UC Irvine

Solid Oxide Fuel Cell – Gas Turbine (SOFC-GT) technology is known to produce continuous electric power with ultra-high efficiency and virtually zero emission of criteria pollutants. Research to date has focused on operation on compressed natural gas (CNG) and stationary power applications. This thesis addresses operation on renewable hydrogen (RH2) in mobile as well as stationary applications, and liquified natural gas (LNG) in two mobile applications (locomotive and tugboat). 10 and 50MW plants are adopted for the stationary applications, and a 3.5MW engine is adopted for the two mobile applications.

The results confirm that SOFC-GT hybrids reach high efficiencies even at small scales. Hybrids in the 10 MW class exceed efficiencies of 68%-LHV while hybrids in the 50 MW class can exceed efficiencies of 70%-LHV. Although SOFC-GT hybrids are modular and cost does not scale linearly with plant size, savings in traditional-of-plant equipment and plant operation lead to a substantial cost of electricity reduction when considering future technological advancement. For example, the Cost of Electricity (COE) for the 10 MW hybrid operating on RH2 is reduced from $197.06/MWh in 2020 to $150.00/MWh in 2030 and $136.79/MWh in 2050. For a 50 MW hybrid operating on RH2, the COE is reduced from $171.94/MWh in 2020 to $126.04/MWh in 2030 and $113.17/MWh in 2050. The feedstock cost of RH2 contributes to more than 75% of COE. To lower the feedstock cost, electricity for the electrolysis of water to hydrogen can be sourced from wind and solar plants during curtailment. Under these circumstances, the COE in 2020 can be reduced by 40% for the 10 MW scale and 44% for the 50 MW scale.

Hybrids in the 3.5 MW long-haul locomotive and the tugboat both exceed efficiencies of 68%-LHV. A novel strategy to incorporate into the cycle the “heat sink” associated with the evaporation of the LNG is shown to significantly increase the overall efficiency.