Renewable hydrogen based direct iron ore reduction and steel making with grid assistance: Energy Conversion and Management

Hydrogen-based direct iron ore reduction with the electric arc furnace (HDRI-EAF) is considered a pivotal low-carbon steel making pathway towards global energy system carbon neutrality. However, electrification will require significant renewable electricity and electrolysis capacity additions. This study investigates the solar/wind electricity and electrolysis capacity requirements for grid-assisted renewable HDRI-EAF from steel emissions and cost perspectives in five selected geographical locations, having different renewable and grid electricity characteristics. Hourly solar-wind and renewable-grid electricity complementarities are evaluated based on renewable energy availability, volatility and price, and correlation with grid emissions and price. At reference conditions (i.e., normalized renewable capacity = 3, wind fraction = 0.6, normalized electrolysis capacity = 1.5), specific emissions range from ∼221 to 537 kgCO2/tLS depending on location, which is 46–84% below natural gas DRI-EAF, and 63–81% below grid-only operation. In parallel, the levelized cost of steel is estimated at ∼500 to 554 USD/tLS, which is comparable to conventional DRI-EAF, excluding emission penalties. Furthermore, a range of moderate renewable and electrolysis capacity combinations yield 70% emissions reduction relative to conventional DRI-EAF (∼310 kgCO2/tLS) within 10% cost increment for all locations (excluding emission penalties). Depending on the local dedicated renewable and grid electricity characteristics, emissions can be minimized down to 113–131 kgCO2/tLS (approaching process-level emissions), at the maximum renewable capacity considered, wind fractions of 0.65–0.85 (corresponding to high and low solar availability locations, respectively), and electrolysis oversizes of 1.2–1.7, with the highest electrolysis capacity requirement observed at the location with the highest renewable volatility. The degree of (anti)correlation between local hourly renewable electricity availability, and grid emissions and price, has a strong influence on steel emissions and cost intensity, and can mitigate unfavorable grid emissions and price conditions, respectively. © 2023 Elsevier Ltd