Renewable Energy Global Innovations features: Electrochemical and photocurrent characterization of polymer solar cells with improved performance after graphene oxide addition to PEDOT:PSS hole transporting layer

Significance Statement

Extensive knowledge exists regarding the predominant role that in bulk heterojunction solar cells donor and acceptor interfaces play in charge carrier formation and separation. Interface improvements by addition of surfactants and by active layer annealing has already been attempted. Interfacial layers have also been optimized so as to avoid charge recombination at the collecting electrodes. These interfacial layers however must qualify as efficient carriers, possess a reduced resistance and be characterized by low light absorption capacities. Consequently, graphene oxide in polymer solar cells possess such qualities that defend their application, contrary to the popularly used tin-doped indium oxide and aluminum electrodes, so as to improve the photovoltaic performance and stability of the devices. Herein, chemically fabricated graphene oxide is added so as to modify the performance and electrochemical properties of bulk heterojunction solar cells of varying architecture.

In a recent research collaboration between Polish and Mexican researchers, Agnieszka Iwan, Felipe Caballero-Briones and colleagues investigated the photocurrent and electrochemical characterization of polymer solar cells with improved performance, after addition of graphene oxide to the PEDOT:PSS hole transporting layer. They focused on applying chemically synthesized graphene oxide in polymer solar cells of varying architectures while altering the placement and amount of the graphene oxide in the polymer solar cells. Their aim was to establish a knowledge base that enlightens on graphene oxide addition in different layers of the same device. Their research work is now published in Solar Energy.

First, the research team obtained the graphene oxide by modified Hummers method and fully characterized by Raman spectroscopy, Fourier Transform Infrared Spectroscopy, X-ray diffraction as well as with cyclic voltammetry. They then constructed bulk heterojunction polymer solar cells with P3HT:PC61BM or PTB7:PC71BM active layers and PEDOT:PSS as hole transport layers. The constructed layers were then subject to investigation relative to: the concentration of graphene oxide in hole transport layer, the acidity of the graphene oxide, the type of polymer used in the active layer, the annealing temperatures of the active layer and the place where the graphene oxide is incorporated in the devices.

The authors observed that the best performance for the polymer solar cells was obtained for the devices with the ITO/PEDOT: PSS:GO/PTB7:PC71BM/Al architecture and at the point where the volume ratio of the graphene oxide to PEDOT:PSS was 1:1. Under these conditions, the researchers noted that higher power conversion efficiency was obtained. They also observed a better active layer performance of the polymer solar cells with the graphene oxide annealed at 130⁰ C.

Herein, the positive effects of incorporation of graphene oxide in bulk heterojunction polymer solar cells, as additive to the hole transport layer PEDOT:PSS with the volume ratio 1:1 are demonstrated. Improved performance of the polymer solar cells is notably achieved in both photocurrent and electrochemical characterization. In totality, the improvement of the polymer solar cells performance upon graphene oxide addition can therefore be comprehended in terms of hole movement and better HOMO-LUMO matching within the structure.

About The Author

Dr. Agnieszka Iwan, assoc. prof. has completed her Ph.D. from Technical University in Silesia (Poland) and postdoctoral studies from Centre National De La Recherche Scientifique in Grenoble (France). She received Ph.D., D.Sc. in Technical University in Wroclaw (Poland). She formerly worked at the Centre of Polymer and Carbon Materials, PAS (Zabrze, Poland) and next at the Electrotechnical Institute (Wroclaw, Poland) as head of the New Technologies Lab., in October 2016 moved to Military Institute of Engineer Technology (Wroclaw, Poland) and has professor position in Institute.

Her research focuses on the organic/polymer/perovskite solar and fuel cells, flexible electronics, nanomaterials such as graphene, TiO₂ or ZnO, liquid crystals and acid-base interactions.

She is author and co-author of more than 260 articles, including 8 book chapters, 3 books and more than 135 presentations in scientific conferences.

About The Author

Dr. Felipe Caballero-Briones, Full Professor, has completed his PhD at the University of Barcelona (Spain) in 2009 and did a postdoctoral stay at Institute of Engineering of Catalonia (IBEC) and Department of Chemical Physics-UB in 2010-2011. From 1999 to 2009 was appointed as associate professor and from 2010 became full professor at the Center for Applied Science and Advanced Technology (CICATA Unidad Altamira) of the Instituto Politecnico Nacional (Mexico) where he is Leader of the Materials and Technologies for Energy, Health and Environment Group (GESMAT).

His research is directed to design and develop graphene-based and semiconducting materials and oxides for photovoltaics, microbial and polymeric fuel cells, supercapacitors, thermoelectrics, and photocatalyts. Other current research interests are graphene-based materials for water remediation, cancer treatment and desalination.

Dr. Caballero-Briones advised or is advising 5 PhD, 14 MSc and 13 BSc thesis and has authored or coauthored 55 articles and more than 200 presentations in scientific conferences; he has 601 cites in Google Scholar (H index 16).

Reference

Agnieszka Iwan, Felipe Caballero-Briones, Michal Filapek, Bartosz Boharewicz, Igor Tazbir, Agnieszka Hreniak, Jesus Guerrero- Contreras. Electrochemical and photocurrent characterization of polymer solar cells with improved performance after graphene oxide addition to the tin-doped indium oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) hole transporting layer. Solar Energy volume 146 (2017) page 230–242.

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Renewable Energy Global Innovations features: Recycled waste black polyurethane sponges for solar vapor generation and distillation

Significance Statement

Owing to the rising global concerns of energy problems, renewable energy resources are being pursued in high demand. Solar power is the most promising and yet naturally unlimited energy source in the foreseeable future. Recently, solar vapor generation has attracted extensive attention owing to the fact that water pollution, water shortages and energy shortages are alarmingly becoming global issues that ought to be addressed. The use of solar energy to enhance evaporation is currently emerging as an attractive strategy for sustainable and practical system such as in desalination, ethanol distillation and sterilization. Plasmonic metallic nanoparticles of noble metals have been widely investigated as solar absorbers due to their unique photo-thermal conversion property despite their limited applicability due to their costly nature. The quest for a high solar-thermal efficiency solar absorbers has led researchers right into the dumpsites, where waste black polyurethane sponge has been observed to possess the desired qualities upon treatment.

Researchers led by professor Yuen Hong Tsang at The Hong Kong Polytechnic University proposed a study to demonstrate that the recycled black polyurethane sponge with porous structure, low thermal conductivity and low mass density to be self-floating, could behave as an ideal absorber for solar vapor generation despite its weak hydrophilicity. Their aim was to present a recycled self-floating black polyurethane sponge which could efficiently generate water vapor after a simple treatment procedure. Their research work is now published in Applied Energy.

The research team begun by modifying the chemical properties by using a facile dopamine solution stirring treatment, so as to achieve the fast dynamic wettability of the black polyurethane sponge, for fluent water supply on the top surface of the absorber. They then used the porous floatable black polyurethane sponge with low thermal conductivity and high durability to generate localized heat at the air-water surface so as to effectively enhance the water evaporation efficiency. Afterwards, they examined the sponge for application in ethanol distillation.

The authors observed that the surface modified black polyurethane sponge showed that the evaporation rate increased by more than 3.5 times compared to the existing natural evaporation processes. They also observed that the black polyurethane sponge for the solar energy distillation application, showed that the sponge could yield up to 25 wt% concentration promotion under each distillation cycle.

The fact that the black polyurethane sponge is a major waste of the packaging industry supports its application for solar energy conversion as an alternative way for disposing it without polluting the environment. It is more advantageous as opposed to other alternative methods since it does not consume any fossil fuel which generate greenhouse gases during combustion.  Based on environmental sustainability and energy costs, the work presented is promising to be an exciting prospect and competitive for applications in practical solar-thermal technologies.

About The Author

Dr. Yuen Hong Tsang has completed his undergraduate and PhD study in the School of Physics and Astronomy, The University of Manchester, UK in 2004. He came back to Hong Kong in 2009 and he is now Assistant Professor in Applied Physics Department, The Hong Kong Polytechnic University. He has published >100 SCI international peer reviewed journals with H-index >20 and total citation >1400.

His current research interests include development of novel materials, e.g. graphene, MoS₂, WS₂ etc. for laser photonics, photo-catalysis, solar energy conversion applications, e.g. photo-catalyst, solar heat absorber, saturable absorber, optical limiter, photo detection, fiber laser, Q-switched and mode locked lasers, etc.

He has involved and successfully completed several research projects funded by some well-known international companies. These projects include 1.  Laser range funder for military applications (funded by Thales.) 2. Imaging system for dental applications (funded by Colgate Palmolive) 3. Narrow linewidth tunable lasers (funded by Huawei) 4. Carbon based mode locking laser system (funded by Fianium Asian Ltd.)

Reference

Sainan Ma, Chun Pang Chiu, Yujiao Zhu, Chun Yin Tang, Hui Long, Wayesh Qarony, Xinhua Zhao, Xuming Zhang, Wai Hung Lo, Yuen Hong Tsang. Recycled waste black polyurethane sponges for solar vapor generation and distillation. Applied Energy volume 206 (2017) pages 63–69.

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Renewable Energy Global Innovations features: GIS application and econometric analysis for the verification of the financial feasibility of roof-top wind turbines in the city of Bari (Italy)

Significance Statement

There has been an increase in the enactment of legislative acts aiming at reinforcing the idea of sustainable energy in industrialized countries, as an ingredient for private as well as public investments. In Italy, for instance, wind solutions for the production of electricity from renewable energy sources have been widely implemented, particularly in regions characterized by excellent geo-climatic conditions. With an increasing pressure to limit soil sealing, more attention has been given to the adoption of renewable energy policies integrated with the current urban establishments.

Pierluigi Morano and Francesco Tajani at Polytechnic University of Bari (Italy) in collaboration with Marco Locurcio at Sapienza University of Rome (Italy) analyzed the financial feasibility originating from the realization of roof-top wind turbines in Bari. The analysis was done via the implementation of a GIS-based decision model. Their second aim was to deal with the explanation of the mathematical relationship between economic and aerodynamic variables of the setup. Their work is published in Renewable and Sustainable Energy Reviews.

The research team implemented a methodology that encompassed the study of the wind climatology of the urban areas of Bari. Adopting the method developed by the MET office, the authors divided the desired territory into homogeneous areas in terms of potential wind energy resources. The map of use of soil and the regional technical map allowed for the implementation of the model developed in the GIS environment, generating two types of thematic maps of Bari, which related to the estimation of the annual mean wind speed and the average annual energy production.

The authors also evaluated the revenues and the costs that concurred to determine the financial feasibility of the wind investment, differentiated on the basis of the thematic maps obtained from the previous stage. The financial parameters identified allowed for the generation of two evaluative maps: the first was a financial feasibility of the investment in the geographic areas of the city of Bari; the second was for the unit land lease values per square meter of the total area covered by buildings. The outputs allowed for the enucleation of the real impact of the aerodynamic parameters on the economic variables to confirm the empirical coherence and report the inconsistencies of the qualitative analysis developed in the first objective.

Above all, the authors constitute a quick reference for a rapid analysis of the convenience of an investment in roof-top wind turbine plants in other regions. After getting the values of parameters that appeared in the econometric model and upon verifying the assumptions adopted for its definition, the authors obtained mathematical expressions that allowed for the evaluation of performance indicators for the entailed parties.

The outcomes of the study represent an evaluative support for operators interested in taking advantage of the incentives offered by energy regulations for the set-up of micro-turbines in windy territory as well as identifying the regions characterized by high power yields.

The approach used in their study, borrowing with a complementary approach GIS tools as well as econometric algorithms, displays an important basis for the formation of homogeneous territorial areas with regards to wind power capacity. The approach entails a straightforward repeatable operative and logical path, which can be implemented in other territorial areas.

About The Author

Pierluigi Morano holds a PhD in Economic Evaluation of Investments and a Master in Urban Planning and Real Estate Market. He is author and co-author of books, journal papers and conference papers on various topics, including the themes of the plans and investments valuation, the appraisal of the cost of the public works, the analysis of the real estate market, the public-private negotiation in urban planning.

About The Author

Francesco Tajani holds a PhD in Economic Evaluation of Investments and a Master in Urban Planning and Real Estate Market. He is author and co-author of published works on various topics, including the study of innovative algorithms as support to real estate appraisal, the evaluation of investments on cultural and environmental assets and the econometric analysis of the dynamics of real estate prices generated by macroeconomic variables. He is a Member of the Royal Institution of Chartered Surveyors (RICS).

About The Author

Marco Locurcio holds a PhD in Architecture and Construction and a Master in Assessment and Retrofitting in Seismic Areas. He is co-author of published works about the analysis of the real estate market, multi-criteria decision analysis and its application.

Journal Reference

Pierluigi Morano, Francesco Tajani, and Marco Locurcio.GIS application and econometric analysis for the verification of the financial feasibility of roof-top wind turbines in the city of Bari (Italy). Renewable and Sustainable Energy Reviews, volume 70 (2017), pages 999–1010.

¹ Department of Science of Civil Engineering and Architecture (DICAR), Polytechnic University of Bari, via Orabona 4, Bari 70125, Italy.

² Department of Architecture and Design (DIAP), University Sapienza of Rome, via Gramsci 53, Roma 00197, Italy.

 

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Renewable Energy Global Innovations features: Energy Resources Intelligent Management using on line real-time simulation: A decision support tool for sustainable manufacturing

Significance Statement

Eco-sustainability of industrial manufacturing has been considered as one of the building blocks of relations between the environment and people. The use of renewable energy has therefore become a fundamental element in view of this vision. A binding global accord was finally reached after several years of vain attempts to rule out an agreement to considerably curtail carbon dioxide emissions from burning fossil fuels.

A number of commonly used renewable energy sources, such as wind and solar, exhibit a problem concerning discontinuity in the production of energy owing to variability in weather as well as climatic conditions. Therefore, there has been increasing efforts by researchers to come up with a new methodology that can be capable of marrying industrial users’ instantaneous need for energy with the generation capability of renewable energy sources, and when necessary, supplemented by energy created via self-production and perhaps from third-party suppliers. This is in the view of minimizing carbon dioxide emissions as well as company energy costs.

In order to manage renewable energy sources effectively and efficiently, predictive models for industrial energy demands as well as production capacity of renewable energy sources is needed. University of Genoa researchers in Italy proposed to provide energy managers in the manufacturing environment with a support tool that can implement the potentialities of Discrete Event Simulation as well as Monte Carlo simulation and incorporated with a unique predictive algorithm to allow optimizing energy supplying mix. Their research work is published in Applied Energy.

Tackling the issue of the supplemented as well as optimal use of energy produced by renewable energy sources in the field of manufacturing, the authors proposed a management method referenced on two steps, fortified by two respective models; the Energy Resources Intelligent Management-Predictor (ERIM-P) and Energy Resources Intelligent Management-Real Time (ERIM-RT). The purpose of the former model was to come up with, 24h in advance, the hourly electrical energy requirement of the manufacturing plant referenced on the production plan made for the next day. The model was also to quantify the possible self-production of renewable energy sources energy based on weather forecast for the next day.

Upon completion of the first model, the latter ERIM-RT will act on the current day taking into consideration through the implementation of an on-line real-time Discrete Event Simulation simulator of what would be happening in real time with the manufacturing plant and the actual instantaneous generation of renewable energy sources. The use of a predictive algorithm would offer a 30min update of the available renewable energy generation prediction for subsequent times of the day.

Counting on the test cases done on the tannery, the outcomes observed showed that the ERIM-RT model allowed for obtaining considerable improvements in real time estimates, both real photovoltaic generation and daily energy demand schedule. In the combined high-variability sub-scenarios, the authors found a clear enhancement in energy performance for the tannery in view of reduction of error, carbon-dioxide emissions, and energy costs. The model was found to be more effective when the larger the deviations were between the prediction made on the day before and the real profiles for the current day.

Their study also highlighted that the more the attributes of the tannery were affected by randomness, the more the need for the ERIM-RT model became essential. With the two sub-scenarios, Demand Lower Production Higher and Demand Higher Production Lower, the ERIM-RT model led to enhancement in predictive performance by, respectively, 7.3 and 7 times greater than with the ERIM-P model alone.

Reference

Lucia Cassettari, Ilaria Bendato, Marco Mosca, and Roberto Mosca. Energy Resources Intelligent Management using on line real-time simulation: A decision support tool for sustainable manufacturing. Applied Energy, volume 190 (2017), pages 841–851.

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Renewable Energy Global Innovations features: Feasibility of a clean CAES system coupled with wind and solar energy in China

Significance Statement

Energies are the important driving force for global social, economic and technological developments. Renewable energy sources, such as wind and solar power, have been discussed as renewable, sustainable and environmentally friendly forms of energies. However, it is a big challenge to utilize them stably. Compressed air energy storage (CAES) is a method of energy storage which can convert the surplus power to the internal energy of compressed air, and regenerates electricity whenever power is needed. This paper proposes a clean CAES system hybrid with wind and solar energy, which uses heat storage/heat exchange devices instead of combustion chamber of traditional CAES, uses the surplus energy of the wind power plant to provide power for compressed air storage, and uses solar energy to provide heat source for heat storage/heat exchange devices, so as to solve the dependence on fossil fuels of traditional CAES systems. The operating variables of the hybrid system include heat exchanger effectiveness, ambient temperature, mass flow rate, total pressure ratio and compressor/turbine stages. The effects of those on the system performances are evaluated, including output power, overall efficiency, energy ratio (ER) and heat ratio (HR). Additionally, the parameters, delineating criteria of the potential development localities for the hybrid CAES system sites, such as solar and wind energy resources, abandoned cavities of mines resources used as compressed air containers and the distribution of cross-transmission lines in China are investigated. We find that more than 13 major zones are of the capability to support the hybrid system in China. Finally, comparing to the conventional thermal power plants, the environmental and economic benefits of this CAES system are calculated.

This paper primarily presented a clean CAES system coupled with wind and solar energy in China and analyzed the technical feasibility, potentially suitable areas, environmental and economic benefits of the system.

About The Author

Jie Chen, associate professor at Chongqing University, Chongqing, PR China. In 2012, he received his Ph.D. degree in College of Resource and Environmental Science from Chongqing University, Chongqing, China. In 2013, he stated Postdoctoral researsh at State Key Laboratory of Rock and Soil Mechanics and Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China.

He has accomplished several significant projects from National Science Foundation (NSF) and China Postdoctoral Science Foundation. His research areas include rock mechanics, damage and self-healing of rock materials, and underground energy storage. He has published more than 60 papers and served as a reviewer for many prestigious journals. (jiechen023@cqu.edu.cn)

About The Author

Deyi Jiang, professor at Chongqing University, Chongqing, PR China. He was born on June 13, 1962, in Sichuan, PR China. He finished his studies at Chongqing University in 1985 and obtained his Ph.D. degree in 2001, in China. He is now the Dean of College of Resources and Environmental Science, Chongqing University. Also, He is the Executive Deputy Director of State Key Laboratory of Coal Mine Disaster and Control from 2011 to present.

His research areas include rock mechanics, solution mining disasters control and salt cavern comprehensive utilization. He has published more than 100 articles in international periodicals, many of which in high-ranking journals, and held more than 30 lectures worldwide. Under his guidance, more than 60 master theses and the same number of Ph.D. dissertations have been done.

About The Author

Wei Liu, lecturer and researcher at Chongqing University, Chongqing, PR China. In 2015, he had received his Ph.D. degree in University of Chinese Academy of Sciences, Wuhan, China. Thereafter, he stated Postdoctoral researsh at College of Resource and Environmental Science in Chongqing University, Chongqing, China. He is now taking charge of several funds supported by the National Science Foundation (NSF) and China Postdoctoral Science Foundation.

His research areas include rock mechanics, permeability and damage of low permeable rock materials and energy storage technologies. He has published more than 40 papers and served as a reviewer for many international journals, such as Energy, Applied Thermal Engineering, and Environmental Earth Sciences.

Journal Reference

Jie Chen ^{a, b}, Wei Liu ^{a, b, *}, Deyi Jiang ^{a, b}, Junwei Zhang ^{a, b}, Song Ren ^{a, b}, Lin Li ^{a, b}, Xiaokang Li ^{a, b}, Xilin Shi ^c. Preliminary investigation on the feasibility of a clean CAES system coupled with wind and solar energy in China. Energy, Volume 127, 15 May 2017, Pages 462-478.

Show Affiliations

^a State Key Laboratory of Coal Mine Disaster and Control, Chongqing University, Chongqing 400044, China.

^b College of Resources and Environmental Sciences, Chongqing University, Chongqing 400044, China

^c State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, The Chinese Academy of Science, Wuhan, Hubei, 430071, China.

 

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Renewable Energy Global Innovations features: Significance of CO2-free hydrogen globally and for Japan using a long-term global energy system analysis

Significance Statement

Various zero emission technologies for mitigating greenhouse gas emissions are being developed to limit the impact of climate change. Nuclear energy, fossil fuels with carbon capture and storage technology and renewable energy are major candidates for zero emission technologies. Hydrogen, which is considered in most global energy models as an energy carrier, is being actively developed but the specifics on its international transportation are yet to be clearly described.

In a recent paper published in International Journal of Hydrogen Energy, Yuki Ishimoto and colleagues at The Institute of Applied Energy studied the importance of hydrogen in both local and global energy systems as well as the amount of deployed carbon dioxide-free hydrogen, with special attention to the case of Japan.

A long-term intertemporal optimization energy model was used with the assumption that carbon dioxide-free hydrogen is produced in all regions and is transported to other regions around the globe. Projections of energy-related statistics were used to estimate the energy demand scenarios in the transportation, power and stationary sectors. The global energy structure of demand and supply was determined to reduce the costs of global energy systems while meeting the energy demand under constraints such as energy resources and carbon dioxide emissions. The simulation base year was 2010 and terminal year was 2050.

There is a rise in fossil fuel prices with time due to increase in primary energy and the associated consumption accumulation. Due to technological progress between the years 2020 and 2030, there is a decrease in hydrogen prices which increases after 2040, as a result of increase in the renewable energy share due to constraints of carbon dioxide emissions.

In the year 2050, the global hydrogen demand is about 621 Mtoe, with the transportation sector using the majority of the hydrogen share. Additionally, the world stock share of fuel cell vehicles is about 18% with their energy consumption share at 23%. The share of internal combustion engines decreases to about 2% due to the increase in use of biofuel and fuel cell trucks.

In Japan, due to severe carbon dioxide emission constraints towards 2050, there is an increase in power generation technologies with zero emissions. Power plants that are fired by natural gas gradually reduce the share of those fired by coal. Internal combustion engines are replaced with fuel cell vehicles, electric vehicles, and plug-in hybrid electric vehicles whose.

The authors compared indicators for both hydrogen and no-hydrogen cases and noted that the global energy system cost difference in the two cases was about 1% in 2050 which translates to about 200 billion USD. This shows an improvement in the energy system cost.

In both cases, the net carbon dioxide emissions in Japan are almost similar until 2040 after which there is a decrease in the hydrogen case. The research team noted that in the power sector, the carbon intensity drops to almost zero in 2050 which is improved due to hydrogen utilization. This results in a wide distribution of primary energy resources as well as the energy self-sufficiency ratio. A reduction in imports of natural gas and increased use of wind for electrolysis significantly improves this ratio. From this, it is observed that carbon dioxide-free hydrogen improves both local and global energy systems.

About The Author

Yuki Ishimoto is a senior researcher at the Institute of Applied Energy. The institute is a non profit research organization specialized for energy technology research. His research focuses on hydrogen energy systems analysis which includes the roles of hydrogen energy systems in global and local energy systems.

His recent works are related to techno-economic analysis of intercontinental energy carrier transportation. He has published 30 peer reviewed papers as first and co-authors in energy related fields.

Reference

Yuki Ishimoto, Atsushi Kurosawa, Masaharu Sasakura, Ko Sakata. Significance of CO₂-free hydrogen globally and for Japan using a long-term global energy system analysis. International Journal of Hydrogen Energy, 42, (2017), 13357-13367.

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Renewable Energy Global Innovations features: Adaptable wind/solar powered hybrid system for household wastewater treatment

Significance Statement

Droughts, explosive population growth and the continuing view that water is an infinite resource are reasons for water shortages in many areas of the world. Reusing wastewater as part of sustainable water management allows water to remain as an alternative water source for human activities reducing the demand on groundwater. Initially, wastewater reuse was focused for irrigation and non-potable purposes, but with more innovative advancements in technology, wastewater reuse domain has significantly expanded. Typical wastewater treatment processes are fit for non-potable water reuse that does not necessitate the wastewater to be treated to drinkable standards.

Treatment of raw water from rivers, lakes and wells must meet drinkable standards. To achieve this, intensive energy is required and this is yet another issue when it comes to energy supply in rural areas. Access to modern energy is an economic and social priority for the rural population owing to its direct environmental and economic benefits.

Jacqueline Stagner and David Ting at the University of Windsor in Canada in collaboration with Akhilesh Soni at Indian Institute of Technology presented a design of a self-sustainable stand-alone water treatment system. The application of the innovative system which is “taking wastewater reuse into another level” was driven by renewable energy sources and was designed for an off-grid community. Their design philosophy was the use of solar energy as a primary source and wind power as a secondary source in powering the purification system. Their research work is published in Sustainable Energy Technologies and Assessments.

The water purification process presented by the authors implemented two models of renewable energy, wind and solar. Wind power was applied to drive a vacuum pump, which reduced the air pressure inside the system. They optimized the number of processing stages to be four. This was based on the fact that increasing the number of stages would not be economically viable. The vapor pressure was maintained in the successive stages of the still at 31, 27, 20, and 18 kPa.

The researchers used constricting nozzles to connect the household drain with the recirculating loop and still. Solar power was used to heat the water in the chambers of the still. This solar energy was transferred to the system from the bottom chamber through a heat exchanger, and from the top of the chamber through heating the water directly.

The authors observed that the fresh water production capacity of the proposed solar-collector four-stage solar still, operating for 6 hours a day and a constant flux of 850W/m², was 17.4kg/m²/day. This value was higher than for conventional solar stills. They found that the annual cost of the system was about Rs7450, and per unit water cost in the range of 0.5-1.2Rs/kg for the wind speed ranging from 1-5m/s. In the absence of wind, a hand-driven wheel could be used to drive the reciprocating pump to propel the water from ground to roof level.

Considering wind speeds of approximately 1-5 m/s, the proposed multistage solar desalination system can meet the fresh water needs for urban as well as rural communities by distilling 25-45kg/day. This wastewater reuse innovation will advance the application of recycled water as a reliable alternative water source.

About The Author

David S-K. Ting worked on Combustion and Turbulence (Premixed Turbulent Flame Propagation) during his graduate years. He then ventured into Convection Heat Transfer and Fluild-Structure Interactions prior to joining University of Windsor. Professor Ting is the founder of the Turbulence & Energy Laboratory. Dr. Ting supervises students on a wide range of research projects primarily in the Energy Conservation and Renewable Energy areas. To date, he has co/supervised over sixty graduate students and co-authored more than one hundred journal papers. Fundamentally, this once a jungle boy of Borneo rainforest is ever astounded by the beautiful, orderly and yet impregnable creation. His love is still faithfully on Flow Turbulence; see
http://ift.tt/2wrHbxe

About The Author

Jacqueline Stagner is the Undergraduate Programs Coordinator in the Faculty of Engineering at the University of Windsor, and an adjunct faculty member in the Department of Mechanical, Automotive, and Materials Engineering. Dr. Stagner co-advises students in the Turbulence and Energy Lab, in the area of solar water desalination. Prior to working at the University of Windsor, she attained a PhD in Materials Science and Engineering, a Master of Business Administration, and a bachelor’s degree in Mechanical Engineering. She also worked as a release engineer in the automotive industry for 6 years.

Reference

Akhilesh Soni, Jacqueline A. Stagner, and David S.-K. Ting. Adaptable wind/solar powered hybrid system for household wastewater treatment. Sustainable Energy Technologies and Assessments. Available online 8 March 2017

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Renewable Energy Global Innovations features: Ultralong cycling stability of carbon-nanotube/LiFePO4 nanocomposites as electrode materials for lithium-ion batteries

Significance Statement

The long cycle stability of electrode materials is required for lithium-ion batteries used in electric vehicles.  The effective conductivity and the stable structure of these electrode materials are critical to the cycle stability. The olivine-type lithium iron phosphate is one such electrode material, that is able maintain its crystal structure stability, which in turn minimizes volumetric changes in the charge-discharge process. Advances geared towards improving the effective conductivity have been made by increasing the electrical conductivity of lithium iron phosphate electrode materials through applying carbon nanotubes in these materials. However, the preparation of uniformly distributed carbon nanotubes in the lithium iron phosphate faces many obstacles that some synthetic techniques have tried to address.

In a recent paper published in Electrochimica Acta and led by Professor Tong De Shen and Professor Yu Qing Qiao at Yanshan University developed an innovative technique of coating carbon nanotubes with polyvinylpyrrolidone, which effectively combines the carbon nanotubes and lithium iron phosphate to produce a nanocomposite that exhibits an excellent ultralong cycling stability and high-rate capacity.

The research team made polyvinylpyrrolidone-carbon nanotube-water dispersions which were subjected to repeated freezing and thawing to produce modified carbon nanotubes. They then prepared lithium iron phosphate particles which were then combined with the modified carbon nanotubes to produce lithium iron phosphate-carbon nanotube electrode material. The polyvinylpyrrolidone acts as a dispersant, surfactant and binder. The nanocomposite was heated at 600 ^OC in the presence of nitrogen to eliminate the polyvinylpyrrolidone, after which the carbon nanotubes were manipulated to form uniform three-dimensional conductive networks in lithium iron phosphate electrode.

The authors deduced that the polyvinylpyrrolidone coating process reduces the amount of disordered and defected carbon atoms. It was observed that the synthesized lithium iron phosphate exhibits a single phase of orthorhombic olivine-type structure. The observed average crystallite size of the lithium iron phosphate was about 30 nm.

The research team observed that the discharge capacity of the lithium iron phosphate electrode material with 3% carbon nanotubes, is about 9.4% greater than the lithium iron phosphate without any carbon nanotubes.

From the impedance spectra, it was deduced that there was a lower charge-transfer resistance in the electrode with 3% carbon nanotubes, which was about a third of the charge transfer resistance of the electrode without any carbon nanotubes. This shows that about 3% carbon nanotubes can develop a conductive network that is highly efficient, and therefore the lithium iron phosphate electron conduction is significantly improved.

The authors noted that the lithium iron phosphate electrode material with 3% carbon nanotubes had a lithium ion diffusion coefficient that was 25 times faster as compared with that without any carbon nanotubes, which shows that the carbon nanotubes effectively improve the diffusion of lithium ions. Also, the conductivity of the former is about 7.5 times higher as compared with the latter.

Further analysis showed excellent cycle stability of the lithium iron phosphate electrode containing about 3% carbon nanotubes, such that after about 1000 charge/discharge cycles at a discharge rate of 10C, there was only 1.6% loss in capacity, and a discharge capacity that was as high as about 123.0 mAhg^-1. Additionally, the nanocomposite was observed to have a cycling lifetime of 3400 cycles as compared with 750 cycles for the commercially available lithium iron phosphate electrode materials.

Loss in capacity of various LiFePO4/carbon nanocomposites with 1D to 3D carbon as conducive agents after 1,000 cycles at a discharge rate of 10C. PVP: polyvinylpyrrolidone; CNSs: carbon nanosheets; CFs: carbon fibers; RGO: reduced graphene oxide; GN: graphene; N-GN: nitrogen-doped graphene; GNO: graphene oxide.

About The Author

Prof. Qiao is a professor with the College of Environmental and Chemical Engineering at Yanshan University. She received her Ph.D. degree in 2006 from Yanshan University. Her current research interests are on the processing and performance of nanostructured electrode materials for energy storage and conversion. She has authored/coauthored more than 50 papers.

About The Author

T.D. Shen is a professor with the Coellege of Materails Science and Engineering at Yanshan University. He obtained the National 1000 Talents award in 2010. He received his B. S. degree in Materials Science from the Zhejiang University in 1986 and his Ph.D. degree in Material Sciences from the Institute of Metal Research, Chinese Academy of Sciences in 1995. He was a postdoctoral associate from 1995 to 1998 and a Staff Member from 1998 to 2008, both with the U.S. Department of Energy’s (DOE) Los Alamos National Laboratory (LANL) in Los Alamos, New Mexico.

His current research interests are on the processing, characterization, and physical/mechanical/electrochemical properties of nanocrystalline, nanostructured, and amorphous materials. He has authored/coauthored more than 100 papers.

Reference

Yu Qing Qiao, Wei Liang Feng, Jing Li, Tong De Shen. Ultralong cycling stability of carbon-nanotube/LiFePO₄ nanocomposites as electrode materials for lithium-ion batteries. Electrochimica Acta 232 (2017) 323-331.

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Renewable Energy Global Innovations features: Controlling Heat Release from a Close-Packed Bisazobenzene–Reduced-Graphene-Oxide Assembly Film for High-Energy Solid-State Photothermal Fuels

Significance Statement

Photo-induced isomerization of organic compounds has shown an excellent approach for utilizing solar energy. In this category, azobenzene can undergo a photo-induced change from low energy trans-isomer to high-energy cis-isomer through the absorption of photons at a particular wavelength. The resulting cis-isomer can reverse back trans-isomer owing to its low thermodynamic stability of when exposed to external stimulus, for example, heat and light.

The reversible photo isomerization attributes makes Azo-based element to be a crucial building block for photo-thermal fuels in view of its capacity to store light energy in chemical bonds and release it later as heat energy. However, the implementation of the photochromic azo compounds as photo-thermal fuels is greatly hindered by their low exothermicity as well as low activation barrier to thermal reversion. For this reason, most research works have been based on ways to enhance isomerization enthalpy and half-life through the design of several substituents.

Multi-branched Azo molecules have exhibited potential for application in photo-thermal fuels thanks to their intermolecular interactions. The isomerization is limited by large steric hindrance, which in turn increases the half-life. The intermolecular hydrogen bonds lead to an increase in isomerization enthalpy counting on the decreased energy of the trans-isomer. For this reason, tuning the steric configuration of the multi-branched Azo molecules is fundamental in the occurrence of a number of molecular interactions.

Researchers led by Professor Wei Feng at the Tianjin University in China presented a template assembly of bisazobenzene that was grafted covalently onto reduced graphene oxide. The two Azo assemblages with varying branched structures were synthesized to analyze the impact of the molecular interactions on the photo-thermal attributes. Their research work is published in ChemSusChem.

The authors prepared the reduced graphene oxide-bisazobenzene solution where it was then irradiated with Ultraviolet light in order to induce trans-to-cis isomerization. This was continuously done until the photo-stationary was noted. The absorbed energy was stored in metastable cis-isomer of the azo benzene on the reduced graphene oxide.

The resulting graphene oxide-bisazobenzene films were then irradiated with the same UV light until a photo stationary state was realized. Long duration irradiation was implemented to initiate trans-to-cis isomerization of azobenzene in the film owing to steric hindrance.

The research team successively prepared uniform photo-thermal fuel implementing a close packed graphic oxide-bisazobenzene. The grafting density was set at 1/23. Reduced Graphene oxide-bisazobenzene-2 posted high energy density of approximately 131Whkg^-1, a power density of 2517Wkg^-1. The compound also posted a long half-life of about 37days with good cyclic performance for about 50 cycles reference to inter- and intramolecular hydrogen bonding and steric performance.

The low isomerization in the solid-state graphene-based bisAzobenzene films led to energy density decrease of about 25% from what was reported for powder sample reference to steric hindrance. The authors also investigated a closed cycle of UV radiation, storage and heat release of the resulting photo-thermal. Graphene oxide based Azobenzene films were able to release and accumulate heat to realize a maximum temperature difference of 15°C. However, the films were observed to retain a temperature difference of more than 10° for about 30 minutes when the temperature difference on the environment was over 100° C.

From the results of their study it was concluded that molecular engineering for high-energy storage as well as an optimized microstructure for high degree isomerization are necessary for high-performance photo thermal fuels. The ability to tune heat release in the solid-state assembly bears a groundbreaking mechanism for developing photo thermal fuels into functional gadgets.

About The Author

Wei Feng received his PhD in 2000 from the Xi’an Jiaotong University of China after studying optic-electric properties and device applications of novel conducting polymers, and then worked at the Osaka University and the Tsinghua University as a JSPS fellow and postdoctoral researcher, respectively. In 2004, he became a full professor at Tianjin University, where he works on functional nanocarbon materials.

About The Author

Yiyu Feng obtained his PhD of materials science from Tianjin University in 2009. He is currently a full research professor at Tianjin University. His scientific interest is focused on designing and developing high-strength and high density hierarchical carbon materials & hybrid for multifunction.

Reference

Xiaoze Zhao, Yiyu Feng, Chengqun Qin, Weixiang Yang, Qianyu Si, and Wei Feng. Controlling Heat Release from a Close-Packed Bisazobenzene–Reduced-Graphene-Oxide Assembly Film for High-Energy Solid-State Photothermal Fuels. ChemSusChem 2017, 10, 1395 – 1404.

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Renewable Energy Global Innovations features: Comparisons among Bat algorithms with various objective functions on grouping photovoltaic power patterns

Significance Statement

Power generation from photovoltaic systems has been the focus of many research studies. The main aim has been to tackle environmental and financial issues of typical power resources. Unstable fossil fuel prices and a considerable portion of environmental pollutions and greenhouse emissions are major concerns when it comes to industrialized countries. Ability to produce electricity for a long time with minimal maintenance and reduction in capital costs are factors to be considered while integrating photovoltaic systems into the electrical grid.

Unfortunately, output power of photovoltaic system is dependent on ambient temperature and irradiation level. In addition, fluctuations in the output power could be experienced owing to shadowing or power quality interference. Therefore, it is important to study the effect of these output power fluctuations before photovoltaic systems installation. To achieve this, simulation implementing historical data and extensive analysis should be done.

Handling this data is computationally expensive and time consuming. Therefore, developing solutions that can ease the burden of extensive studies and simulations relating to integrating photovoltaic systems into the electrical grid is of outmost importance. Clustering methods can be used to group photovoltaic power patterns with similar properties. Thus, a representative power pattern for every group can be integrated in the simulations.

Amr Munshi and Yasser Mohamed from the University of Alberta presented the outcomes of an in-depth analysis of Bat clustering algorithms based on a number of objective functions in a bid to establish the grouping mechanism of photovoltaic power patterns. Their main objective was to enhance the clustering formation of the former clustering algorithm, Bat J. Their research work is published in Solar Energy.

The authors performed and in-depth analysis of the performance of Bat clustering algorithms dictated by a number of integrated objective functions to validate the clustering of photovoltaic power pattern process. They then compared the performance of the K-means and Bat J clustering algorithms with the new Bat clustering on the clustering process of photovoltaic power patterns data.

The researchers also illustrated the original Bat clustering algorithm methods to undertake photovoltaic power patterns grouping. They adopted the principle component analysis in a bid to reduce the dimensionality of the photovoltaic power patterns data.

Bat clustering algorithms were comparable or surpassed K-means in the validity index, compactness and separation values. The within-cluster-sum-of-squares validity index values of Bat were observed to have improved as opposed to K-means by approximately 14.10% and 14.71% over the knee-points for the first and second datasets, respectively. The authors observed that Bat within-cluster-sum-of-squares posted the best outcomes and was capable of enhancing Bat J algorithm that exhibited the best cluster data.

Nevertheless, this corresponded to more complexity since the number of parameters ought to have been priori calibrated. The preferable combination presenting the optimum number of clusters was observed to be Bat within-cluster-sum-of-squares clustering and within-cluster-sum-of-squares validity index. They presented considerably high separated and compact clusters.

Lower within-cluster-sum-of-squares values at a selected partition presented the most preferable combination of separation and compactness. Therefore, Munshi and Mohamed study on the Bat within-cluster-sum-of-squares could offer well-defined photovoltaic power pattern clusters as well as cluster representatives that can be used in photovoltaic output power analyses.

About The Author

Amr A. Munshi received the B.Sc. degree in computer engineering from Umm Al-Qura University, Makkah, Saudi Arabia, in 2008, and the M.Sc. degree in computer engineering from the University of Alberta, Edmonton, AB, Canada, in 2014, where he is currently pursuing the Ph.D. degree in computer engineering. His research interests include machine learning, data mining and big data analytics. Mr. Munshi is a Member of the Golden Key International Honor Society. He is currently an Editor of the Alberta Academic Review Journal.

Reference

Amr A. Munshi and Yasser A.-R.I. Mohamed. Comparisons among Bat algorithms with various objective functions on grouping photovoltaic power patterns. Solar Energy, volume 144 (2017), pages 254–266.

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Renewable Energy Global Innovations features: Thermodynamic analysis of siphon flash evaporation desalination system using ocean thermal energy

Significance Statement

Ocean thermal energy can be described as the thermal potential energy produced by the temperature difference between the warm surface and the cold deep seawaters. Reference to the large ocean area, ocean thermal energy reserves are huge. Ocean thermal energy is considered green in the sense that its production is without pollution. Nevertheless, this renewable energy sources suffers from low temperature difference between the deep seawater and the surface, which is generally in the range of 15-25K. The source also suffers the weakness of low specific heat that is approximately 4J/(gK), while seawater heat of vaporization is approximately 2400J/g.

To enhance the efficiency of the ocean thermal energy, it has been found profound to use the ocean thermal energy for seawater desalination directly. Using it directly can help skip the numerous conversion steps for converting ocean thermal energy to electricity and then converting the resulting electrical energy to chemical energy. Considering the scarcity of fresh water, it becomes paramount to produce fresh water using ocean thermal energy. However, in a previous system, energy consumption on seawater transportation was observed to be very high and this led to poor economic tradeoff of the systems.

In addition, the effect of a number of parameters on the performance of this system was not assessed. Above all, placing the evaporator and the condenser into a single unit caused the system to be very large, and the system’s exergy efficiency should be determined. Therefore, Zhejiang University researchers Zhi-jiang Jin, Hao Ye, Jin-yuan Qian and in collaboration with Hao Wang at Air Liquide Hangzhou Co., Ltd. And Hao Li at Nuclear Power Institute of China explained the working principle of siphon flash evaporation desalination system and analyzed the exergy efficiency of the entire system. They created a simulation model in ASPEN PLUS and analyzed the effects of a number of factors on the functioning of the system through the model. Their work is published in Energy Conversion and Management.

The vapor produced in the flash evaporator is normally absorbed into the condenser chamber reference to the pressure difference between the condenser and the evaporator. The vapor is condensed into freshwater by the cold deep ocean water. Owing to a particular degree of vacuum difference between the evaporator and the condenser, then the vapor can be absorbed into the condenser continuously.

However, the initial vacuum degree of the condenser shell side must be the same as the evaporator. There are two main functions of the ocean thermal energy; one is to generate and maintain the vacuum difference between the flash evaporator and the condenser. This will ensure that the surface water is vaporized continuously and absorbed into the condenser without extra energy consumption. The second function is that the cold deep seawater is used as a condensing agent for condensing the vaporized water into fresh water.

Under design conditions, the authors realized that the exergy efficiency of the entire system turned out very well at 7.81%. This value was higher than the typical utilization of the ocean thermal energy. The exergy efficiency of the flash evaporator was observed to reduce with a rise in the surface seawater temperature, but the condenser efficiency remained unchanged.

The flow rate of the deep seawater decreased with a rise of temperature change of the deep seawater. However, the flow rate of the surface water decreased with the increase in change in temperature of the surface water. The surface water flow rate also influenced the pressure difference between the condenser and the evaporator. Non-condensable gases in the water might have caused this. Therefore, taking into account the influence of non-condensable gases in the actual production is paramount.

About The Author

Zhi-jiang Jin, Ph.D., Professor

Institute of Process Equipment, Zhejiang University, China

Prof. Jin is the Deputy Director of Institute of Process Equipment, Zhejiang University, the Deputy Director of Energy Assessment Center, Zhejiang University. He is also a member of Pressure Vessel Branch Pipeline Committee, China Mechanical Engineering Society, and the Technical Committee of Chinese Safety and Pressure Relief Device Standardization. His research areas are focus on high efficient process equipment design and pressure pipeline safety technology.

About The Author

Jin-yuan Qian, Ph.D

Department of Energy Sciences, Lund University, Sweden

Dr. Qian received the B.Sc. and Ph.D. degrees both in Chemical Process Equipment from Zhejiang University, China in 2011 and 2016, respectively. He was a joint Ph.D. student at TU Bergakademie Freiberg, Germany, from 2013~2014. Currently, he is a postdoc fellow at Department of Energy Sciences, Lund University, Sweden. His research interests include Thermofluids, Micro/Nano Heat Transfer, Flow Control, Hydraulics, Computational Fluid Dynamics et al.

Reference

Zhi-jiang Jin, Hao Ye, Hao Wang, Hao Li, Jin-yuan Qian. Thermodynamic analysis of siphon flash evaporation desalination system using ocean thermal energy. Energy Conversion and Management, volume 136 (2017), pages 66–77.

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Renewable Energy Global Innovations features: Improvement of Cyclability of Li-Ion Batteries Using C-Coated Si Nanopowder Electrode Fabricated from Si Swarf with Limitation of Delithiation Capacity

Significance Statement

Silicon is among the most promising building blocks for negative electrode active materials used in the fabrication of lithium ion batteries. It has been identified that silicon has a theoretical capacity of approximately 3578 mAh/g and this is much more than 372 mAh/g for graphite currently applied in standard lithium ion batteries. Silicon powder prepared by expensive approaches including laser ablation as well as plasma-enhanced chemical vapor deposition has been evaluated to mitigate the stress of silicon caused by the change in size in the course of delithiation and lithiation.

Despite the outstanding attributes of silicon, silicon nanopowder still suffers several problems to use as lithium ion battery electrode active materials. Silicon nanopowder experiences volume expansion of about four times during lithiation, and considerable shrinkage during delithiation. This results in the formation of cracks in the nanopowder. Electrical isolation of the silicon nanopowder is another problem, which leads to an increase in internal resistance, low columbic efficiency and poor cyclability.

In a bid to suppress the volume change of the silicon powder, the lithiation capacity has been limited at 1500 mAh/g and 1200 mAh/g after considerable delithiation. Nevertheless, the impact of limitation of the delithiation capacity after deep lithiation on cyclability has not been studied.

Researchers led by Professor Taketoshi Matsumoto from Osaka University fabricated lithium ion battery half cells using silicon nanopowder generated from silicon swarf and investigated the impact of delithiation and lithiation capacity after deep lithiation at 0.01V on the performance of the cell. They found that the limitation of the delithiation capacity at 1500mAh/g improved the cyclability. Their work is published in Journal of The Electrochemical Society.

Silicon swarf was annealed in hydrogen atmosphere at 1000°C and later at 1000°C in ethylene environment to coat the silicon nanopowder with a 10nm carbon layer. The carbon coated silicon nanopowder was then mixed with polymer binders. The authors coated copper foil with the resulting slurry and the sample was dried where it was then packed as working electrode in a coin cell with a lithium foil counter electrode. The coin cell was also equipped with a polyethylene separator and an electrolyte.

The authors then cycled the cells in the cell voltage range of 0.01-1.5V in the course of 300 cycles using a battery charge-discharge unit. They set delithiation and lithiation current densities at 180mA/g for the first 5 cycles and 1800mA/g for the next 295 subsequent cycles.

The authors observed that limitation of delithiation capacity at 1500mAh/g resulted in the best cyclability. This capacity remained constant at 1500mAh/g until the 290^th cycle, where it reduced slightly to 1480mAh/g at the 300^th cycle. The overvoltage for delithiation-limited case was observed to be lower than that for lithiation-limited case. The low overvoltage as well as excellent cyclability was referenced to suppression of electrical isolation of silicon nanopowder owing to limited shrinkage of the silicon powder in the high lithium concentration zone.

Limitation of lithiation capacity at 1500mAh/g caused the delithiation capacity to remain at 1470mAh/g until the 137^th cycle and then decreased to 860mAh/g at the 300^th cycle. Electrical isolation, high overvoltage, and peeling-off of the silicon nanopowder resulted from low inter-particle contact reference to large size change of the silicon powder.

About The Author

Dr. Taketoshi Matsumoto is an Associate Professor in The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan.  His research is focused on energy related nano-materials and devices.  He has been engaged in research on Li ion batteries, luminous materials, solar cells, ultra-low power thin film transistors and MOS transistors, permanent memories, fuel cells, hydrogen storages and catalysts.

He received his Ph.D. (2001) and M.S. (1998) in Electronic Chemistry from Tokyo Institute of Technology, Japan, and B.S. (1996) in Chemistry from Keio University, Japan.  He was a research fellow of the Japan Society for the Promotion of Science, a Postdoctoral Research Associate in University of Southern California, US, a Lecturer in University of Tsukuba, Japan, a Research Associate in Institute for Molecular Science, Japan, and an Assistant Professor in Osaka University, Japan.

Reference

Katsuya Kimura, Taketoshi Matsumoto, Hirotomo Nishihara, Takatoshi Kasukabe, Takashi Kyotani, and Hikaru Kobayashi. Improvement of Cyclability of Li-Ion Batteries Using C-Coated Si Nanopowder Electrode Fabricated from Si Swarf with Limitation of Delithiation Capacity. Journal of the Electrochemical Society, 164 (6) A995-A1001 (2017).

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Renewable Energy Global Innovations features: Landscape control of nitrous oxide emissions during the transition from conservation reserve program to perennial grasses for bioenergy

Significance Statement

Renewable fuels are an integral part of the liquid fuels portfolio of the United States and in fulfilling the stipulations of the federal threshold of 80 billion liters of ethanol produced from cellulosic sources by 2022. This will necessitate planting approximately 21 million hectares with cellulosic crops such as switchgrass, a perennial grass native to the United States. Land currently enrolled in the Conservation Reserve Program (CRP) – about 12 million hectares – might be suitable for energy crops. Some of this area is seasonally wet, environmentally sensitive, and with limitation for annual cropping. Converting these CRP lands to energy crops may increase the emissions of nitrous oxide, a potent greenhouse gas, particularly when converting lands that are seasonally wet due to soil or topographic attributes. Low carbon footprint is critical to accrue the benefit of energy crops. For such crops to qualify as renewable, their greenhouse gas emissions must be at most 50% of those from fossil fuels. Therefore, nitrous oxide emissions must be kept low in the feedstock production phase. Controlling nitrous oxide emissions from these energy crops requires an in-depth understanding of the interactive effects of landscape properties, crops growth rates, nutrient, and hydrology.

The research conducted by Debasish Saha and colleagues at The Pennsylvania State University identifies the potential of growing sustainable energy crops on these CRP landscapes without increasing greenhouse gas emissions. The researchers measured nitrous oxide emissions from plots converted from CRP to switchgrass and Miscanthus in central Pennsylvania. The physiography of the experimental site, representative of the Appalachian Ridge and Valley region with cropped uplands and wet bottomland that are occasionally under CRP. The emissions from the plots of energy crops were compared to the emissions from adjacent, unconverted CRP land under different landscape positions with varying soil and hydrologic properties. The researchers also established an autonomous network of 144 soil moisture sensors installed at three soil depths in 48 monitoring points in the landscape to continuously measure soil moisture, an important factor for nitrous oxide emissions. The monitoring period extended from May to September of 2013 growing season, which includes a summer storm that saturated the soil – the perfect conditions to expect nitrous oxide emissions. Their research work is published in GCB Bioenergy.

Nitrous oxide is produced by soil microbes when soil mineral nitrogen from organic/inorganic fertilizer and other sources exceeds plant demand and coincides with wet soil conditions usually after a storm or snowmelt event. “The transition phase from CRP to energy crops is critical for nitrous oxide emissions as soil disturbance may increase nitrogen availability in excess of demand when plants are small and the root system is not extensive,” said Saha.

The authors realized that nitrous oxide emissions from energy crops increased above the CRP control baseline only in the wetter footslope positions. “While near-stream footslope soils with prolonged subsoil wetness had higher nitrous oxide emissions from energy crops than CRP, a large portion of the landscape had comparable emissions to those of CRP. The footslope positions of the landscape occupy at most a third of the lower part of the watershed. For this reason, about two-thirds of the set-aside conservation area (CRP) could be used for energy crops production.” Saha further added, “It is expected that large emissions from the footslope can eventually be curtailed as the grasses get established.”

Saha said “Apart from carbon benefits of energy crops, growing energy crops in these seasonally wet CRP lands usually on steep areas of the landscape can offer additional ecosystem services. Energy crops in these landscapes can function as riparian buffers to provide water-quality benefits by curtailing nutrient as well as sediment loads to surface and groundwater. Owing to vigorous biomass production by these grasses and little disturbance of the perennial rooting systems, these crops can store carbon in the soil because of their extensive below-ground carbon allocation.”

The outcomes of their study revealed that managing the conversion from CRP to energy crops while maintaining low nitrous oxide emissions could be optimized by designing a sufficient transition process that curtails co-occurrence of high mineral nitrogen and wet soils.

This research was funded by U.S. Department of Transportation Sungrant, the USDA, and the Richard King Mellon Foundation. Other research team members include Armen Kemanian, associate professor of production systems and modeling and Felipe Montes, research associate in Plant Science, Penn State; Jason Kaye, professor of soil biogeochemistry in Ecosystem Science and Management, Penn State; Paul Adler, research agronomist with the Pasture Systems and Watershed Management Research Unit, USDA-Agricultural Research Service; and Benjamin Rau, former USDA-Agricultural Research Service soil scientist, now a research ecologist with the USDA, Forest Service.

About The Author

Dr. Debasish Saha obtained his BSc in Agricultural Sciences with specialization in Agricultural Chemistry and Soil Science in 2008 from Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India. As a Junior Research Fellow of Indian Council of Agricultural Research (ICAR-JRF), he received his MSc degree in Soil Science from Punjab Agricultural University, Ludhiana, India in 2010. In 2015, he received his Ph.D. in Soil Science and Biogeochemistry under the supervision of Dr. Armen Kemanian at the Pennsylvania State University. His dissertation research investigated nitrous oxide (N₂O) emissions, a potent greenhouse gas, during the transition from Conservation Reserve Program grassland to perennial energy crops switchgrass and Miscanthus for renewable biomass energy production.

He is currently (2015-2017) appointed as a post-doc at the Department of Plant Science at the Pennsylvania State University. His post-doc research is focused on the core theme of enhancing the sustainability of organic cropping systems by mitigating N₂O emissions from soils. His research combines chamber-based N₂O monitoring, N₂O isotopomers, and microbial molecular techniques to quantify soil microbial processes contributing to N₂O production in interaction with tillage, cover crop, and manure management practices in a Reduced-Tillage Organic System Experiments.

For more information: Google Scholar ,  ResearchGate.  

Reference

Debasish Saha, Benjamin M. Rau, Jason P. Kaye, Felipe Montes, Paul R. Adler, and Armen R. Kemanian. Landscape control of nitrous oxide emissions during the transition from conservation reserve program to perennial grasses for bioenergy. GCB Bioenergy (2017) 9, 783–795.

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Renewable Energy Global Innovations features: Thinness- and Shape-Controlled Growth for Ultrathin Single-Crystalline Perovskite Wafers for Mass Production of Superior Photoelectronic Devices

Significance Statement

The commercialization of organic-inorganic hybrid perovskite light-absorber material has been hampered by factors such as environmental stability, substandard interface and defects. Focus has shifted to the single-crystalline perovskite which is believed to be defect free, has better stability, longer carrier lifetime and diffusion length, wider optical absorption spectrum, and lower trap-state-density.

Professor Shengzhong (Frank) Liu and colleagues have successfully used a dynamic flow microreactor system to grow geometry-controlled ultrathin single crystalline perovskite wafers of different ranges of thicknesses. Their work is published in Advanced Materials, 2016, 28, 9204-9209; Adv. Opt. Mater. 2016, 4 (11), 1829-1837; Sci. China Chem. 2017, DOI:10.1007/s11426-017-9081-3.

The authors employed a dynamic-flow reaction system. They used 2 spacers to separate and align 2 thin glass slides so as to limit the crystal growth to a slit channel. A peristaltic pump was used to achieve dynamic flow of the precursor solution.

The research team fabricated single crystalline wafers of approximately 150, 330, 670, and 1440 mm in thickness, which showed that the crystal growth was confined within the microreactor.

The authors observed no obvious grain boundaries and cracks from the scanning electron microscopy examination, indicating that the wafer is of  high single-crystalline quality throughout. The mapping analysis and line scan results of the scanning electron microscopy energy-dispersive x-ray spectroscopy show an even distribution as well as consistency in atomic ratio of carbon, nitrogen, lead, and iodine constituents of the produced wafer.

When the single crystalline perovskite wafer is compared with the microcrystalline thin films in UV-Vis-NIR spectrophotometry, the authors observed that the former displayed a significant red-shifted light absorption edge at 900 nm as compared with 800 nmfor the latter, a significant advantage for PV and optoelectronic applications.

From the thermogravimetric analysis, the single crystalline wafer is similar to bulk single crystals in thermal decomposition,  exhibiting stability at higher temperatures over the microcrystalline films.

The authors designed a hole only device to analyze the trap density of the single crystalline wafer by testing, at different biases, the evolution of space-charge-limited current. The trap density of both the single crystalline wafer and the large single crystals was found to be similar. The Hall effect is also similar for both the single crystalline wafer and the single large crystals.

To simulate an optoelectronic device, the team designed 100 photodetectors on the perovskite wafer, which demonstrated the feasibility of integrated circuits being mass produced on these wafers. At different bias voltages and illumination, the authors observed that at a 2V bias the photocurrent in the wafer was approximately 700 µA, while this was limited to only 2 µA for the microcrystalline thin films which is approximately 350 times smaller. The single crystalline wafer detector showed significant response  at 880 nm while the microcrystalline thin film device shows no response at all, which confirmed that the former has a broader optical absorption than the latter.

Reference

Yucheng Liu, Yunxia Zhang, Zhou Yang, Dong Yang, Xiaodong Ren, Liuqing Pang, and Shengzhong(Frank) Liu. Thinness- and Shape-Controlled Growth for Ultrathin Single-Crystalline Perovskite Wafers for Mass Production of Superior Photoelectronic Devices. Advanced Materials, 2016, 28, 9204-9209.

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