Research on off-grid off-design scheduling strategies for a supercritical CO₂ concentrating solar power cogeneration system

Concentrated solar power (CSP) is a clean energy technology, but due to solar variability, off-design conditions must be considered to better evaluate performance. In this paper, a supercritical CO₂ system integrated with CSP for cogeneration of electricity, industrial hot water, and hydrogen is introduced. Design performance is evaluated through thermodynamic, exergoeconomic, and exergoenvironmental analyses. Based on multi-objective optimization, an off-design model is developed, and an optimal off-grid scheduling strategy is proposed. This strategy combines bypass and inventory scheduling and is enhanced by the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm. The results show that increasing the pressure ratio improves exergy efficiency by 11.29% and 10.85% in two operating modes, respectively, but negatively affects economic costs. The optimized design achieves an exergy efficiency of 34.29%, a product cost of 13.68 $·GJ⁻¹, and an environmental impact of 10.89 mPts·GJ⁻¹. Off‑design analysis shows the DBSCAN algorithm clusters off‑design operating conditions to match bypass and inventory scheduling strategies. This optimal scheduling method improves exergy efficiency by 3.63% and 1.69% over the single strategies at partial load, respectively, achieves up to 19.66% improvement under unfavorable off–design conditions, and reaches an average exergy efficiency of 31.11%, ensuring stable off–grid operation under variable conditions.