Optimal multi-scale capacity planning for power-intensive continuous processes under time-sensitive electricity prices and demand uncertainty. Part II: Enhanced hybrid bi-level decomposition

We describe a hybrid bi-level decomposition scheme that addresses the challenge of solving a large-scale two-stage stochastic programming problem with mixed-integer recourse, which results from a multi-scale capacity planning problem as described in Part I of this paper series. The decomposition scheme combines bi-level decomposition with Benders decomposition, and relies on additional strengthening cuts from a Lagrangean-type relaxation and subset-type cuts from structure in the linking constraints between investment and operational variables. The application of the scheme with a parallel implementation to an industrial case study reduces the computational time by two orders of magnitude when compared with the time required for the solution of the full-space model.