[ green DRI ]
Fig. 3. Operational analysis of electrolysis units based on operation during RES power availability. Each symbol represents two electrolysis units, each with a 20 MW connection.
can be exported. The analysis suggests a 2 GW RES installation with less than 50 % PV and over 560 MW of electrolyzer capacity to meet the hydrogen requirements. The cheapest solution is a 2 GW PVonly installation, but it cannot continuously power the mining operation, which would then have to rely on thermal generators overnight. Electrolyzers would operate 3,900 – 1,650 hours, with 365 – 332 stops, resulting in 10.7 – 5.0 operating hours per stop( Figure 3 right, green profiles).
Technically, a better system would include 1,000 MW PV and 1,000 MW wind with a 400 MW BESS( 6-hour capacity), charging during high RES generation and discharging during low RES generation. This setup allows electrolyzers to operate at baseload with over 8,400 hours and fewer than 60 stops, resulting in 146 – 433 operating hours per stop. Although this requires about 50 % higher investment, it supports green mining operations. However, the BESS would still result in 100 hours of nonavailability of the mining operation annually. Closing this gap requires an additional investment of over $ 2,900 million or using excess green hydrogen for thermal generation in backup units – which would necessitate a redesign with higher investments across all components.
Conclusion
Green hydrogen supply for the direct reduction process is crucial for decarbonizing the steel industry. Various energy systems capable of producing more than 53,000 t H – sufficient for a
2
1 Mt DRI plant – have been discussed. Comparing
renewable generation profiles from Spain, Oman, and Australia shows a high dependency on the PV and wind mix. Both on-grid and off-grid projects require 1.5 – 2 GW of RES installations to power 440 – 1,050 MW of electrolyzer capacity for green hydrogen supply. Adding a large-scale BESS( 200 MW + rating, 4 h + capacity) can reduce the required RES and electrolyzer capacity, improve electrolyzer utilization, and shift from cyclic to baseload operation – lowering overall energy system costs. Future long-duration energy storage systems could further reduce costs and enhance hydrogen production and supply security.
References
¹ Hölling, M., & Gellert, S.( 2018). Direct reduction: Transition from natural gas to hydrogen? Proceedings of the 8th International Congress on Science and Technology of Ironmaking( ICSTI
2018), Vienna, Austria. ² Journal of Cleaner Production, 203( 2018), 736 – 745. ³ Steel Research International, 91( 11)( 2020), 2000110.
4
Results in Engineering, 20( 2023), 101426.
5
Renewables. ninja.( 2019). Dataset: Merra-2( global).
6
National Renewable Energy Laboratory.( 2024). Electricity technologies – Annual Technology Baseline( ATB).
7
European Hydrogen Observatory.( n. d.). Electrolyser cost.
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