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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