Renewable Energy Global Innovations features: A simplified model to study the location impact of latent thermal energy storage in building cooling heating and power system

Significance Statement

Environment protection, industrialization, saving energy and modernization have become pertinent issues in the recent years. Approximately 20-40% of energy consumption in most modern cities can be traced back to buildings. Therefore, the increase in demand for heating and cooling systems in these buildings calls for proper designs.

Building cooling heating and power system can be used to meet varying load demands with a single primary energy. When compared to traditional counterparts, this system posts low pollution, and high economic benefit coupled with high energy efficiency. Nevertheless, the energy supply units within the building cooling heating and power system have low thermal performance under part load working conditions owing to non-synchronized as well as varying electrical and heating user demands. For this reason, a match between the energy supply and user demands is critical in the actualization of the power system.

Tsinghua University researchers led by Dr. Xin Wang in collaborations with Dr. Yin Zhang at Sichuan University developed a simple model of phase change material in thermal energy storage for building cooling heating and power system by taking into account user fluctuating load. This was in a bid to assess the effect of various thermal energy storage locations on the energy consumption of the entire system. They also investigated the effect of number of transfer units of the system. Their work is published in peer-reviewed journal, energy.

The authors settled for a model with a gas turbine, absorption chiller/heat pump, and thermal energy equipment composed of phase change material. In order to reduce the primary energy consumption, the authors performed the numerical simulation of the system with varying phase change material-thermal energy storage positions. How to determine the optimal energy storage position for saving primary energy consumption? Upstream or downstream?

For comparison, the authors collected results from an office unit and a typical hotel. Then, they began to investigate the effects of the performance of the phase change material-thermal energy storage system on the energy saving of the entire system. They did the analysis in summer and winter conditions.

For traditional models without the thermal energy storage equipment, the authors recorded an average gas turbine electricity generation efficiency of 30.9% and 31.5% for the hotel in summer and winter respectively. For the office block, they recorded generation efficiency of 32.4% and 29.3% for summer and winter respectively.

In a bid to enhance the part load performance of the system, the authors integrated a phase change material thermal energy storage device in the building cooling heating and power system, which was located either upstream or downstream. They confirmed from their results that phase change material thermal energy storage improved the energy saving of the developed system and reduced the installed capacity of the energy supply gadget. Also, they found that the energy saving ratio of the proposed system increased with an increase in number of transfer units of the thermal energy storage.

Only the downstream configuration would reduce the installed capacity of absorption chiller/heat pump. Downstream position becomes more preferable when users loads fluctuate greatly. The outcomes of this study provides for a stable means to design efficient phase change material thermal energy storage for integration in the building cooling heating and power systems.

About The Author

Xin Wang
Research interests: Thermal energy storage in built environment，Sustainable energy application, Heat and mass transfer.

She has published 38 international journal papers (SCI H-index: 18) and 2 books or book chapters. She has presided 10 national research projects.

Awards: Second Prize of the Ministry of Housing and Urban-Rural Development of Construction Science and Technology (2015), First Prize of Sichuan Science and Technology Progress (2011), the Ministry of Education Award for New Century Outstanding Talents (2009), Second Prize of the Ministry of Education of Natural Science (2005).

About The Author

Yin Zhang
Research interests: Building energy efficiency, Thermodynamic optimization, Renewable energy system, Thermal Engineering.

He got his Ph.D. degree in Building Service Engineering from Tsinghua University in 2016. He is now a lecturer in Sichuan University. He has published 10 international journal papers.

Reference

Yin Zhang^1,2, Xin Wang¹, Yinping Zhang¹, and Siwen Zhuo¹. A simplified model to study the location impact of latent thermal energy storage in building cooling heating and power system. Energy, volume 114 (2016), pages 885-894.

Show Affiliations

1. Beijng Key Laboratory of Indoor Air Quality Evaluation and Control, Department of Building Science, Tsinghua University, Beijing, 100084, China
2. College of Architecture and Environment, Sichuan University, Chengdu, 610065, China

 

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Renewable Energy Global Innovations features: Geothermal exploitation from depleted high temperature gas reservoirs via recycling supercritical CO2: Heat mining rate and salt precipitation effects

Significance Statement

Geothermal energy is a desirable alternative to fossil energy. It can be exploited continuously and does not require any storage. For example, hot springs and other hot water reservoirs are conventional geothermal resources, while magma systems and hot deep rocks are considered unconventional resources with potential for geothermal exploitation.

Surface facilities as well as existing wells can be used for heat mining from depleted gas reservoirs. This comes with an economic advantage and extends the economic life of the reservoir. However, injecting water into high temperature reservoirs causes formation damage along with wellbore. Therefore, using water for heat transmission may not be applicable for geothermal exploitation. Researchers led by Professor Shaoran Ren from China University of petroleum proposed the use of supercritical carbon-dioxide as an alternative heat transmission fluid owing to its excellent thermal characteristics and unique mobility. Their work is published in journal, Applied Energy.

While using supercritical carbon-dioxide for heat mining, the authors dissolved the injected carbon dioxide in the water phase. They also vaporized water in the carbon-dioxide phase, which a continuous flow of the carbon-dioxide, salt precipitation could occur. Therefore, it wouldn’t be a good idea to ignore formation water evaporation. To simulate salt precipitation, the authors adopted mathematical models of precipitation and salt dissolution.

The authors implemented commercial software to simulate the geothermal exploitation process via carbon-dioxide injection, featuring permeability, salt precipitation, and water evaporation models. The software calculated heat transfer between formation rocks and fluids.

They observed that a change in the reservoir properties as well as the injection pressure affected the rate of carbon-dioxide flow and salt precipitation. This can affect the rate of heat production. They, therefore, used a sophisticated model that would offer guidance on screening depleted gas reservoirs for geothermal exploration.

The effects of salt precipitation were moderate and depended on reservoir conditions and back flow of formation water. However, high saline formation water can initiate reservoir damage. An increase in the injection pressure difference minimized the back flow of formation water, thus lessening the effects of salt precipitation. Also, injecting low saline water before injecting dry carbon-dioxide or after precipitation, are a few methods the authors proposed to reduce the effects of salt precipitation.

This study succeeded in developing a comprehensive model for the exploitation of geothermal resources using supercritical carbon-dioxide. Authors used the model to simulate the effects of formation water evaporation and salt dissolution on the rate of heat mining. They found out that depleted gas reservoirs have huge potential for geothermal exploitation.

Reference

Guodong Cui¹, Liang Zhang¹, Bo Ren², Chioma Enechukwu¹, Yanmin Liu¹ and Shaoran Ren¹. Geothermal exploitation from depleted high temperature gas reservoirs via recycling supercritical CO₂: Heat mining rate and salt precipitation effects. Applied Energy, volume 183 (2016), pages 837–852.

Show Affiliations

1. College of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
2. Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, Austin, TX 78712, USA

 

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Renewable Energy Global Innovations features: Hydrogen production by steam reforming of DME over Ni-based catalysts modified with vanadium

Significance Statement

A major challenge presents in the on-board synthesis of hydrogen from fossil fuels. There’s the need of a fuel processor that can effectively convert hydrocarbon fuels into hydrogen for various applications in fuel cells. However, hydrogen-rich gas for fuel cells application can be synthesized by the catalytic conversion of oxy-compounds and hydrocarbons, including propane, acetone, methanol, and dimethyl ether.

Among these potential compounds, catalytic conversion of dimethyl ether and methanol comes with effective performance and superior selectivity at low temperature. Methanol steam reforming is a potential approach for the on-board hydrogen production, and luckily, dimethyl ether steam reforming can be applied for the same purpose. Dimethyl ether steam reforming comes with lots of benefits including high heating value, superior self-ignition, and its environmentally friendly.

Collaborative research between scientists at Institute of Physical Chemistry Polish Academy of Sciences and University of Málaga in Spain studied the catalysts of vanadium and nickel in the dimethyl ether steam transforming. Their main goal for the study was to investigate hydrogen production and the varying processes undertaken in the steam reforming of dimethyl ether, while considering a second process involving methanol steam reforming. Their work is published in peer-reviewed journal, International Journal of Hydrogen Energy.

The authors prepared Vanadium-nickel catalysts through a multistage impregnation of nickel and vanadium compound making use of an alumina support. By varying vanadium content in the proposed samples, the authors were able to come up with three distinct samples. Ring and powder form specimens were tested.

The authors observed that in the methanol steam reforming at 350^°C, nearly complete methanol conversion was achieved irrespective of vanadium concentration. For non-catalytic analysis using quartz particles with the same size and weight as catalysts applied in the catalytic tests, the authors didn’t observe any activity at 400^° C. They realized that carbon monoxide and hydrogen were the main products without using a catalyst.

However, carbon monoxide and hydrogen were the initial products the authors collected when they fed a mixture of water and hydrogen over vanadium and nickel catalysts. Carbon dioxide appeared when the temperature was raised from 250^°C to above 300^°C. These outcomes indicated that methanol decomposition was the preliminary step when vanadium and nickel are used as catalysts.

The authors evaluated the activity of dimethyl ether without steam over vanadium-nickel catalysts. They recorded no conversion below 250^°C. When they use 0.5% Vanadium-nickel catalysts, the conversion increased linearly with temperature reaching 100% at 350^°C. At this point, methane and carbon dioxide were the principle products with low amounts carbon monoxide. Two main reactions marked the completion of dimethyl ether conversion at 500^°C. Hydrolysis of dimethyl ether and methanol steam reforming, which yielded hydrogen-rich gas reformate produced with hydrogen selectivity c.a. 60-70%.

Reference

Rafael Gonzalez-Gil^1,2, Concepcion Herrera², Maria Angeles Larrubia², Pawel Kowalik³, Izabela S. Pieta¹, and Luis J. Alemany². Hydrogen production by steam reforming of DME over Ni-based catalysts modified with vanadium. International journal of hydrogen energy, volume 41 (2016), pages 19781-19788.

Show Affiliations

1. Institute of Physical Chemistry Polish Academy of Sciences, 01-224 Warsaw, Poland.
2. Departamento de Ingeniería Química, Facultad de Ciencias, Universidad de Málaga, E-29071 Malaga, Spain.
3. New Chemical Syntheses Institute, 24-110 Pulawy, Poland.

 

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Renewable Energy Global Innovations features: Direct Conversion of Cellulose and Hemicellulose to Fermentable Sugars by a Microbially-Driven Fenton Reaction

Significance Statement

Lignocellulose is recalcitrant to enzymatic degradation due to the crystalline structure of the cellulose polymers and strong bonding to lignin, and the main components of lignocellulose include complex carbohydrate and aromatic polymers. Microbial degradation of lignocellulose is conventionally initiated by enzymes produced by lignocellulolytic fungi or bacteria.

A team of researchers led by Professor Thomas J. DiChristina from the Georgia Institute of Technology developed a microbially-driven Fenton reaction that fragments cellulose and hemicellulose, degrades cellodextrins and xylodextrins, and produces short-chain oligosaccharides and monomeric sugars in a single bioreactor. The research work is now published in Bioresource Technology.

According to the authors, the microbially-driven Fenton reaction was introduced to generate extracellular HO radicals that fragmented cellulose and hemicellulose, degraded cellodextrins and xylodextrins, and produced short-chain oligosaccharides and monomeric sugars in a single bioreactor system that operated at neutral pH conditions. Instead of the conventional lignocellulose-degrading enzymes, cellulose and xylan were fragmented and degraded by a microbially-driven Fenton reaction in a single bioreactor.

They confirmed the ability of the microbially-driven Fenton reaction to degrade carboxymethyl cellulose CMC and xylan in Fe(III)-amended liquid batch cultures exposed to nine alternating aerobic and anaerobic phases. The initial 78 h time period shows that the total number of carboxymethyl cellulose and xylan reducing ends increased sharply, indicating that shorter oligosaccharides were produced through degradation of the partially fragmented carboxymethyl cellulose and xylan polymers. The total number of xylan-reducing ends exposed during xylan fragmentation was 2-fold greater than the number of carboxymethyl cellulose reducing ends exposed during CMC fragmentation. The authors found that the rates of microbially-catalyzed Fe(III) reduction and O₂-catalyzed Fe(II) oxidation were not affected by the presence of carboxymethyl cellulose or xylan.

The newly developed microbially-driven Fenton reaction reported in this study was able to produce a suite of short-chain oligosaccharides and fermentable sugars that were subsequently transformed enzymatically to the more readily degradable bioplastic polyhydroxybutyrate (PHB; published in Applied and Environmental Microbiology). Their research thus laid the foundation for development of consolidated bioprocesses for lignocellulose degradation that may be linked to downstream production of a myriad of useful bioproducts, such as ethanol, butanol, biodiesel, bioplastic, and lactic acid.

Microbially-driven Fenton degradation of cellulose and xylan

About The Author

Dr. Thomas J. DiChristina received his BS in Chemical Engineering from the University of Rochester (Rochester, NY), MS in Physical Chemistry from the University of Bordeaux (Bordeaux, France), and PhD in Environmental Engineering Science from Caltech (Pasadena, CA). He was awarded a National Science Foundation Postdoctoral Fellowship to carry out postdoctoral research at the Woods Hole Oceanographic Institution (Woods Hole, MA). He currently holds the title of Full Professor in the School of Biological Sciences at Georgia Tech (Atlanta, GA) where he has been a faculty member for 24 years.

His areas of research expertise include the molecular mechanism of microbial metal respiration, bioremediation of hazardous organic and inorganic contaminants, and novel techniques for production of biofuel and biorefinery products from renewable lignocellulosic biomass.

About The Author

Dr. Ramanan Sekar received his B. Tech in Chemical Engineering from Anna University (Chennai, India), MS degree in Chemical Engineering from SUNY Buffalo (NY), and PhD in Biology from Georgia Tech.

His areas of research expertise include bioremediation of hazardous organic contaminants, and novel techniques for biofuel and biorefinery products from renewable lignocellulosic biomass. He recently joined Intel Corporation (Hillsboro, OR) as a Process Engineer in lithography.

About The Author

Dr. Hyun-Dong Shin received his PhD in Genetic Engineering from Kyungpook National University (Daegu, South Korea) and is currently a Research Scientist in the School of Biological Sciences at Georgia Institute of Technology (Atlanta, GA). He is author of approximately 130 scientific papers.

His areas of research expertise include enzyme and metabolic engineering for production of biofuel and biorefinery products from renewable lignocellulosic biomass and bioremediation of radionuclides by anaerobic metal-reducing microorganisms.

References

Ramanan Sekar, Hyun Dong Shin, Thomas J. DiChristina, Direct Conversion of Cellulose and Hemicellulose to Fermentable Sugars by a Microbially-Driven Fenton Reaction, Bioresource Technology 218 (2016) 1133–1139.

Sekar, R., H-D. Shin, and T. DiChristina. 2016. Activation of an otherwise silent xylose metabolic pathway in Shewanella oneidensis.  Applied and Environmental Microbiology, 82:3996-4005.

School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, United States.

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Renewable Energy Global Innovations features: Reproducing Statistical Property of Short-term Fluctuation in Wind Power Profiles

Significance Statement

Wind power generation which serves as a source of renewable energy faces certain challenges due to short-term fluctuations in power output. This led to the addition of a battery system in order to reduce these pitfalls and as a result, the effect of the short-term fluctuations in relation to the battery system needs to be evaluated. One means of evaluating this effect is the use of a power flow simulation.

A group of researchers from , Waseda University in Japan, proposed an innovative method whereby synthetic wind power profiles with high temporal resolutions for power flow simulation can be generated by reproducing plausible statistical behavior of a realistic short-term fluctuation. The work is now published in journal, Energy Procedia.

In order to achieve a realistic short-term fluctuation which occurs in wind power generation, the power flow simulation observes the time-series statistical behaviors. The methods used in achieving the realistic short-term fluctuation include; the previously used autoregressive mean average approach and the block bootstrap approach.

The authors further compared the statistical property of the short-term fluctuations generated from three different approaches; naive bootstrap, autoregressive mean average bootstrap approach and the block bootstrap coupled with evaluations made by finding the autocorrelation functions of the detrended sequence which stands for the typical short-term fluctuation in wind power generation.

Following the generation of ten plausible short-term fluctuations for each approach from a dataset of a case study in Japan, the lowest root mean square error of the autocorrelation functions was observed in the block bootstrap approach. This shows that the block bootstrap approach gave the highest accuracy amongst the three. It improved 26.5% from the autoregressive mean average approach.

The lowest root mean square error for variance sequences was also observed with the block bootstrap approach, which indicates that the generated short-term fluctuations possess realistic volatility.

The block bootstrap approach which exhibited plausible volatility and accuracy of the detrended sequence indicated an imaginative time-series statistical property of the real-world fluctuation in wind power generation which would be of relevance in determining the effects of the short-term fluctuations on battery systems of future wind energy technologies.

About The Author

Seigo Furuya received his B.Eng and M.Eng degree in electrical engineering and bioscience from Waseda University, Japan, in 2014 and 2016, respectively. His research interests are generating synthetic wind power generation profiles by statistical approach.

About The Author

Yu Fujimoto received his Ph.D. in engineering from Waseda University, Tokyo, Japan, in 2007. He is an Associate Professor at the Advanced Collaborative Research Organization for Smart Society (ACROSS), Waseda University.

His primary areas of interest are machine learning and statistical data analysis. His current research interests include data mining in energy domains especially for operating and controlling devices in smart grids, and statistical prediction of the power fluctuation under the large introduction of renewable energy sources. He is a Member of Information Processing Society of Japan.

About The Author

Noboru Murata received the B. Eng, M. Eng, and Dr. Eng degrees in mathematical engineering and
information physics from the University of Tokyo in 1987, 1989, and 1992, respectively. After working at the University of Tokyo, GMD FIRST in Germany, and RIKEN in Japan, since April 2000, he joined Waseda University in Japan where he is currently a professor.

His research interest includes the theoretical aspects of learning machines such as neural networks, focusing on the dynamics and statistical properties of learning.

About The Author

Yasuhiro Hayashi received his B. Eng., M. Eng., and D. Eng. degrees from Waseda University, Japan, in 1989, 1991, and 1994, respectively. In 1994, he became a Research Associate with Ibaraki University, Mito, Japan. In 2000, he became an Associate Professor with the Department of Electrical and Electronics Engineering, Fukui University, Fukui, Japan. He has been with Waseda University as a Professor of the Department of Electrical Engineering and Bioscience since 2009; and as a Director of the Research Institute of Advanced Network Technology since 2010. Since 2014, he has been a Dean of the Advanced Collaborative Research Organization for Smart Society at Waseda University.

His current research interests include optimization of distribution system operation and forecasting, operation, planning, and control concerned with renewable energy sources and demand response. Prof. Hayashi is a Member of the Institute of Electrical Engineers of Japan and the International Council on Large Electric Systems.

Reference

Furuya, S., Fujimoto, Y., Murata, N., Hayashi, Y. Reproducing Statistical Property of Short-term Fluctuation in Wind Power Profiles, Energy Procedia 99 ( 2016 ) 130 – 136.

Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.

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Renewable Energy Global Innovations features: W(Nb)Ox-based efficient flexible perovskite solar cells

Significance Statement

Perovskite solar cells are emerging photovoltaics that have attracted significant attention in industrial applications. Based on the superior attributes of the perovskite semiconductors, significant progress has been made. With planar and mesoporous architectures, high power conversion efficiency have been recorded in perovskite solar cells.

Electron selective layer is crucial to the photovoltaic performance of solar cells. High temperature treatment of the electron selective layer is imperative to achieve highly condensed and crystallized films for efficient perovskite solar cells. This extreme process increases the production cost and energy payback time. It also limits the application of perovskite solar cells in gadgets fabricated on plastic substrate. For this reason, it is indispensable to explore low-temperature substitutes.

A number of feasible approaches have been adopted to fabricate electron selective layers on plastic conductive substrates. Most of these methods implement planar configurations and do not employ mesoporous scaffold layer, which is normally synthesized at high temperature. Therefore, Dalian University of Technology researchers in China prepared amorphous niobium-modified tungsten oxide as an electron selective layer for flexible perovskite solar cells. The authors proved that WOx as a building block for electron selective layer could be fabricated at low temperature. Their work has been published in peer-reviewed journal, Nano Energy.

The authors prepared the electron selective layers from a mixture of tungsten ethoxide, ethanol and niobium ethoxide. The obtained precursor mixture was coated on the polyethylene naphthalate substrate and heated below 150 ^oC to achieve a smooth layer. They mixed 4-tert-butyl pyridine with lead chloride and N,N-dimethylformamide in a bid to optimize the crystallization process of perovskite layer. Silver was then evaporated on the samples’ surface to give the back contact.

The results from the x-ray diffraction spectroscopy indicated that the obtained electron selective layers were amorphous. Moreover, x-ray photoelectron spectroscopy results indicated that the predominant valence state of the layers was W⁶⁺ in addition to small amounts of W⁵⁺. The compound was therefore named WO_X.

The authors prepared for the first time amorphous WO_X though the solution approach. They found that this was a promising building block for low-temperature preparation of flexible perovskite solar cells. They developed an approach to modify optoelectronic behavior of electron selective layer using NbOx, which resulted in enhanced conductivity and donor density, suppressed charge combination and reduced surface traps states.

Using niobium-modified tungsten oxide as electron selective layer, high power conversion efficiencies up to 15.65% have been attained by flexible perovskite solar cells. The cells with electron selective layers prepared at room temperature also recorded a power conversion efficiency of 13.14%. The authors assessed the effect of the layer thickness on hysteresis characteristics of the cells. They suggested that a capacitance existed across the layer in the perovskite structure. The suggestion explained the effect of the layer thickness on the hysteresis attributes. The proposed approach will facilitate the development of novel and functional materials.

About The Author

Kai Wang received his bachelor degree in 2012 at Dalian University of Technology, China. And now he is a Ph.D candidate under supervisions of Professor Tingli Ma and Yantao Shi at the same university. His research interests focus on developing novel low temperature functional material as photo-anode for dye-sensitized solar and perovskite solar cells.

About The Author

Yantao Shi graduated from Lanzhou University in 2005 with a Bachelor’s degree, then studied at Tsinghua University for his Master’s degree and Ph.D from 2005 to 2010. As a visiting scholar, he worked at the Department of Physics, Hong Kong University of Science and Technology (HKUST) in the following two years. In 2012, he joined Dalian University of Technology as a lecture. Currently, he is a full professor in the Department of Chemistry at the same university.

His research interests focus on the third generation thin film solar cells, e.g. dye-sensitized solar cells and perovskite solar cells. His contributions include synthesizing novel photoelectric materials, revealing the effects of nanostructures on cell performance, improving long-term durability, and so on. He has published around 60 papers with more than 800 citations by other researchers.

About The Author

Tingli Ma graduated from Kyushu University with a Ph.D degree. In 2007, she was employed as a professor in state key laboratory of fine chemicals of Dalian University of Technology. In 2014, she joined the School Petroleum and Chemical Engineering of Dalian University of Technology in Panjin Campus, China. At the same time, she worked at the Graduate School of Life Science and Systems Engineering of Kyushu Institute of Technology, Japan.

She mainly studied on the third generation thin film solar cells including the dye-sensitized solar cells, quantum dot sensitized solar cells, and perovskite solar cells. Her contributions include developing novel electrode material, optimizing the device architecture, revealing the charge kinetic process, improving long-term durability, and so on.

Reference

Kai Wang¹, Yantao Shi¹, Liguo Gao², Rihan Chi¹, Kun Shi¹, Bingyi Guo¹, Liang Zhao¹, Tingli Ma^2,3. W(Nb)Ox-based efficient flexible perovskite solar cells: From material optimization to working principle. Nano Energy, volume 31 (2017), pages 424–431.

Show Affiliations

1. State Key laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, Dalian 116024, China
2. School Petroleum and Chemical Engineering, Dalian University of Technology, Panjin Campus, Panjin 124221, China
3. Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2–4 Hibikino, Wakamatsu, Kitakyushu, Fukuoka 808-0196, Japan

 

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Renewable Energy Global Innovations features: Co-Combustion Characteristics of Hydrothermally Treated Municipal Solid Waste with Coal in a Fluidized Bed

Significance Statement

Co-combustion of municipal solid biomass wastes and coal at high efficiency has been a challenge in recent time due to the hazardous nature of the waste gases generated in the process. Utilization of bubbling fluidized beds reactors, that use coal, has been called into question due these pollution effects. Measures have been taken to try and solve this problem that originates from the use of coal. In this paper, numerical and experimental models have been adopted for the simulation of the combustion process, within a bubbling fluidized bed reactor, so as to determine temperatures at which coal could be substituted with hydrothermally treated municipal solid waste.

A research team led by Professor Kunio Yoshikawa from Tokyo Institute of Technology and Associate Professor Tamer Ismail from Suez Canal University in Egypt, with Dr. Liang, Dr. Abd El-Salam and Prof. Yuqi Jin investigated the co-combustion characteristics of hydrothermally treated municipal solid waste with coal in a fluidized bed reactor. Their aim was to present models that use composite fuel (coal and municipal solid wastes) at least reactor modification. Their work is now published in the peer-reviewed journal Fuel Processing Technology.

Foremost, experiments had to be conducted using reliable CFD in order to predict crucial results and critical requirements for curbing and ensuring efficiency. The three approaches that were available for numerical simulations were: Euler-Lagrange approach, Euler-Euler approach and Discrete Element Method. Euler-Euler approach was adopted where ratios of 10, 20, 30 and 50% of the hydrothermally treated municipal solid waste were chosen to be tested at 700°C, 800 °C and 900 °C so as to determine the temperatures at which coal could be replaced with the hydrothermally treated municipal solid waste.

The research team had to determine the right temperature and mixture of the system that had the least emissions and yet could be operated at the least cost. They observed that for mixing ratios of 10 and 20% of the HT MSW there was a significant reduction in the CO outflow emission during the co-combustion with coal. Additional mixing of coal with the HT MSW lead to a further decrease in SO₂ emission from the combustion. Low levels of HCL were recorded for all the mixtures displaying a positive effect of the mixture. Nitrogen levels were also kept to a minimal as the blending mixing ratios of the HT MSW were increased.  Initially, high levels of NO were recorded due to increase in temperature but with the mixing of the HT MSW to 30% level, a significant drop was observed for all temperatures.

This research paper shows that with accurate simulation, trends for co-combustion can be predicted for various emitted gas species in the bed. This research sheds light into a promising way to simulate the combustion of solid waste in bubbling fluidized beds when using minimal coal. This study also reveals the features of a detailed structure for the combustion process inside the solid bed. Finally, it indicates the possibility of accepting the mixing ratio of the hydrothermally treated municipal solid waste, co-combusted with coal up to 30% without major modification of the coal-fired bubbling fluidized beds reactor.

About The Author

Dr. Tamer M. Ismail is an associate professor of Department of Energy and Fuel Science, Suez Canal University, Egypt. He obtained PhD in 2010, in Mathematical Modelling of MSW Incineration. He is one of the expert in the field of CFD of solid combustion and gasification having several research in this field. He is considered the pioneer in this field in Suez Canal University. He has a patent for CFD simulation code called, COMMENT- Code. Also, in the field of waste to energy he has several special work in designing many reactors, such as, fluidized bed, chemical looping combustor and bioreactor fermentor.

His major research areas are energy conversion, thermal engineering, combustion, gasification, waste treatment technologies, and he wrote many papers in this field. He works as research associate in Harbin Institute of Technology, Tokyo Institute of Technology and nstituto Politécnico de Portalegre, Universidade de Trás-os-Montes e Alto for combustion and gasification technologies.

About The Author

Dr. Kunio Yoshikawa is a professor of Department of Environmental Science and Technology, Tokyo Institute of Technology, Japan. He graduated from Tokyo Institute of Technology and obtained PhD in 1986. After graduation from Tokyo Institute of Technology, Prof. Yoshikawa worked for Mitsubishi Heavy Industries for one year, and then went back to his home university to become a research associate, associate professor and professor.

His major research areas are energy conversion, thermal engineering, combustion, gasification, waste treatment technologies and atmospheric environmental engineering, and he wrote more than 200 papers. He is an associate editor of Applied Energy. His main awards are AIAA (American Institute of Aeronautics and Astronautics) Best Paper Award in 1999, ASME (American Society of Mechanical Engineers) James Harry Potter Gold Medal in 2001, JSME (Japan Society of Mechanical Engineers) Environmental Technology Achievement Award in 2006, Fellow of JSME in 2008 and Best Educator Award of Tokyo Institute of Technology in 2014.

Reference

Liang Lu¹, T.M. Ismail², Yuqi Jin³, M. Abd El-Salam⁴, Kunio Yoshikawa¹. Numerical and experimental investigation on co-combustion characteristics of hydrothermally treated municipal solid waste with coal in a fluidized bed.  Fuel Processing Technology volume 154 (2016) pages 52–65.

Show Affiliations

1. Department of Environmental Science and Technology, Tokyo Institute of Technology, G5-8, 4259 Nagatsuta, Midori-Ku, Yokohama 226-8502, Japan
2. Department of Mechanical Engineering, Suez Canal University, Ismailia, Egypt
3. State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou 310027, China
4. Department of Basic Science, Cairo University, Giza, Egypt

 

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Renewable Energy Global Innovations features: Hysteresis-Suppressed High-Efficiency Flexible Perovskite Solar Cells Using Solid-State Ionic-Liquids for Effective Electron Transport

Significance Statement

Metallic oxides used as electron transport material in perovskite solar cells normally undergo high temperature process to attain their desired structural characteristics. However, the recent incorporation of friendly, low-temperature electron transport material also faces positive demanding situations due to the high cost of production and resultant low electron mobility.

In order to improve this technology, new research must be conducted in view of producing high electron mobility electron transport material, well-suited to a low-temperature process technology coupled with a low-cost production approach.

Researchers led by Professor Shengzhong (Frank) Liu from Shaanxi Normal University in China investigated a solid-state ionic-liquid as an electron transport material with the use of low-temperature processing to attain high efficiency flexible perovskite solar cells with good reproducibility. The research work is now published in the journal, Advanced Materials.

The authors discovered a reduction  in work function of indium-tin-oxide cathode whilst coated with 1-benzyl-3-methylimidazolium chloride solid-state ionic-liquid, enabling electron collection as a result of decreased interface barrier between the cathode and the perovskite absorber. The addition of the solid-state ionic-liquid also led to enhanced short-circuit current density and fill factor in the perovskite solar cells due to their wider bandgap.

The solid-state ionic-liquid coated with flexible poly(ethylene terephthalate)/indium-tin-oxide PET/ITO had a higher transparency and average transmittance approximately 88% in region of 400-450 nm and 400-800 nm respectively compared to the bare samples thereby showing its anti-reflective properties.

The authors were able to provide an appropriate solid-state ionic-liquid layer thickness of flexible perovskite solar cells because of their major role in output performance. A layer thickness of 10nm for the solid-state ionic-liquid was chosen.

Results from current density-voltage curves also showed a higher power conversion efficiency PCE of value 16.09% for perovskite solar cells based on (HC(NH₂)₂PbI₃)_0.85(CH₃NH₃PbBr₃)_0.15 with the solid-state ionic-liquid as an electron transport material compared with the absent electron transport material. Incident photon-to-current conversion efficiency, short-circuit current density, fill factor and energy levels were also confirmed with higher values.

The authors also discovered a heavily suppressed hysteresis in the current density-voltage. This was attributed to the increase in higher electron mobility as a result of the solid-state ionic-liquid as an electron transport material.

Results from dark current-voltage analysis showed a significant decrease of electron trap density in perovskite films deposited on substrates of the solid-state ionic-liquid coated with indium-tin-oxide which results in a large short-circuit current density.

With these attributes, the solid-state ionic-liquid used in this study as an electron transport material meets the requirement of a low-temperature processing and low-cost manufacturing process favors the technology involved in high efficiency flexible perovskite solar cells.

Reference

Yang, D.¹, Yang, R.², Ren, X.¹, Zhu, X.¹, Yang, Z.¹, Li, C.², Liu, S.^1,2 Hysteresis-Suppressed High-Efficiency Flexible Perovskite Solar Cells Using Solid-State Ionic-Liquids for Effective Electron Transport, Advanced Material 28 (2016) 5206-5213.

Show Affiliations

1. Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an, 710119, P. R. China.
2. Dalian National Laboratory for Clean Energy, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, P. R. China.

 

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Renewable Energy Global Innovations features: High-Efficiency Nanowire Solar Cells with Omnidirectionally Enhanced Absorption Due to Self-Aligned Indium-Tin-Oxide Mie Scatters

Significance Statement

Photovoltaic cells implementing high-index planar materials suffer from reflection losses. Micro-sized scattering particles as well as antireflection coatings have been applied to lessen this reflection. Nanoimprinted dielectric materials have been used to enhance the in-coupling of light in planar materials. The enhanced coupling can be discussed in terms of Mie resonances that scatter the light in the forward direction.

Nanowire solar panels are an important field owing to intrinsic benefits over the planar solar devices, leading to higher photocurrent and photovoltage. However, the size and shape of the nanowire are necessary for attaining high absorption efficiency and the highest photocurrent of the III-V nanowire solar cell has been below that of the optimum planar cells fabricated with the same materials.

Dutch scientists led by professor Jos Haverkort at the Eindhoven University of Technology developed a InP nanowire solar cell where the indium-tin-oxide reflection loss was reduced significantly and the nanowire absorption enhanced with respect to a planar contact by applying Mie scattering of the nanostructured transparent contact layer. Their work is published in peer-reviewed journal, ACS Nano.

In a bid to produce the cells, n-and p-doped InP layers were fabricated on an InP substrate. An etching mask was made of a silicon nitride layer was realized by nanoimprint lithography. The nanowires were then etched in a plasma etching chamber. The side walls were then etched by surface oxidation. Chemical etching followed to scrap the oxide. The nanowires were covered with silicon oxide and the spaces between them filled with benzocyclobutene. Finally, an indium-tin-oxide layer was deposited as a conductive layer. The full cell was exposed to light. Photocurrent density was then calculated.

The authors fabricated solar cells based on InP nanowires, which were then covered with silicon oxide to enhance adhesion with the material surrounding the layer. Benzocyclobutene layer was applied for insulation and planarization. It was then etched back to expose the ends of the nanowires. Benzocyclobutene was selected owing to its electrical insulation properties and transparency in the visible infrared. The indium-tin-oxide formed spherical particles because the deposited material stuck better on the InP than on the benzocyclobutene surface. The current-voltage of the nanowire solar cell was measured independently.

This paper shows that appropriately designed hemispherical nano-particles on top of the transparent top contact of the nanowire solar cell can enhance the absorption efficiency for the full wavelength and incident angle gap. Calculations as well as simulations indicated that forward Mie scattering was the approach behind this improvement. The absorption improvement that is wavelength averaged at normal incidence makes the self-aligned indium-tin-oxide hemispheres elementary design building blocks for solar cells based on nanowires. In this approach, the authors demonstrated a nanowire solar cell that was 17.8% efficient with a short-circuit current of 29.3 mA/cm2 measured at 1 sun incident light. This record efficiency is among the highest of III-V solar cells.

“Nanowire solar cells show enhanced light incoupling due to forward Mie scattering of the hemispherical ITO nanoparticles, but they also fundamentally outperform planar solar cells due to an enhanced light outcoupling in comparison with a planar solar cell. At V=Voc, a solar cell is not generating any current, implying that in a lossless cell, all absorbed light should be emitted externally”. Said Dr. Jos Haverkort.

About The Author

Dr. Jos E.M. Haverkort is a lecturer at the Eindhoven University of Technology. He currently specializes on III/V semiconductor nanowires for photovoltaic applications and in the optical study of hexagonal crystal phase group IV and III/V nanowires. Under his guidance, an 11.1% efficiency InP nanowire array solar cell was reported in 2013.

He has shown in a recent Nano Letter paper that a nanowire solar cell fundamentally outperforms a planar solar cell, which resulted in a top-down etched InP nanowire solar cell with 17.8% efficiency.

Journal References

Dick van Dam† , Niels J. J. van Hoof†‡, Yingchao Cui†, Peter J. van Veldhoven†, Erik P. A. M. Bakkers†§ , Jaime Gómez Rivas†‡, and Jos E. M. Haverkort*†. High-efficiency nanowire solar cells with omnidirectionally enhanced absorption due to self-aligned indium-tin-oxide mie scatters. ACS Nano, volume 10 (2016), pages 11414-11419.

Show Affiliations

† Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
‡ Dutch Institute for Fundamental Energy Research DIFFER, P.O. Box 6336, 5600 HH Eindhoven, The Netherlands
§ Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands  

Go To ACS Nano 

Y. Cui, D. van Dam, S.A. Mann, N.J.J. van Hoof, P.J. van Veldhoven, E.C. Garnett, E.P.A.M. Bakkers, J.E.M. Haverkort, Boosting solar cell photovoltage via nanophotonic engineering, Nano Lett 16, 6467-6471 (2016).

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)