Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries
Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries Significance Statement Li-ion batteries are among the most promising, efficient and common high-energy-density systems for electrochemical energy storage. There have been increasing demands for high-performance, inexpensive and safe batteries for electronics, electric vehicles and other energy storage applications In batteries, electrolytes play the role as the medium for the transfer of charges between a pair of electrodes i.e. cathode and anode. At present, gel polymer electrolytes (GPEs) have gained much attention compared to both solid polymer electrolytes and liquid electrolytes. Gel polymer electrolytes are faster charging/discharging, and potentially higher power density compared to liquid electrolytes. However, ion permeability of gel polymer electrolytes is orders of magnitude lower than that of liquid electrolytes, mainly because of the polymeric structure which limits the ion mobility. The development of high capacity anode to replace carbon-based materials, commonly used for commercial LIBs, is another active research area for high-performance LIBs. Li-alloying anodes (Si, Sn, Ge etc.) have much higher Li storage capacity than commercial carbon-based anodes. Among them, Silicon (Si) has been identified as one of the best candidates. Si has a high theoretical specific capacity of 4200 mAh g-1, a very low lithiation potential < 0.5 V vs. Li/Li+, and is naturally abundant and environmentally benign. In this research by Pandey et al, two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. The infiltrated gel electrolyte was able to effectively accommodate the stress/strain due to the very large Si volume change (up to 400%) during charge-discharge which has been a critical limiting factor for Si anodes. The Si-VACNFs electrodes show high specific capacity, good rate performance and long cycling stability in such a solid-like, flexible GPE. The results of this study may lead to the development of solidstate lithium-ion batteries using the vertical 3D nanostructured electrodes and may be applicable for novel flexible thin-film microbatteries.
Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries
Figure Legend:The figure shows the optical images of a flexible gel polymer electrolyte film, SEM images of a VACNF array sputter-coated with silicon shell as a Li-ion battery anode and the electrode infiltrated with the gel electrolyte film, the charge/discharge curves at specified cycles, and the long-term cycling stability.
Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries
About The Author Jun Li is a Professor in the Chemistry Department of Kansas State University. He received Ph.D. in Chemistry from Princeton University in 1995. His research is focused on integrating nanostructured materials, particularly carbon nanotubes and inorganic nanowires, into biosensors, neural electrical interface, thermal interface materials, nanoelectronics, pathogen detection, and three-dimensional architectured electrode materials for solar energy conversion and electrical energy storage.
About The Author Gaind P. Pandey is a Research Associate at Department of Chemistry, Kansas State University, KS, USA. He received Ph.D. degree in Physics from Pt. Ravishankar Shukla University, Raipur, India in 2010. Before joining the present group at Kansas State University, he was Postdoctoral Associate at Center for Autonomous Solar Power (CASP), Binghamton University, USA. His research focuses on the developing solid-state Li-ion batteries and high energy density supercapacitors using solid-like gel polymer electrolytes including ionic liquid gels.
Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries
Journal Reference ACS Appl. Mater. Interfaces, 2015, 7 (37), pp 20909–20918. Gaind P. Pandey1, Steven A. Klankowski1, Yonghui Li2, Xiuzhi Susan Sun2, Judy Wu3, Ronald A. Rojeski4, Jun Li*1 Show Affiliations 1. Department of Chemistry,Kansas State University, Manhattan, Kansas 66506, United States 2. Department of Grain Science and Industry,Kansas State University, Manhattan, Kansas 66502, United States 3. Department of Physics and Astronomy,University of Kansas, Lawrence, Kansas 66045, United States 4. Catalyst Power Technologies, 200 Carlyn Avenue, Suite C, Campbell, California 95008,United States Abstract This study demonstrates the full infiltration of gel polymer electrolyte into silicon-coated vertically aligned carbon nanofibers (Si-VACNFs), a high-capacity 3D nanostructured anode, and the electrochemical characterization of its properties as an effective electrolyte/separator for future all-solid-state lithium-ion batteries. Two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. In the first method, the drop-casted gel polymer electrolyte is able to fully infiltrate into the open space between the vertically aligned core–shell nanofibers and encapsulate/stabilize each individual nanofiber in the polymer matrix. The 3D nanostructured Si-VACNF anode shows a very high capacity of 3450 mAh g–1 at C/10.5 (or 0.36 A g–1) rate and 1732 mAh g–1 at 1C (or 3.8 A g–1) rate. In the second method, a preformed gel electrolyte film is sandwiched between an SiVACNF electrode and a Li foil to form a half-cell. Most of the vertical core–shell nanofibers of the SiVACNF anode are able to penetrate into the gel polymer film while retaining their structural integrity. The slightly lower capacity of 2800 mAh g–1 at C/11 rate and ∼1070 mAh g–1 at C/1.5 (or 2.6 A g–1) rate have been obtained, with almost no capacity fade for up to 100 cycles. Electrochemical impedance spectroscopy does not show noticeable changes after 110 cycles, further revealing the stable interface between the gel polymer electrolyte and the Si-VACNFs anode. These results show that the infiltrated flexible gel polymer electrolyte can effectively accommodate the stress/strain of the Si shell due to the large volume expansion/contraction during the charge–discharge processes, which is particularly useful for developing future flexible solid-state lithium-ion batteries incorporating Si-anodes. Copyright © 2015 American Chemical Society
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/effective-infiltration-gel-polymer-electrolyte-siliconcoated-vertically-aligned-carbon-nanofibers-anodes-solid-state-lithium-ion-batteries/
Renewable Energy Global Innovations the World’s leading source of renewable energy research news: featuring the technologies and innovations that will lead to a greener tomorrow (https://reginnovations.org )
A eutectic mixture of galactitol and mannitol as a phase change material for latent heat storage
A eutectic mixture of galactitol and mannitol as a phase change material for latent heat storage Significance Statement Galactitol and mannitol are promising candidates for use in thermal energy storage (TES) applications due to their high volumetric energy densities, sharp phase change temperatures, non-corrosive properties, and large abundances in Nature. However, the polyols suffer from poor cyclic thermal stability and eventually oxidize to derivatives that exhibit relatively poor heat capacities when used separately. In this work, we have studied the thermophysical properties and cyclic stability of a eutectic mixture of galactitol and mannitol to establish its suitability as a phase change material (PCM) for use in thermal energy storage applications. The eutectic mixture showed minimal change in the latent heat of fusion as well as melting point after 20 heating/cooling cycles in air or under an atmosphere of nitrogen and exhibited excellent oxidative stability. Furthermore, the eutectic mixture displayed a negligible change in melting point and latent heat of fusion after 100 heating/cooling cycles under an atmosphere of nitrogen. These results indicate that a eutectic mixture of galactitol and mannitol may constitute a potential phase change material for use in medium temperature thermal energy storage applications and contribute to the understanding of phase equilibria of polyol-blends.
A eutectic mixture of galactitol and mannitol as a phase change material for latent heat storage
About The Author Abhijit Paul earned his M.S. in Polymer Science from Tezpur University in 2003. He has 4 years of industrial experience in rubber compounding and formulation of high performance organic coatings. He received his Ph.D. in Polymer Chemistry from Oklahoma State University in 2012. He worked as a postdoctoral fellow from 2012-2015 at The University of Texas at Austin. Currently, he is working as a postdoctoral research associate in the Department of Polymer Science and Engineering, University of Massachusetts, Amherst.
About The Author Li Shi received a B.E. degree in Thermal Engineering from Tsinghua University, a M.S. in mechanical engineering from the Arizona State University and a Ph.D. in Mechanical Engineering from the University of California, Berkeley. He is currently a Professor in the Department of Mechanical Engineering at the University of Texas at Austin where he leads efforts directed toward the synthesis and study of nanomaterials for use in a broad range of thermal applications.
A eutectic mixture of galactitol and mannitol as a phase change material for latent heat storage
About The Author Christopher W. Bielawski received a B.S. in chemistry from the University of Illinois, Urbana-Champaign and a Ph.D. in chemistry from the California Institute of Technology. After spending about 10 years in Austin as a professor of chemistry, he moved his research program to the Ulsan National Institute of Science and Technology where he is a part of a new initiative that is focused on the development of novel carbon-based materials.
A eutectic mixture of galactitol and mannitol as a phase change material for latent heat storage
Journal Reference Energy Conversion and Management, Volume 103, 2015, Pages 139–146. Abhijit Paul1,Li Shi2,Christopher W. Bielawski3,4 1. Department of Chemistry and Biochemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, United States 2. Department of Mechanical Engineering, University of Texas at Austin, 204 E. Dean Keaton St. Stop C2200, Austin, TX 78712, United States 3. Center for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan 689-798, Republic of Korea 4. Department of Chemistry and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea Abstract The thermophysical properties of mixtures of galactitol and mannitol were examined via differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD) analysis. The aforementioned sugars were found to form a eutectic mixture at a 30:70 molar ratio of galactitol and manntitol, and displayed a melting point of 153 °C while maintaining a high latent heat of fusion (ΔHfus = 292 J g−1). The XRD data revealed that the eutectic mixture contained the α, β, and δ forms of mannitol with the δ form being the major component. By varying the temperature ramp rates utilized in the DSC measurements from 0.5 °C min−1 to 20 °C min−1, the heat of crystallization as well as the crystallization temperature increased (c.f., ΔHcrys: 64 J g−1 → 197 J g−1; Tc: 68 °C → 105 °C). In addition, the temperature and the enthalpy of crystallization were also improved by up to 34% through the addition of small quantities (up to 0.5 wt%) of nucleating agents, such as graphite powder or silver iodide. After 100 heating/cooling cycles under an atmosphere of nitrogen, the heat of fusion of the eutectic mixture decreased by only 4% with no change in the melting point, and the mixture appeared to be chemically stable according to a Fourier transform infrared (FT-IR) spectroscopic analysis. Collectively, these data indicate that the eutectic mixture exhibits excellent cyclic stability under ambient atmospheres and offers potential for use in thermal energy storage applications.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/correlations-among-structure-compositionelectrochemical-performances-wo3-anode-materials-lithium-ion-batteries/
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Correlations among structure, composition and electrochemical performances of WO3 anode materials for lithium ion batteries
Correlations among structure, composition and electrochemical performances of WO3 anode materials for lithium ion batteries Significance Statement Lightweight, Lowcost batteries with high energy and power densities can meet the continuous energy demands and realize the cyclic nature of renewable energy source effectively. Rechargeable lithium-ion batteries are one of the most prosing power sources for portable electronics (e.g. mobile phones and computers), defence, and hybrid electric vehicles (HEVs), etc. due to its high energy dencity, light weight design and flexibility. In batteries, electrode plays an important role for the electrochemical performance. Among the various anode materials, nanostructured transition metal oxides attract particular interests due to their substantial advantages such as short transport path length for both electrons and Li+, large contact surface area between the electrode and electrolyte, and large flexibility and toughness for accommodating strain introduced by Li+ insertion and extraction. However, the poor capacity retention upon cycling and poor rate capacity remain the major challenges for practical applications. In general, structural properties are strongly related to the electrochemical perforamnce of anode materials for Li-ion batteries. In this work, the correlation among structure, composition and electrochemical performance of WO3 anode materials for lithium ion batteries were reported. The results of this study as follows: Firstly, the effects of residual precursor ion in the channels and crystal structure on the charge/discharge performance of WO3 were studied. It was found that NH4+, NH3 and Li+ in the precursor can incorporate into the newly formed hexagonal tunnels. Residual NH4+, NH3 and Li+ in the channels are crucial for stabilizing hexagonal WO3. However, most of the NH4+ and NH3 molecule were released during the heat treatment or insertion/extraction process, meanwhile, Li+ are two small to stabilize the hexagonal structure. So the hexagonal framework collapsed in an exothermic/electrochemical reaction into monoclinic structure. The releasing of NH3 during the insertion/extraction process caused the irreversible lithiation. Therefore, the electrochemical properties strongly depend on the intercalation of stabilizing nutral or cationic species. Thus, the monoclinic structure is more stable than hexagonal structure during the insertion/extraction process, and shows a better cycle life. Secondly, the lithiation noticeably improves the specific capacity and rate capacity of WO3. Two effects of lithiation are considered: On the one hand, the amount of Li+ remained in the solid structure of WO3 can reduce irreversible change of monoclinic structure during charging-discharging process and as a compensation for the loss of discharge capacity.Morever, Li+ can increase the electron conductivity of WO3. This work sheds some lights for the development of high performance anode materials through the modification of crystal structure and ions in the channels.
Correlations among structure, composition and electrochemical performances of WO3 anode materials for lithium ion batteries
Figure Legend: The figure shows the schematic crystal structure, TEM images and the cycling performance of hexagonal and monoclinic WO3.
Correlations among structure, composition and electrochemical performances of WO3 anode materials for lithium ion batteries
About The Author Pu Li is currently a graduate student at the Southwest Petroleum University. His research interest is focusing on the preparation of transition metal oxides and its application in lithium ion batteries. His current research is focusing on the influence of structure of anode materials on the electrochemical properties.
About The Author Ying Zhou is a professor at the School of Materials Science and Engineering, Southwest Petroleum University, Chengdu, China. He received his BSc and MSc in materials science from Central South University, China, in 2004 and Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, in 2007, respectively. In 2010, he received his PhD under the supervision of Prof. Greta R. Patzke at University of Zurich, Switzerland. After staying in the same group as a postdoctoral researcher, he received Humboldt Fellowship and worked with Prof. Jan-Dierk Grunwaldt at Karlsruhe Institute of Technique, Germany. His research interests are in the areas of functional materials for energy conversion and storage as well as in situ characterization (FT-IR, XRD and XAFS) techniques.
Correlations among structure, composition and electrochemical performances of WO3 anode materials for lithium ion batteries
Journal Reference Electrochimica Acta, Volume 192, 20 February 2016, Pages 148–157. Pu Li1,2, Xing Li2, Ziyan Zhao2, Mingshan Wang2, Thomas Fox3, Qian Zhang2, Ying Zhou1,2 Show Affiliations 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Xindu Rd. 8, Chengdu 610500, China 2. The Center of New Energy Materials and Technology, School of Materials Science and Engineering, Southwest Petroleum University, Xindu Rd. 8, Chengdu 610500, China 3. Department of Chemistry, University of Zurich, Wintherthurestrasse 190, CH-8057 Zurich, Switzerland Abstract Suitable host structure for lithium insertion and extraction is crucial for lithium-ion batteries. Tungsten trioxides (WO3) are particularly interesting materials for this purpose. In this work, the influences of structure and composition of WO3 on the charge/discharge performances of Li-ion batteries are systematically investigated. Firstly, lithiated tungsten trioxides (Li-WO3) are successfully synthesized by a hydrothermal method followed by annealing at different temperatures (200–600 °C). It is found that the hexagonal framework collapses and gradually transforms to the monoclinic phase due to the release of NH4+ and NH3 molecules. Unexpectedly, monoclinic WO3 reveals better performances than that of hexagonal WO3. Among all the investigated samples, the lithiated WO3 annealed at 500 °C exhibits the highest discharge capacity and cycle performance (703 mAh g−1 after 10 cycles). We believe that the Li+ remained in the solid structure of WO3 can lead to a more stable structure. In addition, Li+ could inhibit the oxidation of W5+ during the heat treatment process, which increases the electron conductivity of WO3. Our results indicate that the electrochemical properties of WO3 are strongly related to the residual precursor and crystal structure.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/correlations-among-structure-compositionelectrochemical-performances-wo3-anode-materials-lithium-ion-batteries/
Renewable Energy Global Innovations the World’s leading source of renewable energy research news: featuring the technologies and innovations that will lead to a greener tomorrow (https://reginnovations.org )
A Sustainable Route from Biomass Byproduct Okara to High Content Nitrogen-Doped Carbon Sheets for Efficient Sodium Ion Batteries
A Sustainable Route from Biomass Byproduct Okara to High Content Nitrogen-Doped Carbon Sheets for Efficient Sodium Ion Batteries Significance Statement Biomass is confirmed as potential sustainable feedstock to develop low-cost, high-capacity, and naturalabundant energy storage devices. Recently, the group of Prof. Yan (from Soochow University, China) synthesized carbon-based materials derived from biomasses such as organic waste products that otherwise possess no economic value, and explored their applications in wearable sodium ion battery (as shown in the picture). They developed a sustainable route from biomass byproduct okara that have a high level waste each year around the globe to high content (about 9.89 at.%) nitrogen-doped carbon sheets for sodium ion batteries. The reported materials provides a straightforward way to develop electrode materials for inexpensive and surprisingly long cycle-life sodium ion battery, which delivers a specific capacity of 292.2 mAh g-1 and be stable for 2000 cycles with nearly 100% coulombic efficiency. Moreover, our materials shows an energy density as high as 146.1 Wh kg−1 (Fig. 4B), which is much higher than those reported in the literature for conventional hard carbon (109.3 Wh kg−1), carbon nanofibers (87.1 Wh kg−1), and reduced graphene oxide (87.2 Wh kg−1). The feasibility of the material in full sodium ion battery is confirmed to deliver a stable capacity of 103 mAh g−1, which provides a wide range of applications in the field of energy storage coming from the solar energy, hydropower, tidal energy, and geothermal heat.
A Sustainable Route from Biomass Byproduct Okara to High Content Nitrogen-Doped Carbon Sheets for Efficient Sodium Ion Batteries
About The Author Chenglin Yan is a full professor at the Soochow University and executive director of key laboratory of advanced carbon materials and wearable energy technology in Suzhou, China. He received his PhD from Dalian University of Technology in 2008. In 2011 he became a staff scientist and a group leader at the Leibniz Institute in Dresden. In 2013, the IFW-Dresden awarded Dr. Chenglin Yan the ‘‘IIN Research Prize 2013’’ for his group’s excellent research work. He received the Thousand Young Talents Award from the Chinese Thousand Talents Program in the year of 2014.
A Sustainable Route from Biomass Byproduct Okara to High Content Nitrogen-Doped Carbon Sheets for Efficient Sodium Ion Batteries
Journal Reference Advanced Materials, January 20, 2016, Volume 28, Issue 3, Pages 393–587. Tingzhou Yang,Tao Qian, Mengfan Wang, Xiaowei Shen, Na Xu, Zhouzhou Sun, Chenglin Yan College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou Key Laboratory of Advanced Carbon Materials and Wearable Energy Technology, Soochow University, Suzhou, China Abstract A sustainable route from the biomass byproduct okara as a natural nitrogen fertilizer to high-content Ndoped carbon sheets is demonstrated. The as-prepared unique structure exhibits high specific capacity (292 mAh g−1) and extremely long cycle life (exceeding 2000 cycles). A full battery is devised for the practical use of materials with a flexible/wearable LED screen.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-energy-storage-system/sustainable-route-biomass-byproduct-okarahigh-content-nitrogen-doped-carbon-sheets-efficient-sodium-ion-batteries/
Renewable Energy Global Innovations the World’s leading source of renewable energy research news: featuring the technologies and innovations that will lead to a greener tomorrow (https://reginnovations.org )
Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint and fouling mitigation
Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint and fouling mitigation Significance Statement The latest report of Energy Consumption in the UK (2015, Chapter 4) stated that the total industrial energy consumption in the UK was 24.0 million tonnes of oil equivalent (Mtoe) in 2014. The major process industries (Chemicals, food, steel, mechanical engineering and paper) were responsible for 45.5% of total industrial energy consumption. Heat integration technologies have been widely studied because of increasing the concerns about how energy is utilized and recovered in the existing industrial processes. An industrial plant may need to be retrofitted several times throughout its lifetime to improve energy efficiency and/or to meet the increased production rate. There are various strategies to achieve energy savings in industry, for example, reducing the use of utilities, modifying appropriate heat network topology, upgrading heat transfer units, installing additional heat transfer area, repiping streams and reassigning heat recovery matches. In this work, heat transfer intensified techniques have been developed in the context of process integration. The use of heat transfer intensification in process integration has many benefits. First, intensified heat exchangers require less heat transfer area for a given heat duty because of higher heattransfer coefficients. Second, the heat transfer capacity for the given heat exchanger can be increased without changing its physical size. Third, the use of heat transfer intensification can mitigate exchanger fouling problems which are commonly expressed as production losses, health and safety hazards, increased energy consumption with related greenhouse-gas emissions, and maintenance costs due to antifouling and cleaning costs. The new proposed approach presents a detailed heat exchanger network (HEN) retrofitting model comprising well-known empirical equations for fouling and the equations for exchanger performance (such as cleaning, heat transfer intensification, pressure drops, energy balance, and temperature driving force). A two-loop iterative algorithm has been developed to solve the large scale HEN mathematical programming problems efficiently. From industrial cases, it can be found that, the traditional methods that didnâ&#x20AC;&#x2122;t considering fouling effects might be not suitable for HEN retrofitting problems due to the considerable energy losses if frequent cleaning activities occur in many exchangers. More importantly, according to operational safety, the pressure drop of each exchanger must be restricted under a maximum value to avoid the damage caused by the unit over-vibration. Thus, the new proposed approach has advantages over the existing methods. It can achieve greater retrofit profits with higher energy saving, longer exchanger operating times, and reasonable pressure drops, demonstrating the best economic trade-offs among energy savings, investment and operating periods in HEN retrofit problems.
Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint and fouling mitigation
About The Author Dr. Ming Pan is currently working as a research associate at the Department of Chemical Engineering and Biotechnology at University of Cambridge (from Sep 2014), and previously worked (research associate) in the School of Chemical Engineering and Analytical Science at University of Manchester (from Nov 2009 to Sep 2014). He has interdisciplinary research skills from Engineering (industry design and analysis), Applied Mathematics (modelling and optimisation), Energy (heat recovery and integration, power plants and CO2 capture), Operational Research (scheduling, planning, supply chain), and Computer Science (programming, semantics, data analysis, and software development). He is interested in Process systems engineering, Energy systems engineering, Mathematical programming, Modeling, Optimization, Ontology, Semantics, Big Data, Eco-industrial park, Process integration, Heat exchanger networks, Power plant, CO2 capture, Supply chain, Smart Grids, Scheduling, and Planning.
Improving heat recovery in retrofitting heat exchanger networks with heat transfer intensification, pressure drop constraint and fouling mitigation
Journal Reference Applied Energy, Volume 161, 1 January 2016, Pages 611-626. Ming Pan1, Igor Bulatov2, Robin Smith2 Show Affiliations 1. Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA, UK 2. Centre for Process Integration, School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M13 9PL, UK Abstract Implementing heat transfer intensified techniques are now recognised as an efficient retrofit way of improving energy saving in heat exchanger networks (HENs). This not only increases heat recovery, but also prolongs exchanger operating time due to its effect on fouling mitigation. Compared with most of the existing work of HENs based on very simple assumptions for fouling effect, this paper addresses more accurate and complex fouling models reported recently (Yang et al., 2012). Due to the dynamic features of fouling, integration of dynamic equation of fouling rate is used to estimate fouling resistance at different operational times. The novelty of this paper is to present new insights to implementation of heat transfer intensified technologies for HEN retrofitting. It is the first study to implement hiTRANÂŽ (one commercial tube-insert technology) into heat exchangers to increase HEN heat recovery with the consideration of detailed exchanger performances including heat transfer intensifications, pressure drop constraints, and fouling mitigation. The overall retrofit profit is maximized based on the best trade-off among energy savings, intensification implementation costs, exchanger cleaning costs, and pump power costs. To solve such complex optimization problems, a new mixed-integer linear programming (MILP) model has been developed to consider fouling effects in retrofitting HENs with heat transfer intensification. An efficient iterative optimization approach is then developed to solve the MILP problem. In case studies, the new proposed approach is compared with the existing methods on an industrial scale problem, demonstrating that the new proposed approach is able to obtain more realistic solutions for practical industrial problems.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/improving-heat-recovery-retrofitting-heat-exchangernetworks-heat-transfer-intensification-pressure-drop-constraint-fouling-mitigation/
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Steady-state investigation of water vapor adsorption for thermally driven adsorption based greenhouse air-conditioning system
Steady-state investigation of water vapor adsorption for thermally driven adsorption based greenhouse air-conditioning system Significance Statement Photosynthesis and evapotranspiration are the basic phenomena in plants’ growth by which the water vapors are released into the air and increases the greenhouse humidity continuously. Therefore, plants remain in danger of insects’, pests’, and fungus’ attack and condensation/dripping of water vapors. During photosynthesis, the plant releases half of the water vapors into the air which was sucked from the roots. In addition, humidity is also increased due to evapotranspiration i.e. evaporation from the soil and transpiration from the plants. Ideal temperature and humidity requirements for a plant depends on its ideal vapor pressure deficit which varies according to the growth/maturity stage, weather conditions, and water stresses. Therefore, present study investigates adsorption based air-conditioning (AC) systems in order to achieve the sensible and latent load of greenhouse AC distinctly. These systems are environment friendly and can be operated on solar energy and/or low grade waste heat. The study shows that greenhouse AC involves in higher relative humidity (RH) than humans AC. Therefore, two kinds of carbon based adsorbents (CBAs) are experimentally investigated for water vapor adsorption equilibrium, and the results are compared with conventional water adsorbent, silica-gel. The results are analysed by various adsorption models, and consequently isosteric heat of adsorption is determined. Dubinin–Astakhov and Guggenheim–Anderson–De Boer adsorption models successfully represent the adsorption equilibrium of CBAs and silica-gel, respectively. Analysis on ideal adsorption AC cycle are performed, and steady-state moisture cycled (MCSS) is determined for three demand categories of RH i.e. 60%, 40% and 20%. For RH ≥ 40%, it is revealed that the CBAs possess not only much higher MCSS as compared to silica-gel but also requires much lower regeneration temperature. On the other hand silica-gel based AC systems were found the only applicable solution for RH ≤ 20%. The study concludes that the CBAs could be potential adsorbents for greenhouse AC and can also be operated on low regeneration temperature preferably via solar heat.
Steady-state investigation of water vapor adsorption for thermally driven adsorption based greenhouse air-conditioning system
About The Author Muhammad Sultan (Engr. Dr.) is a Teaching/Research Faculty Member in the Department of Agricultural Engineering, Bahauddin Zakariya University, Multan, Pakistan since 2009. He is an HEC Approved Supervisor by Higher Education Commission Pakistan. He also worked as Research Support Staff at International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University from 2014-2016. He received Dr. Eng. (Ph.D.) in Energy & Environmental Engineering from Kyushu University, Japan in 2015. He obtained B.Sc. and M.Sc. (Hons.) in Engineering from University of Agriculture, Faisalabad, Pakistan with specialization in Agricultural and Environmental Engineering, respectively. By means of experiments and numerical simulation, his key research is focused on adsorption cooling, desiccant air-conditioning, adsorption heat pump, and evaporative cooling, particularly for: characterization of adsorbent/refrigerant pairs, system performance, agricultural and livestock applications, and M-Cycle application etc.
About The Author Takahiko Miyazaki (Prof. Dr.) is an Associate Professor in the Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University, Japan. He is also actively working in Thermal Science and Engineering Division, International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, Japan. He received Ph.D. degree in Engineering with specialization in Thermal Engineering. With experiments and numerical simulations, his research areas are focused on adsorption heat pump, adsorption heat exchangers, waste heat utilization, close and open cycle adsorption cooling, desiccant air-conditioning, M-Cycle, renewable energy utilization etc. He has published many scientific articles in international journal and conferences. Furthermore, he also holds many book chapters in the relevant field.
Steady-state investigation of water vapor adsorption for thermally driven adsorption based greenhouse air-conditioning system
Journal Reference Renewable Energy, Volume 86, February 2016, Pages 785-795. Muhammad Sultan1,3, Takahiko Miyazaki2,3, Bidyut Baran Saha1,3, Shigeru Koyama1,2,3 Show Affiliations 1. Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-koen 6-1, Kasuga-shi, Fukuoka 816-8580, Japan 2. Faculty of Engineering Sciences, Kyushu University, Kasuga-koen 6-1, Kasuga-shi, Fukuoka 8168580, Japan 3. International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan Abstract In the present study, water vapor adsorption onto silica-gel, activated carbon powder (ACP) and activated carbon fiber (ACF) has been experimentally measured at 20, 30 and 50 °C using a volumetric method based adsorption measurement apparatus for greenhouse air-conditioning (AC). The Guggenheim–Anderson–De Boer and Dubinin–Astakhov adsorption models are used to fit the adsorption data of silica-gel and ACP/ACF, respectively. The isosteric heat of adsorption is determined by Clausius– Clapeyron relationship. The adsorbents are evaluated for low-temperature regeneration with aim to develop solar operated AC system for greenhouses. Ideal growth zone for agricultural products is determined by which the steady-state desiccant AC cycle is evaluated on the psychometric chart and adsorption isobars. Steady-state moisture cycled (MCSS) by each adsorbent is determined for demand category-I, II and III which are based on 60%, 40% and 20% relative humidity of dehumidified air, respectively. In case of demand category-I, the ACP enables maximum MCSS at all regeneration temperatures (Treg), ideally sitting at 47 °C. The ACF enables double MCSS as compared to silica-gel during demand category-II at Treg ≥59 °C. However, the silica-gel is found the only applicable adsorbent for the demand category-III.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/steady-state-investigation-water-vapor-adsorptionthermally-driven-adsorption-based-greenhouse-air-conditioning-system/
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Water vapor permeation and dehumidification performance of poly(vinyl alcohol)/lithium chloride composite membranes
Water vapor permeation and dehumidification performance of poly(vinyl alcohol)/lithium chloride composite membranes Significance Statement For countries in the tropics, air conditioning consumes up to 40% of the total electricity in a country. Although many commercially available systems employ inexpensive and yet effective desiccants for drying air/gas streams, however, such adsorbent-based dehumidification requires adsorbents to be regenerated with temperatures greater than 100 degree Celsius. Other disadvantages of the desiccant systems include high maintenance of moving parts and potential contamination of the conditioned air. In the Department of Mechanical Engineering, National University of Singapore, my team and I have patented an innovative membrane technology to dehumidifying moist air. The nano-woven membrane comprised of a substrate-supported layer of specially selected hydrophilic polymeric chemicals that can selectively sieve out water vapor molecules at high flux without the need of thermal regeneration process of conventional desiccant and hence energy efficient. It is the first ever membrane based dehumidifier designed for the tropics. Our innovative design focuses on the use of a membrane-based dehumidifier with reduced pressure drop and requiring no thermal energy for regeneration. Key aspects of the membrane-based dehumidifier include: (i) the potential for improving the performance, consistency and reliability of air moisture removal as the membrane requires minimal energy input, no regenerative heat and is environmental friendly; (2) induces low pressure drop for air passing through the membrane dehumidifier, saving fan power for the airflow; (3) lowering humidity of the moist air with high vapor-to-air selectivity; and (4) the membrane can be functionalized with nano-particles for enhancing water vapor capture and activate air disinfection. In addition, the foil-like membranes have superior mechanical strength which is designed to handle high air flow within a compact air-handling unit (AHU). The developed composite membrane inherits unique and valuable properties of each component (ceramic and polymer) such as strength, flexibility and durability of ceramic scaffold, and high selectivity of the hydrophilic polymer. The membrane dehumidification performance can be sustained for three to four months without any major degradation – physically or performance sustainability. In addition, the composite membrane can be configured as a flat-sheet multi-membrane or hollow-fiber system tailored to different industries with varying humidity control needs and meet desired space constraints. The key objectives of this work are to enhance the membrane’s performance to minimize energy consumption and carbon emission while being cost effective and environmentally responsible. In addition, membrane system is environmental friendly because no regenerative heat is needed and no environmental emission is caused. Our air dehumidification system is a unique plug-and-play flat-sheet or hollow-fiber module which can readily be attached to any existing or new air ducts system to realize immediate air-con energy and carbon emission reductions by at least 35%. This ground-breaking technology is strategically poised to enable the world to markedly improve energy efficiency in buildings (residential, commercial and industries). In addition, another major aim is for our membranes to realize air at very low humidity specifically for the sustainable operations of delicate equipment such as field hospitals, armored personnel carriers and operation decks of navy ships, aircrafts, etc. This work has demonstrated an invaluable technology to achieve high cooling efficiencies in tropical climates; from the current typical plant efficiency of 0.85±0.05 kW/Rton to 0.5±0.05 kW/Rton – more than 35% improvement in energy efficiencies.
Water vapor permeation and dehumidification performance of poly(vinyl alcohol)/lithium chloride composite membranes
Figure Legend: Novel composite membrane in flat-sheet and hollow fiber configurations for air dehumidification.
Water vapor permeation and dehumidification performance of poly(vinyl alcohol)/lithium chloride composite membranes
About The Author Dr. Chua Kian Jon Ernest is currently an Associate Professor of Mechanical Engineering at NUS and an expert in basic and applied research on heat and mass transfer processes in building energy systems, including heating ventilation and air-conditioning. His key research thrust areas at the component level include state-of-the-art hybrid membranes, composite desiccant systems, and high-performing dew-point evaporative cooling. At the system level, his research interests include district cooling, cogeneration and trigeneration and hybrid cogeneration/trigeneration district cooling through absorption cum adsorption technologies. Together with his research team members, they have developed state-of-the-art membrane dehumidifiers and composite desiccant systems. This work has bridged the gap between material fundamentals and nano-science to evolve superior dehumidification systems for air-conditioning applications. He is presently the principal investigators of several research projects with a total direct research funding of SG$10.7 million. In addition, he has hosted a number of specialty seminar/workshops on heat and mass transfer as well as innovative building energy systems and efficiency. He has authored and co-authored more than 110 peer-reviewed international publications and 6 book chapters. His works are highly cited by the global research committee. His total citation count is more than 1800 (from Scopus). His H-index and citations per paper (based on Scopus) as of March 2016 are 23 and 16.8, respectively. For his research contributions to innovative cooling and membrane dehumidification, He was recently awarded several prestigious awards, namely, (1) IES (Institution of Engineers, Singapore) Prestigious Engineering Award 2013; (2) Ministry of National Development R&D Distinguished Award 2015; (3) IES (Institution of Engineers, Singapore) Prestigious Engineering Award 2015; and (4) ASEAN Outstanding Engineering Achievement Award 2015.
Water vapor permeation and dehumidification performance of poly(vinyl alcohol)/lithium chloride composite membranes
Journal Reference Journal of Membrane Science, Volume 498, 15 January 2016, Pages 254â&#x20AC;&#x201C;262. Duc Thuan Bui1, Aqdas Nida1, Kim Choon Ng2, Kian Jon Chua1 Show Affiliations 1. National University of Singapore, Department of Mechanical Engineering, 9 Engineering Drive 1, Singapore 117576, Singapore 2. Water Desalination & Reuse Centre, King Abdullah University of Science & Technology, Thuwal, Saudi Arabia Abstract Thin and robust composite membranes comprising stainless steel scaffold, fine and porous TiO2 and polyvinyl alcohol/lithium chloride were fabricated and studied for air dehumidification application. Higher hydrophilicity, sorption and permeation were observed for membranes with increased lithium chloride content up to 50%. The permeation and sorption properties of the membranes were investigated under different temperatures. The results provided a deeper insight into the membrane water vapor permeation process. It was specifically noted that lithium chloride significantly reduces water diffusion energy barrier, resulting in the change of permeation energy from positive to negative values. Higher water vapor permeance was observed for the membrane with higher LiCl content at lower temperature. The isothermal air dehumidification tests show that the membrane is suitable for dehumidifying air in high humid condition. Additionally, results also indicate a trade-off between the humidity ratio drop with the water vapor removal rate when varying air flowrate.
Original Renewable Energy Global Innovations release can be found online at: https://reginnovations.org/key-scientific-articles/water-vapor-permeation-dehumidificationperformance-polyvinyl-alcohollithium-chloride-composite-membranes/
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