Applied Mechanics and Materials Vols. 316-317

Abstract: The chemical-looping combustion process of solid fuels has been investigated using thermogravimetric analysis (TGA). Experimental results showed that CuO showed high reactivity during reduction process with coal. The coal conversion rate increased with the increase of reaction temperature, and the optimum reaction temperature was about 800 °C. When CuO was supported on TiO₂, the temperature to initiate the reaction decreased and the coal conversion rate also increased. Candlenut wood ash, which contained high amount of alkali metal, displayed catalytic activity in mixtures with coal during the CLC process. A key issue is to find the ways for increasing the gasification rates during the CLC process in an industrial process.

Abstract: Chemical-looping combustion (CLC) is a new method for the combustion of fuels with inherent separation of carbon dioxide, which can simultaneously improve combustion efficiency and reduce environmental pollution. Since solid coal is considerably more abundant than natural gas, it would be highly advantageous if the CLC process could be adapted for solid fuels. The present review introduces the technical approaches for the solid fuels CLC process, and the existing technical problems in solid fuels CLC are discussed. The demands in oxygen carriers of chemical looping combustion for solid fuels are analyzed, and the recent advances in metal oxides oxygen carriers (Cu-, Ni- and Fe-based) and calcium based oxygen carrier are summarized. The recent advances in reactor design are outlined. The main problems in reactor deign are mentioned and the relative measures are pointed.

Abstract: Steam gasification of biochar from catalytic pyrolysis of biomass was studied in a fixed bed reactor at atmospheric pressure. The experiments were carried out at bed temperature of 700, 750, 800 °C at steam flow rate of 0.1 g/min with reaction time of 3h. The gases produced included mainly H2, CO, CO2 and some small molecular hydrocarbons. The results showed that high gasification temperature was favorable for the production of hydrogen-rich gases. The maximum concentration of hydrogen exceeded 85% at 800 °C and the total gas yield increased with temperature rising. Meanwhile, the conversion efficiency of biochar at 700, 750, 800 °C was 48%, 60%, 72% respectively.

Abstract: The system of a 24V solar photovoltaic DC refrigerator was studied and analyzed in the paper. Solar energy is the only energy source used to power the refrigerator. The USB data acquisition instrument was used to collect the data of voltage, current and freezer temperature of the system during the operation. Experimental results demonstrate that the solar photovoltaic DC refrigerator can run normally; the running rate of the refrigerator is about 48.8% when it runs steadily with no-load and the average consumption of power is about 28.8W.

Abstract: The building energy consumption simulation software DeST is used to analyze the effects of fixed shading over external window on energy consumption and efficiency, on the base of a residential building in Shanghai. The simulation results show that the fixed shading over south window has little effect on the overall energy saving of residential building. For east and west external window, if window area is not very large and its shading performance is better, the effect of fixed shading installation on energy saving is not obvious. On the contrary, if its area is large and its shading performance is ordinary, the effect is remarkable. Furthermore, when room ventilation capacity is poor, the effect of energy saving by fixed shading installation is more prominent.

Abstract: Heat transfer and fluid flow in the microchannel cooling passages with three different types of the MTPV systems are numerically investigated. The heat transfer characteristics and thermal performance of the microchannels are analyzed using different Reynolds numbers and hydraulic diameters. Local heat transfer coefficient, total pumping power, heat transferred are obtained from the simulations and the performance is discussed in terms of heat transfer coefficient and thermal efficiency. Results indicated enhanced performance with the smaller hydraulic diameters, and slighter penalty in pumping power. The increase in Reynolds number cause an increase in the heat transfer coefficient at the expense of decreased thermal efficiency. It is also found that the highest heat transfer coefficient is expected in rod bundles microchannels. However, round microchannels have a better thermal efficiency than others.

Abstract: The presented work aimed at investigating the hydrogasification of low-oxygen semi-coke. For comparison, the hydrogasification of lignite was conducted. Variation of gaseous products concentration and reaction rate of the semi-coke hydrogasification process were investigated. The results shown that the methane yield of low-oxygen semi-coke is 24.8% greater than the lignite, but also the hydrogen consumption reduced greatly; the hydrogasification process can be divided into three stages: hydro-pyrolysis stage, rapid hydrogasification stage and slow speed hydrogasification stage; the difference of the reactive is attributed to different carbon structure forms .

Abstract: In the research of electricity market, electricity pricing is a key issue. Transmission pricing affects the interests of generation company, transmission company and consumer. In this paper, a new method of transmission pricing is proposed .It is based on the short term marginal cost method and further considers capacity cost. Simulation results show that the method proposed can not only lead to short-run market efficiency by providing effective economic signals to generators and consumers, but also ensure the balance between income and expenditure of transmission companies as well as help them accumulate special fund for transmission network expansion.

Abstract: Transmission planning is a complex optimization problem with multiple deciding variables and restrictions. The mathematical model is non-linear, discrete, multi-objective and dynamic. It becomes complicated as the system grows. So the algorithm adopted affects the results of planning directly. In this paper, a fast non-dominated sorting genetic algorithm (NSGA-II) is employed. The results indicate that NSGA-II has some advantages compared to the traditional genetic algorithms. In transmission planning, NSGA-II is feasible, flexible and effective.

Abstract: Battery lifetime has become one of the key control parameter of mobile devices design. Maximizing battery lifetime is a difficult task because of both the nonlinear for battery capacity consumption and the correlation between capacity consumption and battery load. In this paper we address the problem how Dynamic Voltage Scaling (DVS) policy optimizes battery utilization according to battery discharge characteristic for the discrete voltage systems. We analyze the battery discharge characteristic and find that the whole battery discharge takes on a linear discharge phase and a nonlinear discharge phase successively. The proposed DVS policy utilizes different methods to generate the voltage schedule during the different discharge phases. Simulation results show that the policy can effectively reduce battery capacity consumption and increase the workload performed during the battery lifetime.