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Load optimisation of cogeneration system via P-graph framework considering variable output-input ratios

Author

Listed:
  • Er, Hong An
  • Termizi, Siti Nor Azreen Ahmad
  • Rohman, Fakhrony Sholahudin
  • Wan Alwi, Sharifah Rafidah
  • Manan, Zainuddin Abd
  • Lim, Jeng Shiun
  • Liew, Peng Yen
  • Tan, Raymond Girard
  • Aviso, Kathleen
  • Tapia, John Frederick D.
  • Lee, Peoy Ying
  • Suzuki, Michihisa

Abstract

Load optimisation within the cogeneration system is crucial in enhancing energy efficiency. Instead of constructing the mathematical optimisation model or applying the commercial utility optimisation software with a licensing fee, this study proposes a holistic P-graph method to model and optimise the cogeneration system using the free and user-friendly software, P-graph Studio. To consider actual performance of unit operations, novel slope-constant element is introduced in the P-graph structure to adapt the variable output-input ratios in the form of linear performance model with non-zero constant. This overcomes the functionality of the conventional P-graph structure that only considers fixed output-input ratio. A case study of an industrial cogeneration system is optimised using the proposed P-graph method, resulting in 1.24 % reduction of operating cost and CO2 emission: equivalent to savings of RM 12,822,300/year and 4,300 tonnes CO2 emission/year. Two operating strategies are proposed to revise the optimal operating method by modifying the P-graph superstructure to ensure adequacy of the utility margin in meeting the potential maximum utility demand. The operating cost saving of 0.53 % is achieved after revision to meet both operational efficiency and reliability of the cogeneration system which results in savings of RM 5,454,900/year and 1,800 tonnes CO2 emission/year.

Suggested Citation

  • Er, Hong An & Termizi, Siti Nor Azreen Ahmad & Rohman, Fakhrony Sholahudin & Wan Alwi, Sharifah Rafidah & Manan, Zainuddin Abd & Lim, Jeng Shiun & Liew, Peng Yen & Tan, Raymond Girard & Aviso, Kathlee, 2025. "Load optimisation of cogeneration system via P-graph framework considering variable output-input ratios," Energy, Elsevier, vol. 326(C).
    • Handle: RePEc:eee:energy:v:326:y:2025:i:c:s0360544225017906
    DOI: 10.1016/j.energy.2025.136148
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