# Green Hydrogen Production--Fidelity in Simulation Models for Technical-Economic Analysis
Proton exchange membrane water electrolyzer (PEMWE) technologies boast higher current densities (1-2 Acm\({}^{-2}\)) than alkaline water electrolyzers (AWEs) and produce a higher purity of hydrogen up to 99.9999% [17]. Barriers associated with those systems have been gathered and recapped to identify key solutions that could aid in their removal. Likewise, in a study, the results found that a 4.2% reduction in the amount of electrical energy needed for electrolysis showed that barriers to solar hydrogen generation are related to the industry of PV cells, atmospheric conditions affecting PV cells' performance, and those related to solar-to-hydrogen (STH) production and storage [18]. According to [19], by connecting a solar module with the voltage at its maximum power point (Vmpp) to a high-efficiency PEM electrolyzer, the group was able to achieve a solar-to-hydrogen efficiency of 12.4%, compared to a past system that only reached 2-6%. This study utilized a 20-cell PEM electrolyzer stack and various PV modules with different output voltages and current levels. In this context, the modeling of large-sized electrolyzers has also been studied for real-time simulation and the possibility of frequency support by electrolyzers [20]. Also, electrolyzers have been found to support frequency stability more effectively than conventional generators, benefiting the power system's stability. The development of a generic electrolyzer model has allowed simulations to analyze the impact of electrolyzers on power system stability, showing promising results. Field measurements and simulations have validated the model's ability to replicate the behavior of real electrolyzers, highlighting their potential to support frequency and voltage stability in future power systems. In the same line, the reference [21] explores the impact of the operational constraints and the control strategies on the effectiveness of hydrogen electrolyzers in providing frequency control services; the results show that hydrogen electrolyzers can effectively contribute to helping prevent widespread load shedding in power systems. Also, in the studies carried out by [22; 23], the results present that proton exchange membrane hydrogen electrolyzer units are a suitable candidate for virtual inertia response, regulation, and contingency frequency control ancillary services, potentially replacing the need for battery installations in future power systems. Electrolyzers can regulate power off-take based on grid frequency. A techno-economic model optimizes revenue by considering power band and ancillary services. Operating the electrolyzer at optimal values maximizes revenue. Offering symmetric primary reserve is a valid option for revenue generation [24]. On the other hand, high-fidelity mathematical models used to perform simulations in the fields of chemical engineering and fluid dynamics can take hours or even days to simulate due to the large amount of data and parameter tuning required in these models. To address these challenges, high-fidelity component-level models can be replaced with reduced-order models that balance accuracy in exchange for lower computational complexity. To create a static reduced-order modeling ROM, curve fitting, look-up tables, and neural networks can be used to create a suitable model [25; 26]. This could directly influence the time required for the simulation process of the electrolyzer and the micro-grid system. Therefore, the point of interest is specifically to analyze the energy production and determine the amount of hydrogen that can be produced. Parameters must be taken into account for a technical-economic study. Consequently, all these factors represent a gap in research for the generation of green hydrogen. Some studies present technical-economic analyses for different countries, which do not allow the approach to be generalized due to the economic power of each one. In addition, there are different conditions for renewable resource generation.