Design and analysis of a new wave energy converter based on a point absorber and a hydraulic system harvesting energy from waves near the shore in calm seas

The aim of this paper is to illustrate the design of a new wave energy converter, composed of a point absorber and a hydraulic system (power take off) and sized for recovering energy in calm seas from waves near the shore. The point absorber is consisting of a rectangular shaped buoy integrating a piston pump. The set buoy‐pump oscillates under the waves action and moves natural water in a closed circuit hydraulic system (power take off) composed of a piping connecting the piston pump itself, a pressurized reservoir, a hydraulic turbine and a discharge tank. The methodology adopted for designing the main constituents involves a 1D mathematical model, settled for understanding the motion of the buoy under the hypothesis of regular waves and fully developed sea, and a sizing procedure applied for the design of all the components of the hydraulic system. The project related to the Calabrian site of Cetraro (Mediterranean Sea—south Italy) led to designing a system with a 4 m large buoy, associated with a small 13 cm diameter micro Pelton turbine, so that more than 22 000 kWh could be recovered in a year.     

Sizing of Packed Deaeration Columns

Removal of oxygen from feedwater is of paramount importance for safe boiler operation. Insufficient extraction of oxygen in deaeration vessels will lead to limited efficiency of oxygen scavengers and unsafe plant operation. The presented sizing procedure for packed deaeration columns is based on the similarity theory between heat and mass transfer and existing procedures. The goal of the proposed technique is not to achieve optimization of column dimensions, but to ensure that there is no undersizing of the packing height. This approach is justified considering the relatively low capital costs of deaeration columns in boiler plants. The proposed equations are based on an experimental setup involving several hundred operating regimes which have been verified and confirmed to have a high degree of accuracy.     

A sizing methodology based on Levelized Cost of Supplied and Lost Energy for off-grid rural electrification systems

Off-grid renewable systems can play a pivotal role in the process of rural electrification, thus promoting local development. Moreover, scientific literature is increasingly addressing this issue through the concept of sustainability and appropriate technologies. With regards to this topic, we present a sizing methodology which better relates the results and the sizing process itself to the local context. Specifically, we address the research area of sizing methodologies for off-grid PV systems. Typically, the Loss of Load Probability (LLP) is a key parameter in these methodologies, but is difficult to set as regards the specific context. The proposed methodology employs the concept of Levelized Cost of Supplied and Lost Energy, it is based on the estimate of an economic Value of Lost Load, and eventually, the LLP results to be an output of the process. Therefore, the methodology uses only data characterizing the local situation and results better fit with population conditions. We also propose a simple approach to compute the Value of Lost Load and we apply the methodology for a rural area of Uganda. The results show that the methodology identifies a reliable system which supplies electricity with a fair cost while minimizing the energy bill of the consumers.     

Comparison of piezo electric particle monitor with laser diffraction technique

A piezo electric particle monitor was used to record droplet size distributions at 5 bars with nitrogen as gas phase and Exxol D60 as liquid phase. The measurements were compared with a laser diffraction technique. A discussion of the limitations of the methods is given. The results show that the piezo electric particle monitor is a good method for measuring droplet size distributions at given conditions.     

Automating the sizing of transistors in CMOS gates for low‐power and high‐noise margin operation

This paper presents an automatic method for sizing the transistors in CMOS gates. The method utilizes a feedback control system to efficiently optimize the transistor sizes in small and large fan‐in gates, with the primary goal of enhancing noise robustness (as characterized by the static noise margin). The gates retain their robustness under threshold‐voltage variations over a range of supply voltages. The optimized gates not only expend reduced power and energy, but also take up less area than the conventional ones. These multi‐faceted gains, however, do incur some performance loss. Copyright © 2014 John Wiley & Sons, Ltd.     

基于改进粒子群的分布式电源选址定容优化

随着分布式电源并网推广,它对配电网中的节点电压、线路潮流、短路电流、可靠性等会带来影响,且其影响程度与分布式电源的位置和容量密切相关。分布式电源的位置和规模不合理,可能会导致电能损耗以及网络电压的稳定性。传统的粒子群在解决选址定容上存在易陷入局部最优解,收敛速度慢。提出一种模糊自适应粒子群的方法自适应改变参数来对分布式电源的选址定容问题求解,以网损最小为目标函数,得到分布式电源接入的最优方案。通过测试IEEE30节点的系统,仿真结果表明算法是有效的。     

考虑相关性的间歇性分布式电源选址定容规划

节能减排背景下,以分布式风电和光伏为代表的间歇性分布式电源得到了快速发展。考虑风速、光照强度和负荷间的相关性,以年综合费最小为目标,利用机会约束规划方法建立了间歇性分布式电源选址定容规划模型。采用秩相关系数矩阵表征风速、光照强度和负荷间的相关性,利用拉丁超立方采样和Cholesky分解生成相关性样本矩阵。应用动态小生境差分进化算法对规划模型进行求解。IEEE 33节点配电网算例的仿真结果验证了模型的合理性。     

主动管理模式下分布式风电源选址定容规划

节能减排背景下,以分布式风电源(DWG)为代表的可再生能源发电得到了快速发展。考虑风速和负荷间的时序相关性,采用联合概率分布法对其进行多场景构建。在此基础上,考虑调节有载调压变压器抽头、削减DWG有功出力、调节DWG功率因数和需求侧管理4种主动管理措施,建立了主动管理模式下DWG选址定容双层规划模型,上层规划以年综合费用最小为目标,下层规划则以每个场景的配电网运行费最小为目标。提出改进差分进化算法和原对偶内点法相结合的混合策略对规划模型进行求解。IEEE 33节点配电网算例的仿真和分析验证了模型的可行性和所提求解方法的有效性。     

上浆量对碳纤维的立体织造损伤及其复合材料拉伸性能的影响

结合立体织造技术和树脂传递模塑(RTM)工艺制备了不同上浆量国产碳纤维的2.5D经向增强复合材料。使用毛羽测试法、复丝拉伸法及SEM分析了不同上浆量预制织物中经纱、衬经纱和纬纱的织造损伤情况。结果表明:碳纤维织造损伤率随着上浆量的增加而减小;2.5D经向增强复合材料中纱线的损伤率大小依次为纬纱、经纱、衬经纱。复合材料拉伸性能测试结果表明:当国产碳纤维上浆量为2.01%时,2.5D经向增强复合材料的性能最佳。     

KH560改性聚乙烯醇的制备及其表面施胶性能研究

本研究利用硅烷偶联剂γ-缩水甘油醚丙基三甲氧基硅烷（KH560）分别对不同聚合度和醇解度的聚乙烯醇（PVA）进行接枝改性,探讨了其物理化学性能,以及利用其进行表面施胶对纸张物理性能的增强作用。结果表明,得益于存在的高活性硅羟基,其与纸张纤维羟基脱水缩合形成Si—O—C键,与羟基间氢键共同作用,形成三维交联网络,KH560-PVA1799具有优异的表面施胶性能。KH560-PVA1799施胶后纸张耐折度为232次,挺度为71.7 mN,撕裂指数为14.9 mN?m²/g,接触角为63°,施胶度26 s,与未改性PVA施胶后的纸张相比,分别提高了112.8%、39.0%、90.2%、23.5%、136.3%。