Off-grid hydrogen supply from solar or wind sources to hydrogen-based steelmaking can reduce CO₂ emissions. However, the techno-economic feasibility of different supply chain configurations remains uncertain. This study evaluates 61 off-grid hydrogen supply chains for a 15 Mt. steel/year plant in 2030, considering renewable energy sources (onshore/offshore wind, solar, and overseas options), transmission technologies (cables, pipelines, trucks, and ships), storage technologies (compressed gaseous hydrogen, liquid hydrogen, ammonia, methanol, and liquid organic hydrogen carriers), and seasonal storage locations (at the energy source or steelmaking plant). Onshore truck transmission of hydrogen is found to be unpromising due to the significantly higher cost compared to alternative transmission technologies. When the transmission technology is not truck, chains with underground compressed hydrogen storage achieve the lowest levelized cost of hydrogen (LCOH) at 3.8–5.6 €₂₀₂₀/kg H₂, outperforming other options. When underground hydrogen storage is not feasible, liquid organic hydrogen carriers present the next lowest cost. Chains utilizing ammonia, methanol, and liquid hydrogen exhibit lower efficiency, higher renewables capacity requirement, and consequently higher LCOH, making them less attractive. Electricity transmission lowers the LCOH of compressed hydrogen chains compared to hydrogen pipeline transmission, but for other chains the trend is reversed. Hydrogen storage near the steelmaking plant reduces costs by enabling the reuse of boil-off hydrogen in liquid hydrogen chains, but for other chains storing hydrogen near the renewable energy source lowers the cost. Impacts of input uncertainties on the LCOH, limitations of this study, and suggestions for future studies are also presented.

Proper thermal management can improve the efficiency of hydrogen storage chains based on liquid organic hydrogen carriers (LOHC). The energy and exergy efficiencies of 24 LOHC chains, which are differentiated by two hydrogen sources (SEL: hydrogen from electrolyzer and SINDU: industrial by-product), three hydrogen consumers (CPEMFC: proton exchange membrane fuel cell, CSOFC: solid oxide fuel cell, and CINDU: industrial consumer), and four LOHC pairs are calculated based on thermodynamic modeling. Possible strategies for the heat integration between the heat sources (including hydrogenation heat, heat generated by hydrogen consumer, and the high-temperature LOHC fluids) and the heat sinks (including LOHC preheating, hydrogen preheating, dehydrogenation, and external heating purposes) are designed for these chains. In the four selected LOHC pairs, dibenzyltoluene (DBT) is found to be the most favorable LOHC pair for the implementation of WHR strategies, mainly because of low heat demand for preheating (8.9% of the stored hydrogen energy) and a high dehydrogenation rate. The WHR strategies significantly improve the energy efficiency of LOHC chains by up to 21.7% points for the chains with CINDU and 40.8% points for chains with CSOFC or CPEMFC, which makes LOHC chains more efficient than traditional compressed or liquid hydrogen chains in several scenarios, i.e., the DBT chain with CPEMFC have the highest energy efficiency (70.4% for SEL/69.5% for SINDU), while the DBT chain with SINDU and CSOFC has the highest exergy efficiency (60.6%). For the remaining combinations of the remaining hydrogen sources and consumers, the compressed hydrogen chains are the most efficient.