GE Delivers Coal-Fueled, Solid Oxide Fuel Cell (SOFC) Prototype
Technology Review captures it nicely: "GE's advance allows for a solid-oxide fuel cell to use coal-based fuels at costs approaching that of conventional power plants". This is a 6 kW prototype fuel cell, delivered for their partner, the US Department of Energy, to test. Positives include a nice breakthrough in fuel efficiency (49%, vs 35% for a conventional coal-fired electricity generating plant); a dramatic lowering of manufacturing costs compared to previous SOFCs (down to about $800/kW); and, the ability to utilize a hydrogen by-gas stream from a "clean coal" syngas plant. Drawbacks: the feedstock processing step is capital intensive, and has a large environmental footprint (as does all coal); any sulfur in the coal-based fuel would eventually "poison" the SOFC's electrolyte, requiring near-perfect desulferization efficiencies at the syngas plant. Bright side analysis: assuming that the syngas plant effectively sequesters sulfur as a co-product or safe, solid waste stream, the GE SOFC design offers a strong incentive for operators to keep per kW sulfur emissions associated with the SOFC to zero. Dark-side analysis: if the Federal Government offers slack air and water discharge permit conditions to coal syngas plants, the precedent will likely never be overcome, and sulfer acid gas emissions per kW will be not much better than existing coal-fired generators. Note: chemical markets need only so much elemental sulfur or sulfuric acid and any excess if these will eventually have to be disposed of. Typically, sulfuric acid would be neutralized with limestone to create gypsum, or calcium sulfate. If a syngas plant's aqueous acid stream contained heavy metals from coal washing and off-gas scrubbing, the gypsum so-created may not be suitable for soil amendment purposes and, instead, may have to be managed as hazardous waste. Unless, of course, yet another permit exemption were offered. In other words, we can't call the prototype SOFC a "green" technology until we see what the syngas plant footprint is. Photo credit: GE, via Technology Review.