," said Vincent Sprenkle, chief engineer of the lab’s solid oxide fuel cell development program. "However, [our] research shows that smaller solid oxide fuel cells are a viable option for highly efficient, localized power generation."
Several new technologies helped PNNL achieve the higher efficiencies. The cells use a lab-developed micro-channel technology in the system's heat exchangers. This allows more efficient heat transfer compared to other designs. Additionally, the system recycles the system’s exhaust, reducing the need for an electric device to heat water to create steam. Reusing the steam, which is mixed with fuel, also means the system is able to use up some of the leftover fuel it wasn't able to consume when the fuel first moved through the fuel cell.