New continuous-time scheduling formulation for continuous plants under variable electricity cost

Pedro M. Castro, Iiro Harjunkoski, Ignacio E. Grossmann

Research output: Contribution to journalArticleScientificpeer-review

86 Citations (Scopus)


This work addresses the scheduling of continuous plants subject to energy constraints related to time-dependent electricity pricing and availability. Discrete-and continuous-time formulations are presented that can address these issues together with multiple intermediate due dates. Both formulations rely on the resource-task network process representation. Their computational performance is compared for the objective of total electricity minimization with the results favoring the discrete-time model due to the more natural way of handling such a wide variety of discrete events. In particular, it can successfully handle problems of industrial size. Nevertheless, the new continuous-time model is a major breakthrough since it is the first model of its type that is able to effectively incorporate time-variable utility profiles. When compared to a simple manual scheduling procedure, the proposed scheduling approaches can lead to potential electricity savings around 20% by switching production from periods of high to low electricity cost.

Original languageEnglish
Pages (from-to)6701-6714
Number of pages14
JournalIndustrial and Engineering Chemistry Research
Issue number14
Publication statusPublished - 15 Jul 2009
MoE publication typeA1 Journal article-refereed


  • continuous time models
  • discrete-time model
  • energy constraint
  • Resource-task network
  • scheduling

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