# Scenario-Based Techno-Economic Analysis of Steam Methane Reforming Process for Hydrogen Production
## 3 Results and Discussion
### Uncertainty Analysis  
From the results of the sensitivity analysis in the previous section, feedstock price, CO2 capture cost, and IRR are identified as critical parameters. We perform the Monte Carlo simulations (10,000 trials) for Sc 6 to quantify the uncertainty in the H2 production cost by randomly sampling from the triangular distribution of these three parameters [47].  
Figure 6a shows the cumulative probability of H2 production cost with two economic parameters (feedstock cost and CO2 capture cost) ranging from \(\pm\)10% to \(\pm\)50% for a fixed IRR of 10%. The range of \(\pm\)10% results in an increase in the H2 production cost from $1.68/kg-H2 to $1.92/kg-H2, while a range of \(\pm\)50% results in a larger change in H2 production cost from $1.22/kg-H2 to $2.40/kg-H2. This implies that the fluctuations in the H2 production cost increase as the uncertainty of the two influential costs increases.  
The cumulative probability also varies with IRR difference (10.0-20.0%), as shown in Figure 6b. with the two key economic parameters (feedstock cost and CO2 capture cost) of \(\pm\)20%. The cumulative probability curves indicate that as the IRR decreases, the probability of a low H2 production cost increase. When the IRR is 20.0%, the H2 production cost corresponding to a cumulative probability of 0.5 is 2.17/kg-H2; the lower bound (when the cumulative probability is 0) and the upper bound (when the cumulative probability is 1) are $1.93/kg-H2 and $2.40/kg-H2, respectively.  
The CO2 capture cost and CO2 selling price affect the H2 production cost. Accordingly, we further study the attributes associated with CO2, including CO2 capture rate and CO2 emission allowances as well as CO2 capture cost and CO2 selling price, as shown in Figure 7. The white line is the production cost of the base case ($1.80/kg-H2). The upper left and lower right regions of the white line indicate unfavorable and favorable economics, respectively.  
Figure 6: Cumulative probability of H2 production cost in Sc 6 using the Monte Carlo method with (**a**) different influential economic parameters from \(\pm\)10% to \(\pm\)50% and a fixed internal rate of return of 10%, and (**b**) different internal rates of return from 10.0% to 20.0% and two key parameters (feedstock cost and CO2 capture cost) of \(\pm\)20%.  
Figure 7a shows the changes in the H\({}_{2}\) production cost against the changes in the CO\({}_{2}\) selling price and CO\({}_{2}\) capture cost. The H\({}_{2}\) production cost is determined by the ratio of CO\({}_{2}\) capture cost to CO\({}_{2}\) selling price, resulting in H\({}_{2}\) production costs represented by the values in the straight line. The low CO\({}_{2}\) selling price and high CO\({}_{2}\) capture cost cause a prohibitive region of the H\({}_{2}\) production cost, whereas the high CO\({}_{2}\) selling price and low CO\({}_{2}\) capture cost drive it into a favorable economic region.  
Figure 7b shows the changes in the H\({}_{2}\) production cost against the changes in the CO\({}_{2}\) capture rate and CO\({}_{2}\) emission allowances. The white line in Figure 7b is not straight because of the small effect of CO\({}_{2}\) emission allowances on the H\({}_{2}\) production cost when the CO\({}_{2}\) capture rate is high and the large effect of CO\({}_{2}\) emission allowances on the H\({}_{2}\) production cost when the CO\({}_{2}\) capture rate is low. As can be seen in Figure 7a,b, the CO\({}_{2}\) selling price is a more dominant parameter in determining the H\({}_{2}\) production cost than the CO\({}_{2}\) emission allowances if the CO\({}_{2}\) capture is considered.