Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session X20: Alternative Energy and Biofuels |
Hide Abstracts |
Sponsoring Units: GERA Chair: Shudipto Dishari, Univ of Nebraska - Lincoln Room: LACC 308B |
Friday, March 9, 2018 8:00AM - 8:12AM |
X20.00001: S-P ORBITAL HYBIRDIZION: A STRATEGY FOR EFFICIENT PHOTOCATALYSIS WITH HIGH CARRIER MOBILITY Weichang Hao A narrow band gap, effective separation of photoexcited charge carriers, and proper band-edge positions, which depend on the band structure of the photocatalyst,are crucial for solar-energy conversion efficiency. Carrier mobility of semiconductors is assosicated with their effective mass, which is intrinsicly decided by the dispersion of energy band. Under the guidance of this principle, electron structures are desgined for novel photocatalytic material discovery, whereby the S-P orbital hybridyzation (efficient coorperation between s and p orbitals) to dispersing the energy band and achieving small effective mass of charge carriers in crystalline materials. Theories related to S-P orbital hybridization are sumarized and strategies for apllications are promoted, which will enable it utilized in advanced performance semoconductors. Effective cooperation of s and p orbital is required and strong S-P orbital hybridyzation should be pronounced in materials composed of elements with rich s and p electrons, close packed crystal structure and large szie of atoms. |
Friday, March 9, 2018 8:12AM - 8:24AM |
X20.00002: Towards photoexcited diamond as a source for solvated electrons Anna Zaniewski, Jonathon Barkl, Robert Nemanich Chemically recycling carbon dioxide into fuels via artificial photosynthesis requires an electron source to reduce carbon dioxide. In this talk, we explore how photoexcited diamond has potential to be be used as this electron source. When the surface is treated with hydrogen, diamond has the rare property of posessing a negative electron affinity, meaning that its conduction band minimum lies above the vacuum. Thus, photoexcited diamond freely emits electrons, which can in turn be used for reducing molecules such as carbon dioxide. Such electron emission has been demonstrated previously with above-gap ultraviolet light in water, producing free electrons that can drive high energy chemical reactions. Notably, sub-gap light on n-type nanocrystalline diamond on metal substrates has also been shown as a vacuum electron source, and holds the record for the lowest photo-threshold of any non-cesiated material at 1.5eV. In this work, we show recent results generating solvated electrons with diamond, chemical reactions enabled by these solvated electrons, and discuss the stability of the diamond surface for long-term use. |
Friday, March 9, 2018 8:24AM - 8:36AM |
X20.00003: Alternative Power Source with Nanotechnology Millicent Gikunda, Paul Thibado Recent emphasis has been placed on scavenging vibrational energy as an alternative to batteries. A notable breakthrough is the discovery that freestanding graphene naturally possesses an intrinsic rippled structure, which can be used to harvest thermal energy from its vibrations. |
Friday, March 9, 2018 8:36AM - 8:48AM |
X20.00004: Thermodynamic Analysis and Modeling of Extremely Large Pressurized Nitrogen for Alternative Energy Production Geoffrey Kemmerer, Thomas Gross, Kevin Anderson This paper presents the results of thermodynamic modeling and analysis of a novel Nitroen (N2) cyle to be used for alternative energy production.The extremely high pressurization of the N2 on the order of 90,000 psi (620.3 MPa / 6205 bar) is used for two processes: i) isothermal compression and ii) adiabatic expansion. The isothermal compression is accomplished by mixing Mercury (Hg) bubbles into the N2. Since the compression is based on the density of the liquid being used, Hg lends itself to the best candidate bubble fluid to use. Preliminary inspection of the enthalpy values for Hg in the pressure regime of interest suggests that Hg is a viable candidate for the bubble fluid to compress the N2. The thermodyanmic computational simulations are carried out in MATLAB and use the NIST REFPROP database for modeling the high presure N2 state points. The paper presents results of the thermodynamic efficeincy, work output and exergy/availability analysis of this proposed cycle. Preliminary results indicate work output on the order of 17 kJ per mole of N2. |
Friday, March 9, 2018 8:48AM - 9:00AM |
X20.00005: A Wireless Triboelectric Nanogenerator Sai Sunil Kumar Mallineni, Yongchang Dong, Herbert Behlow, Apparao Rao, Ramakrishna Podila We demonstrate a new paradigm for the wireless harvesting of mechanical energy |
Friday, March 9, 2018 9:00AM - 9:12AM |
X20.00006: Wind Turbines Electro-Mechanical System: Mathematical Modeling and Geometric Controllability Sameh Eisa, Elham Vakil Asadollahei, Haithem Taha In recently published papers, we introduced mathematical modeling and analysis for wind turbines dynamics. The published results provided analytical proofs of boundedness, existence and uniqueness for the electro-mechanical system of wind turbines under the control limits. Also, we provided stability and simulation results for the system in challenging physical conditions, such as sudden wind speed changes or drop in the impedance of the power grid. Currently, we are working on formulating the wind turbines system in geometric framework to study controllability of the system in difficult physical situations. Differential geometric tools can capture some of the missing information in regular linearization analyses. We are searching for possible unconventional directions or interactions in the vector fields of the system using Geometric control theory. These new unconventional directions may lead to new control strategies or designs to improve our use and production of wind energy. In our presentation, we summarize the published work and the current progress in our research. |
Friday, March 9, 2018 9:12AM - 9:24AM |
X20.00007: V–VO2 core–shell structure for potential thermal switching Keshab Dahal, Qian Zhang, Yumei Wang, Ishwar Mishra, Zhifeng Ren The efficiency of internal combustion engine is vey low at cold start than when the engine is warm. By using thermal switching material, the engine can be warm up quickly after the engine starts. In this work, we discuss about the potential thermal switching material V-VO2 core-shell structure. The V-VO2 core-shell structure was formed by converting the outer surface of V particles into VO2 by controlled thermal annealing in air. In such core-shell structure, in insulator phase of VO2 electrons confine inside the vanadium particles and in metallic phase electrons will be transfered from V into VO2, which resulted in electrical conductivity increased from 2.1 × 105 to 5.1 × 105 S m−1 through the insulator-to-metal transition. Due to the increase in electrical conductivity, corresponding electrical thermal conductivity increased from 1.51 to 4.87 W m-1 K-1 which finally resulted on switching of total thermal conducitivity by 22% across the phase transition temperature. |
Friday, March 9, 2018 9:24AM - 9:36AM |
X20.00008: Design and Synthesis of Graphene-Based Nanocomposites for Energy Conversion and Storage Lifeng Dong, Liyan Yu, Beili Pang, Hongzhou Dong, Xichang Bao, Renqiang Yang
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Friday, March 9, 2018 9:36AM - 9:48AM |
X20.00009: Multijunction thermophotovoltaic cell for efficient power generation out of the waste heat in solid oxide fuel cell Seyed Moein Rassoulinejad-Mousavi, Tianjun Liao, Poorya Shobeiry, Yuwen Zhang Multijunction thermophotovoltaic (MTPV) cells, with integrated back surface reflector, are combined in solid oxide fuel cells (SOFCs) as a highly efficient novel hybrid system to exploit waste heat. The intellectual merit of using MTPV cell is verified analytically in terms of power output density and efficiency of the TPV cell, SOFC and designed hybrid system. Optimum performance analysis of the hybrid system is obtained based on the ratio of the emitter area to the surface area of the contact electrode, back surface reflectivity, the band gaps, as well as the number of junctions. Optimal key parameters of the systems were suggested at the maximum power density. Use of MTPV eliminated the historical tradeoff between efficiency and power density of TPV converters to provide practically-viable high performance TPV systems. The proposed model significantly increases the employment of the waste heat produced in SOFCs for conversion to electricity. Results showed that, the innovative use of MTPV in the hybrid system, leads to a more efficient hybrid system than other SOFC-based ones because of obtaining higher efficiency and power density. |
Friday, March 9, 2018 9:48AM - 10:00AM |
X20.00010: Optimization principles and the figure-of-merit for triboelectric generators Jun Peng, Stephen Kang, Jeff Snyder Energy harvesting with triboelectric nanogenerators is a burgeoning field, with a growing portfolio of creative application schemes attracting much interest. While power generation capabilities and its optimization is one of the most important subjects, a satisfactory elemental model that illustrates the basic principles and sets the optimization guideline remains elusive. We use a simple model to clarify how the energy generation mechanism is electrostatic induction, but with a time-varying character that makes the optimal matching for power generation more restrictive. By combining multiple parameters into dimensionless variables, we pinpoint the optimum condition with only two independent parameters, leading to predictions of the maximum limit of power density which allows us to derive the triboelectric material and device figure-of-merit. We reveal the importance to optimize device capacitance, not only load resistance, and to minimize the impact of parasitic capacitance. Optimized capacitances can lead to a more than ten-times overall increase in power density. |
Friday, March 9, 2018 10:00AM - 10:12AM |
X20.00011: Plant Cell Wall Inspired Functional Ion Conducting Nanomaterials for Energy Applications Shudipto Dishari Current initiatives to minimize the global carbon footprints demand the best utilization of renewable energy resources and development of environment friendly next generation materials for energy conversion and storage. The proposed work takes inspiration from plant cell walls and utilizes the major polymer lignin present in plant cell walls to design highly functional ion conducting materials. Lignin imparts mechanical strength to plant cell walls. Lignin exhibits Young’s modulus 25 times higher than the most popular ion conducting polymer, Nafion used for proton exchange membrane fuel cells. Moreover, lignin is heavily functionalized with hydrophilic hydroxyl (-OH) groups which facilitate ion channel formation for efficient proton conduction. The high glass transition temperature and segmental motion in the presence of little or no moisture make lignin ideal for high temperature and low humidity ion conduction where current ionomers lag behind. Our recent work shows that sulfonated lignin (by-product of paper industries) can offer great material strength and ion conductivity in micro to nanoscale thick materials, yielding cheaper, efficient ion conducting ionomers for many energy conversion and storage devices. |
Friday, March 9, 2018 10:12AM - 10:24AM |
X20.00012: Measuring Dynamic Storage and Predicting Flow Dynamics in Adsorbed Natural Gas Systems Matthew Prosniewski, Ernie Knight, Andrew Gillespie, Adam Smith, Peter Pfeifer Gas adsorption measurements are traditionally made in equilibrium conditions on small amounts of adsorbent material. While these measurements accurately determine a material’s optimal storage capacity, they do not provide much information on the system’s storage evolution. When attempting to implement large scale adsorption systems, such as those proposed to be used as automotive fuel tanks, the temperature rise seen during gas loading decreases the adsorbent's storage capacity. The low permeability of the adsorbent can also cause pressure gradients in the system. Implying the storage capacity may vary throughout the system. Accounting for these pressure and temperature gradients makes experimentally determining adsorption in non-equilibrium systems difficult. In this work, we propose a new technique for experimentally measuring the dynamic storage of adsorbents. Using the temperature change in the system, along with the adsorbent's heat of adsorption, the amount of adsorbed gas can be determined. Once the amount of adsorbed gas is determined, an average system pressure can be calculated and used to predict system flow dynamics. The method has been shown to accurately predict the storage evolution in a 40 L natural gas tank and provide insights on the systems pressure evolution. |
Friday, March 9, 2018 10:24AM - 10:36AM |
X20.00013: Operando SANS Study on Ion Adsorption in Conductive Porous MOF Electrodes Lilin He, Luming Yang, Rui Zhang, Jianlin Li, Mircea Dinca Insights into the molecular mechanisms of transport and adsorption of electrolyte ions in porous materials under applied potentials are essential to control the performance of double layer capacitors for rapidly emerging high power energy storage, water purification and desalination. Here we present an extensive small-angle neutron scattering (SANS) characterization of ions with different sizes and chemical characteristics adsorbed into a conductive metal-organic framework (MOF) under operating conditions. The scattering curve of dry MOF revealed that the structure was divided into two regimes. The regime I consisted mainly of cylindrical mesopores of radius of ~24 Å. The correlation peak at 0.35 Å-1 was attributed to ordered arrangement of micropores in regime II. Significant drop of scattering intensity at low q region and disappearance of correlation peak at high q region upon the addition of dueterated dimethylformamide (DMF) implied that the majority of the pores were accessible to the solvent. The ions diffused into mesopores immediately after the salts were added, which was evidenced by the increased scattering intensity. The negligible changes in scattering intensity between charging and discharging seemingly suggested the anion-cation exchange mechanism in mesopores. |
Friday, March 9, 2018 10:36AM - 10:48AM |
X20.00014: Band bending and band alignment at reconstructed perovskite-electrolyte interfaces under applied voltage Yihuang Xiong, Ismaila Dabo Perovskite photoelectrodes have been extensively studied at the first-principles level in search for photocatalytic materials for hydrogen production through water splitting. The solar-to-fuel efficiency for these materials is critically dependent on the voltage-dependent restructuring of the electrode-electrolyte interface. Here, we develop an embedded quantum-mechanical method using the self-consistent continuum solvation (SCCS) model to predict the relation between band alignment and band bending at photoelectrochemical interfaces under electrical bias taking into account the polarization of the depletion region of the semiconductor electrode over length scales of thousands of nanometers. Using this comprehensive model, we calculated the voltage-dependent Schottky barriers and the full electrical response of various reconstructions of SrTiO3 photoelectrodes. The results reveal that interfacial charge trapping exerts primary control on the Schottky barriers at the redox potentials of hydrogen and oxygen, thereby affecting the driving force for charge separation and charge transfer at SrTiO3-water interfaces. Our results highlight the necessity to account for voltage-dependent interface reconstruction in assessing the photocatalytic activity of candidate perovskite materials. |
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