Industrial H₂ supply for H₂-DRI steelmaking presents a structurally inverted inventory problem: demand is rigid and non-interruptible (50–80 kg H₂/t-DRI, 24 h/day, 100% service level), while supply is stochastic and driven by variable renewable electricity. Classical inventory theory cannot represent this system without fundamental reinterpretation: storage technologies introduce technology-specific decay rates (boil-off, leakage), pressure-constrained minimum inventory levels analogous to safety stock, energy-intensive cycling, and strict purity requirements. This study develops an inventory-centric mixed-integer linear programme (MILP) at hourly resolution (T=8,760 h) that jointly optimises electrolyser capacity, storage capacity, and hourly dispatch under zero unmet demand. Five technologies are benchmarked at the Ilva Taranto plant (250 Mt/yr H₂ demand): salt caverns (CAV), compressed gas (CGH₂), liquid hydrogen (LH₂), liquid organic hydrogen carriers (LOHC), and ammonia (NH₃). The LCOH ranking is CAV (4.43 EUR/kg) < CGH₂ (4.57 EUR/kg) < NH₃ (4.92 EUR/kg) < LOHC (5.11 EUR/kg) < LH₂ (5.18 EUR/kg). The 0.75 EUR/kg spread is driven by conversion-energy burdens and standing losses, not by CAPEX per unit stored. Optimal electrolyser capacity ranges from 2.90 GW (CAV) to 3.73 GW (LOHC), a EUR 460M CAPEX difference, confirming that storage technology selection directly shapes production capacity decisions. All inventory trajectories exhibit a seasonal charge–plateau–discharge pattern with a stress window in days 230–310. Imports (EUR 5.0/kg) are activated every day (365/365) and periodically bind the daily cap of 213,192 kg/day. Hydrogen storage in H₂-DRI behaves as a perishable, energy-coupled inventory. Optimal policy is governed by decay rate, cycling energy cost, and minimum operating level rather than CAPEX per kg stored. Low-conversion-penalty technologies (CAV, CGH₂) enable more cost-efficient temporal load-shifting. Firm external supply provides insurance value that reduces domestic overinvestment even when priced above electrolysis cost. The study formalises six structural differences between hydrogen and classical inventory with direct modelling implications for operations management. EU Project Hy-Edu 2024-1-PL01-KA220-HED-000251501
Hydrogen inventory sizing and storage technology selection for Green Steel: a MILP framework applied to the Ilva Taranto plant
Lucio Zavanella;Beatrice Marchi;Giuseppe Tomasoni;
2026-01-01
Abstract
Industrial H₂ supply for H₂-DRI steelmaking presents a structurally inverted inventory problem: demand is rigid and non-interruptible (50–80 kg H₂/t-DRI, 24 h/day, 100% service level), while supply is stochastic and driven by variable renewable electricity. Classical inventory theory cannot represent this system without fundamental reinterpretation: storage technologies introduce technology-specific decay rates (boil-off, leakage), pressure-constrained minimum inventory levels analogous to safety stock, energy-intensive cycling, and strict purity requirements. This study develops an inventory-centric mixed-integer linear programme (MILP) at hourly resolution (T=8,760 h) that jointly optimises electrolyser capacity, storage capacity, and hourly dispatch under zero unmet demand. Five technologies are benchmarked at the Ilva Taranto plant (250 Mt/yr H₂ demand): salt caverns (CAV), compressed gas (CGH₂), liquid hydrogen (LH₂), liquid organic hydrogen carriers (LOHC), and ammonia (NH₃). The LCOH ranking is CAV (4.43 EUR/kg) < CGH₂ (4.57 EUR/kg) < NH₃ (4.92 EUR/kg) < LOHC (5.11 EUR/kg) < LH₂ (5.18 EUR/kg). The 0.75 EUR/kg spread is driven by conversion-energy burdens and standing losses, not by CAPEX per unit stored. Optimal electrolyser capacity ranges from 2.90 GW (CAV) to 3.73 GW (LOHC), a EUR 460M CAPEX difference, confirming that storage technology selection directly shapes production capacity decisions. All inventory trajectories exhibit a seasonal charge–plateau–discharge pattern with a stress window in days 230–310. Imports (EUR 5.0/kg) are activated every day (365/365) and periodically bind the daily cap of 213,192 kg/day. Hydrogen storage in H₂-DRI behaves as a perishable, energy-coupled inventory. Optimal policy is governed by decay rate, cycling energy cost, and minimum operating level rather than CAPEX per kg stored. Low-conversion-penalty technologies (CAV, CGH₂) enable more cost-efficient temporal load-shifting. Firm external supply provides insurance value that reduces domestic overinvestment even when priced above electrolysis cost. The study formalises six structural differences between hydrogen and classical inventory with direct modelling implications for operations management. EU Project Hy-Edu 2024-1-PL01-KA220-HED-000251501I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
