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Xie, Yu

Publications and source records attributed to Xie, Yu.

At least 163 records · Page 9
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DOE OSTI2016

Performance Analysis of Transposition Models Simulating Solar Radiation on Inclined Surfaces

Transposition models have been widely used in the solar energy industry to simulate solar radiation on inclined photovoltaic panels. Following numerous studies comparing the performance of transposition models, this work aims to understand the quantitative uncertainty in state-of-the-art transposition models and the sources leading to the uncertainty. Our results show significant differences between two highly used isotropic transposition models, with one substantially underestimating the diffuse plane-of-array irradiances when diffuse radiation is perfectly isotropic. In the empirical transposition models, the selection of the empirical coefficients and land surface albedo can both result in uncertainty in the output. This study can be used as a guide for the future development of physics-based transposition models and evaluations of system performance.

14 SOLAR ENERGY↗
DOE OSTI2016

Performance Analysis of Transposition Models Simulating Solar Radiation on Inclined Surfaces: Preprint

Transposition models are widely used in the solar energy industry to simulate solar radiation on inclined photovoltaic (PV) panels. These transposition models have been developed using various assumptions about the distribution of the diffuse radiation, and most of the parameterizations in these models have been developed using hourly ground data sets. Numerous studies have compared the performance of transposition models, but this paper aims to understand the quantitative uncertainty in the state-of-the-art transposition models and the sources leading to the uncertainty using high-resolution ground measurements in the plane of array. Our results suggest that the amount of aerosol optical depth can affect the accuracy of isotropic models. The choice of empirical coefficients and the use of decomposition models can both result in uncertainty in the output from the transposition models. It is expected that the results of this study will ultimately lead to improvements of the parameterizations as well as the development of improved physical models.

14 SOLAR ENERGY↗
DOE OSTI2016

Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint

Solar radiation can be computed using radiative transfer models, such as the Rapid Radiation Transfer Model (RRTM) and its general circulation model applications, and used for various energy applications. Due to the complexity of computing radiation fields in aerosol and cloudy atmospheres, simulating solar radiation can be extremely time-consuming, but many approximations--e.g., the two-stream approach and the delta-M truncation scheme--can be utilized. To provide a new fast option for computing solar radiation, we developed the Fast All-sky Radiation Model for Solar applications (FARMS) by parameterizing the simulated diffuse horizontal irradiance and direct normal irradiance for cloudy conditions from the RRTM runs using a 16-stream discrete ordinates radiative transfer method. The solar irradiance at the surface was simulated by combining the cloud irradiance parameterizations with a fast clear-sky model, REST2. To understand the accuracy and efficiency of the newly developed fast model, we analyzed FARMS runs using cloud optical and microphysical properties retrieved using GOES data from 2009-2012. The global horizontal irradiance for cloudy conditions was simulated using FARMS and RRTM for global circulation modeling with a two-stream approximation and compared to measurements taken from the U.S. Department of Energy's Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains site. Our results indicate that the accuracy of FARMS is comparable to or better than the two-stream approach; however, FARMS is approximately 400 times more efficient because it does not explicitly solve the radiative transfer equation for each individual cloud condition. Radiative transfer model runs are computationally expensive, but this model is promising for broad applications in solar resource assessment and forecasting. It is currently being used in the National Solar Radiation Database, which is publicly available from the National Renewable Energy Laboratory at http://nsrdb.nrel.gov.

14 SOLAR ENERGY↗
DOE OSTI2016

Effect of metal ion intercalation on the structure of MXene and water dynamics on its internal surfaces

MXenes are a recently discovered class of 2D materials with an excellent potential for energy storage applications. Because MXene surfaces are hydrophilic and attractive interaction forces between the layers are relatively weak, water molecules can spontaneously intercalate at ambient humidity and significantly influence the key properties of this 2D material. Using complementary X-ray and neutron scattering techniques, we demonstrate that intercalation with potassium cations significantly improves structural homogeneity and water stability in MXenes. Furthermore, in agreement with molecular dynamics simulations, intercalated potassium ions reduce the water self-diffusion coefficient by 2 orders of magnitude, suggesting greater stability of hydrated MXene against changing environmental conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Control of electronic properties of 2D carbides (MXenes) by manipulating their transition metal layers

In this paper, a transition from metallic to semiconducting-like behavior has been demonstrated in two-dimensional (2D) transition metal carbides by replacing titanium with molybdenum in the outer transition metal (M) layers of M 3 C 2 and M 4 C 3 MXenes. The MXene structure consists of n + 1 layers of near-close packed M layers with C or N occupying the octahedral site between them in an [MX] n M arrangement. Recently, two new families of ordered 2D double transition metal carbides MXenes were discovered, M' 2 M"C 2 and M' 2 M" 2 C 3 – where M' and M" are two different early transition metals, such as Mo, Cr, Ta, Nb, V, and Ti. The M' atoms only occupy the outer layers and the M" atoms fill the middle layers. In other words, M' atomic layers sandwich the middle M"–C layers. Using X-ray atomic pair distribution function (PDF) analysis on Mo 2 TiC 2 and Mo 2 Ti 2 C 3 MXenes, we present the first quantitative analysis of structures of these novel materials and experimentally confirm that Mo atoms are in the outer layers of the [MC] n M structures. The electronic properties of these Mo-containing MXenes are compared with their Ti 3 C 2 counterparts, and are found to be no longer metallic-like conductors; instead the resistance increases mildly with decreasing temperatures. Density functional theory (DFT) calculations suggest that OH terminated Mo–Ti MXenes are semiconductors with narrow band gaps. Measurements of the temperature dependencies of conductivities and magnetoresistances have confirmed that Mo 2 TiC 2 T x exhibits semiconductor-like transport behavior, while Ti 3 C 2 T x is a metal. Finally, this finding opens new avenues for the control of the electronic and optical applications of MXenes and for exploring new applications, in which semiconducting properties are required.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Nanoscale elastic changes in 2D Ti 3 C 2 T x (MXene) pseudocapacitive electrodes

Designing sustainable electrodes for next generation energy storage devices relies on the understanding of their fundamental properties at the nanoscale, including the comprehension of ions insertion into the electrode and their interactions with the active material. One consequence of ion storage is the change in the electrode volume resulting in mechanical strain and stress that can strongly affect the cycle life. Therefore, it is important to understand the changes of dimensions and mechanical properties occurring during electrochemical reactions. While the characterization of mechanical properties via macroscopic measurements is well documented, in-situ characterization of their evolution has never been achieved at the nanoscale. Two dimensional (2D) carbides, known as MXenes, are promising materials for supercapacitors and various kinds of batteries, and understating the coupling between their mechanical and electrochemical properties is therefore necessary. Here we report on in-situ imaging, combined with density functional theory of the elastic changes, of a 2D titanium carbide (Ti 3 C 2 T x ) electrode in direction normal to the basal plane during cation intercalation. The results show a strong correlation between the Li+ ions content and the elastic modulus, whereas little effects of K+ ions are observed. Moreover, this strategy enables identifying the preferential intercalation pathways within a single particle.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Computational discovery of ferromagnetic semiconducting single-layer CrSnTe 3

Despite many single-layer materials being reported in the past decade, few of them exhibit magnetism. Here we perform first-principles calculations using accurate hybrid density functional methods (HSE06) to predict that single-layer CrSnTe 3 (CST) is a ferromagnetic semiconductor, with band gaps of 0.9 and 1.2 eV for the majority and minority spin channels, respectively. We determine the Curie temperature as 170 K, significantly higher than that of single-layer CrSiTe 3 (90K) and CrGeTe 3 (130 K). This is due to the enhanced ionicity of the Sn-Te bond, which in turn increases the superexchange coupling between the magnetic Cr atoms. We further explore the mechanical and dynamical stability and strain response of this single-layer material for possible epitaxial growth. Lastly, our study provides an intuitive approach to understand and design novel single-layer magnetic semiconductors for a wide range of spintronics and energy applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Full-dimensional multilayer multiconfigurational time-dependent Hartree study of electron transfer dynamics in the anthracene/C60 complex

Electron transfer at the donor-acceptor heterojunctions plays a critical role in the photoinduced process during the solar energy conversion in organic photovoltaic materials. We theoretically investigate the electron transfer process in the anthracene/C60 donor-acceptor complex by using quantum dynamics calculations. The electron-transfer model Hamiltonian with full dimensionality was built by quantum-chemical calculations. The quantum dynamics calculations were performed using the multiconfigurational time-dependent Hartree (MCTDH) theory and multilayer (ML) MCTDH methods. The latter approach (ML-MCTDH) allows us to conduct the comprehensive study on the quantum evolution of the full-dimensional electron-transfer model including 4 electronic states and 246 vibrational degrees of freedom. Our quantum dynamics calculations exhibit the ultrafast anthracene → C60 charge transfer process because of the strong coupling between excitonic and charge transfer states. This work demonstrates that the ML-MCTDH is a very powerful method to treat the quantum evolution of complex systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Retrievals of Cloud Fraction and Cloud Albedo from Surface-based Shortwave Radiation Measurements: A Comparison of 16 Year Measurements

Ground-based radiation measurements have been widely conducted to gain information on clouds and the surface radiation budget; here several different techniques for retrieving cloud fraction (Long2006, Min2008 and XL2013) and cloud albedo (Min2008, Liu2011 and XL2013) from ground-based shortwave broadband and spectral radiation measurements are examined, and sixteen years of retrievals collected at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site are compared. The comparison shows overall good agreement between the retrievals of both cloud fraction and cloud albedo, with noted differences however. The Long2006 and Min2008 cloud fractions are greater on average than the XL2013 values. Compared to Min2008 and Liu2011, the XL2013 retrieval of cloud albedo tends to be greater for thin clouds but smaller for thick clouds, with the differences decreasing with increasing cloud fraction. Further analysis reveals that the approaches that retrieve cloud fraction and cloud albedo separately may suffer from mutual contamination of errors in retrieved cloud fraction and cloud albedo. Potential influences of cloud absorption, land-surface albedo, cloud structure, and measurement instruments are explored.

albedo↗
DOE OSTI2014

Synthesis and electromagnetic properties of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites

Graphical abstract: Due to combining different functions and characteristics of individual materials, hybrid nanocomposite materials can strengthen their applications. Magnetic-conductive nanocomposites are the promising materials with electromagnetic loss, which have synergetic behavior between magnetic and conductive materials. It is the first time to report the synthesis of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide (BF/TD) composites by the gel-precursor self-propagating combustion process. The influence of mass ratio of BF and TD on the electromagnetic properties of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites was studied. The tgδ{sub μ} and tgδ{sub ε} of BF–TD composites. - Highlights: • It is the first time to report BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites. • The composites are prepared by the gel-precursor self-propagating combustion. • The electromagnetic properties could be adjusted by the mass ratio of BF and TD. • The introduction of TD enhances the dielectric loss and widens the frequency bands. • BF/TD composites will be microwave absorption materials with wide frequency band. - Abstract: Doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites have been prepared by the gel-precursor self-propagating combustion process. The characterization of the composites are performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Differential thermal analysis-thermo gravimetry (DTA–TG), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and network analyzer. Both XRD and FT-IR indicate that the doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites are successfully synthesized and there are some interactions between BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. DTA–TG analysis of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide composites shows that the composite gel decomposition process mainly includes two stages: the first stage is the crystallized water and the residual moisture evaporation; the second stage is the nitrate and citric acid decomposition reaction. SEM demonstrates that the doped BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19}/titanium dioxide solid solution has formed. The magnetic parameters indicate that the electromagnetic properties of the composites could be well adjusted by the mass ratio of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. When the mass ratio of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide is 4:5, the composites have the best magnetic loss. The composites with the mass ratio 6:5 of BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide. BaFe{sub 11.92}(LaNd){sub 0.04}O{sub 19} and titanium dioxide possess good dielectric loss. The introduction of titanium dioxide enhances the dielectric loss and widens the frequency bands. The composites will be promising microwave absorption materials with wide frequency band.

36 MATERIALS SCIENCE↗