Using Natural Gas as an Environmentally Sustainable
Power Source with Solid Oxide Fuel Cells
Carmine Difiglio, Danial Esmaeili, Serhat Yesilyurt
Research, pilot projects and government policies to commercialize carbon capture in the power sector have focused on coal plants. However, the expected world-wide consumption of natural gas in the power sector is not consistent with a sustainable environmental future without also employ-ing carbon capture technologies to natural gas plants. One reason carbon capture from natural gas has not received much attention is, as will be discussed below, the very high cost of carbon capture from natural gas plants compared to the already considerable cost of carbon capture from coal plants. Capture of carbon with conventional natural gas turbines is not currently economically practical. A different natural gas to electricity technology may be needed if carbon capture with turbines (for example, see Zhu, et. al.i on the use of chemical looping) proves not to be cost-effective. This different alternative electric-generating technology should not have a higher LCOE than natural gas turbines and it must permit carbon capture at low cost. Ideally, the cost of carbon capture should be significantly lower than from coal plants as measured by the cost per ton of cap-tured CO2
Solid oxide fuel cells (SOFCs) are one of the leading technologies to meet these requirements, SOFC emissions of CO2 without carbon capture are relatively low due to their high efficiency. Significantly, in the SOFC exhaust, CO2 is only comingled with water and unreacted CH4. This enables low-cost separation of CO2. In addition, the efficiency losses from the application of car-bon capture are minimal compared to the significant efficiency losses when carbon capture is ap-plied to coal power plants or natural gas turbines.
The primary barrier to the uptake of SOFCs is the development of a grid-scale SOFC with a com-parable cost and reliability compared to the natural gas turbine. With a cost-competitive grid scale SOFC technology, the additional cost of carbon capture would be minimal compared to the cost-prohibitive carbon capture technologies that are available for coal power plants and natural gas turbines. Consequently, commercialization of carbon capture could be achieved a lower cost with a lower burden on the economy than is now the case. While the current research to achieve cost-competitive and reliable SOFCs for grid-scale application is encouraging, these efforts should be significantly increased in order to achieve more rapid technology development and the opportunity to achieve grid-scale commercial application, a necessary step that enables further cost reduction.