Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P47: Recent Advances in Energy Conversion Devices |
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Sponsoring Units: GERA Chair: Jeffrey Owrutsky, United States Naval Research Laboratory Room: BCEC 213 |
Wednesday, March 6, 2019 2:30PM - 2:42PM |
P47.00001: Battery alternative: Harvesting energy from vibrations Millicent Gikunda, Paul Thibado Development of energy harvesting systems is becoming increasingly important. This is due to an increased need to produce self-charging, portable, implantable and wireless electronics with extended lifespans. Operation of these devices require low power which is normally supplied by batteries that require regular replacement. Emphasis has been placed on scavenging vibrational energy as an alternative to batteries. A notable breakthrough is the discovery that mechanical buckling (change of curvature from concave to convex and vice versa) in freestanding graphene occurs spontaneously at room temperature. This spontaneous mechanical buckling is a source of renewable energy that is to be harvested. Here, I will discuss the relationship between the energy barrier which separates the two lowest energy configurations to strain and height of the ripple and model the ripple curvature inversion dynamic due to thermal energy using Langevin’s equation for freestanding graphene. Mechanical power calculations estimates that a naturally occurring ripple can yield up to and a ripple can yield Thus a quartz wristwatch whose approximate consumption is can be powered by a ripple. |
Wednesday, March 6, 2019 2:42PM - 2:54PM |
P47.00002: Efficiency Optimization in a Simple Mathematical Model of Underground Thermal Energy Storage Anders Carlsson Underground thermal energy storage (UTES) using boreholes is a promising technology for handling the intermittency of renewable energy sources. Because efficiency requires large installations, simulation is crucial in system design. The goal of this study is to develop general explicit relationships for the system efficiency in terms of basic systems parameters, within a highly idealized model of UTES. The boreholes carrying the heat-transporting fluid are described as a density Cs(r) of sources or sinks. The system is charged for a time tc, and then discharged for an equal time. Heat diffuses with coefficient Dth in the soil during both phases. By numerically solving the corresponding reaction-diffusion partial differential equations, we obtain the total energy extracted Eout given Cs(r). We then use functional differentiation to find the function Cs(r) that maximizes Eout given a total amount Ctot of Cs. A step-function form for Cs(r), with width Rs, is very close to optimal. We obtain explicit formulas for Eout and Rs. For Dth=0, Eout is proportional to (Ctot tc ) and Rs is proportional to (Ctot tc )1/3. The loss in Eout from thermal diffusion is proportional to -(Dth)1/2, while Rs is essentially independent of Dth. |
Wednesday, March 6, 2019 2:54PM - 3:06PM |
P47.00003: Using Piezoelectric Generator to Estimate Energy Harvesting with Graphene Ferdinand Harerimana, Paul Thibado Recent STM studies suggest graphene membranes exhibits spontaneous mirror buckling, a phenomenon which can be exploited to harvest ambient energy. This behavior compels us to investigate into different mechanical to electrical energy converters that can be used to harvest low power energy from graphene. One mechanism is to attach a piezoelectric cantilever on a graphene mesh and convert its mechanical energy to electricity. To understand power output from such device, we conduct experimental studies on a hand-shakable piezoelectric device. The generator comprises of multiple PVDF cantilevers connected in parallel, a full-bridge rectifier to change AC signal to DC, a dielectric capacitor to store harvested charges, and an LED for power consumption. We measure the power output and the efficiency of the device. Our results show a low maximum power output after 10 minutes of shaking and efficiency values lower than expected. With a piezoelectric intrinsic capacitor of and an external charge storing capacitance of , the system behaves as a charge source damping . We attribute these low values to high impedance of the intrinsic capacitor due to low frequency domain and its low capacitance. We think these results can be improved with graphene, which vibrates at high frequency. |
Wednesday, March 6, 2019 3:06PM - 3:18PM |
P47.00004: Visible-light-enhanced Mechanical Energy Harvesting using Polarization-Graded InGaN Nanorod Piezoelectric Nanogenerators Sheng Shong Wong, Chun-Yeh Lin, Shu-Ju Tsai, Chung-Lin Wu Piezoelectricity in wide band-gap III-nitride semiconductors is believed to have great potential for harvesting mechanical energy from our living environments. However, under visible-light illumination, the direct band gap of III-nitrides results in very high generation rate of photon-excited free carriers which in turn leads to easily screen the piezoelectric field, which would remarkably decrease the piezoelectric performance of III-nitrides nanorod nanogenerators. Here we proposed a vertically integrated nanogenerator (VING) with polarization-graded InGaN nanorods have high output voltage/current (~3V/~100 nA) and can be further increased under red and green light illumination, totally avoid the disaster of screen effect. The results could assist the design of energy harvesting processes that are more energy efficient and compact than current hybrid solar/piezoelectric nanogenerators. |
Wednesday, March 6, 2019 3:18PM - 3:30PM |
P47.00005: Maximum Thermal Insulation by Nanoporous, Particulate Materials Pia Ruckdeschel, Alexandra Philipp, Markus Retsch Efficient thermal insulation is of high importance to decrease the overall power consumption for heating and cooling applications. Good thermal insulation materials possess a high degree of porosity typically, like foams or aerogels. The low density of such materials mainly drives this. |
Wednesday, March 6, 2019 3:30PM - 3:42PM |
P47.00006: Reversing Thermal Equilibration by Differential Magneto-Thermal Force Weili Luo, Jun Huang, Darian Smalley, T. S. Liu A special magnetic body force was proposed to reverse thermal equilibration in a fluid [1]. In this work, we discuss the fulfilment of the requirements for this force and the experiment to verify it. We present experimental [2-3] and analytical [4] results that clearly demonstrate: 1) approaching thermal equilibrium in our magnetic fluid sample was indeed “reversed” as the magnetic body force introduces the localized flows that stop the conventional convective heat transfer; 2) The differential magneto-thermal force density calculated with experimental parameters agrees with the design principle. These results prove the feasibility of the proposed mechanism for a new generation of heat transfer apparatus that has high efficiency and no exhaust, a clean energy source that will improve our environmental protection. |
Wednesday, March 6, 2019 3:42PM - 3:54PM |
P47.00007: Development of Thermoacoustic Arrays for Power. Orest Symko, Seo Young Ahn Themoacoustic heat engines with piezoelectric devices provide a simple approach to converting heat to electricity. Heat generates sound in an acoustic resonator, which is converted to electricity. For high power, arrays of engines are used. The development of such approach deals with the coupling of engines for synchronization, frequency tuning of resonant components, stability, and performance. Standing wave thermoacoustic engines (2 to 6) at ~2.5 kHz were mounted on a cavity housing piezoelectric devices for converting sound to electricity, and the cavity provided coupling. Above a threshold temperature difference, oscillations were initiated, and they appeared synchronized. The engines were tuned to the piezos. Temperature changes led to detuning. This was compensated by using two piezos of different resonant frequencies, and each piezo was coupled to a Helmholtz resonator, making broadband response and maintaining sensitivity. The increase in power density in the above-coupled engines can be eventually applied to large systems, i.e. arrays. |
Wednesday, March 6, 2019 3:54PM - 4:06PM |
P47.00008: Electronic, Magnetic and Magnetocaloric Properties of Hole-Doped La2MnFeO6 and their Potential for Magnetic Refrigeration C. Gauvin-Ndiaye, Andre-Marie Tremblay, Reza Nourafkan Magnetic refrigeration at room-temperature is a technology that could potentially be more environmentally-friendly, efficient and affordable than traditional refrigeration. Known ferromagnets that satisfy the requirements of near room temperature Curie temperature and large refrigerant capacity are expensive. Double Perovskites La2MnXO6 with X=Ni,Co have refrigerant capacity comparable to the more expensive materials but their Curie temperature Tc is low [1]. Previous theoretical studies have reproduced the trend in Tc of these materials and shown that strong electronic interactions in Fe-d orbitals [2] make the X=Fe compound a ferrimagnet. Based on this insight, we use ab initio, mean-field and Monte-Carlo calculations to propose two materials with promising magnetocaloric properties. They are obtained by hole doping the X=Fe compounds by substituting half of the lanthanum with Sr or Ba, LaBaMnFeO6 and LaSrMnFeO6 [3]. |
Wednesday, March 6, 2019 4:06PM - 4:18PM |
P47.00009: Photoelectrochemical water splitting systems for the sustainable growth of hydrogenotroph biomass Camilla Tossi, Lassi Hällström, Erich See, Michael Lienemann, Juha-Pekka Pitkänen, Marja Nappa, Peter Blomberg, Jussi Jäntti, Merja Penttilä, Ilkka Tittonen An important and presently not yet deeply investigated application of photoelectrochemical (PEC) water splitting is the use of the generated hydrogen to feed a population of hydrogenotroph bacteria. Such bacteria exist in a sufficient variety to satisfy different demands, from fuel components to edible and highly proteic biomass. |
Wednesday, March 6, 2019 4:18PM - 4:30PM |
P47.00010: Density functional theory study of water splitting on ZnO catalyst adsorbed on Graphene Oxide Duwage Perera, Jayendran C Rasaiah We discuss results from density functional theory (DFT) calculations of water splitting on ZnO surfaces using the hybrid B3LYP exchange functional and the 6-311G basis sets. The production of H2 and O2 occurs through the formation of a Zn-H bond generated from the hydrolyzed product of ZnO. We discuss the Transition state of the reaction using the Synchronous Transit-Guided Quasi-Newton (STQN) method following calculations of the Intrinsic Reaction Coordinate (IRC) using the same level of theory. We discuss an extension of our work using RB3LYP/DGDZVP method for water splitting on ZnO adsorbed on graphene oxide (GO) surface (GO-ZnO) which forms a p-n hetero junction enhancing the rate of H2 evolution as it does for a GO-TiO2. GO sheet can facilitate exciton formation and acts as an electron sink to store the separated electrons. Hydrogen production was observed on the GO-ZnO surface using five different GO models. |
Wednesday, March 6, 2019 4:30PM - 4:42PM |
P47.00011: Synthesis of Zn-doped MoS2-graphene heterostructure for efficient water splitting MD DELOWAR HOSSAIN, Zhengtang Luo The demand of renewable energy increases day by day as we progress towards near future. Here we report new type of 2D heterostructures which show superior electrochemical performance towards both hydrogen and oxygen evolution reaction. We demonstrate the synthesis of heterostructure by mixing graphene oxide, Mo-salt, and thiourea via hydrothermal method at 180 oC for 12 hrs. The heterostructure has lots of defected area which enhanced the active sites for both reactions, was revealed by SEM, TEM characterization. Later on, we have performed density functional theory calculation, which demonstrate that the activity mainly comes from sulfur and zinc sites of this heterostructure represented by Gibbs free energy diagram. The density of states calculation shows that the presence of zinc in MoS2-graphene heterostructure increases the electron density throughout the whole structure. Finally, the band structure calculation reveals that zinc reduces the band gap for heterostructure and increases the water splitting capacity into hydrogen and oxygen. |
Wednesday, March 6, 2019 4:42PM - 4:54PM |
P47.00012: Engineered Photo-electrochemical Properties of Nano-Structured SnO2 Zineb Kerrami In the present study, photo-electrochemical properties of SnO2 Thin-film have been examined using first principles calculation. Increasing SnO2 film thickness from 0.3 nm to 2.5 nm results in band gap decrease, which revealed a strong quantum confinement effect. Our results indicate that visible-light absorption and charge carrier’s mobility of a chosen SnO2 film (2.5 nm) could be improved by applying tensile strain. Although, large pH value (pH ≥ 10) is needed to enhance band edges positions relative to the water redox (H2O/H2) levels. All these improvements make tensile strained-SnO2 a potential candidate for hydrogen production through water splitting. |
Wednesday, March 6, 2019 4:54PM - 5:06PM |
P47.00013: Close Space Sublimation Synthesis and Photoelectrochemical Efficiency of Vertical Tin Disulfide (SnS2) Nanoflake Photoanodes Binod Giri, Pratap Rao Tin disulfide (SnS2) is a 2-dimensional material similar to MoS2 and WS2, with layers held together by weak Van der Waals forces. It has excellent optical and electronic properties that are suitable for a number of applications. Because of its high optical absorption coefficient, moderate band gap, and conduction and valence band edges that straddle the reduction and oxidation potentials of water, SnS2 is a promising material for photoelectrochemical (PEC) water splitting. Several reports describing fundamental properties and synthesis methods have been published, however very few have successfully realized SnS2-based photoanodes. |
Wednesday, March 6, 2019 5:06PM - 5:18PM |
P47.00014: 2D Photocatalysts on GaN Nanowires Xianghua Kong, Dawei Kang, Baowen Zhou, Zetian Mi, Hong Guo Hydrogen generation via PEC water splitting is an appealing approach for conversion of solar energy into chemical fuel. PEC requires photocatalysts to function and 2D photocatalysts have received tremendous attention. We report an investigation of solar fuel generation using defect-free GaN nanowires as linker between planar Si wafer and 2D photocatalyst MoS2, focusing on the modeling side [1]. The electronic interaction as well as excellent geometric-matching structure between GaN and MoS2 enable excellent electron-migration channels for high charge carrier extraction efficiency, leading to outstanding photocatalytic performance. Our approach[1] of constructing super-heterostructures offers clear benefits for solar water splitting, including the use of low-cost, large-area Si wafer for light harvesting, earth-abundant MoS2 catalyst for proton reduction, and defect-free GaN nanowires for highly efficient charge carrier extraction and for exposing a high-density of active sites. We further report a general numerical procedure for quantitative estimation of band edge positions and band edge shifts and microscopic origins of these shifts for solid/liquid system[2]. |
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