Lim Chee Ming

Potential natural sensitizers extracted from the skin of Canarium odontophyllum fruits for dye-sensitized solar cells.

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs. The detected pigment constituents of the extract consist of aurone (maritimein), anthocyanidin (pelargonidin) and anthocyanidin (cyanidin derivatives). When tested in DSSC, the highest conversion efficiency of 1.43% is exhibited by cyanidin derivatives, and this is followed by conversion efficiencies of 0.51% and 0.79% for aurone and pelargonidin, respectively. It is shown that individual pigments, like cyanidin derivatives and pelargonidin, exhibit higher power conversion efficiency when compared to that of C.odontophyllum skin pigment mixture (with a conversion efficiency of only 0.68%). The results indicate a possibility of masking effects of the pigments when used as a mixture. The acidification of C.odontophyllum skin pigments with concentrated hydrochloric acid improves the conversion efficiency of the mixture from 0.68% to 0.99%. The discussion in this paper will draw data and observations from the variation in absorption and adsorption properties, the HOMO-LUMO levels, the energy band gaps and the functional group compositions of the detected flavonoids.

Study of the Enhancement of Cell Performance of Dye Sensitized Solar Cells Sensitized With Nephelium lappaceum (F: Sapindaceae)

We have studied the performance of dye sensitized solar cells sensitized with pigments extracted from the fruit sheath of Nephelium lappaceum (F: Sapindaceae). The pH of the pigment solution used for impregnation was controlled by adding concentrated HCl (50:0.2 v/v). The UV-Vis spectroscopic results revealed that the extract consists of the pigment of Anthocyanin, with an additional absorption peak appearing around 540nm at a lower pH of the pigment solution. Also the band gap of the pigment was reduced by 1eV at low pH conditions. The solar cells fabricated with pigment extracted from the fruit sheath of Nephelium lappaceum showed photo-response with the conversion efficiency of 0.26%, with an open-circuit voltage (VOC) of 453mV, short-circuit current density (ISC) of 1.17mA cm � 2 , and fill factor (ff) of 0.48. The conversion efficiency was significantly enhanced when pH of the pigment solution was lowered by adding concentrated HCl. The conversion efficiency of the dye sensitized solar cells (DSSCs) sensitized after HCl treatment of the pigment was increased to 0.56%, with an open-circuit voltage (VOC )o f 404mV, short-circuit current density (ISC) of 2.71mA cm � 2 , and fill factor (ff) of 0.35. The HOMO level of the pigment at low pH was shown to be shifted towards more positive values with respect to vacuum level, giving rise to an enhanced DSSC efficiency. The overall efficiency enhancement of the low pH pigment was due to the combined effect of increased UV-Vis absorption and efficient adsorption of dye molecules onto the TiO2 semiconductor surface. [DOI: 10.1115/1.4023877]

DC Picogrids as power backups for office buildings

Office buildings in developing countries employ battery backups with inverters and/or diesel generators to power essential loads such as lighting, air conditioning and computing loads during power cuts. Since these backup solutions are expensive and inefficient, they form a significant proportion of the operating expenses. To address this problem, we propose using a personal comfort system (an illustrative configuration can comprise a LED light and a DC desk fan) that is powered by batteries in computing devices. With this approach, cost savings are realized through two mechanisms, (i) by reducing the dependence on high-power lighting and air conditioning during times of power outage, and (ii) by charging the batteries at optimal times, taking advantage of the variable cost of power supply. Simulations show that the expected energy savings from this methodology are in the region of 26%, compared with the current system. In this paper, we present various architectures for the load-battery combination, a dynamic programming based framework that generates optimal charging/discharging schedules, and an experimental evaluation of the proposed approach.

Bi2O3 and La10Si6O27 composite electrolyte for enhanced performance in solid oxide fuel cells

Adding suitable metal oxide into lanthanum silicate apatite can produce a composite with a good oxygen ion-conducting electrolyte that enhances the performance of solid oxide fuel cells (SOFCs). In this paper we present the synthesis and characterisation of Bi2O3 and La10Si6O27 composite prepared by a solid state reaction. The sintering temperature of the composite was 1500°C for 10 hours with the heating and cooling rates of 10°C per minute. The properties of the resulting composite have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ionic conductivity measured by an a.c. impedance spectroscopy (IS). Rietveld refinement of XRD data shows that the composition is purely the mixture of Bi2O3 and La10Si6O27 with the unit cell parameters of the main phase as a = 9.9810 (8) and c = 7.3239 (6) A. The room temperature crystal structure was hexagonal with space group P63/m. The highest ionic conductivity of 1.76 × 10-2 Scm-1 with a corresponding activation energy of 0.39 eV was obtained at 750°C. SEM images show the material is densed enough to use as an electrolyte for SOFCs.

Algorithms for upgrading the resolution of aggregate energy meter data

Metering of the energy supplied to consumers is an important component of operations for utility providers. Several schemes have been employed for this purpose, including traditional postpaid and prepaid metering, and more advanced smart metering technology. Analysis of the data generated by these meters has the potential to provide insights into consumer characteristics and power consumption patterns, including consumer segmentation and anomaly detection. We describe the different types of power purchase and consumption data, as well as the analytics algorithms that can be applied to them. Most applications developed for energy meter data require high resolution information of the type provided by smart meters, thus leaving aggregate prepaid or postpaid meter schemes at a disadvantage. In this paper, we present analytics-based methodologies to upgrade aggregate prepaid and postpaid meter data resolution, which will allow smart meter analytics to be applied without expensive infrastructure upgrades.

Optimization of a Novel Composite Cathode for Intermediate Temperature SOFCs Applications

Ba0.95FeY0.05O2.81 was prepared by solid state reaction method to study its structure, conductivity and thermal expansion coefficients. X-ray powder diffraction at elevated temperatures showed the pure phase at 100 - 600 °C, then the phase changed at 700 - 800 °C. Electrical conductivity measurements at different temperatures showed that the conductivity increased with an increasing amount of Co2O3. The highest conductivity was observed for 10 wt%Ba0.95FeY0.05O2.81 + 90 wt%Co2O3. Thermal expansion coefficients were measured for different compositions to determine the compatibility with Ce0.9Gd0.1O1.95 electrolyte. Results showed that the conductivity and thermal expansion coefficient were sensitive to the composition. The optimum composition was 10 wt%BFY532 + 90 wt%Co2O3, which gave the highest conductivity at 600 - 800 °C. The thermal expansion coefficient was 12.79×10 -6 o C -1 at 40 - 800 °C, which is compatible with the Ce0.9Gd0.1O1.95 electrolyte.

Synthesis of La 10 Si 6-2x Bi 2x O 27-x as Possible Electrolyte Materials for Solid Oxide Fuel Cells

La10Si6-2xBi2xO27-x (x = 0.22, 0.46 and 0.72) ceramics have been synthesized by the solid-state reaction method. The calcination temperature of La10Si6-2xBi2xO27-x was 900°C for 4 hours and the sintering temperature was 1500°C for 5 hours with the heating and cooling rates of 10°C per minute. Crystal structures of La10Si6-2xBi2xO27-x have been characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Room temperature XRD patterns of La10Si6-2xBi2xO27-x ceramics doped with Bi3+ show hexagonal apatite structure with space group P63/m as the primary compound with minor appearance of La2SiO5 impurity as the secondary compound. As the bismuth oxide content increased the La2SiO5 impurity also increased. La10Si5.56Bi0.44O26.78 has the highest bulk density of 5.2 gcm-3 and good microstructure compared to La10Si5.08Bi0.92O26.54 and La10Si4.56Bi1.44O26.28.

YSr2Fe3-xCoxO8 as a Potential Cathode Materials for SOFCs

The composition YSr2Fe3-xCoxO8 (for x = 0.5, 3.0) has been investigated as an alternative cathode material for Solid Oxide Fuel Cells (SOFCs). X-ray diffraction (XRD) pattern shows that the composition YSr2Fe2.5Co0.5O8 crystallizes with cubic symmetry in the space group Pm-3m and YSr2Co3O8 crystallizes with tetragonal symmetry in the space group P4/mmm. Rietveld refinement of XRD data shows the cell parameter of the cubic YSr2Fe2.5Co0.5O8 is a = b = c = 4.1964(2) (Å) and tetragonal YSr2Co3O8 is a = b = 9.8998(9) (Å) and c = 8.9617(6) (Å). Scanning electron microscropy (SEM) images show porous structure for both the samples, which is favourable as a cathode for Solid Oxide Fuel Cells.

DFT/TD-DFT Studies on the Lawsone (Henna) as a Photosensitizer for Dye-Sensitized Solar Cells

In this study, the parameters of the photo-electrochemical properties, such as the ground state geometries, excitation energy, electronic structures, optical properties and electronics transition of lawsone were investigated by using density functional theory ( DFT ) and time dependent - DFT with B3LYP/6-31G( d) method. The solvent effect was considered in the DFT calculations and compared with the value of vacuum. From the analyses of electronic and optical properties, it is found that the lawsone satisfy the condition for good conversion efficiency as DSSCs device.