• Energy Research
• Closed Access close
• UNSW Sydney close

Abstract During the operation of vanadium redox flow battery, the vanadium ions diffuse across the membrane as a result of concentration gradients between the two half-cells in the stack, leading to self-discharge reactions in both half-cells that will release heat to the electrolyte and subsequently increase the electrolyte temperature. In order to avoid possible thermal precipitation in the electrolyte solution and prevent possible overheating of the cell components, the electrolyte temperature needs to be known. In this study, the effect of the self-discharge reactions was incorporated into a thermal model based on energy and mass balances, developed for the purpose of electrolyte temperature control. Simulations results have shown that the proposed model can be used to investigate the thermal effect of the self-discharge reactions on both continuous charge–discharge cycling and during standby periods, and can help optimize battery designs and fabrication for different applications.

Pulsed laser polymerization experiments have been performed on the bulk polymerization of dimethyl itaconate over the temperature range 20–50 °C. The activation energy and frequency factor were calculated as 24.9 kJ/mol−1 and 2.15 × 105 L/mol−1s−1, respectively. The activation energy is comparable with the methacrylate series of monomers. The frequency factor is relatively small and reflects steric hindrance in the transition state caused by the bulky 1,1, disubstitution in the monomer (and consequently the radical). The Mark–Houwink–Kuhn–Sakurada constants were also determined for poly(dimethyl itaconate) in tetrahydrofuran, these are reported as 46 × 10−5 dL/g (K) and 0.51 (α). The influence of penultimate units (γ-substituents) on homopropagation reactions is discussed particularly for polymerizations leading to significant 1,3 interactions in the resultant polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2192–2200, 2000

The lifetime of high energy phonons in a QD superlattice is computed for plausible model materials from Time Dependent Perturbation Theory (TDPT). Klemens decay can be inhibited for a range of high energy phonons if a significant phonon bandgap exists. Ridley-type decays can compete with Klemens for speed due to the large density of states available for decay products on some decay paths and are typically a few picoseconds. In diamond superlattices where QDs occupy the majority of the unit cell, computed lifetimes can be as long as hundreds of picoseconds for certain symmetry directions.

Abstract Efficient hydrogen production from water by photocatalysis under sunlight requires a significant improvement in light-harvesting capability. Zinc sulfide is a promising, inexpensive hydrogen generation photocatalyst, but in its pure, bulk form it is only active under ultra-violet light. Here, we show clear evidence of photoelectrochemical activity of ZnS thin films under visible-light irradiation without any co-catalysts, achieved through defect engineering. Fabrication of nanostructured ZnS under controlled conditions introduces defects, and hence intermediate electronic states within the band gap, which allow significant absorption of light at energies below the band gap energy of pure, bulk ZnS. The measured band gap of the ZnS thin films is ~2.4 eV, while the photocurrent density exceeds 1.5 mA/cm2 under visible-light irradiation (λ≥435 nm). This is the first measurement of such high photocurrents for undoped ZnS under visible light.

In this paper, we investigate how to apply industrial unmanned aerial vehicles (UAVs) for autonomous power line inspection in smart grid from an energy efficiency perspective. Firstly, the energy consumption minimization problem is formulated as a joint optimization problem, which involves both the large-timescale optimization and the small-timescale optimization. Then, the NP-hard joint optimization problem is transformed to a two- stage optimization problem based on energy consumption magnitude and optimization timescale differences. Next, the first-stage and second-stage problems are solved by exploring dynamic programming (DP) and auction matching, respectively. Finally, the proposed algorithm is verified based on realistic power grid topology. Simulation results demonstrate that the proposed scheme achieves significant energy consumption reduction.

This paper presents an emergency frequency control potential of Electric Vehicles (EV)s in a wide area network. Lyapunov energy function is used to maximize the rate of reduction of total kinetic energy in a two-area grid after a contingency event. The effectiveness of the proposed control strategy on damping the oscillations is studied, exploring the locations aspect of the model with the charging stations either in the center of grid-connected areas or in the corners.

Cocoa beans (Theobroma cacao L.) are the raw material for chocolate production. Fermentation of cocoa pulp by microorganisms is crucial for developing chocolate flavor precursors. Yeasts conduct an alcoholic fermentation within the bean pulp that is essential for the production of good quality beans, giving typical chocolate characters. However, the roles of bacteria such as lactic acid bacteria and acetic acid bacteria in contributing to the quality of cocoa bean and chocolate are not fully understood. Using controlled laboratory fermentations, this study investigated the contribution of lactic acid bacteria to cocoa bean fermentation. Cocoa beans were fermented under conditions where the growth of lactic acid bacteria was restricted by the use of nisin and lysozyme. The resultant microbial ecology, chemistry and chocolate quality of beans from these fermentations were compared with those of indigenous (control) fermentations. The yeasts Hanseniaspora guilliermondii, Pichia kudriavzevii, Kluyveromyces marxianus and Saccharomyces cerevisiae, the lactic acid bacteria Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus fermentum and the acetic acid bacteria Acetobacter pasteurianus and Gluconobacter frateurii were the major species found in control fermentations. In fermentations with the presence of nisin and lysozyme, the same species of yeasts and acetic acid bacteria grew but the growth of lactic acid bacteria was prevented or restricted. These beans underwent characteristic alcoholic fermentation where the utilization of sugars and the production of ethanol, organic acids and volatile compounds in the bean pulp and nibs were similar for beans fermented in the presence of lactic acid bacteria. Lactic acid was produced during both fermentations but more so when lactic acid bacteria grew. Beans fermented in the presence or absence of lactic acid bacteria were fully fermented, had similar shell weights and gave acceptable chocolates with no differences in sensory rankings. It was concluded that lactic acid bacteria may not be necessary for successful cocoa fermentation.