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Power-to-gas (PtG) is a promising technology for the production of hydrogen via electrochemical reactions in water electrolyzers to manage intermittent power generation from renewable energy sources, such as wind and solar energy. Water electrolyzers generate hydrogen and highly purified oxygen as by-products. In this study, process analysis was performed on oxy-fuel combustion in a coal and biomass power plant and a PtG plant, which uses highly purified oxygen obtained from a water electrolyzer. The power-generation efficiency of an oxy-fuel power plant supplied with oxygen through an air separation unit and that of an oxy-fuel power plant supplied with oxygen in a polymer electrolyte membrane (PEM) water electrolysis process were also compared. Furthermore, we analyzed a combined system comprising an oxy-fuel power plant and PtG plant and found the resulting net power generation and power-generation efficiency to be higher than those of the individual oxy-fuel power plant that was supplied with oxygen through an air separation unit. This process efficiency was further improved when applying biomass to fuel the oxy-fuel combustion boiler rather than coal, and in cases where the steam-water is in a supercritical condition. Comparing with other methods, power generation using biomass is environment-friendly and sustainable. Finally, an economic analysis of hydrogen production showed that the levelized hydrogen cost was deduced to approximately $3.67/kg-H2, which is similar to the 2030 target value for hydrogen economy revitalization roadmap of the Korean government of 4000 KRW/kg-H2.

A prediction model was developed for the wildfire fuel load of Korean red pine (Pinus densiflora) stands with susceptibility to forest fire based on the forest-growth model. Furthermore, a time-series analysis was performed on the variation in forest-fire fuel load according to forest management. National Forest Inventory stand data of 1434 plots for P. densiflora stands were used, and the final forest-fire fuel load prediction model was developed using the Weibull function and mortality model. The fit index of the diameter distribution model ranged from 0.58 (0th percentile) to 0.96 (50th percentile), and that of the mortality model was 0.68. The prediction of the stand growth variation after 20 years based on the growth data of managed and unmanaged stands indicated a mean stand density of 1518 trees per ha for unmanaged stands, and 885 trees per ha for managed stands. Regarding the variation in the available canopy fuel load distribution, the predicted annual increase was approximately 0.7 ton/ha for unmanaged stands and approximately 0.5 ton/ha for managed stands. These findings will contribute to setting fuel management criteria to prevent forest fire spread while providing the quantitative data of the characteristics of stand growth variation and the predicted wildfire fuel load.

A molten carbonate fuel cell (MCFC) is a high-performance electric power generation system, but much research is still required to develop technologies to enhance its power efficiency, because the exhaust gases of an MCFC contain sensible energy. The high level of heat energy in the exhaust gases leads to a poor performance, with an increased electricity rate and decreased efficiency. This study investigated the supercritical carbon dioxide cycle with three different configurations as a bottoming cycle using the exhaust gases of an MCFC stand-alone system and compared the supercritical carbon dioxide cycle with a combined heat and power system in terms of economical operational strategies. The thermodynamic characteristics of each cycle were determined by varying the turbine inlet pressure and isentropic efficiency of the turbomachinery. The results of an analysis found that optimal discharge pressure of compressor, are remarkable parameter for supercritical carbon dioxide cycle. Furthermore, the net power efficiency was increased (3.41%–4.6%) compared to that of the MCFC stand-alone system. In addition, the levelized cost of electricity values for the supercritical carbon dioxide cycle and combined heat and power system were calculated, and sensitivity analyses were conducted for factors such as the heating cost and major equipment cost. The results showed that using the supercritical carbon dioxide cycle as the MCFC bottoming cycle was more economical when the heating cost was less than $28/Gcal and the printed circuit heat exchanger cost was less than $100/kW.