Tae-won Song

Biomass Solid Oxide Fuel Cell-Microgas Turbine Hybrid System: Effect of Fuel Composition

Performance analysis of the solid oxide fuel cell-microgas turbine (SOFC-MGT) hybrid system has been made. We assume a fuel composition that is methane based with varying concentrations of other species that are expected to be present in biomass-derived gas streams in preparation for the study of biomass fueled SOFC-MGT hybrid system. This is based on the fact that the chemical composition of biomass fuel produced from different fuel production processes is diversified, i.e., in one case one chemical species rich in concentration and in another case another chemical species rich. In the analysis, the multistage model for internal reforming SOFC module developed previously with some modification is used. With this model, studies cover not only the performance of the hybrid system but also the spatial distributions of temperature and concentration of some chemical species inside the module, namely, in the cell stack and in the internal reformer.

Direct band gap measurement of Cu(In,Ga)(Se,S)2 thin films using high-resolution reflection electron energy loss spectroscopy

To investigate the band gap profile of Cu(In1−x,Gax)(Se1−ySy)2 of various compositions, we measured the band gap profile directly as a function of in-depth using high-resolution reflection energy loss spectroscopy (HR-REELS), which was compared with the band gap profile calculated based on the auger depth profile. The band gap profile is a double-graded band gap as a function of in-depth. The calculated band gap obtained from the auger depth profile seems to be larger than that by HR-REELS. Calculated band gaps are to measure the average band gap of the spatially different varying compositions with respect to considering its void fraction. But, the results obtained using HR-REELS are to be affected by the low band gap (i.e., out of void) rather than large one (i.e., near void). Our findings suggest an analytical method to directly determine the band gap profile as function of in-depth.