Renewable Energy Global Innovations features: Nanostructure anode: A key to low-temperature SOFC

Significance Statement

In a recent article done by Park et al. and published in Journal of Power Sources, investigations showed that electrochemical properties of thin film solid oxide fuel cells (TF-SOFCs) at low temperature is also a function of grain size of nanostructured Ni-yttria-stabilized zirconia (Ni-YSZ) composite anode.

This was achieved by analyzing the output power and impedance spectra at various cells by operating conditions in order to compare electrode reaction mechanism due to amount of grain size of anode in full-cell test.

Despite high efficiency of solid oxide fuel cell (SOFC), its high operating temperature of (≥ 700-800 °C) has been a major setback due to its fast degradation and poor reliability. Lowering the operating temperature of SOFC has been a major case of study because unwanted chemical reactions are prevented and use of less expensive material such as stainless steel are allowed. However at lower operating temperatures, electrode activity of SOFC worsens hence its performance is determined by polarization losses induced by electrode reaction at low temperature.

Although extensive research has been made on nanostructured cathodes due to its polarization loss in low temperature performance of SOFCs, it has also been predicted that loss of anode at temperature (≤ 600 °C) also has significant effect as that of cathode. Since metals are used as catalyst in nanostructured anode, fabrication has been difficult due to agglomeration of metal-phase at SOFC operating temperature leading to reduction in triple-phase boundary (TPB) length, loss of conductivity and cell stability degradation. However, fabrication of a uniform nanostructured Ni-YSZ was successful using PLD. Its layer was designed to suppress Ni agglomeration and effectively support thin-film electrolytes with thickness approximately 1µm or less which has a higher TPB density to that of conventional Ni-YSZ anodes.

Discerning the impact of nanostructured anode functional layer (nano-AFL) has proved difficult experimentally due to the fact that nano-AFL is so thin that catalyst amount in layer is minute in compares to that of whole anode support and it has been extremely difficult to build thin electrolytes directly over supports without nano-AFL due to the surface condition of the supports. Nevertheless, Park et al. has been successful in building TF SOFCs with and without nano-AFL and effect of nano-scale grain-size of AFL has been studied effectively.

In experiment set-up, two different unit cells; one with nano-scale Ni-YSZ AFL was denoted as NS-cell and that without nano-AFL is denoted by MS-cell. Cell operating temperature varied from 650 °C to 500 °C at intervals of 50 °C while electrochemical impedance spectra (EIS) and current-voltage-power (I-V-P) curves were obtained at each temperature. From the results, the peak power density of NS-cell at 650 °C reached 1775 mWcm^-2 which is better than MS-cell with 1650 mWcm^-2.

It was also noticed that performance ratio (P_NS-cell/P_MS-cell) increases with decrease in temperature at 0.7 V as performance of NS-cell was twice higher than MS-cell at 500 °C and I-V drop of MS-cell was faster at lower current density. These two results show that the influence of nano-AFL on the full cell performance increases with decreasing temperature and electrode activation loss is significant in MS- cell.

With each EIS observed over a frequency of 10⁵ Hz to 10^-1 Hz at AC amplitude impedance of 50 mV, impedance in frequency range of 10 Hz ≤ f ≤ 10⁴ Hz was considered to be a major contributor to total impedance of both cells and exhibits a significant temperature dependency, however an overlay in impedance was noticed in two stages; (10² Hz ≤ f ≤ 10³ Hz) and (10³ Hz ≤ f ≤ 10⁴ Hz).

From the Bode plots, first frequency impedance was mainly related to the cathode while at second frequency impedance, temperature was reduced during anode half-cell test and impedance at this stage increased. It was also seen from the Bode plots of NS and MS cells that the resistance of anode reaction is much smaller in the NS-cell than in MS-cell due to small particles size of nano-AFL.

These results prove that performance improvement of NS-cell with respect to MS-cell at lower temperature is due to facilitation of charge transfer at the anode. This shows that anode performance can significantly affect cell performance at low temperature.

Park et al. study proves that anode reaction also affects cell performance at low temperature significantly. Substantial conclusion was also made that it’s important to minimize grain size of Ni-YSZ despite its possible fabrication in order to obtain reasonable cell performance at low temperatures which also aids the lowering of SOFCs operating temperature.

 

About The Author

Dr. Ji-Won Son is a principal researcher at the High-temperature Energy Materials Research Center, Korea Institute of Science and Technology (KIST), and an adjunct professor at Univ. of Science and Technology (UST) and Hanyang Univ., Rep. of Korea. She studied Inorganic Materials Science and Engineering at Seoul National University (SNU) and received BS and MS degrees at SNU. During her master course, she studied the sintering mechanism of transparent conducting oxides used for electronic applications. Afterwards, she entered the graduate school of Stanford University, Dept. of Materials Science and Engineering and received the Ph. D. degree in 2005. Her Ph. D. topic was about oxide thin film materials for optical applications.

Based on her expertise both on oxide bulk materials and thin film materials, she has worked on implementation of thin film and nanostructure materials to high-temperature operating solid oxide fuel cells (SOFCs) in order to lower the operating temperature since she joined the Solid State Ionics Lab at KIST, 2005. By realizing multi-scale-architectured structure at the anode, she successfully achieved both the high performance at lower operating temperatures and the thermomechanical stability of the thin film and nanostructure-base anode-supported SOFCs.

For her achievement, she received the Women of the Year Award in Science and Technology in Korea, 2013, and the Prime Minister Award, 2016.

Journal Reference

Jung Hoon Park^1,2, Seung Min Han², Kyung Joong Yoon^1,3, Hyoungchul Kim^1,3, Jongsup Hong¹, Byung-Kook Kim¹, Jong-Ho Lee^1,3, Ji-Won Son^1,3 . Impact of nanostructured anode on low-temperature performance of thin-film-based anode-supported solid oxide fuel cells. Journal of Power Sources, Volume 315, 31 May 2016, Pages 324–330.

Show Affiliations

1. High-temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 02792, South Korea
2. Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
3. Nanomaterials Science and Engineering, Korea University of Science and Technology, KIST Campus, Seoul 02792, South Korea

 

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Renewable Energy Global Innovations features: Nano “Zylon” Fiber Makes Battery Safer

Significance Statement

Safe and powerful lithium based batteries are important for various technologies, such as electric vehicles, smartphones, and laptops. One of the biggest problems facing this industry is the growth of dendrites sprout from the surfaces of lithium electrodes over the course of several charge/discharge cycles, particularly at a fast rate. The dendrites can spread across the electrolytes and reach the other electrodes, making the batteries short-circuited. The consequent high electric currents may lead the batteries to rapidly overheat and even catch fire.

Researchers in Beijing Institute of Technology, China, and Northwestern University, USA have developed a new type of advanced battery separators to solve this problem. These separators are made of lightweight and ultrastrong materials typically used in Zylon, a commercial microfiber with mechanical properties higher than the well-known Kevlar.

The process for making this advanced battery separators is quite scalable. Zylon microfibers are exfoliated into nanofibers through a special processing step, and then blade-cast into thin and nanoporous membranes. These membranes have a combination of high strength, low ionic resistance, and high heat tolerance, making them exceptionally good separators for preventing dendrite growth in lithium batteries.

The new separators have several advantages in comparison to one of the current state-of-the-art battery separators, Celgard 2400. The electrodes in batteries with the Celgard 2400 show mossy surfaces as a result of dendritic lithium growth, whereas electrode surfaces with the new separator membranes still remain smooth even after 700 hours. The suppression of dendrite formation results in good performance of batteries, including higher long-term stability and higher efficiencies.  As the materials in the separators are highly heat-tolerant, these separators can be used for batteries required in high-temperature environment.

As a comparison, the typical Celgard 2400 separators begin to melt at about 125 °C and make the batteries unusable, while batteries with the new advanced separators can continue to operate up to 185 °C, upon which the electrolytes decompose. In addition, these separators may be applied in other energy storage systems in which dendrite growth is a problem.  

About The Author

Dr. Xiaoming Hao graduated from Beijing Institute of Technology in 2015, and now work at The National Center for Nanoscience and Technology, Chinese Academy of Sciences as a postdoctoral fellow.  

About The Author

Dr. Jian Zhu is currently a postdoctoral fellow at the Northwestern University, USA. He is interested in the assembly of nanomaterials, and their applications in advanced structural and electrical materials.  

About The Author

Dr. Zhenhua Wang worked at Beijing Institute of Technology as an associate professor and vice dean of chemistry and chemical engineering college. His research interests mainly focus on solid oxide fuel cells and various lithium batteries.  

About The Author

Professor Kening Sun is the Cheung Kong Scholar Chair Professor at Beijing Institute of Technology. His research interests mainly focus on fundamental electrochemistry, advanced energy materials, solid oxide fuel cells and various lithium batteries.

Journal Reference

Xiaoming Hao¹ , Jian Zhu^*3, Xiong Jiang¹, Haitao Wu¹, Jinshuo Qiao¹, Wang Sun¹, Zhenhua Wang^*1,2, Kening Sun^*1,2. Ultrastrong Polyoxyzole Nanofiber Membranes for Dendrite-Proof and Heat-Resistant Battery Separators. Nano Lett., 2016, 16 (5), pp 2981–2987.

Show Affiliations

1. Beijing Key Laboratory for Chemical Power Source and Green Catalysis, School of Chemical Engineering and Environment,
2. Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Institute of Technology, No. 5 Zhongguancun South Avenue, Haidian District, Beijng, 100081, P. R. China
3.  Department of Materials Science and Engineering, Northwestern University, 2200 Campus Drive, Evanston, Illinois 60208, United States

 

 

 

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Renewable Energy Global Innovations features: Oxidized Ni/Au Transparent Electrode in Efficient CH3NH3PbI3 Perovskite/Fullerene Planar Heterojunction Hybrid Solar Cells

Significance Statement

The p-type semiconducting inorganic NiO_x thin film, owing to the high optical transparency, the chemical stability, the good conductivity of hole, the suitable work function, as well as the capability to block the electrons to reach the positive electrode, would be the ideal p-type electrode interlayer for fabricating perovskite solar cells made of a conventional OPV architecture. However, the electric conductivity of NiO_x layer is still insufficient to be solely used as a TCO electrode. The NiO_x needs to function reliably with the highly conductive ITO layer underneath to sustain the electric conduction of the charges.

This work first and successfully demonstrates the application of the well-developed nickel (Ni)/gold (Au) transparent electrode in GaN light-emitting diodes industry for fabricating efficient perovskite-based solar cells. We apply a thermally oxidized, Ni/Au transparent electrode on the glass substrate to prepare methylammonium lead iodide (CH₃NH₃PbI₃) perovskite/fullerene (C₆₀) planar heterojunction hybrid solar cells.

The combination of the oxidized Ni (NiO_x) with the interconnected network Au forms a functionalized Au:NiO_x electrode, capable of transporting holes and blocking electrons from CH₃NH₃PbI₃ perovskite to reach the electrode. Changing Ni/Au compositions and the thermal treatment conditions modulates the optical transparency, electrical conductivity, the work function of Au:NiO_x electrode, as well as the photovoltaic parameters of hybrid cells.

To prepare the electrode and electrode interlayer in one single process simplifies fabricating procedures, and poses to the new design of the functionalized electrode in perovskite-based hybrid devices.

We report both ITO and PEDOT:PSS free devices with the potential for cost-effective, low-weight and stable cell in future application. The merits of the methods and materials we developed in the paper represent a new paradigm for hybrid perovskite-based solar cells of a conventional OPV architecture.  

About The Author

C. Lai received the B.S. degree in electrical engineering from the Feng-Chia University, Taiwan, in 1993, and the M.S. and the Ph.D. degrees in electrical engineering from the National Cheng Kung University (NCKU), Tainan, Taiwan, in 2001. In 2001, he was a Postdoctoral Associate with the Department of Electrical Engineering, NCKU.

He is currently with the Department of Photonics, NCKU, Taiwan, as a professor. His research interest includes the growth and Characterization of III–V nitride semiconductors and devices.

About The Author

Kun-Wei Lin received the B.S. degree in mechanical engineering from the National Taiwan University of Science and Technology, Taipei, Taiwan, in 2001, and the M.S. degree in mechanical engineering from National Cheng Kung University, Tainan, Taiwan, in 2003, where he is currently pursuing the Ph.D. degree with the Department of Photonics.

About The Author

Peter C.-Y Chen. He received Ph. D. from the Photonic Program in EPFL Switzerland at 2009 under the supervision of Prof. Michael Graetzel. Then he moved to Monash University in Australia as a post-doctoral research fellow with Prof. Udo Bach. He joined the Dept. of Photonic in National Cheng Kung University in 2010 and became associate Professor in 2014.

Currently his research interests are in the area of various photovoltaic devices including dye-sensitized solar cells (DSCs), hybrid organic-inorganic perovskite-based solar cells (HOIPs) and semiconductor-sensitization solar cells.

About The Author

Tzung-Fang Guo received the Ph.D. degrees in Materials Science and Engineering from University of California Los Angeles in 2002. He is currently the professor and chairman at Department of Photonics, National Cheng Kung University.

His research focuses on high-performance O/PLEDs, polymer and perovskite-based PVs, n-type pentacene OTFTs, and the magneto conductance responses of organic electronic devices.

 

Journal Reference

Advanced Materials, Volume 28, Issue 17, pages 3290–3297, May 4, 2016. 

Wei-Chih Lai^1,2, Kun-Wei Lin¹, Yuan-Ting Wang¹, Tsung-Yu Chiang¹, Peter Chen^1,3, Tzung-Fang Guo^1,2,3. Oxidized Ni/Au Transparent Electrode in Efficient CH3NH3PbI3 Perovskite/Fullerene Planar Heterojunction Hybrid Solar Cells Show Affiliations

1. Department of Photonics, National Cheng Kung University, Tainan, Taiwan
2. Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan
3. Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan

 

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Renewable Energy Global Innovations features: Reliability-Based Design Optimization Wind Turbine to Reduce Levelized Cost of Energy

Professor K.K. Choi and his team have recently collaborated with Professor Hiroyuki Sugiyama and his student Huaxia Li at the University of Iowa to extend it to reliability-based design optimization of wind turbine drivetrain using multibody gear dynamics simulation considering wind load uncertainty. They have improved the gear fatigue life reliability from 8.3% to 97.725% while increasing the gear weight by 1.4%.

 

 

 

 

About The Author

Weifei Hu received his B.S. (2008) from Zhejiang University, China, M.S. (2010) from Hanyang University, South Korea, and Ph.D. (2015) from University of Iowa, USA, all in mechanical engineering.

Currently, he is a postdoctoral research associate at Cornell University, Ithaca, New York.  Dr. Hu specializes in a wide range of wind energy topics including wind turbine aerodynamics and structure analysis, fatigue analysis of wind turbine composite materials, wind gust detection, wind turbine condition monitoring, and reliability-based design optimization (RBDO) of wind turbine systems.

He is a technical committee member and the secretary (2016-2017) of the Renewable and Advanced Energy Systems committee in the Power Division of ASME. 

About The Author

Hyunkyoo Cho earned his B.S. (2003) and M.S (2005) from Seoul National University, South Korea, in Naval Architecture and Ocean Engineering. He received Ph.D. (2014) from University of Iowa in Mechanical Engineering.

In addition, Dr. Cho has five years of industry experience at the Samsung Heavy Industries, South Korea. Currently, he is working as a Postdoctoral Research Scholar and an Adjunct Assistant Professor at University of Iowa. His research has focused on design optimization under input variability and uncertainty, which includes reliability analysis, reliability-based design optimization (RBDO), RBDO using insufficient input data, and applications of RBDO to engineering projects.

About The Author

Dr. K.K. Choi is Roy J. Carver Professor in the Mechanical and Industrial Engineering Department at the University of Iowa.  He was appointed as a World Class University Professor at the Seoul National University in Korea during 2008-2013.

His research areas are uncertainty quantification, reliability analysis, reliability-based design optimization, design sensitivity analysis, and mathematical theory of optimization and its applications.  He has co-authored 364 papers, including 152 journal papers in leading national and international engineering journals.

He has co-authored several graduate engineering texts (Design Sensitivity Analysis of Structural System, 1986; Methods of Engineering Mathematics, 1993; Design Sensitivity Analysis of Linear and Nonlinear Structural Systems – Two Volume, 2004).

At the University of Iowa, he is a founding member of the Iowa Board of Regents approved Center for Computer Aided Design (CCAD).  He has served as Associate Director (1990-93), Deputy Director (1993-95), and Director (1995-2003) of CCAD.  He is associate editor of five national and international journals including Journal of Mechanics Based Design of Structures and Machines and Journal of Optimization Theory and Applications.

He is Fellow of American Society of Mechanical Engineers (ASME), Fellow of American Institute of Aeronautics and Astronautics (AIAA), Fellow of Society of Automotive Engineering (SAE), and President Elect of the International Society for Structural and Multidisciplinary Optimization (ISSMO, 2007-2011). 

Reliability-based design optimization of wind turbine blades for fatigue life under dynamic wind load uncertainty

Journal Reference

Structural and Multidisciplinary Optimization, October 2016, Volume 54, Issue 4, pp 953–970.

Weifei Hu, K. K. Choi, Hyunkyoo Cho.

Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, USA

Abstract

This paper studies reliability-based design optimization (RBDO) of a 5-MW wind turbine blade for designing reliable as well as economical wind turbine blades. A novel dynamic wind load uncertainty model has been developed using 249 groups of wind data to consider wind load variation over a large spatiotemporal range. The probability of fatigue failure during a 20-year service life is estimated using the uncertainty model in the reliability-based design optimization process and is reduced to meet a desired target reliability. Meanwhile, the cost of composite materials used in the blade is minimized by optimizing the composite laminate thicknesses of the blade.

In order to obtain the reliability-based design optimization optimum design efficiently, deterministic design optimization (DDO) of the 5-MW wind turbine blade is carried out first using the mean wind load obtained from the wind load uncertainty model. The reliability-based design optimization is then initiated from the DDO optimum. During the reliability-based design optimization iterations, fatigue hotspots for reliability-based design optimization are identified among the laminate section points.

For an efficient reliability-based design optimization process, surrogate models of 10-min fatigue damages D₁₀ at the hotspots are accurately created using the Kriging method. Using the wind load uncertainty model and surrogate models, probability of fatigue failure during a 20-year lifespan at the hotspots and the design sensitivities are calculated at given design points. Using the probability of fatigue failure and design sensitivity, reliability-based design optimization of the 5-MW wind turbine blade has been successfully carried out, satisfying the target probability of failure of 2.275 %.

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Renewable Energy Global Innovations features: Monte Carlo analysis of life cycle energy consumption and greenhouse gas emission for biodiesel production from trap grease

Significance Statement

Trap grease is a mixture of wastewater, solids, fats, oils and greases (FOG) generated in the sewer system. The handling and disposal of trap grease have been a long-standing issue for the US. Every year, several million tonnes of trap grease are landfilled, causing various environmental concerns. Recently, utilizing the FOG portion of the trap grease for biodiesel production has been recognized as a potently viable solution to minimize the pressure on landfill. While the technical feasibility of this solution is being tested and improved, understanding the energy consumption and greenhouse gas emission emission during the trap grease biodiesel production life cycle is an indispensable step toward evaluating its cost-effectiveness and sustainability.

This study presents, for the first time, a life cycle model that evaluates the energy consumption and greenhouse gas emission emission for producing biodiesel from trap grease. Regression equations (in supporting material) for material use and energy input/output are derived from a comprehensive review of the existing literature. For the nominal scenario (4% FOG in trap grease and solids used for anaerobic digestion), the total energy consumption is 31.39 MJ/gal biodiesel produced and the energy return on investment (EROI) is 1.7. The corresponding greenhouse gas emission emission is -55.5 g CO₂-eq/gal, which is due to the significant carbon credit from avoiding the use of electricity from grid.

This study also identifies the uncertainties within trap grease composition and anaerobic digestion (AD) process, and applied a Monte Carlo simulation to quantify their effect on the modeling results. The energy consumption values range from 20 to 760 MJ/gal, with over 80% of the data points ≤ 100 MJ/gal. The greenhouse gas emission emission values range from -2,700 to 25,000 g CO₂-eq/gal, with over 90% of the data points ≤ 10,000 g CO₂-eq/gal. The sensitivity analysis shows that FOG concentration and methane generation rate (from AD) have the highest influence on the results.

The comparison with benchmark studies (biodiesel from other feedstocks) shows that trap grease could be a low energy consumption and low greenhouse gas emission emitting feedstock under ideal conditions (e.g. high fats, oils and greases concentration, low FFA concentration, high AD performance). The life cycle model presented in this study could be used by wastewater treatment plants to evaluate the potential of utilizing trap grease for biodiesel production by using site-specific data. This model may also be used to evaluate the trap grease-to-biodiesel fuel pathway against certain greenhouse gas emission-related programs (e.g. Renewable Fuel Standard).  

 

About The Author

Dr. Qingshi Tu is a Postdoctoral Associate in Department of Chemical and Environmental Engineering at Yale University. His primary research interest is to promote the development and implementation of sustainable technologies via life cycle assessment (LCA), techno-economic analysis (TEA) and computational modeling approaches (e.g. agent-based modeling).

Qingshi completed his PhD in Environmental Engineering at the University of Cincinnati. His doctoral work was focused on technology development and environmental impact assessment for producing biofuels and bioenergy from waste fats, oils and greases (FOG), which provides a sustainable solution to the long-standing issue of FOG management. His email contact: Qingshi.tu@yale.edu 

Journal Reference

Qingshi Tu¹, Bryant E. McDonnell² . Monte Carlo analysis of life cycle energy consumption and greenhouse gas emission for biodiesel production from trap grease.  Journal of Cleaner Production, Volume 112, Part 4, 2016, Pages 2674–2683.

Show Affiliations

1. Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, 2600 Clifton Avenue, Cincinnati, OH 45221, USA
2. Water Resources Engineer, ARCADIS-U.S., Inc., 4335 Cornell Road, Cincinnati, OH 45241, USA

 

 

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Renewable Energy Global Innovations features: Most efficient continuous-wave 1064nm solar laser emission within a laboratory

Significance Statement

The conversion of sunlight into laser light by direct solar pumping is of increasing importance because broadband sunlight can be converted into laser light, which is an extraordinarily useful source of narrowband, collimated, either continuous-wave or rapidly pulsed, radiation with the possibility of obtaining extremely high brightness and intensity. Entirely avoiding arc lamps or semiconductor laser arrays along with their associated electrical power generation and power conditioning equipment, direct solar laser pumping might exhibit very promising potential in partially replacing electrically-powered lasers in the future, enabling the most reliable, especially space borne, renewable laser emissions over a multitude of years.

Simplicity, low cost, and easy laser power scalability are the most distinguishing features of solar-pumped lasers. Among the potential space applications of solar lasers are remote sensing from space, wireless space power laser beaming, asteroid deflection, nudge space debris off course, fuel-free photonic thruster etc. Back to Earth, solar laser has also large potentials for many terrestrial applications such as ultra-high temperature materials processing and renewable reduction of Magnesium from Magnesium Oxide. All the above-mentioned applications can only be feasible with significant progress in solar laser efficiencies.

High beam quality, most preferably, TEM₀₀-mode solar laser emission has become a vital issue since it produces the smallest beam divergence, the highest power density and, hence, the highest brightness. All research efforts are, therefore, concentrated on achieving the most efficient solar-powered lasers with the highest efficiency, most preferably with high beam quality.

Previous record-high solar laser was pumped through a large Fresnel lens mounted on a solar tracker. Its solar laser head moved together with whole solar tracking structure, an optical fibre was hence necessary for the transportation of solar laser radiation to a fixed target position. This, in turn, affected negatively the efficiency of whole solar laser system due to optical fibre transmission loss. Therefore, the advantage of having a stationary laser head at the focus of a primary concentrator becomes much more pronounced for many applications such as laser material processing where a vacuum chamber can be easily installed nearby.

We report here significant progresses in both multimode and TEM₀₀–mode solar-pumped laser collection efficiencies by end-side-pumping a 4.0 mm diameter 35.0 mm length Nd: YAG
single-crystal rod with a heliostat-parabolic mirror solar energy concentration system.

An aspheric fused silica lens was used to couple the concentrated solar radiations from the focal zone of a 1.4 m effective diameter parabolic mirror into the laser rod within a conical pumping cavity. 37.2 W continuous-wave multimode 1064nm solar laser power was measured, corresponding to 31.5 W/m² multimode collection efficiency and 8.9% slope efficiency, corresponding to the highest solar laser efficiency to date. By adopting an asymmetric large-mode laser resonant cavity, 9.3 W
continuous-wave TEM₀₀-mode (M² ≤ 1.2) 1064nm solar laser power was also measured, resulting in 7.9 W/m² fundamental mode laser collection efficiency, being 2.6 times higher than the previous record by a Fresnel lens and nearly 2.0 times higher than the previous record by a parabolic mirror.

Stable emission of the most efficient solar laser radiation from a stationary solar laboratory, both in multimode and fundamental mode regimes, could constitute one step further for many interesting applications by solar-powered lasers. 

Most efficient continuous-wave 1064nm solar laser emission within a laboratory

Most efficient continuous-wave 1064nm solar laser emission within a laboratory 31.5 W/m2 multimode, 7.9 W/m2 TEM00-mode solar laser collection efficiencies.

About The Author

Dr. Dawei Liang is an Assistant Professor of the Physics Department of the New University of Lisbon. He is now the vice-coordinator of Centre of Physics and Technological Research, New University of Lisbon.  He obtained his B.S. and M.Sc. degrees in Precision Instrumentation from Tianjin University. He obtained his Ph.D. degree in Optoelectronics from Chongqing University.

He obtained an equivalent Ph.D. degree in Optoelectronics and Microelectronics from New University of Lisbon. He accomplished fiber optic smart skins project for Strathclyde University. He initiated thin disk laser optical fiber beam shaping research for Stuttgart University.

He has also accomplished several SFERA solar laser projects in PROMES-CNRS, France since 2011. He has 70 publications and was a reviewer for 22 prestigious journals like Optics Express and Optics Letters. He was awarded outstanding reviewer statuses by both Solar Energy Materials & Solar Cells and Optics & Laser Technology in 2015.

He is the Topic Editor of International Journal of Modern Physics: Advances in Theory and Applications. Several world records in solar laser collection efficiency and beam quality have been established by his team in recent years. Some of his researches on solar-pumped lasers were highlighted by Editors of CSP Today, Spotlights on Optics in 2012, Laser Focus World, Photonics Online in 2013, Renewable Energy Global Innovations, and the Next Big Future in 2014. http://ift.tt/2dz459P 

About The Author

Joana Almeida is a Ph.D. student in the solar-pumped laser laboratory of the Physics Department of New University of Lisbon. She obtained her B.S. and M.Sc. degrees in Biomedical Engineering from New University of Lisbon.

She has contributed significantly to the progress of solar-pumped lasers in Lisbon. She has also participated actively in several SFERA projects in PROMES-CNRS, France since 2011. She has 30 publications and was a reviewer for 2 prestigious journals. Some of her contributions on solar-pumped lasers were highlighted by Editors of CSP Today, Spotlights on Optics in 2012, Laser Focus World, Photonics Online in 2013, Renewable Energy Global Innovations, and the Next Big Future in 2014. 

About The Author

Dr. Cláudia R. Vistas obtained her PhD degree under the MIT-Portugal program in bioengineering systems by Instituto Superior Técnico, University of Lisbon. She obtained her B.S. and M.Sc. degrees in biotechnological engineering from University of Algarve.

As a post-doctoral researcher, she has participated actively in solar-pumped lasers research of New University of Lisbon in recent years. She has also participated in three SFERA solar laser projects in PROMES-CNRS, France since 2014. She has published 13 journal articles, 10 of which are related to improving solar-pumped lasers efficiencies and beam qualities. 

About The Author

Emmanuel Guillot is instrumentation engineer, M.Sc.E. at École Nationale Supérieure d’Ingénieurs du Mans. He is head of the Solar Facility and Associated Instruments since 2007. His activities are related to 1/concentrated radiative flux measurement, 2/solar data measurement, 3/control and monitoring software development, 4/solar experiments development. He coordinated a work package in SFERA (FP7) and coordinates a work package in SFERA2 (FP7). He is the author or co-author of about 15 international scientific articles, 10 of which are related to solar-pumped laser. 

 

Citation: Dawei Liang¹ , Joana Almeida¹, Cláudia R. Vistas¹, Emmanuel Guillot² . Solar-pumped Nd:YAG laser with 31.5 W/m2 multimode and 7.9 W/m2 TEM00-mode collection efficiencies.  Solar Energy Materials and Solar Cells, Volume 159, January 2017, Pages 435–439.

Show Affiliations

1. CEFITEC, Departamento de Física, FCT, Universidade NOVA de Lisboa, 2829-516, Campus de aparica, Portugal
2. PROMES-CNRS, 7 rue du Four Solaire, 66120 Font Romeu, Odeillo, France

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Renewable Energy Global Innovations features: Sobol’s sensitivity analysis for a fuel cell stack assembly model with the aid of structure-selection techniques

Significance Statement

    This work presents a novel method for identifying the main parameters affecting the stress distribution of the components used in assembly modeling of proton exchange membrane fuel cell (PEMFC) stack. This method is a combination of an approximation model and Sobol’s method, which allows a fast global sensitivity analysis for a set of uncertain parameters using only a limited number of calculations.

Seven major parameters, i.e., Young’s modulus of the end plate and the membrane electrode assembly (MEA), the contact stiffness between the MEA and bipolar plate (BPP), the X and Y positions of the bolts, the pressure of each bolt, and the thickness of the end plate, are investigated regarding their effect on four metrics, i.e., the maximum stresses of the MEA, BPP, and end plate, and the stress distribution percentage of the MEA.

The proposed method was demonstrated to be feasible and effective at determining the most influential model parameters. Moreover, it enhances our understanding of the assembly of a PEMFC stack, and provides a valuable tool for a sensitivity analysis of a PEMFC stack assembly model.

The analysis reveals the individual effects of each parameter and its interactions with other parameters on the model performance regarding four metrics. The main findings from the results obtained are summarized as follows:

(1) The position of each bolt has a significant influence on the maximum stresses of the BPP and end plate, whereas the thickness of the end plate has the most crucial role in the maximum stress and stress distribution percentage of the MEA.

(2) The contact stiffness between the MEA and BPP has little effect on the maximum stresses of the BPP and end plate, and on the stress distribution percentage of the MEA. Moreover, it is not the most important factor affecting the maximum stress of the MEA when measured using a total-order sensitivity index. However, the contact stiffness interacting with the thickness of the end plate has a highly sensitive interaction effect on the maximum stress of the MEA.

(3) The parameter interactions contribute to a significant portion of the variation in the metric considering the maximum stress of the BPP. The interaction effects include the following: the thickness of the end plate interacts with its material property as well as the Y position of each bolt, the X position of each bolt interacts with its Y position, and the Y position of each bolt interacts with the pressure. 

About The Author

Dr. Wei Zhang received his B.Eng. in Engineering Mechanics from Hunan University, China in 2005, his M.Eng. and Ph.D. in Mechanical Engineering also from Hunan University, China in 2010 and 2013, respectively. He was an assistant engineer at Special Aircraft Research Institute of China from Aug. 2005 to Jun. 2007, and was a Post-Doctoral fellow at Department of Mechanical Engineering, Inha University, Korea from Nov. 2013 to Nov. 2015.

His research interests are in computational inverse techniques, uncertainty management and bioinspired design in composites. He is currently a research fellow at School of Mechanical & Aerospace Engineering, Queen’s University Belfast, UK. 

About The Author

Prof. Chongdu Cho received his B.Eng. in Mechanical Engineering from Seoul National University, Korea in 1983, his M.Eng. in Mechanical Engineering from KAIST, Korea in 1985 and his Ph.D. in Mechanical Engineering from University of Michigan, USA in 1991. He has been a visiting scholar in UCLA, USA from Jul. 2000 to Jul. 2001, and in Cornell University, USA from Aug. 2009 to Aug. 2010, respectively.

He has been developing FEA applications for various engineering products. He has published more than 150 referenced journal papers. Now, he is a fellow professor at Department of Mechanical Engineering, Inha University, Korea. 

Journal Reference

Journal of Power Sources, Volume 301, 2016, Pages 1–10.

Wei Zhang¹, Chongdu Cho¹, Changhao Piao¹, Hojoon Choi²

Show Affiliations

1. Department of Mechanical Engineering, Inha University, Incheon 402-751, South Korea
2. Korea Institute of Industrial Technology, Incheon 406-840, South Korea

Abstract

This paper presents a novel method for identifying the main parameters affecting the stress distribution of the components used in assembly modeling of proton exchange membrane fuel cell (PEMFC) stack. This method is a combination of an approximation model and Sobol’s method, which allows a fast global sensitivity analysis for a set of uncertain parameters using only a limited number of calculations. Seven major parameters, i.e., Young’s modulus of the end plate and the membrane electrode assembly (MEA), the contact stiffness between the MEA and bipolar plate (BPP), the X and Y positions of the bolts, the pressure of each bolt, and the thickness of the end plate, are investigated regarding their effect on four metrics, i.e., the maximum stresses of the MEA, BPP, and end plate, and the stress distribution percentage of the MEA. The analysis reveals the individual effects of each parameter and its interactions with the other parameters. The results show that the X position of a bolt has a major influence on the maximum stresses of the BPP and end plate, whereas the thickness of the end plate has the strongest effect on both the maximum stress and the stress distribution percentage of the MEA.

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Renewable Energy Global Innovations features: Catalytic fuel cell used as an analytical tool for methanol and ethanol determination. Application to ethanol determination in alcoholic beverages

Significance Statement

DMFC device used as an analytical tool for ethanol and methanol determination: applications to the analysis of real matrices.

Recently our research group has performed an experimental research [1,2], devoted to the utilization of Direct Methanol Fuel Cell (DMFC) as an analytical device, for methanol, or ethanol determination in real samples. After optimizing the best, among possible measurement formats, i.e. the open circuit, kinetic and potentiostatic format (the latter has been demonstrated the better) and discussing the effects of cross-over and temperature, it has been showed as a small commercial DMFC fuel cell can be useful to determine ethanol in alcoholic beverages, i.e. several wine and beer commercial samples. The obtained results have been compared both with ethanol content declared by the producer firm and with data obtained analyzing the same samples using a commercial amperometric catalase enzyme sensor [3]. The obtained correlation was found satisfactory and the precision, or lifetime of two methods comparable, only the measurement time was longer using the fuel cell. Nevertheless the possibility of improving the features, from the analytical point of view, of the catalytic fuel cell for methanol and ethanol, by introducing an enzyme (alcohol dehydrogenase), immobilized into a dialysis membrane small bag, in the anodic area of the fuel cell, has been recently demonstrated [4]. Using the enzymatic DMFC device, we have reached the goal concerning the drastic reduction of the measurement time by the fuel cell used for analytical purposes, enhancing at the same time its sensitivity [4]. Lastly the determination of other organic molecules, which contain an alcoholic function (although with a much lower sensitivity than methanol or ethanol) in real matrices, which do not contain high concentrations of possible alcoholic interfering compounds, was also demonstrated [4].

References

[1] M.Tomassetti, R.Angeloni, G. Merola, M. Castrucci, L.Campanella. Catalytic fuel cell used as an analytical tool for methanol and ethanol determination. Application to ethanol determination in alcoholic beverages. Electrochimica Acta, 191 (2016) 1001–1009.

[2] M. Tomassetti, R. Angeloni, G. Merola, M. Castrucci, L. Campanella. Catalytic Fuel Cell as an Analytical Tool for Methanol and Ethanol Determination. Proceedding of  2015 XVIII AISEM Annual Conference. 978-1-4799-8591-3/15/$31.00 ©2015 IEEE.

[3] R. Angeloni, M. Tomassetti, M. Castrucci, L. Campanella. Ethanol Determination in Alcoholic Beverages Using Two Different Amperometric Enzyme Sensors. Current Analytical Chemistry, 11 (2015) 56-67.

[4] M. Tomassetti, G. Merola, R. Angeloni, S. Marchiandi, L. Campanella. Further development on DMFC device used for analytical purpose. “manuscript in preparation”.

      

 

Figure Legend: DMFC H-TEC Model F111 Fuel Cell, obtained from Fuel Cell Store (College Station, TX, USA).

 

About The Author

Prof. Mauro Tomassetti, bachelor  in Chemistry (1969) and in Pharmacy (1977).  Full Professor of Analytical Chemistry at the University of Rome ‘La Sapienza’ since 2003; already Associate Professor since 1985 to the same University.

His research interests are in the development of electrochemical sensors, biosensors and immunosensors working both in aqueous and organic solvents and in their application to environmental, biopharmaceutical and food analysis.

He has also interest in thermal analytical studies (TG, DTA, DSC) for the purity control, or the characterisation of several materials (drugs, foodstuffs, polymers, etc.) and in the study and characterisation of archaeological finds and cultural heritages, investigated by means of several instrumental techniques of chemical analysis.

Member of teaching staff of  PhD in Engineering and Process.

Member of “Centro di ricerche applicate alla Protezione dell’Ambiente e dei Beni Culturali (CIABC)“, Sapienza University.

Member of “Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)” of CNR .

Associate Editor of Current Analytical Chemistry.

Member of Editorial Board of Current Pharmaceutical Analysis.

Author of about 506 papers, 243 of which original research paper published on international Journals, and of about 460 communications to congress, overall in the above recorded fields of  research. 

Journal Reference

Electrochimica Acta, Volume 191, 10 February 2016, Pages 1001–1009.

Mauro Tomassetti*, Riccardo Angeloni, Giovanni Merola, Sergio Marchiandi, Mauro Castrucci, Luigi Campanella.

Department of Chemistry, University of Rome “La Sapienza”, p.le Aldo Moro, 5, 00185, Rome, Italy.

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Renewable Energy Global Innovations features: Comparison and verification of the deviation between guaranteed and measured wind turbine power performance in complex terrain

 

Journal Reference

Energy, Volume 85, 2015, Pages 23-29.

Hyunseok Oh¹, Bumsuk Kim²

Show Affiliations

1. Korean Register of Shipping, 6F, Haewoon-Bldg, Gukhoe-daero68-gil 17, Yeongdeungpo-gu, Seoul, 151-742, Republic of Korea
2. Faculty of Wind Energy Engineering, Jeju National University, Jejudaehak-ro 102, Jeju-si, Jeju Special Self-Governing Province, 690-756, Republic of Korea

Abstract

After a wind farm construction is completed, the power performance guaranteed by the wind turbine manufacturer is usually verified based on the international standard IEC61400-12-1. Because of an insufficient project budget and the constraint on the minimum separation distance of the meteorological mast from the installed wind turbines, it is a common practice to verify the power performance of one representative wind turbine and apply the result as the reference power performance guarantee for all the wind turbines. In this study, the power performances of five wind turbines operating at a commercial wind farm located on complex terrain were measured and analyzed. The results showed large power performance differences between the turbines. Because the power performance of one representative wind turbine cannot guarantee the power performances of all the wind turbines in a wind farm located on complex terrain, we submit that it is necessary to carry out power performance verifications on many or all of the wind turbines.

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About The Author

Bumsuk Kim received his B.S. in Mechanical Engineering from Korea Maritime and Ocean University in 2001 and M.S. and Ph.D. from the same university in 2003 and 2005. After receiving his Ph.D., he worked as a Principal Research Engineer at New & Renewable Energy Research Center of Korean Register of Shipping from 2006 to 2013. He was a Head of Wind Energy Business Group at Innovation KR from 2013 to 2014. He is currently working at Faculty of Wind Energy Engineering of JEJU National University as an Assistant Professor from 2014. His research interests include wind energy, ocean energy converters and CAE application for engineering simulation. 

 

About The Author

Hyunseok Oh received his B.S. in Mechanical Engineering from JEJU National University in 2009 and M.S. from the same university in 2011. After receiving his M.S, he worked as a Principal Research Engineer at Korean Register of Shipping from 2011. He is currently a Ph.D. candidate at JEJU National University, where his research interests include power performance uncertainty analysis and load measurement of large wind turbines.

 

 

 

 

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Renewable Energy Global Innovations features: Assessment of grouted samples from monopile wind turbine foundations using combined non-destructive techniques

About The Author

Mr Iliopoulos is a graduate mechanical engineer of the National Technical University of Athens, Greece. Currently, he is a PhD student of the Vrije Universiteit Brussel (VUB)focusing on the development of modal based techniques for response estimation and fatigue assessment of offshore wind turbines.  

Journal Reference

Construction and Building Materials,  8 December 2015.

A.N. Iliopoulos1 D. Van Hemelrijck1, J. Vlassenbroeck2, D.G. Aggelis1

Show Affiliations

1. Vrije Universiteit Brussel, Department of Mechanics of Materials and Constructions, Pleinlaan 2, B-1050 Brussels, Belgium
2. Inside Matters NV, Sylvain Van der Guchtlaan 24, 9300 Aalst, Belgium

Abstract

The vast majority of offshore wind farms uses wind turbines on monopile foundations for cost effective designs. These foundations are complex structures consisting of steel and a high strength cementitious grout that fills the annulus between the two concentric steel pipes known as monopile and transition piece. The grouted connection is potentially prone to structural failures when subjected to harsh offshore conditions due to combinations of extreme wind and wave excitations. Already grouting failures related to slippage of the transition piece relative to the monopile due to weakening of the adhesion between the grout and the steel have been observed at several windfarms during the construction phase. Therefore, a thorough investigation of the grouted connection is of utmost importance. In this study, a large population of cementitious cores were sampled from as many as four offshore wind turbines. The samples were subjected to Ultrasonic Pulse velocity (UPV) non-destructive testing (NDT) and compression testing while a smaller set of samples was subjected to X-ray analysis as well. This paper presents the results of the combined use of the UPV and X-ray techniques as well as correlations with compressive strength results and critically discusses the possibility of using the techniques for in situ application. To the authors’ knowledge it is the first time that these techniques are applied for assessment of the grouted connection of offshore wind turbines on monopile foundations.

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