In recent years, the fast growth of computational power has allowed the application of computational fluid dynamics (CFD) in a wide range of areas of interest, such as gas–solid unit operations. In this context, the multiphase particle-in-cell (MP-PIC) method appears as an option to represent fluid–particle and particle–particle interactions, avoiding the complexity of tracking each particle and the high computational cost derived from this. The MP-PIC method can represent the particles as a group with the same characteristics, allowing the simulation of gas–solid systems at different scales. To achieve this, the particle–particle interactions are simplified using the solid stress tensor to represent them; this does not require explicit expressions. This approach has a low computational cost, allowing the simulation of industrial cases using just workstations. This paper provides a review of the literature on the solid stress tensor and its commercial and non-commercial applications, including its historical and mathematical development in the description of particle–particle interactions. In addition, to consolidate the knowledge and advancing understanding in this crucial aspect of multiphase flow simulations, this review identifies the current challenges and opportunities for future research in multiphase systems based on the solid stress tensor. In addition, this review identifies the current challenges and opportunities for future research in multiphase systems based on the solid stress tensor.

The Chilean government has proposed an ambitious plan to reduce emissions by 2050 and become a net-zero-emission country, including producing clean energy via green hydrogen generated from renewable sources. One goal is to achieve a cost of 1.5 USD/kg ${\mathrm{H}}_2$ to be competitive. This study presents a techno-economic analysis of the production of green hydrogen using commercially available electrolyzers—HySTAT (alkaline) and HyLYZER (PEM)—for locations in northern, central, and southern Chile. The Antofagasta (northern), Bio-Bio (central), and Magallanes (southern) regions were evaluated based on their renewable energy sources—wind and solar—which vary in proportion and quantity by geographical location. The results show that the Magallanes region is the most competitive location. We calculated values of 4.43 USD/kg ${\mathrm{H}}_2$ (HySTAT) and 4.81 USD/kg ${\mathrm{H}}_2$ (HyLYZER). The economic evaluation of the HySTAT electrolyzer in Magallanes shows that a modest price above the break-even level yields substantially positive returns (Net Present Value (NPV) up to 2,684,250 USD, Internal Rate of Return (IRR) 19.5%). An optimized scenario combining lower electricity prices, higher capacity factor, and improved electrolyzer efficiency approaches the national target of 1.5 USD/kg ${\mathrm{H}}_2$, but only through simultaneous improvements beyond current commercial technology. These results suggest that Magallanes, paired with alkaline technology, represents a promising option for producing green hydrogen and merits further analysis, aligning with national decarbonization targets and global low-carbon fuel markets. Although the current LCOH values are far from the goal of 1.5 USD/kg ${\mathrm{H}}_2$, there are opportunities to reduce costs, either through the cheapest energy agreements or new technology developments.