Development of a 30 W class direct formic acid fuel cell stack with high stability and durability

A medium-scale DFAFC stack was designed and fabricated in this work. The power output of this stack was high to 32 W, which can satisfy the power requirement of most portable electrical devices. The ultrasonically mixed Pt/C + Pd/C catalyst was optimized as the anode catalyst for the stack fabrication by using a single cell. The feeding formic acid concentration and oxygen flow rate respectively in anode and cathode side were also experimentally optimized before the stack fabrication. Under the optimal operation conditions, the life time test was carried out for the DFAFC stack using the optimal anode catalyst. The stack can stably operate for about 50 h with 1.5 L fuel supplied, and its high durability was confirmed by the 240 h continuous life time test.     

Homogeneous vapor nucleation of water in 3 M NaCl solution within a nanopore

Homogeneous vapor nucleation of water in the electrolyte solution within a nanopore at its superheat limit was studied using the bubble nucleation model based on molecular interaction. The wall motion of the bubble that evolved from the evaporated water was obtained using the Keller–Miksis equation and the distribution of temperature inside the bubble was obtained by solving the continuity, momentum and energy equations for the vapor inside the bubble. Heat transfer at the interface was also considered in this study. The nucleation rate of the 3 M NaCl solution at 571 K is estimated to be approximately 0.15 × 10²⁸ clusters/(m³ s). With this value of the nucleation rate, the complete evaporation time of the 50 nm radius of the electrolyte solution is approximately 0.60 ns. The calculated life time of the bubble that evolved from the evaporated solution, or the time duration for the growth and subsequent collapse of the bubble, is approximately 32 ns, which is close agreement with the observed result of 28 ns. The bubble reaches its maximum radius of 301 nm at 13.2 ns after the bubble evolution.     

Development of a 1 W passive DMFC

In this paper, development techniques for a passive DMFC prototype in the 1 W range are described in detail. The prototype includes a fuel cell stack, a fuel tank and a passive ancillary system (termed “thermal-fluids management system” in this paper). The fuel cell stack in this study incorporates a window-frame structure that provides a large open area for more efficient mass transfer and is modular. Two stack units connected in series, with a total combined active area of 72.0 cm², are used in the prototype. The thermal-fluids management system utilizes passive approaches for fuel storage and delivery, air-breathing, water management, CO₂ release, and thermal management. The air filter also serves as a waterproof layer for the cathode in order to prevent water contamination. Water immersion tests are conducted to evaluate the air filter. The performance evaluation of the prototype is performed in two fuel feeding modes: dilute methanol solution and pure methanol. A peak power output of 1.5 W is achieved with the dilute methanol solution feed.     

射频消融联合肝动脉化疗栓塞治疗肝癌的应用

B.G. Prashantha  M.S. Govinde Gowda  S. Seetharamu  G.S.V.L. Narasimham 《亚洲传热研究》2014,43(7):577-591

经导管眼动脉灌注化疗治疗晚期视网膜母细胞瘤30例

摘要】 目的 评估经导管眼动脉灌注化疗术的（TOAC）治疗眼内晚期化疗失败的视网膜母细胞瘤的临床疗效及安全性。方法 回顾性分析2009年1月—2011年4月收治的经化疗失败的视网膜母细胞瘤患儿30例39只患眼行SOAI治疗的临床资料。39只患眼共行TOAC术82次,平均每眼行2.1次,随访时间2 ~ 28个月,平均13.6个月。术后评估肿瘤控制的有效率、并发症及有无局部肿瘤进展。结果 84次眼动脉插管中,82次成功插至眼动脉,技术成功率为97.6%。术后30只眼肿瘤有不同程度的缩小,有效率76.9%,其中D期、E期分别为17、13只眼,分别占同期治疗眼的85.0%、68.4%;其余9只眼（9/39,23.1%）行眼球摘除。TOAC术后10只眼（10/39,25.6%）出现过球结膜充血,7只眼（7/39,17.9%）发生眼睑肿胀,3只眼（3/39,7.7%）多泪,均自行恢复。全部患儿均未出现血流感染等严重全身并发症。结论 TOAC是治疗眼内晚期化疗失败的视网膜母细胞瘤的安全有效的治疗方法。

     

Development of preheating methodology for a 5 kW HT-PEMFC system

Compared to the low-temperature proton exchange membrane fuel cell (LT-PEMFC) system, the high-temperature proton exchange membrane fuel cell (HT-PEMFC) system has a simple balance of plant (BOP) configuration and high heat recovery efficiency. However, to commercialize this system, the start-up time should be shortened. This study aims to develop a preheating methodology for the 5 kW HT-PEMFC system, which is the target system. The entire start-up time of this system is dominated by the warm-up time of the stack among various other system components. An advanced preheating method was experimentally verified by combining three heating methods of the stack: coolant heating, reaction heating, and air heating. Additionally, considering the power consumption of the target system, a method to reduce the warm-up time was proposed. Ultimately, we found that the combined coolant and reaction heating method was the best. Furthermore, a case study revealed that using an oil heater with variable heating capacity on the target system can reduce the start-up time by 23% compared to a fixed capacity heater.     

Development of 1 kW SOFC power package for dual-fuel operation

A compact SOFC power generation system was developed by integrating a 1 kW SOFC stack and balance-of-plant. The system was designed for dual-fuel operation using both natural gas (NG) and liquefied petroleum gas (LPG). An adiabatic pre-reformer was employed in a fuel processing system to convert C₂₊ hydrocarbons in the fuel into CH₄-rich gas which was further processed in a main reformer to produce H₂-rich gas for the SOFC stack. The SOFC system was operated for 350 h under thermally self-sustaining condition, and on-load fuel switching from NG to LPG was carried out during the operation. The system performance was not significantly affected by NG/LPG composition ratios and the performance was stable during continuous operation in NG or LPG.     

Behavioral modeling of grid-connected photovoltaic inverters: Development and assessment

This paper describes and assesses a behavioral model for grid-connected photovoltaic inverters. The model allows us to simulate the electrical behavior of commercial single-phase and three-phase inverters in accordance with the limits of EN50160 power quality. Regarding power strategies for current inverters, both voltage and current control loops have been explicitly modeled, providing suitable simulations of the injected AC-current waveform under either power dynamics or grid voltage disturbances. Additionally, irradiance oscillations and dynamic Maximum Power Point Tracking performance have been also considered in the proposed solution. Internal inverter variables are not needed to fit the model parameters, being estimated from basic data-sheet information provided by manufacturers and simple AC-collected values from the PV power plants. This characteristic avoids any additional DC-side measurement, being a significant contribution in comparison with previous approaches.The proposed model is assessed using real data collected in Spanish photovoltaic power plants along several years. The obtained results are compared with previous behavioral model approaches and also included in the paper.     

Enhancement of capacity and cycle-life of Sn4 + δP3 (0 ≤ δ ≤ 1) anode for lithium secondary batteries

Various compositions of tin-rich, non-stoichiometric, solid solutions of Sn_4 + δP₃ are synthesized by a mechanochemical method. The materials are tested as anodes for lithium secondary batteries to enhance reversible capacity and cycleability. Investigative analyses show that the region for the solid-solution formation of Sn_4 + δP₃ is 0 ≤ δ ≤ 1. The reaction mechanism of the tin-rich solid solutions is similar to that of stoichiometric Sn₄P₃, except for the absence of a topotactic lithium insertion reaction during the first cycle. As the tin content is increased, tin-rich phosphide exhibits better cycleability and retains a higher reversible capacity, namely, about 20% more than that of stoichiometric Sn₄P₃.     

Development of a 2 W direct methanol fuel cell power source

A series of microfuel cell DMFC prototypes in the 1–2 W range has been developed at Motorola Labs. Design criteria, technical issues and the solution to those issues, system and component performance criteria are all discussed in detail with regards to the demonstrated systems. In particular, the industry-wide problem of long-term voltage degradation is explored with the implementation of a successful engineering solution to this issue which resulted in over 1200 h of system lifetime at the average degradation rate of 41 μV/(h per cell). With sufficient fuel for 1 week of continuous operation, the system energy density in the 2 W DMFC prototype was 490 Wh/kg and 368 Wh/L, respectively, at an overall system efficiency of 20% (includes both fuel conversion and BOP efficiencies).     

Development and performances of a 0.5 kW high-pressure alkaline water electrolyser

The purpose of this research paper is to describe the characteristics and electrochemical performances of a pressurized alkaline water electrolysis short stack (5-cells, 0.5 kW) operated at 80 °C, from atmospheric pressure up to 100 bars. Expanded grids of metallic nickel covered with specific porous catalytic structures have been used as working electrodes. A polysulfone-based diaphragm with a high ionic conductivity has been specifically designed for operation in pressurized alkaline water electrolysis cells. I–V polarization curves have been recorded at current densities up to 1000 mA/cm², at temperatures up to 80 °C and under pressures up to 100 bars. The water electrolysis efficiency of this short-stack has been determined. A specific energy consumption of ca. 4.4–4.5 kWh/Nm³ has been obtained in the high current density range. Durability tests have been performed on the short stack over 1000 h. A limited degradation rate <5 μV/h has been recorded over that period of test.     

钻井用大功率柴油机测控系统开发

根据钻井用柴油机的工作特性,确定了钻井用柴油机测控系统的实现要求,制定了测控系统的结构方案;通过对比筛选,完成了系统硬件设计、选型、组装等工作;采用面向对象的可视化程序语言,编写了钻井用柴油机测控系统软件;对整个系统的调试表明,该测控系统能够满足钻井用柴油机的测控需要,可以为柴油机的安全管理提供技术支持。     

Optimization of a 30 kW SOFC combined heat and power system with different cycles and hydrocarbon fuels

Solid oxide fuel cells (SOFCs) could generate power cleanly and efficiently by using a wide range of fuels. Through the recovery and utilization of the energy in the SOFC tail gas, SOFC combined heat and power (CHP) systems achieve efficient cascade utilization of fuels. In this article, an efficient 30 kW SOFC CHP system with multiple cycles is designed based on a commercial kw-level SOFC device. The energy and substances could be recycled at multiple levels in this system, which makes the system do not need external water supply anymore during working. Meanwhile, the performance, fuel applicability, flexibility and reliability of the system are investigated. Finally, an optimized operating condition is confirmed, in which the electrical efficiency is 54.0%, and the thermoelectric efficiency could reach 88.8% by using methanol as fuel.     

Development of a 700 W anode-supported micro-tubular SOFC stack for APU applications

A 700 W anode-supported micro-tubular solid-oxide fuel cell (SOFC) stack for use as an auxiliary power unit (APU) for an automobile is fabricated and characterized in this study. For this purpose, a single cell was initially designed via optimization of the current collecting method, the brazing method and the length of the tubular cell. Following this, a high-power single cell was fabricated that showed a cell performance of at 0.7 V and using H₂ (fuel utilization=45%) and air as fuel and oxidant gas, respectively. Additionally, a fuel manifold was designed by adopting a simulation method to supply fuel gas uniformly into a single unit cell. Finally, a 700 W anode-supported micro-tubular SOFC stack was constructed by stacking bundles of the single cells in a series of electrical connections using H₂ (fuel utilization=49%) and air as fuel and oxidant gas, respectively. The SOFC stack showed a high power density of ; moreover, due to the good thermo-mechanical properties of the micro-tubular SOFC stack, the start-up time could be reduced by 2 h, which corresponds to 6/min.     

Fabrication and performance evaluation of 3-cell SOFC stack based on planar 10 cm × 10 cm anode-supported cells

This study reports the development of planar-type solid oxide fuel cell (SOFC) stacks based on an internal gas manifold and a cross-flow type design. A single-columned, 3-cell, SOFC stack is assembled using 10 cm × 10 cm anode-supported unit cells, metallic interconnects and glass-based compression-seal gaskets. The power-generating characteristics of the unit cell and stack are characterized as a function of temperature. The practical viability of the stack and stack components is investigated via long-term operation and thermal cycling tests. According to performance evaluation at 700 °C, the short stack produces about 100 W in total power at an average cell voltage of around 0.7 V. There are, however, some scale-up problems related to multi-cell stacking. This work addresses key issues in stack fabrication and performance improvement.     

Electrical properties of vegetable oils between 20 Hz and 2 MHz

Electrical properties (permittivity and conductivity) of vegetable oils were determined in the frequency range from 20 Hz to 2 MHz. Commercial samples of corn, sunflower, soybean, grapeseed, cottonseed, olive, canola and chia oils were measured at temperatures between 300 K and 343 K (stabilized within 0.1 K). The calibration uncertainty in the measuring system was below 1%.     

Life cycle analysis of 4.5 MW and 250 W wind turbines

Electric generation by wind turbine is growing very strongly. However, the environmental impact of wind energy is still a matter of controversy. This paper uses Life Cycle Assessment, comparing two systems: a 4.5 MW and a 250 W wind turbines, to evaluate their environmental impact. All stages of life cycle (manufacturing, transports, installation, maintenance, disassembly and disposal) have been analysed and sensitivity tests have been performed. According to the indexes (PEPBT (primary energy pay back time), CO₂ emissions, etc.), the results show that wind energy is an excellent environmental solution provided first, the turbines are high efficiency ones and implemented on sites where the wind resource is good, second, components transportation should not spend too much energy and, third, recycling during decommissioning should be performed correctly. This study proves that wind energy should become one of the best ways to mitigate climate change and to provide electricity in rural zones not connected to the grid.