Renewable Energy Global Innovations features: Predicting the performance of a floating wind energy converter in a realistic sea

Significance Statement

This research paper focuses on the methods for predicting the working of a floating wind energy converter, for instance, a wind turbine set up on a floating platform moored to the sea bed. Practically, the performance analysis of the floating wind energy converter is normally performed by solving the converter motion equation with a complex convolution integral term that represents the hydrodynamic effects.

The computation of the convolution integral term is complicated, time consuming and demands a large amount of memory on the selected computing machine. Above all, most research works have investigated the performances of the wind energy converters in an ideal unidirectional random sea. The researchers have applied the wave spectra in these works as uni-directional spectra, meaning that the wave energy travels in one direction. However, wind-generated energy propagates in various directions.

Researchers led by Professor Yingguang Wang from Shanghai Jiao Tong University, China, investigated rigorously the performance of a floating wind energy converter set up in a realistic, multi-directional random sea. They considered in the numerical simulation process, all the wind loads acting on the energy converter. Above all, the authors adopted the new state space model, the FDI-SS model, to solve the motion equation of the floating wind energy converter. This was in a bid to enhance the efficiency of the simulation. Their work is published in Renewable Energy.

The authors adopted a 5MW wind turbine with a 3-blade turbine with 126m rotor diameter. The hub diameter was 3m and was 90m high above the still water surface. In order to analyze the performance of the proposed wind energy converter, they numerically integrated the vector-form time domain motion equations with a convolution integral term.

The researchers selected specific load cases for the operation condition. The 10-min average wind speed was 11.2m/s at the top of the tower and 0.15 turbulence wind intensity. They applied a Kaimal power spectrum to characterize the turbulence wind random field over the turbine’s rotor plane. The turbulence wind information was applied to calculate the wind loads prior to the numerical integration. The JONSWAP wave spectrum was adopted in the simulation process of the unidirectional random waves.

In the study, the wave height for a selected sea state was 5m, spectral peak period was 12.4s and peakedness factor was 2.0. The JONSWAP wave spectrum was unidirectional in the sense that the wave energy was travelling in one direction. However, in a realistic sea, wind generated wave energy propagates and spreads in various directions. Therefore, the authors multiplied the uni-directional wave spectrum by a spreading function in a bid to obtain a directional spectrum.

The results of their paper demonstrated a great need for using a realistic, multidirectional sea state when determining electrical generation as well as dynamic responses of the floating wind energy converter. Above all, with an aim of improving the simulation efficiency, the authors used a new state space model to estimate the convolution integral term when solving the motion equation of the floating converter.

Yingguang Wang and Lifu Wang systematically analyzed and compared the simulation results and confirmed the precision and efficiency of the proposed model. They found that the new FDI-SS model could be a helpful tool for the design of floating wind turbines, therefore, helping in the exploitation of renewable wind energy.

Figure caption: Simulated sea surfaces on a square of 128 [m] by 128 [m] based on a directional JONSWAP wave spectrum with Hs=7m, Tp=11s and a cos-2s type spreading function (s=15)).

About The Author

Dr. Yingguang Wang earned a B. S. degree and a M. S. degree from Shanghai Jiao Tong University and the University of Washington at Seattle, respectively. He received his Ph. D degree from Shanghai Jiao Tong University in 2008.

Presently he is an Associate Professor in the Department of Naval Architecture and Ocean Engineering at Shanghai Jiao Tong University (SJTU). He has been teaching in the Department of Naval Architecture and Ocean Engineering of SJTU since February, 2003. The SJTU course “Principles of Naval Architecture” he teaches was honored in 2007 by the Chinese Ministry of Education as a national level excellent course. The textbook “Marine Structural Analysis and Design” sole authored by him is honored as a “China’s 12th Five-Year Plan national key book”.

Dr. Yingguang Wang’s research efforts have focused on the development of techniques for predicting the dynamics and stability of ships and floating offshore systems subject to random environmental loads. Systems exhibiting nonlinear behavior and/or exposed to risk inducing conditions receive his particular attention. In addition, his international academic renown also has much to do with his superb work on the prediction of extreme waves critical to the design of marine structures, including oil and gas facilities as well as ocean renewable energy systems. During the past ten years, his research work in the aforementioned areas has resulted in 32 outstanding journal papers as the sole author or first author in peer-reviewed journals, many of which are leading academic journals in the world. One of his first-authored papers was honored in 2015 as one of the “Top articles in outstanding scientific and technical journals of China” by the Chinese Ministry of Science and Technology. On November 2010, he won a prestigious second-class Science and Technology Advancement Award bestowed by Shanghai municipal people’s government.

Reference

Yingguang Wang, Lifu Wang. Predicting the performance of a floating wind energy converter in a realistic sea.  Renewable Energy,  volume 101 (2017),  pages 637-646.

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Renewable Energy Global Innovations features: Effect of additives on the properties of nickel molybdenum carbides for the tri-reforming of methane

Significance Statement

In many chemical industries, syngas, a mixture of carbon monoxide and hydrogen gases, plays a crucial role as an important feedstock for numerous desirable chemical processes such as hydroformylation, ammonia synthesis and the Fischer-Tropsch reaction. There are three eminent methane processes that have been widely used for the production of syngas, namely: the partial oxidation of methane, stream reforming of methane and dry reforming of methane. Recently, combination of the three reactions in a reactor (tri-reforming of methane) has attracted considerable attention due to the many desirable attributes associated with it.

Nickel catalysts have already been highlighted as the most promising desirable catalysts for the tri-reforming process. However, the stability of the nickel catalysts at elevated temperatures and coke generation are the main obstacles hampering their widespread application. Consequently, transition metal carbides, such as molybdenum carbide or tungsten mono-carbide, have been proposed as potential substitutes for noble metals due to their low cost and superior performance in the methane reforming process.

Researchers led by professor Hanbo Zou from the Department of Chemistry and Chemical Engineering at Guangzhou University in China investigated the effect of additives on the attributes of nickel and molybdenum carbides for the tri-reforming of methane gas. Their main objective was to synthesize a series of promoted nickel molybdenum carbides and observe the effects of the varying additives on their catalytic performance for the tri- reforming of methane gas. Their work is now published in International Journal of Hydrogen Energy.

The team found out that the presence of nickel species in the nickel-molybdenum series carbides stimulated the dissociation of methane and supplied the active carbon for the carburization process. Cerium and cobalt additives were observed to deteriorate the activities of the nickel-molybdenum carbides due to the larger particle size. Magnesium additive was observed to favor the coke generation. They then noted that the addition of potassium suppressed the carburization process of molybdenum oxide species and caused the phase transformation of active γ-aluminum oxide to less active θ- aluminum oxide. They realized that the oxidation of carbidic species and the agglomeration of small particles and the carbon deposition decreased the catalytic activities of nickel molybdenum series carbides for the tri-reforming of methane.

Doping the nickel-molybdenum series with different additives has presented a platform for thorough analysis of each additive element individually. Of most concern is that the lathanum additive which has been seen to facilitate the topotactic transformation of the oxidic precursors and refine the particles. The aggregation of the fine particles, reduction of carbidic species and the carbon deposition would all deteriorate the activities of the nickel molybdenum series carbides. The effects of each individual doping additive are therefore critical for the realization of better tri-reforming of methane process.

 

 

About The Author

Hanbo Zou, associate professor in Guangzhou University. My research interests are developing the transition metal nitrides, carbides confined in the mesoporous sieve, carbon nanotubes for novel heterogeneous catalysis. I have explored the use of advanced inorganic materials, the self-assemblies of nanoparticles and nanocomposites for the production of hydrogen and the renewable and clean energy research. Research work involves chemical synthesis, testing and detailed characterization of novel solid state materials.

About The Author

Shengzhou Chen, professor in Guangzhou University. I have engaged in electrocatalysis research for more than twenty years. I have explored hydrogen and methanol oxidation electrocatalysts, technologies for hydrogen generation and so on.

Recently, the major research fields focus on low-platinum and non-platinum supported ORR electrocatalysts and supercapacitors，controllable preparation of ternary transition metal nitride and its electrocatalytic activity of oxygen electroredution, controllable preparation of micro nanofibers-aerogels flexible material and the mechanism of heat transfer. I have published more than 30 scientific papers in IJHE, Applied Surface Science, and etc.

Reference

Hanbo Zou, Shengzhou Chen, Jiangnan Huang, Zhaohui Zhao. Effect of additives on the properties of nickel molybdenum carbides for the tri-reforming of methane. International journal of hydrogen energy volume 41(2016) pages 16842-16850.

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Renewable Energy Global Innovations features: Silicon-Multi-Walled Carbon Nanotubes-Carbon Microspherical Composite as High-Performance Anode for Lithium-Ion Batteries

Significance Statement

Researchers have been facing the challenge of increasing better performance of storage devices in order to meet up with the required demands for the future. Their investigations are mostly based on obtaining the most appropriate electrode materials.

In view of having a better performance of lithium-ion batteries, electrode materials such as anode and cathode are major factors that need to be considered as they contribute effectively to enhancement of energy density of these batteries. Required features for anode materials include high capacity, high cyclability, high coulombic efficiencyand the excellent rate performance amongst others.

From previous research, silicon when used as anode materials shows certain attractive attributes. However, their poor cyclability remains a bane to their advantages as it often leads to pulverization due to the huge volume change over repeated cycles.

Researchers later discovered that silicon nanoparticles when used as an anode in lithium-ion batteries exhibits high cyclability, but the morphological bindings of these nanoparticles and their connection towards current collector during lithiation-delithiation process still remains a challenge that needs to be overcome.

A new research led by Professor Jinbao Zhao at Xiamen University in China involved the fabrication of silicon-multi-walled carbon nanotubes-carbon (Si- MWNTS-C) microspheres via ball milling and spray drying method by a carbonization process for the latter in view of analyzing their performance towards enhancement of lithium-ion batteries. The work was published in Journal of Materials Science.

They characterized the features of the fabricated silicon-multi-walled carbon nanotubes-carbon with the aid of scanning electron microscopy, transmission electron and x-ray diffraction coupled with electrochemical measurements with the aid of cyclic voltammetry and electrochemical impedance spectra.

Results from the characterization techniques confirmed carbon as the effective conductive agent between silicon nanoparticles and the multi-wall carbon nanotubes microspheres which provides a 3D conductive network thereby resulting to a high electrical conductivity. They also possessed good porosity which makes them adapt to large changes in volume during discharge-charge process.

At a current density of 0.2 Ag^-1, the authors observed while using the ball-milling method that the specific capacity of the silicon-multi-walled carbon nanotubes-carbon to be 1100 m Ah g^-1 while also possessing high capacity retention of about 90% after 60 cycles. This was not the case for the ordinary silicon nanoparticles as it showed drastic reduction after 50 cycles. Further results also confirmed an enhanced columbic efficiency which was also found when using the spray drying method. The silicon-multi-walled carbon nanotubes-carbon also possessed high rate performance and reversibility when observed at current densities range from 0.1 to 0.6 A g^-1.

In order to test the performance of the silicon-multi-walled carbon nanotubes-carbon in a lithium-ion battery, LiCoO₂ was used as the cathode. A high cyclic stability was still observed and no morphological changes were observed when viewed after 100 cycles except for growth spherical particles.

The authors of the study provided an improved performance for silicon nanoparticles with the aid of multi-walled carbon conductor link, which shows a potential improvement for lithium-ion batteries.

Reference

Zhang, Y., Li, K., Ji, P., Chen, D., Zeng, j., Sun, Y., Zhang, P., Zhao, J. Silicon-Multi-Walled Carbon Nanotubes-Carbon Microspherical Composite as High-Performance Anode for Lithium-Ion Batteries, Journal of Materials Science 52 (2017) 3630-3641.

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Renewable Energy Global Innovations features: Hierarchical micro-lamella-structured 3D porous copper current collector coated with tin for advanced lithium-ion batteries

Significance Statement

Lithium-ion battery appears to be one of the most preferred power sources applied in portable devices such as laptops, smart phones, smart grid, and electric vehicles. With the ever rising demand for high capacity power sources, advanced lithium-ion batteries need to have higher energy density, higher stability and higher power density. To realize this, most researchers have focused on the development of new anode materials in view of the fact that the type of anode active materials used for lithium storage in the course of charge and discharge greatly affects the performance of the battery.

Graphite has been used as the most popular anode active material, but exhibits insufficient theoretical capacity. Therefore, graphite is not suitable for high capacity and high power battery applications. Tin appears to be the next advanced anode material exhibiting twice as much theoretical capacity than graphite. However, tin undergoes volumetric expansion during insertion and extraction of lithium ions. This means that over repeated discharge and recharge cycles, this volumetric change may lead to pulverization and insufficient electrical contact at the electrode.

Using active materials at nanometer dimension such as nanowires and nanosheets appears to be a better solution to the volumetric expansion problem. To be more precise, the scaffold of a 3-D porous current collector made from copper or nickel then thinly coated with active material can be a better solution. Therefore, Ms. Hyeji Park and her colleagues at Kookmin University in Republic of Korea prepared a 3D tin-copper architecture as an anode material for application in a lithium-ion battery. They used micro-lamellar-structured 3D copper foam as the anode current collector. Their research work is now published in Applied Surface Science.

The authors used copper oxide with 40-80 nm particle size as the starting material. The copper oxide powder was mixed with water and binder, and the slurry was then poured into a Teflon mold on a copper rod. The cupric oxide was reduced to copper and sintered. The resulting three-dimensional porous copper foam was elongated and aligned pores formed. The copper scaffold was cut into thick coins, which were used as anode current collector.

The research team subsequently applied electroless tin plating onto the resulting three-dimensional copper scaffold forming tin-coated copper anode. After plating and subsequent washing, the tin-coated copper foam anode specimens were heat-treated at elevated temperature.

The electroless plating process onto the copper foam enabled the authors to fabricate a 3D tin-coated copper foam integrated with a current collector as well as an active material that was free of a binder and a conducting material. The 3D scaffold architecture exhibited excellent cyclic stability and superior capacity when compared to the electrochemical performance of the typical copper foil current collector coated with tin.

This high electrochemical performance is attributed to the short lithium-ion diffusion path as well as regular void spaces, which accommodated the volume expansion in the tin-copper scaffold. The formation of Cu₁₀Sn₃ phase could enhance the cyclic stability of the 3D tin-copper foam after heat-treatment at 500 °C by alleviating the volume expansion of the tin oxide when tin oxide conversion reaction was initiated.

The outcomes of this study show that the tin-copper scaffold synthesized by applying freeze-casting, electroless plating, and heat treatment possesses application potential as a self-supporting advanced anode architecture for application in high capacity lithium-ion batteries.

 

About The Author

Ms. Hyeji Park was born in Seoul, South Korea in 1990. She is currently a Ph.D. candidate in the department of Materials Science and Engineering at Kookmin University in Seoul. Hyeji has also received her B.S. and M.S. from the department of Materials Science and Engineering at Kookmin University. Her research interests include the processing and mechanical properties of metals and their potential applications for use in energy areas. Recently, she has been actively working on the processing and mechanical properties of Co- and Ni-based superalloy foams for their ultra-high temperature filter applications.

She has authored or co-authored a total of 11 peer-reviewed international journal articles including the papers published in Applied Surface Science, Angewandte Chemie International, and Materials Science and Engineering A. since her active participation as an undergraduate in the Prof. Choe’s lab at Kookmin University in 2012.

In her free time, she travels to explore both domestic and international tourist sites for new experiences of food and culture.

Reference

Hyeji Park, Ji Hyun Um, Hyelim Choi, Won-Sub Yoon, Yung-Eun Sung, Heeman Choe. Hierarchical micro-lamella-structured 3D porous copper current collector coated with tin for advanced lithium-ion batteries. Applied Surface Science, volume 399 (2017), pages 132–138.

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Renewable Energy Global Innovations features: Study of ITO-free roll-to-roll compatible polymer solar cells using one-step doctor blading technique

Significance Statement

Nowadays almost all of the high-performance polymer solar cells are solution-processed by a spin coating method in conjunction with the expensive and brittle indium tin oxide as the transparent electrode, which are totally ill-suited to a cheap large-area roll-to-roll process in accompany with the great solution waste problem.

The doctor-blading technique, which is fully suitable to a continuous roll-to-roll process, can perfectly solve these problems by using cheap conducting materials like PEDOT:PSS as the top transparent anode.

It is confirmed that the insertion of the interfacial buffer layer between the photoactive layer and the cathode is highly necessary in polymer solar cells. However, the addition of the interfacial buffer layer certainly increases the fabrication complexity in the large-area roll-to-roll processing due to the requirements of rigorous alignment of multiple layers, accurate thicknesses and limited mutual solubility, which are needed to be improved.

Researchers led by Professor Lintao Hou from Jinan University in Guangzhou of China investigated an easy spontaneous vertical separation self-assembled technique by doping interfacial buffer material directly into the bulk photoactive layer. An interfacial buffer layer can be formed in the bottom and a photoactive layer on the top via a single doctor-blading step, which has not yet been investigated. This work is published in the Journal of Materials Chemistry A.

The authors discovered that the performance of one-step doctor-blading ITO-free inverted polymer solar cells is primarily influenced by the inherent interfacial buffer layer stratification purity rather than the fine donor/acceptor phase separation for the rigid backbone PTB7 system, which is significantly different from that of the conventional two-step doctor blading devices.

The surface energy results strongly demonstrate that the formation of the interfacial layer between the ITO-free cathode and the photoactive layer is significantly controlled by the in situ solvent drying time, which determines the self-assembly quality and can be greatly manipulated from 2700 to 1200 s by different substrate temperatures. The pure interfacial layer formed at low substrate temperatures improves charge separation and transport, whereas high substrate temperatures limit its growth, leading to the decrease of device performance.

Results from impedance spectroscopy also showed that the self-assembly interfacial layer has a big effect on the internal resistance and capacitance of devices. The invariation of resistance and capacitance is perfectly in accordance with the device performance, confirming that the performance of one-step doctor-blading ITO-free inverted polymer solar cells is primarily influenced by the inherent interfacial buffer layer stratification other than the photoactive donor/acceptor phase separation.

The authors also discovered the spatial and local distribution of photocurrent is uniform over the one-step doctor-blading device at a low substrate temperature.

For comparison, bulk heterojunction morphology of another highly crystalline donor polymer, synthesized by Ergang Wang group from Chalmers University of Technology in Sweden, seems to play a bigger role in improving the doctor-blading device performance than that in the homogeneous donor polymer, indicating the different donor systems should be dealt with each case on its merits for the one-step doctor-blading technique.

Encouraging power conversion efficiency of 6.56% is achieved from environment-friendly simple one-step doctor-blading ITO-free polymer solar cells at a very low substrate temperature, which is energy saving and appropriate to industrialized roll-to-roll production. In contrast, the highest power conversion efficiency of 7.11% ever reported for two-step doctor-blading ITO-free inverted polymer solar cells was obtained at a high substrate temperature for achieving a fine morphology without regard to the vertical delamination.

 

About The Author

Dr. Lintao Hou is a professor at Jinan University, Guangzhou, China. He specialized in organic optoelectronics and device development. He obtained his PhD degree in 2006 from South China University of Technology under the supervision of Prof. Yong Cao and studied on Prof. Olle Inganäs group at Sweden from 2009 to 2011.

As first author and/or corresponding author he has published more than 40 peer reviewed papers in the following journals: Advanced Functional Materials, Solar Energy Materials and Solar Cells, Journal of Materials Chemistry A, ACS Applied Materials & Interfaces, Journal of Materials Chemistry C, Macromolecules, Applied Physics Letters, etc. His some novel research works were reported as news, highlights and journal cover in several journals and scientific websites. He also holds more than 20 patents.

About The Author

Yuanbao Lin received her bachelor degree in applied physics from Jinan University in 2015. He is currently a postgraduate student in Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials under the supervision of Prof. Lintao Hou.

His main research interest is the development of highly efficient bulk heterojunction polymer solar cells by printing techniques and the application potential of cheap transparent electrodes in polymer solar cells.

Reference

Yuanbao Lin¹, Chaosheng Cai¹, Yangdong Zhang¹, Wenhao Zheng¹, Junyu Yang¹,  Ergang Wang², Lintao Hou^1,*. Study of ITO-free roll-to-roll compatible polymer solar cells using the one-step doctor blading technique. Journal of Materials Chemistry A, 2017,5, 4093-4102.

Show Affiliations

 ¹ Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Key Laboratory of Optoelectronic Information and Sensing Technologies of Guangdong Higher Education Institutes, Department of Physics, Jinan University, Guangzhou 510632, PR China, Email: thlt@jnu.edu.cn

² Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden. 

 

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Renewable Energy Global Innovations features: Quantifying Rooftop Photovoltaic Solar Energy Potential

Significance Statement

The need to increase the use of non-conventional energy sources in order to reduce the energy demand and greenhouse gas emissions is currently one of the world’s main challenges. Buildings need to become much more energy efficient and the energy demand should be primarily (increasingly) satisfied through renewable energy resources (e.g. solar energy).

One way to increase the production of renewable energy is to promote the solar energy deployment in cities particularly through the use of PV technology. To achieve this aim, a comprehensive assessment of solar PV potential is required. Different approaches have been implemented by researchers in order to study the large-scale solar PV potential of rooftops. Among several methodological approaches, the following have been widely used in order to quantify the available potential of rooftop solar photovoltaic panels. The methods include sampling techniques, statistical methods, aerial images and Geographic Information Systems (GIS) together with LiDAR (Light Detection and Ranging) data.

In a recent paper published in Solar Energy, Dan Assouline, Nahid Mohajeri and Jean-Louis Scartezzini from the Solar Energy and Building Physics Laboratory at Ecole Polytechnique Fédérale de Lausanne in Switzerland used a combination of data-driven methods including a machine-learning algorithm and GIS together with LiDAR data to estimate photovoltaic solar energy potential on building roofs. They investigated the rooftop solar photovoltaic potential of about 1901 communes (the smallest administrative division) in Switzerland. They estimated monthly global horizontal solar radiation (diffuse horizontal, global horizontal and extra-terrestrial horizontal radiation) as well as global tilted solar radiation over rooftops.

A support vector regression (a kernel-based machine learning technique) model was developed and its performance evaluated by the root mean square error (RMSE) and the normalized root mean square (RRMSE). The geographical potential which includes the available roof area and shading factors for the installation of solar photovoltaic is estimated. The authors finally provide an estimation of the technical potential of the rooftop solar photovoltaic energy production per month. Assuming 80% performance ratio and 17% efficiency of solar photovoltaic solar panels, the team found an annual photovoltaic power generation of 17.86 TWh which was equal to 28% of Switzerland’s power consumption as at 2015.

They further found that 15% of the investigated communes provided 53% of electricity used in the country. Maximum values of electricity derived from solar photovoltaic were obtained from large cities like Zurich, Bern and Basel. However, the highest photovoltaic electricity production per capita was found in less populated areas. The total available area for PV installation on the rooftops in the urban areas of Switzerland was found to be 328 km². The total available roof area per capita was also estimated, that is, 41m²/capita. With an annual increase in cell efficiency of the crystalline silicon wafers of 0.3% per year, the PV panel efficiency will increase to 27.2% by 2050. Assuming an increase to 90% of the performance ratio, the rooftop solar PV electricity production for urban areas in Switzerland in 2050 is expected to reach about 32 TWh. This PV electricity production would then provide 37% of the total forecasted (IEA scenario) electricity use in Switzerland in 2050.

About The Author

Dan Assouline is currently a PhD candidate in Swiss Federal Institute of Technology in Lausanne (EPFL) at the Solar Energy and Building Physics Laboratory. He has received a Bachelor’s degree in Applied Mathematics from Lycée Saint Louis (Paris, France), a Master’s degree in Engineering from Ecole Spéciale Des Travaux Publics (Cachan, France) and a Master of Science in Civil and Environmental Engineering from UC Berkeley (California, USA).

His research focuses on the spatio-temporal estimation of large scale renewable energy potential, specifically in urban areas, using Geographic Information Systems and Machine Learning algorithms.

About The Author

Dr Nahid Mohajeri is currently employed as a Postdoctoral Fellow at the Solar Energy and Building Physics Lab (Swiss Federal Institute of Technology in Lausanne, EPFL). She has finished her PhD at University College London (UCL), focusing on the general topic of complex urban systems. Her research interests include statistical modelling of geometric urban patterns, their energy efficiency and ecological impacts.

Her research is also on the physics of urban form and sustainable urban development, as well as impacts of urban form on the renewable energy potentials, for which she uses a variety of techniques. For example, GIS and spatial data analysis, and in particular, the relevant principles from thermodynamics and statistical mechanics/information theory. From September 2017, she will be Assistant Professor at Chalmers University of Technology (Institute of Building Futures Areas of Advance).

About The Author

Professor Dr Jean-Louis Scartezzini is director of the Solar Energy and Building Physics Laboratory (LESO-PB) of the Swiss Federal Institute of Technology in Lausanne (EPFL) and Professor in Building Physics. His scientific research is dedicated to sustainability in the built environment, with a special focus on advanced daylighting systems and green lighting.

He is the author of more than 200 scientific publications and member of several federal commissions and international work groups as well as Associate editor of Solar Energy Journal and the International Journal of Building Physics. He has MSc in Geophysics from University of Lausanne (1981) and MSc in Physical Engineering from EPFL (1980), and PhD in Physics from EPFL (1986).

(Web link: )

Reference

Assouline, D., Mohajeri, N., Scartezzini, J.L. Quantifying Rooftop Photovoltaic Solar Energy Potential: A Machine Learning Approach, Solar Energy 141 (2017) 278–296.

Solar Energy and Building Physics Laboratory (LESO-PB), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.

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Renewable Energy Global Innovations features: High-Performance CuO/Cu Composite Current Collectors with Array-Pattern Porous Structures for Lithium-Ion Batteries

Significance Statement

The use of lithium-ion battery has developed a lot of interest as a result of their attractive features in energy delivery which has led to researchers providing ways whereby their performance and capacity could be increased.

In order to increase the efficiency and capacity of a lithium-ion battery, researchers have discovered that when copper oxide is used as an anode at certain morphologies and compositions, positive results such as increase in energy density and life cycle of a lithium-ion battery could be achieved.

It should be noted that morphologies of current collectors play a major role in determining the electrochemical activities of lithium-ion batteries. With this, various fabrication methods for development of current collectors have also been carried out and certain improvement in performance of lithium-ion batteries has been achieved. However, the joints effects of material composition and surface structure of current collectors in electrochemical performance of lithium-ion batteries have not been provided.

A comprehensive study on the combined effects of surface structure and material composition of current collectors in view of lithium-ion battery electrochemical performance was provided by team of researchers led by Professor Wei Yan from School of Mechanical and Automotive Engineering at South China University of Technology.

The research work which is now published in Electrochimica Acta involved preparation of composite current collector of copper oxide layers from formed array-pattern porous blind holes on thin copper plates via chemical etching method while mesocarbon microbead graphite powders were used as anode material.

They also investigated the electrochemical performances of the developed porous composite current collectors and that of its complanate structures which didn’t involve an ultraviolet exposure machine and a developer solution compared to the former, followed by electrochemical testing and characterization of the material with the aid of CR2032 coin half-cell test, voltammetry test, scanning electron microscopy and electrochemical impedance spectroscopy.

At first, they discovered a higher electrical conductivity in the porous composite current collector compared to the complanate ones as a result of contact increase between the electrode material and current collector. The oatmeal-like structure of the copper oxide layer on the array-pattern blind holes played the major role in this.

Also, the discharge capacity of the porous composite current collector at a constant current delivery was found to be 383.9m Ah g^-1 compared to the complanate ones with value of 309.6m Ah g^-1. After certain rate cycles, the discharge capacity was also higher in the former compared to the latter.

Outcomes from the discharge-charge voltage profiles of lithium-ion battery after the 1st, 5th, 15th and 20th cycle indicated a gradual increase in columbic efficiency and a minute loss in discharge-charge capacity for the porous current collectors compared to the complanate current collectors.

A higher cycling stability was also observed for the porous current collector compared to the complanate ones. These results were also attributed to the oatmeal-like morphologies of the copper oxide layers.

Results from electrochemical impedance spectroscopy also indicated lesser alternating current impedance and total resistance of lithium-ion batteries with the porous composite collector compared to the complanate ones. As a result of this, electrochemical performance of the lithium-ion battery was enhanced.

The authors were able to provide a significant improvement on the efficiency and capacity of lithium-ion batteries with the use of the developed composite current collector of copper oxide layers with an array-pattern porous structure on thin copper plates.

 

About The Author

Dr. Wei Yuan is a professor in School of Mechanical and Automotive Engineering in South China University of Technology (SCUT), and the executive deputy director of Guangdong Engineering Laboratory of Intelligent manufacturing for functional structures and components, a research center dedicated to the design and intelligent manufacturing of functional surface structures for components. He received his Ph.D. degree in Mechanical Manufacturing and Automation in 2012 from South China University of Technology. The scientific interests of Dr. Yuan mainly include design, manufacture, optimization and application of fuel cells and lithium-ion batteries.

Up to now, Dr. Yuan have published over 70 journal papers in the journals like Applied Energy, Journal of Power Sources, Renewable Energy, Electrochimica Acta and so on. He also has been granted over 20 China patents related to the energy devices. His latest scientific studies mainly focus on the synthesis of nanostructured electrode materials, as well as structure control of current collector for lithium-ion batteries.

His research is financially supported by many government programs from the National Natural Science Foundation of China Natural Science Foundation of Guangdong Province, Guangdong/Guangzhou Science and Technology Plan Program and Fundamental Research Funds for the Central Universities.

About The Author

Jian Luo is a M.S. candidate in School of Mechanical and Automotive Engineering in South China University of Technology (SCUT) in China, under the supervision of Prof. Wei Yuan. He specializes in the synthesis of nanostructured electrode materials and structure control of current collector for lithium-ion batteries. He received his Bachelor’s degree in Mechatronic Engineering from South China University of Technology in 2016. He is a member of Guangdong Engineering Laboratory of Intelligent manufacturing for functional structures and components.

His research focuses on structure design and optimization of current collector and electrode materials for lithium-ion batteries. This research aims to enhance the electrochemical performance of lithium-ion batteries in terms of reversible capacity, cycling stability and electrical conductivity by the structure control of current collector with new environmentally friendly and inexpensive method. Over the past year, he has published 2 papers in the international journal indexed by Science Citation Index (SCI).

Reference

Yuan, W., Luo, J., Yan, Z., Tan, Z., Tang, Y. High-Performance CuO/Cu Composite Current Collectors with Array-Pattern Porous Structures for Lithium-Ion Batteries, Electrochimica Acta 226 (2017) 89–97.

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