Designing cost-effective electricity-heat integrated energy systems for sustainable alumina production

Electricity-heat integrated energy systems (EH-IES) offer a promising pathway for supplying electricity and multi-pressure steam to support conventional alumina production decarbonization. However, existing approaches still fail to adequately represent the system-level interactions among condensate return, electric heating, staged steam generation and pressure-matched steam delivery. Here, a new EH-IES for sustainable alumina production is proposed and a mixed-integer linear programming (MILP) framework is developed for integrated system design and operation, with total annual cost (TAC) and greenhouse gas (GHG) emissions as competing objectives. The ε-constraint method combined with TOPSIS is further employed to quantify the trade-off between economic performance and emissions mitigation. Using a 2 million ton yr −1 green alumina plant as a case study, the results show that the economic-driven design minimizes TAC, yet remains highly dependent on conventional combined heat and power and gas-fired boilers, whereas the renewable-dominated design achieves greater variable renewable integration at substantially higher cost. The Pareto-optimal design delivers the lowest GHG emissions and provides a favorable trade-off between economic performance and emission reduction, with a TAC of 682.91 million CNY and GHG emissions of 238.25 kton, representing an approximately 55.64% increase in cost and a 58.20% reduction in emissions relative to economic-driven case. This performance is underpinned by the coordinated deployment of wind power, electrode boilers, and high- and low-pressure solid thermal storage boilers, which together enable electricity-heat decoupling and stable multi-pressure steam supply. These findings provide valuable insights and practical guidelines for cost-effective EH-IES designs for green alumina production.