The path to fully decarbonising an off-grid phosphate complex: MILP formulation and techno-economics

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Chinese explanation / 中文解读

中文解读待补充：本站会优先为光伏效率、钙钛矿太阳能电池、储能技术、太阳能热利用、BIPV、并网技术等高价值论文补充中文说明。

Original abstract

Abstract This study develops a sequential two-pass lexicographic mixed-integer linear programme (MILP) for the decarbonisation of an off-grid phosphate complex in Saudi Arabia. The baseline comprises approximately 21 MWe of continuous electricity demand and 115 MW $$_{\textrm{th}}$$ of dryer heat, supplied by diesel generation and heavy fuel oil (HFO), respectively. The model co-optimises photovoltaic generation (PV), concentrating solar power with thermal energy storage (CSP-TES), battery energy storage (BESS), and PEM electrolysis to replace diesel-based electricity and substitute HFO with green hydrogen. Pass 1 minimises annual unserved critical site electricity ; Pass 2 minimises annual net cost over the reliability-feasible set, preserving a security-first design hierarchy without weighted objective trade-offs. Inter-annual solar uncertainty is represented through a Conditional Value-at-Risk (CVaR) extension using hourly NASA POWER irradiance data for 2013–2022. The site-only formulation applies $$\alpha =0.95$$ , while the full site-plus-hydrogen formulation applies $$\alpha =0.80$$ . Across the deterministic campaign, critical site electricity is fully protected in all cases. Under commercial-style financing, remains in a low-investment partial-substitution regime, whereas shifts to a high-investment design with approximately 1.24 BUSD of CAPEX, 19.74 kt yr −1 of hydrogen production, and 68.13 GWh yr −1 of residual unmet hydrogen service. Activating the hydrogen-service penalty raises production to 21.15 kt yr −1 and reduces unmet service to 1.07 GWh yr −1 . Representative gross hydrogen cost is 3.85−4.39 USD kg −1 under a 2% financing assumption. The CVaR results quantify the resilience premium associated with multi-year solar resource risk. Relative to the deterministic design, the full-penalty CVaR solution increases CAPEX from 1.305 to 2.202 BUSD, eliminates 53.9 GWh yr −1 of unserved energy, and raises hydrogen production from 20.0 to 21.2 kt yr −1 . Across deterministic and risk-aware runs, the preferred architecture remains TES-dominant rather than BESS-dominant, indicating that temporal firmness and sustained electrolyser utilisation matter more than short-duration battery shifting alone. Overall, environmental pricing improves the case for deep decarbonisation, but the cost of capital is the stronger determinant of whether ambitious hydrogen-substitution targets are realised.

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