Economic scales for first-generation biomass-gasifier/gas turbine combined cycles fueled from energy plantations

This paper assesses the scales at which commercial, first-generation biomass integrated-gasifler/gas turbine combined cycle (BIG/GTCC) technology is likely to be most economic when fueled by plantation-derived biomass. First-generation BIG/GTCC systems are likely to be commercially offered by vendors beginning around 2000 and will be based on either pressurized or atmospheric-pressure gasification. Both plant configurations are considered here, with estimates of capital and operating costs drawn from published and other sources. Prospective costs of a farm-grown energy crop (switchgrass) delivered to a power plant are developed with the aid of a geographic information system (GlS)for agricultural regions in the North Central and Southeast US in the year 2000 and 2020. A simplified approach is applied to estimate the cost of delivering chipped eucalyptus from an existing plantation in Northeast Brazil. The "optimum" capacity (MW_opt), defined as that which yields the minimum calculated cost of electricity (COE_m), varies by geographic region due to differences in delivered biomass costs. With pressurized BIG/GTCC plants, MW_opt is in the range of 230-320 MWefor the sites considered, assuming most of the land around the power plant is farmed for energy crop production. For atmosphericpressure BIG/GTCC plants, MWopl ranges from 110 to 142 MW_e. When a lower fraction of the land around a plant is used for energy farming, values for MW_opt are smaller than these. In all cases, the cost of electricity is relatively insensitive to plant capacity over a wide range around MW_opt.