[ green DRI ]
The system must reliably produce and deliver the required hydrogen over several years. To achieve this, the above-mentioned energy system’ s building blocks can be considered independently or as one integrated system to find the best operational and financial configuration. The following section will discuss the boundary conditions and options.
The energy system for green hydrogen production
Hölling et al.¹ calculated the hydrogen requirement for hot briquetted iron( HBI) production using the direct reduction process based on the production at ArcelorMittal’ s Hamburg plant. With an annual production of 1 Mt HBI and a specific hydrogen demand of 528 Nm ³/ t HBI, plus a purging rate of 10 %, a demand of 635 Nm ³/ t HBI is needed. These values are confirmed by other authors.², ³ This study uses the value of 635 Nm ³/ t HBI, resulting in an annual hydrogen demand of 53,404 t H for a 1
2
Mt DRI process plant – or about 6.1 t H 2
/ h. To keep the reduction process efficient, this level of hydrogen must be supplied continuously over the years.
According to M. El-Shafie 4, modern electrolyzers can produce hydrogen at up to 19 kg H 2
/ MWh. Considering a 1 % annual degradation rate, an average constant production rate of 18 kg H / 2 MWh over 10 years is assumed for both baseload and cyclic operation. This requires electrolyzers with a capacity of about 338 MW and a power purchase agreement( PPA) of at least 2.967
TWh for hydrogen production. To meet the steel industry’ s decarbonization targets, the power demand should be generated with as high a share of renewable energy as possible.
As stated above, the main challenge for a reliable green hydrogen supply arises when intermittent RES like wind and PV are used. To evaluate green hydrogen production, different boundary conditions based on hourly generation profiles in various countries are considered. These profiles – sourced from renewables. ninja 5 and based on 2019 weather data – are analyzed throughout the whole year( see details in Table 1). For onshore wind, the hub height has been adjusted according to assumptions by the National Renewable Energy Laboratory( NREL) of the U. S. Department of Energy, to align with their published installation costs.
The RES profiles for Spain and Oman assume grid connection, allowing the use of non-RES power. In a second stage, a BESS is added to further reduce the carbon footprint of hydrogen production – up to producing it completely green.
Australian profiles are assumed to be off-grid, prioritizing power for a 24 / 7 mining operation as the primary consumer. Remaining RES generation can be used for hydrogen production, either for export to the steel industry offshore( for the 1 Mt DRI plant) or for producing green pig iron locally.
The energy system was optimized for the lowest investment costs, with accuracies of ± 50 MW for RES generation, ± 10 MW for electrolyzer
Table 1. Data selected for RES power generation. 5 For the wind profiles, a Vestas V90-2000 was selected with adjusted hub heights. Country Latitude Longitude PV Configuration a Wind Onshore b
Australia
Oman
Spain
– 20.6514 – 20.6514
19.8993 19.8993
37.4481 / 43.1664 a
PV configuration: Tilt = 35 °, Azimuth = 180 °, Tracking = No b
Wind onshore: Hub height 98 m
119.6709 119.6709
56.9852 56.9852
– 6.6978 / – 2.9851
X
X
X
X
X
X
26 Hydrogen Tech World | Issue 21 | April 2025