# Green Hydrogen Production--Fidelity in Simulation Models for Technical-Economic Analysis
## 4 Simulation Results and Discussion
### Comparative of Hydrogen Using Natural Gas  
On the other hand, a comparative analysis has been carried out on the production of hydrogen from natural gas. For this purpose, the process was modeled through steam methane reforming, which is the most common method for producing hydrogen from natural gas, which involves two main reactions:  
1.--Methane reforming:  
\[CH_{4}+H_{2}O\to CO+3H_{2} \tag{33}\]  
2.--Water-gas shift reaction (optional):  
\[CO+H_{2}O\to CO_{2}+H_{2} \tag{34}\]  
Figure 17: Sensitivity of LCOH versus PV generation cost variation.  
Figure 18: Analysis of LCOH versus variations in electrolyzer costs.  
Using the molecular weight of hydrogen \(M_{H_{2}}=2.016\ \frac{\text{g}}{\text{mol}}\), we convert 0.287 kg of hydrogen to moles:  
\[\text{Moles of }H_{2}=\frac{287\ \text{g}/\text{day}}{2.016\ \text{g}/\text{mol}}=142.3 \ \text{mols}/\text{day} \tag{35}\]  
The second step was to calculate the required methane and water. Since 1 mole of methane produces 3 moles of hydrogen in the stem methane reforming (SMR) process, the amount of methane required is  
\[\text{Moles of }CH_{4}=\frac{\text{Moles of }H_{2}}{3}=\frac{142.3}{3}=47.3\frac{ \text{moles}}{\text{day}} \tag{36}\]  
The water requirement is the same as the methane requirement (based on a 1:1 stoichiometric ratio).  
Figure 19 represents a simulation of hydrogen production via steam methane reforming (SMR). It can be observed that methane (CH\({}_{4}\)), initially at approximately 50 moles, is rapidly consumed, reaching nearly zero within the first 100 s. The water (H\({}_{2}\)O), similarly to methane, begins at around 50 moles and is consumed at a similar rate, reaching near-zero. The amount of carbon monoxide (CO) increases rapidly in the beginning but stabilizes at a constant value of approximately 37 moles after a short time. The carbon dioxide (CO\({}_{2}\)) is produced in small amounts and stabilizes at a low concentration after an initial peak. Hydrogen is the main product of the reaction, increasing sharply in the first moments and stabilizing at around 142.36 moles, showing a successful hydrogen production via SMR, equivalent to 0.287 kg/day, which closely matches the results in Figure 15.  
The literature [42] indicates that hydrogen production via steam methane reforming (SMR) of natural gas (CH\({}_{4}\)) remains the most cost-effective method for producing hydrogen gas today. Our aim in Table 9 was to make a comparison, and indeed, SMR continues to be the least expensive, even in terms of water consumption. However, it is evident that SMR has a significant environmental impact in terms of carbon emissions, an issue that photovoltaic hydrogen production mitigates entirely. In the context of Ecuador, carbon certificates can be traded, with the current price at USD 50 per ton of CO\({}_{2}\), providing an estimated USD 950 to avoid 19 tons of carbon emissions per year.  
Figure 19: Energy consumption per kilogram of natural hydrogen gas as inlet.  
However, if we calculate the return on investment through carbon certificates at Ecuador's prices, we obtain an approximate payback period of 1.17 years under this mechanism as shown in the following Equation (37):  
\[\begin{split}\text{Carbon certificate price (CCP)}&=50\text{ USD}\\ \text{Total Annual Cost (TAC)}&=27947.9\text{ USD}\\ \text{Mitigated Carbon Emissions (MCE)}&=19\text{ Tons}\\ \text{project lifetime (PL)}&=25\text{ year}\\ \text{Return on Investment}&=\frac{\text{TAC}}{\text{CCP} \times\text{MCE}\times\text{PL}}\\ &=\frac{27947.19}{50\times 19\times 25}=1.17\text{ years}\\ \end{split} \tag{37}\]