Toward a green steel production powered by a hybrid renewable energy system: Techno-economic and environmental assessment

The steel supply chain consists of several stages, with the most energy-demanding phase being the direct reduction iron process. Syngas, used in this stage, is typically produced from fossil fuels like natural gas, which leads to substantial greenhouse gas emissions. In this study, the direct reduction iron production stage was replaced with a proposed process aimed at reducing both energy consumption and emissions while maintaining economic viability. The proposed process (Solid Oxide Electrolyzer − Direct Reduction Iron) was introduced as a potential solution and was compared technically, environmentally, and economically with the conventional (Steam Methane Reforming − Direct Reduction Iron) process. In the proposed process, solid oxide electrolysis cells are used to produce syngas, with the required electrical and thermal energy supplied from renewable sources, solar power and biogas. The results were validated after modeling the process and performing an economic analysis. The comparison between key performance indicators of the two processes highlighted three main findings: first, energy consumption per unit of production decreased by 17 %, from 3.06 MWh/ton_DRI to 2.53 MWh/ton_DRI, while energy efficiency improved by 33 %, rising from 52 % to 85 %. Second, the proposed process resulted in near-zero emissions (Green Steel) production due to the use of renewable energy sources. Third, from an economic perspective, considering the carbon emission penalty, the levelized cost of production for the conventional process was 245 $/ton_DRI, making it comparable to the 249 $/ton_DRI cost for the proposed process.