• Energy Research

Abstract In integrated Photovoltaic (PV) systems, integrating the back side of the PV module with building wall insulate it from the surrounding air causing a dramatically increase of the PV temperature. The increase of the PV temperature causes a substantial decrease of its efficiency and output power. The idea of the present work is the investigation of the thermal regulation and efficiency enhancement of PV-building integrated system using phase change materials (PCM) and Al2O3 nanoparticles. The approach of the study is experimentally testing three separate PV modules integrated with building wall, pure PCM and PCM/Al2O3 nanoparticles compound at the same time and location. Temperatures distributions, open-circuit voltage, short- circuit current, output power and the modules efficiencies were recorded and analyzed. The results show that (i) integrating the PCM to the back side of the integrate PV modules regulates the module temperature and improves its efficiency, (ii) adding Al2O3 nanoparticles to the PCM further increase the possibility of the temperature regulation and the thermal efficiency of the integrated modules, and (iii) integrating the PV with pure PCM and enhanced PCM by nanoparticles can drop the temperature of the modules by 8.1 and 10.6 °C and increase its efficiency by 5.7 and 13.2%, respectively.

Contents 40 I. 40 II. 41 III. 44 IV. 48 V. 49 VI. 49 VII. 52 VIII. 53 53 References 53 SUMMARY: In the last decade, analyses of both molecular and morphological characters, including nodulation, have led to major changes in our understanding of legume taxonomy. In parallel there has been an explosion in the number of genera and species of rhizobia known to nodulate legumes. No attempt has been made to link these two sets of data or to consider them in a biogeographical context. This review aims to do this by relating the data to the evolution of the two partners: it highlights both longitudinal and latitudinal trends and considers these in relation to the location of major land masses over geological time. Australia is identified as being a special case and latitudes north of the equator as being pivotal in the evolution of highly specialized systems in which the differentiated rhizobia effectively become ammonia factories. However, there are still many gaps to be filled before legume nodulation is sufficiently understood to be managed for the benefit of a world in which climate change is rife.

Premature training quenches are usually caused by the transient energy released within the magnet coil as it is energised. Two distinct varieties of disturbances exist. They are thought to be electrical and mechanical in origin. The first type of disturbance comes from non-uniform current distribution in superconducting cables whereas the second one usually originates from conductor motions or micro-fractures of insulating materials under the action of Lorentz forces. All of these mechanical events produce in general a rapid variation of the voltages in the so-called quench antennas and across the magnet coil, called spikes. A statistical method to treat the spatial localisation and the time occurrence of spikes will be presented. It allows identification of the mechanical weak points in the magnet without need to increase the current to provoke a quench. The prediction of the quench level from detailed analysis of the spike statistics can be expected.

This tutorial and review of multi-objective optimization (MOO) gives a detailed explanation of the 5 steps to create, solve, and then select the optimum result. Unlike single-objective optimization, the fifth step of selection or ranking of solutions is often overlooked by the authors of papers dealing with MOO applications. It is necessary to undertake a multi-criteria analysis to choose the best solution. A review of the recent publications using MOO for chemical process engineering problems shows a doubling of publications between 2016 and 2019. MOO applications in the energy area have seen a steady increase of over 20% annually over the last 10 years. The three key methods for solving MOO problems are presented in detail, and an emerging area of surrogate-assisted MOO is also described. The objectives used in MOO trade off conflicting requirements of a chemical engineering problem; these include fundamental criteria such as reaction yield or selectivity; economics; energy requirements; environmental performance; and process control. Typical objective functions in these categories are described, selection/ranking techniques are outlined, and available software for MOO are listed. It is concluded that MOO is gaining popularity as an important tool and is having an increasing use and impact in chemical process engineering.

Biodiesel commonly experiences oxidative and hydrolytic degradation, leading to problems of low storage stability and corrosion of fuel containers. This study investigates the fabrication and use of electrodeposited nickel and nickel–tungsten alloys as potential coating materials that effectively protect steel-based biodiesel containers from corrosion. Through long-term static immersion, surface analyses of the coatings, and assessments of the biodiesel’s acidity, it is determined that the electrodeposited nickel is well compatible with biodiesel, whereas the addition of tungsten deteriorates the corrosion resistance of nickel. Tight control of the tungsten content in nickel deposits is required to enhance both mechanical integrity and corrosion resistance of the deposits exposed to biodiesel environments.

The binding energies of manganese cluster ions Mn(N)+ (N = 5-7) were determined by the photodissociation experiments in the near-infrared and visible-photon-energy ranges. The bond dissociation energies of Mn(N)+, D0(Mn(N-1)+...Mn), were obtained to be 1.70+/-0.08, 1.04+/-0.10, and 1.46+/-0.11 eV, respectively, for N = 5, 6, and 7 from the threshold energies for the two-atom loss processes and the bond dissociation energies of Mn3(+) and Mn4(+) reported previously [A. Terasaki et al., J. Chem. Phys. 117, 7520 (2002)]. Correspondingly, binding energies per atom are obtained to be 0.99+/-0.03, 1.00+/-0.03, and 1.06+/-0.03 eV/at. for N = 5, 6, and 7, respectively. A gradual increase in the binding energy from N = 2 to N = 7 shows an increasing contribution of nonbonding 3d orbitals to the bonding via weak hybridization with valence 4s orbitals as the cluster size increases. These binding energies per atom are still much smaller than the bulk cohesive energy of manganese (2.92 eV/at.), and this finding indicates exceptionally weak metal-metal bonds in this size range.

ABSTRACT This paper is geared toward answering the questions of the small to intermediate-size oil and gas operator, who does not have the resources to hire an environmental consultant or manager to handle all of his environmental compliance problems. The paper presupposes no prior understanding or familiarity with the applicable environmental laws or regulations. The main objective is to convey, in very concise format, exactly what an oil and gas producer (onshore and/or offshore) needs to do in order to be in compliance with all current federal and state environmental regulations regarding oil spills. Relevant legislation and regulations contained in and resulting from the Clean Water Act; the Oil Pollution Act of 1990; the Texas Oil Spill Prevention and Response Act; national, regional, area, and state spill contingency plans; and Texas Railroad Commission regulations are briefly reviewed. This legislation and regulations are summarized in a checklist of seven essential requirements for operators to follow in order to comply with all applicable federal regulations and state regulations specific to Texas. Regulations in other states will vary. Texas is utilized here as an example which is representative of most states in the U.S.

International audience; Magnitudes of differential stress in the lithosphere, especially in the crust, are still disputed. Earthquake-based stress drop estimates indicate median values ca. 180 MPa, corresponding to a friction angle of ca. 10° to maintain the topographic relief between lowland and plateau for >10 Ma. The relative contribution of crustal strength to total lithospheric strength varies considerably laterally. In the region between lowland and plateau and inside the plateau the depth-integrated crustal strength is approximately equal to the depth-integrated strength of the mantle lithosphere. Simple analytical formulae predicting the lateral variation of depth-integrated stresses agree with numerically calculated stress fields, which show both the accuracy of the numerical results and the applicability of simple, rheology-independent, analytical predictions to highly variable, rheology-dependent stress fields. Our results indicate that (1) crustal strength can be locally equal to mantle lithosphere strength and that (2) crustal stresses must be at least one order of magnitude larger than median stress drops in order to support the plateau relief over a duration of ca. 10 Ma.

Graphite is a stack of honeycomb (graphene) layers bound together by nonlocal, long-range van der Waals (vdW) forces, which are poorly described by density functional theory (DFT) within local or semilocal exchange-correlation functionals. Several approximations have been proposed to add a vdW correction to the DFT total energies (Stefan Grimme (D2 and D3) with different damping functions (D3-BJ), Tkatchenko-Scheffler (TS) without and with self-consistent screening (TS + SCS) effects). Those corrections have remarkly improved the agreement between our results and experiment for the interlayer distance (from 3.9 to 0.6%) [corrected] and high-level random-phase approximation (RPA) calculations for interlayer binding energy (from 69.5 to 1.5%). [corrected]. We report a systematic investigation of various structural, energetic and electron properties with the aforementioned vdW corrections followed by comparison with experimental and theoretical RPA data. Comparison between the resulting relative errors shows that the TS + SCS correction provides the best results; the other corrections yield significantly larger errors for at least one of the studied properties. If considerations of computational costs or convergence problems rule out the TS + SCS approach, we recommend the D3-BJ correction. Comparison between the computed π(z)Γ-splitting and experimental results shows disagreements of 10% or more with all vdW corrections. Even the computationally more expensive hybrid PBE0 has proved unable to improve the agreement with the measured splitting. Our results indicate that improvements of the exchange-correlation functionals beyond the vdW corrections are necessary to accurately describe the band structure of graphite.

Abstract The present research aims to suggest a three-step guideline towards selecting a proper Nanofluid regarding the heat transfer effectiveness. To do so, employing two-step technique, the nanofluid’s samples were prepared in various nanoparticles’ concentrations (0.125, 0.25, 0.5, 0.75, and 1%) of MWCNT-ZnO hybrid nanoparticle in a thermal oil. The samples’ stability has been examined employing the Zeta potential analysis. The samples’ thermal conductivity has been experimentally measured at various temperatures (15, 25, 35, 45, and 55 °C) and solid concentrations. After that, a three-step guideline to select a proper nanofluid as a heat transfer fluid has been proposed. Then, for both the internal laminar and turbulent regimes, variations of pumping power due to adding hybrid nanoparticle has been theoretically studied. Furthermore, the possible effects of adding nanoparticles on the convective heat transfer coefficient in a microchannel heat sink have been investigated. The results declared that the convective heat transfer coefficient had been enhanced by 42%. It is concluded that the produced nanofluid, as coolant fluid, would bring a certain benefit in heat transfer applications. These pre-assessment process would ease the decision-making process in selecting a new coolant which possesses superior heat transfer properties in comparison to the conventional coolants (i.e., water and oil).

Abstract The thermalization of a burst of fast neutrons after injection into a graphite stack of dimensions 101 × 101 × 81 cm 3 has been studied by the reaction rates method. The Cd/Hg reaction ratio was measured in the centre and near one face of the stack over the period 90–1290 μus after neutron injection. Characteristic prompt gamma rays from both indicator materials were detected simultaneously using a small Ge(Li) detector placed within the stack. The results compare favourably with previous theoretical determinations of the time-dependent Cd/Hg ratio and with ratios calculated from time-dependent differential neutron spectra.

Establishment of a sustainable carbon sink by producing and adding carbonized materials to soils provides a promising way to reduce atmospheric CO2 concentrations and mitigate the progressing climate change. Production of hydrochars via hydrothermal carbonization represents an energy- and CO2-efficient method to carbonize biomass and also allows the usage of new feedstocks including wet materials (e.g. sewage sludge or other wet waste materials). There is a dearth of information on hydrochar effects on soil biota and plants, which is important to inform potential larger scale applications. Here we tested hydrochar derived from spent brewer's yeast in a greenhouse study with Medicago sativa and in a 5-month soil incubation study in order to examine its effects on plant growth, root symbionts (arbuscular mycorrhiza abundance and root nodulation) and, for the first time, on soil aggregation. We decided to wash the hydrochar material in order to separate adhering water soluble components resulting from the production process and used the resulting leachate as a separate treatment. In both studies, soil aggregation was positively influenced by addition of the hydrochar. However, in contrast to a previous study, this hydrochar had no positive effects on AM fungal abundance; in fact we found a clearly negative effect on AM-fungal root colonization especially when both, hydrochar and its leachate were applied. Conversely, increased rates of root nodulation were found. Clearly, biota groups diverged in their response to hydrochar; this needs to be considered in test designs. These results highlight that it is necessary to carefully test materials derived from hydrothermal carbonization before applying them at an agricultural scale in order to prevent negative effects on soil biota.

This article considers the use of an unmanned aerial vehicle (UAV) for covert video surveillance of a mobile target on the ground and presents a new online UAV trajectory planning technique with a balanced consideration of the energy efficiency, covertness, and aeronautic maneuverability of the UAV. Specifically, a new metric is designed to quantify the covertness of the UAV, based on which a multiobjective UAV trajectory planning problem is formulated to maximize the disguising performance and minimize the trajectory length of the UAV. A forward dynamic programming method is put forth to solve the problem online and plan the trajectory for the foreseeable future. In addition, the kinematic model of the UAV is considered in the planning process so that it can be tracked without any later adjustment. Extensive computer simulations are conducted to demonstrate the effectiveness of the proposed technique.

Hydropower projects are site specific which require huge investment and have long gestation periods. These characteristics expose hydropower projects to various uncertainties and risks such as economic, environmental, social, geological, regulatory, political, technological, financial, climate, natural, and safety. These risk factors, if not managed in time, lead to schedule and cost overruns which ultimately cause delays in the availability of power that too at a higher cost and in extreme cases lead to project failures. Sustainability has also become a critical and unavoidable issue in hydropower development due to associated environmental and social impacts. Sustainable development is related to techno-economic development along with preserving the environment. Hence, to assure this equity and manage the critical risks more efficiently, there arises a strong need for comprehensive risk management in hydropower projects. This paper presents a systematic review of risk management in hydropower projects with a specific focus on sustainable development. The paper discusses various risk assessment techniques and recommends sensitivity analysis as a primary method to evaluate the significant risk factors. The construction phase of hydropower projects is identified as the most critical phase associated with uncertainties and involves considerable cost. Thus, the review highlights the need for incorporation of risk analysis in the cost estimation process and the provision for finance with sufficient margin on the ex-ante base cost to account for uncertainties, especially for developing countries. For future research, the use of fuzzy hybridized with artificial neural network and genetic algorithm is suggested for risk assessment of hydropower projects.

This study uses integrated hydrometeorological simulations over the Alabama-Coosa-Tallapoosa (ACT) River Basin in the southeastern United States to understand the impact of climate change on probable maximum precipitation.

Abstract Modeling the physical conditions of interstellar medium requires knowledge of accurate rate coefficients for collisional excitation of molecules by the abundant chemical species like He and H2. The present paper aims to study transitions in the low rotational levels in the ground vibrational state of CN+(X 1Σ+) by collisions with helium atoms. We computed ab initio two-dimensional (rigid-rotor) potential energy surface for the He-CN+ van der Waals collision complex using multi-reference configuration interaction method employing augmented correlation consistent polarized valence quadruple-ζ basis set. The bound-states of the van der Waals complex are obtained by coupled channel approach. The state-to-state rotational excitation cross sections are computed by exact close-coupling quantum mechanical formalism up to center of mass collision energy of 2000 cm−1. The corresponding rate coefficients are obtained up to 300 K temperature.

The acetylcholinesterase from synaptosomal membranes is inhibited by anesthetics: Nembutal, brietal, and thiopental. Nembutal and brietal decrease the Km for acetylthiocholine, without changes in Vmas. A noncompetitive type of inhibition is produced by thiopental. This anesthetic decreases Arrhenius plot discontinuity by about 4 degrees C and increases activation energies. Nembutal and brietal do not change Arrhenius plot discontinuities, but they increase activation energies. These results suggest that barbiturates change lipid-protein interactions in synaptosomal membranes.

In Antarctica, we investigated the energy consumption of Adelie (Pygoscelis adeliae), Gentoo (P. papua) and Chinstrap (P. antarctica) penguins while resting in the water (8.4 W-kg−1) and swimming underwater at various speeds, using a 21m long canal filled with sea-water at 4°C in conjunction with respirometry. The birds swam at will and consumed 15.7, 16.1 and 10 W·kg−1 at the speed where cost of transport was minimal (2.1, 2.3 and 2.5 m·s−1 in Adelie, Gentoo and Chinstrap penguins, respectively). Thermal conductance in pygoscelid penguins was 3.3 W·°C−1. m−2 and energy expenditure (Pi, W·kg−1) while resting in the water is given by Pj = -0.3 ta+9.6, where ta is water temperature in °C. During the breeding season, pygoscelid penguins spend 25–40% of their daily energy expenditure while foraging at sea. The importance of accurate estimates of at-sea activity and energy consumption is discussed.

En el presente artículo los autores presentan y exponen los resultados obtenidos en la conformación de unlaboratorio virtual asistido con Matlab, para el diseño de un controlador multivariable en una columna dedestilación. Aquí se expone el estudio de un método de desacoplamiento el cual es basado en la matriz defunciones de transferencia del proceso. El aspecto novedoso de la metodología empleada radica en el usode un modelo experimental de una columna de destilación para implementar a través de la simulación uncontrol por desacoplamiento clásico, con una correspondiente evaluación de su desempeño. Los resultadosfinales son mostrados en respuestas temporales usando Matlab. In this paper the authors present and discuss results obtained on the conformation of a practice of virtuallaboratory attended with Matlab, for the design of a multivariavels controller for a distillation column. It'scarried out a study of the decoupling method to be implemented, which is based on the use of the transferfunctions matrix of the researched process. The innovative aspect of the employed methodology lies onthe use of the experimental model of a real distillation column in order to implement, through simulation,techniques of classical decoupling with the correspondent performance evaluation. The final results areshown through the obtained time responses using Matlab.