Cost benefits of designing carbon capture processes for part-load operation of power plants

Abstract

As fossil power plants increasingly cycle to balance variable renewable generation, carbon capture plants must be designed for a wide range of part-load operating conditions, to avoid excessive capital costs. However, accounting for the variability in design optimization yields higher computational complexity, and is therefore not a current design methodology. Here, we apply two-stage stochastic optimization to identify optimal carbon capture plant designs accounting for part-load flue gas conditions. We reduce computational complexity through a data-driven approach-to-equilibrium model of the absorption and desorption processes. Operating scenarios are derived from real-world part-load operation data of coal and natural gas combined cycle power plants. Our results demonstrate that designs optimized over multiple operating scenarios substantially reduce equipment sizes, lowering capital costs by 5-9 % at the expense of higher operating costs, resulting in a moderate reduction in total annualized cost by 0.5-1.6 %. The lowest costs are achieved when targeting an average capture target across operating scenarios, which allows CO2 capture to be shifted from full-load to part-load periods to reduce peak equipment sizes without compromising overall CO2 emission reductions. These cost benefits are robust across sensitivity analyses and increase with higher shares of part-load operation. Thus, part-load variability should be considered at the design stage, particularly for plants subject to variable load.