United States Department of Energy

About: United States Department of Energy is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Catalysis & Coal. The organization has 13656 authors who have published 14177 publications receiving 556962 citations. The organization is also known as: DOE & Department of Energy.

Reduced graphene oxide/titanium dioxide composites for supercapacitor electrodes: shape and coupling effects

Abstract: TiO2 nanobelts (NBs) and nanoparticles (NPs) have been coupled with the chemically reduced graphene oxide (rGO) to form nanocomposites which are used as supercapacitor electrodes. The specific capacitance of rGO–TiO2 composites is higher than that of monolithic rGO, TiO2 NPs or NBs. The optimal electrochemical performance is achieved with the rGO–TiO2 composites at a rGO:TiO2 mass ratio of 7:3. In addition, the rGO–TiO2 NBs exhibit better performance than the rGO–TiO2 NPs in terms of specific capacitance, rate capability, energy density and power density. The specific capacitances of rGO–TiO2 NBs and rGO–TiO2 NPs with a mass ratio of 7:3 are 225 F g−1 and 62.8 F g−1 at a discharge current density of 0.125 A g−1, respectively. The better performance of the rGO–TiO2 NBs is attributed to the nanobelt's unique shape, better charge transport property and larger area of contact with the rGO nanosheet.

Optimization of Pressure Swing Adsorption and Fractionated Vacuum Pressure Swing Adsorption Processes for CO2 Capture

Abstract: This work focuses on the optimization of cyclic adsorption processes to improve the performance of CO2 capture from flue gas, consisting of nitrogen and carbon dioxide. The adopted processes are the PSA (pressure swing adsorption) process and the FVPSA (fractionated vacuum pressure swing adsorption) process, modified from the FVSA (fractionated vacuum swing adsorption) process developed by Air Products and Chemicals, Inc. The system models are currently bench scale and adopt zeolite13X as an adsorbent. The high-temperature PSA is better for high purity of product (CO2), and the high-temperature FVPSA is much better than the normal-temperature PSA processes. The main goal of this study is to improve the purity and recovery of carbon dioxide. The Langmuir isotherm parameters were calculated from experimental data taken at National Energy Technology Laboratory (Siriwardane, R.; NETL, DOE, 2004). Moreover, efficient optimization strategies are essential to compare these processes. To perform optimization work...

Development of the Risø wind turbine airfoils

Abstract: This paper presents the wind turbine airfoil development at Riso. The design method is described together with our target characteristics for wind turbine airfoils. The use of the CFD code Ellipsys2D for prediction of final target characteristics is described together with the VELUX wind tunnel testing setup. Three airfoil families were developed; Riso-A1, Riso-P and Riso-B1. The Riso-A1 airfoil family was developed for rotors of 600 kW and larger. Wind tunnel testing and field testing showed that this airfoil family is well suited for stall and active stall control. However, sensitivity to roughness was higher than expected. Field tests of a 600 kW active stall wind turbine showed an estimated reduction in blade fatigue loading of up to 15% at the same annual energy yield and at the same time reduced blade weight and blade solidity. The Riso-P airfoils were developed to replace the Riso-A1 airfoils for use on pitch controlled wind turbines. Improved design objectives should reduce the sensitivity to roughness, but measurements are not yet available. The Riso-B1 airfoil family was developed for variable speed operation with pitch control of large megawatt sized rotors. Wind tunnel testing verified the high maximum lift for these airfoils, and the airfoils were found to be very insensitive to leading edge roughness. Performance with vortex generators and Gurney flaps in combination was found to be attractive for the blade root part. Field testing of a 1·5 MW rotor is in progress. Copyright © 2004 John Wiley & Sons, Ltd.

Notes on Contributions to the Science of Rare Earth Element Enrichment in Coal and Coal Combustion Byproducts

Abstract: Coal and coal combustion byproducts can have significant concentrations of lanthanides (rare earth elements). Rare earths are vital in the production of modern electronics and optics, among other uses. Enrichment in coals may have been a function of a number of processes, with contributions from volcanic ash falls being among the most significant mechanisms. In this paper, we discuss some of the important coal-based deposits in China and the US and critique classification systems used to evaluate the relative value of the rare earth concentrations and the distribution of the elements within the coals and coal combustion byproducts.

State-to-state chemistry with fast hydrogen atoms. Reaction and collisional excitation in H + CO2

Abstract: We present a detailed theoretical study of vibrational–rotational excitation and reaction in collisions of CO2 with 1.9–2.6 eV hydrogen atoms. Minima and saddle points on the potential surface have been characterized using ab initio configuration interaction calculations, and a global surface has been developed by a combination of many-body expansion and surface-fitting methods. The collision dynamics have been studied using quasiclassical trajectories, with the CO2 vibrational states characterized by a Fourier-transform action calculation. For non-reactive scattering there is reasonable correlation between the vibrational modes that are excited and the regions of the potential surface sampled during the collisions. Most of the lower states of CO2 are excited by direct collisions that do not sample potential wells. Collisions which do sample wells lead to short-lived HOCO and HCO2 complexes, in which either the H dissociates to produce highly excited overtone and combination states of CO2, or a CO bond breaks to give OH + CO having close to statistical vibrational–rotational distributions. Comparison of cross-sections and final-state distributions with experiment is excellent for the reactive collisions, and is good on a relative but not absolute basis for the non-reactive collisions.