Use of alternative hydrogen energy carriers in SOFC–MGT hybrid power plants

SOFC–MGT hybrid power plants are a very attractive near-term option, as they achieve efficiencies of over 60% even for small power outputs (200–400 kW). The SOFC hybrid systems currently developed are fuelled with natural gas, which is reformed inside the same stack at about 800–900 °C. However, the use of alternative fuels with a lower reforming temperature can improve performance of the hybrid plant. This paper is concerned with a comparative performance analysis of internally reformed SOFC–MGT power plants fuelled with methane, methanol, ethanol and DME. Since the reforming temperature of methanol and DME (250–350 °C) is significantly lower than that of methane (700–900 °C), the performance of externally reformed SOFC–MGT power plants using these fuels has been also evaluated. The comparative analysis has demonstrated that simply replacing methane with methanol, ethanol or DME in SOFC–MGT power plants with internal reforming slightly reduces efficiency and power output. However, using methanol and DME in externally reformed hybrid plants improves significantly efficiency (by about 4.0% points better than methane for methanol and 1.5 for DME). The study also shows that external reforming enhances efficiency on account of improved exhaust waste heat recovery and of the higher cell voltage produced by the greater hydrogen partial pressure at the anode inlet.