Economic assessment of the impact of plant size on coal-gasification/combined-cycle plants. Final report

This screening study evaluates the impacts on plant performance, capital cost, and cost of electricity of varying the capacity of coal gasification-combined cycle power plants from 1000 MW to 50 MW. Five cases are evaluated using the Texaco coal gasification process and Illinois No. 6 coal. The cases cover the nominal capacities of 1000 MW, 500 MW, 250 MW, 100 MW, and 50 MW. The 1000 MW case is a modified version of Case EXTC-79 covered in EPRI Report AP-1624. The results of the study show that, when the nominal plant capacity decreases from 1000 MW to 50 MW, the levelized cost of electricity for an investor owned utility more than doubles, from approximately 51 mills/kWh to 83 mills/kWh. However, the change in the cost of electricity is relatively small between 1000 MW and 250 MW, compared to the change between 250 MW and 50 MW. This trend reflects the effects of plant investment and performance. Plant investment in $/kW increases only moderately between 1000 MW and 250 MW, primarily because most of the plant undergoes a simple reduction in the number of operating trains of equipment. There is a substantial increase in the investment cost per kW for themore » 100 MW and 50 MW cases, however, due to increased spare capacity, loss of economies of scale, and increased proportional contribution of the general facilities cost. Total capital requirement ranges from $1377/kW for the 1000 MW case to $3116/kW for the 50 MW case (in 1981 dollars). As in the case of plant investment, heat rate tends to increase moderately from 1000 MW to 250 MW (from 9676 to 9801 Btu/kWh), while it increases substantially from 250 MW to 50 MW (from 9801 to 10583 Btu/kWh). The increase in heat rate is due primarily to reduced steam turbine efficiency and increases in internal power consumption per unit of feed. 9 figures, 30 tables.« less