## 5 Conclusions  
In this study, modeling and simulation of a hydrogen-based HRES were conducted in order to find the optimal configuration of the system that can be used to meet the electrical load requirement of a typical Japanese household located in a residential area in Shinchi-machi, Fukuoka prefecture, Japan. The modeling framework was developed using both the cost minimization and profit maximization approaches. The simulation part was developed to estimate the hourly electrical power generated by the proposed HRES, taking into account the variation of the weather parameters and given the demand load. The optimization model's main goal was set to find the optimal configuration of the system subject to satisfying the required demand load, considering two scenarios: (1) minimization of the total cost of the system in an off-grid mode and (2) maximization of the total profit obtained from using renewable electricity and selling surplus solar electricity to the grid, considering the feed-in-tariff (FiT) scheme in a grid-tied mode. As indicated by the model results, the proposed HRES could generate about 47.3 MWh of electricity in all scenarios, which was needed to meet the external load requirement in the selected study area. The LCOE of the system in scenarios 1 and 2 was estimated at 55.92 JPY/kWh and 56.47 JPY/kWh, respectively. Comparison between scenario 1 and scenario 2 showed that the capacity of electrolyzer and PV module with limited biomass feedstock increases. The limited availability of biomass feedstock resulted in increasing the share of the PV panels and decreasing the share of the fuel cell in the total supply mix. The results of the profit maximization problem revealed the role of the PV module in increasing the profit by selling back the surplus electricity to the grid, using the FiT mechanism. Therefore, the reduction of the cost of the solar-hydrogen system turned out to be by far the most critical cost driver under the profit maximization scenario, when the FiT system was enforced. However, the big challenge facing residential HRES that we discussed in this paper is their economic viability and cost-effectiveness. Rather, cost-conscious policymakers often remain reluctant to invest financial resources in this area. Despite limited incentives provided by the local governments such as feed-in-tariff and J-Credit to compensate for the capital investments of a number of large-scale commercial and independent power producers, there are no major regulatory efforts that have focused specifically on the promotion of the hybrid residential microgrids in Japan. Providing long-term policies and effective incentive strategies leads to the widespread deployment of residential microgrids in the whole country. The demonstration programs such as those we discussed in this paper will help the government to set long-term goals and an initial foundation for microgrid development in cities. On the basis of the detailed technical insights obtained from this study, the economic benefits of the proposed HRES for customers, utilities, and society can be evaluated, and then policies can be implemented to ensure the hybrid residential microgrid owner receives incentives or other support to monetize those benefits. \begin{table}
\begin{tabular}{p{42.7 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt}} \hline \hline \multirow{2}{*}{**Scenarios**} & \multicolumn{2}{c}{**Power**} & \multicolumn{2}{c}{**Annual Hydrogen**} & \multicolumn{2}{c}{**Annual Biomass Consumption (JPY/year)**} & \multicolumn{2}{c}{**Annual Profit (JPY/kWh)**} & \multicolumn{2}{c}{**LCOE, Including the Annual Profit (JPY/year)**} \\ \cline{2-9}  & **PV** & **FC** & **PV** & **SCWG** & **(kg)** & & **(JPY/year)** \\ \hline Scenario 1 & 78 & 22 & 90 & 10 & 264.3 & v244,550 & v55.92 & - \\ \hline Scenario 2 & 81 & 19 & 90 & 10 & 264.3 & v262,100 & v59.93 & v56.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Techno-economic analysis results for the two scenarios. **Author Contributions:** Methodology, N.T.