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[en] Highlights: • A novel portable solar collector mechanism is optimally designed. • Wireless power transfer is first applied to cooling systems. • A supercapacitor stores electricity and outputs a regulated supply. • The proposed cooling system shows high efficiency in a limited space. - Abstract: As the greenhouse effect becomes increasingly serious, cooling a vehicle cabin parked under the blazing sun without running the engine or using an electric vehicle’s power has received considerable attention. In this paper, we develop a novel portable, renewable, solar energy-powered cooling system with wireless power transfer (WPT) and supercapacitors to cool the vehicle cabin. The proposed system consists of a solar collector mechanism, an energy conduit, and a temperature control and cooling module. First, consisting of folding solar photovoltaic (PV) panels, the solar collector mechanism making the proposed system portable. Once collected, the solar energy is converted into electricity and stored in the supercapacitors through wireless power transfer without breaching the vehicle body. Automatic temperature regulation is achieved with the cooling device via the temperature control and cooling module. The experimental results indicate that a maximum output power of 2.181 W and a maximum WPT efficiency of 60.3% are achieved when the prototype loaded with 3 Ω and 5 Ω respectively. Meanwhile, the simulation shows the temperature inside the cabin is reduced by as much as 4.2 °C in average, demonstrating that the proposed solar energy-powered cooling system is effective and feasible in cooling a hot vehicle cabin.
[en] To study the dynamics resonances of the Cl + HD reaction which was proposed to proceed via abstraction mechanism with no clear resonances, we perform dynamics calculations by the multiconfiguration time-dependent Hartree (MCTDH) method based on recently developed neural-networks potential energy surface (Science 347 (2015), 60). The HD molecule in (GS), (EX1), (EX2), and (EX3) states is used for the reactant. For GS, no distinctive resonance peak is found, while for EX1 two distinctive peaks at kinetics energies of and eV are investigated. These resonance peaks are well consistent with the previous results (Science 347 (2015), 60). Moreover, the present MCTDH calculations predict well-marked resonance peaks at , and eV for EX2 and EX3, which indicates that anticipation of the chemical bond softening model (Science 327 (2010), 1501) is confirmed in this work.
[en] Highlights: • An analysis-forecast system for wind speed uncertainty modeling is proposed. • Recurrence analysis is developed to study the characteristics of wind speed. • Feature selection is developed to determine optimal system input. • An improved multi-objective optimizer is first proposed to optimize the system further. • The proposed system shows a greater advantage over benchmark models considered. - Abstract: The uncertainty analysis and modeling of wind speed, which has an essential influence on wind power systems, is consistently considered a challenging task. However, most investigations thus far were focused mainly on point forecasts, which in reality cannot facilitate quantitative characterization of the endogenous uncertainty involved. An analysis-forecast system that includes an analysis module and a forecast module and can provide appropriate scenarios for the dispatching and scheduling of a power system is devised in this study; this system superior to those presented in previous studies. In order to qualitatively and quantitatively investigate the uncertainty of wind speed, recurrence analysis techniques are effectively developed for application in the analysis module. Furthermore, in order to quantify the uncertainty accurately, a novel architecture aimed at uncertainty mining is devised for the forecast module, where a non-parametric model optimized by an improved multi-objective water cycle algorithm is considered a predictor for producing intervals for each mode component after feature selection. The results of extensive in-depth experiments show that the devised system is not only superior to the considered benchmark models, but also has good potential practical applications in wind power systems.
[en] Ongoing climate change affects complex and long-lived infrastructures like electricity systems. Particularly for decarbonized electricity systems based on variable renewable energies, there is a variety of impact mechanisms working differently in size and direction. Main impacts for Europe include changes in wind and solar resources, hydro power, cooling water availability for thermoelectric generation and electricity demand. Hence, it is not only important to understand the total effects, i.e., how much welfare may be gained when accounting for climate change impacts in all dimensions, but also to disentangle various effects in terms of their marginal contribution to the potential welfare loss. This paper applies a two-stage modeling framework to assess RCP8.5 climate change impacts on the European electricity system. Thereby, the performance of two electricity system design strategies - one based on no anticipation of climate change and one anticipating impacts of climate change - is studied under a variety of climate change impacts. Impacts on wind and solar resources are found to cause the largest system effects in 2100. Combined climate change impacts increase system costs of a system designed without climate change anticipation due to increased fuel and carbon permit costs. Applying a system design strategy with climate change anticipation increases the cost-optimal share of variable renewable energy based on additional wind offshore capacity in 2100, at a reduction in nuclear, wind onshore and solar PV capacity. Compared to a no anticipation strategy, total system costs are reduced.
[en] The Kitaev-Heisenberg model is source of a topological quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. The material -RuCl is composed of weakly van der Waals bound honeycomb layers of edge sharing RuCl octahedra which has recently emerged as a prime candidate for realising such physics. We studied -RuCl by means of thermal transport measurements, a valuable tool to probe elementary excitations of systems with low dimensional spin structure. While the in-plane, longitudinal heat transport is governed by heat conduction of phonons that strongly scatter off the magnetic excitations present in the system, studying the thermal Hall effect (Rhighi-Leduc effect) opens up a new path towards detecting a direct contribution of unconventional magnetic excitations to entropy transport. We have observed a sizeable transversal heat conductivity , the agreement of which with the theoretical predictions for the pure Kitaev model being suggestive of heat transport by fractionalised quasiparticles in -RuCl.
[en] Recent structure studies on 64Zn with two protons outside the major shell (Z = 28) has become essential in describing their energy spectrum that are obtained experimentally. Statistical theory of hot rotating nuclei (STHRN) method has been implied to investigate the effect of pair breaking phenomena for temperature (T > 1 MeV) and spin (M = 0 - 15ħ). The energy eigenvalues were obtained by diagonalizing Cranked Nilsson Hamiltonian for deformation parameter ε = 0.0 to 0.6 and shape parameter γ= -1800 to -1200. Excitation energy calculated using STHRN method gives very good comparison with the experimentally found excited levels. Back bending phenomenon and Moment of inertia plot serves as an evidence for the occurrence of pair breaking of nucleons around M = 6ħ and a shape transition from collective prolate to non-collective oblate is also observed. It is found that the value of neutron separation energy decreases (Sn) and proton separation energy (Sp) increases around the angular momentum M = 6ħ. The decrease in the value of Sn indicates that the neutrons are loosely bound to the nucleus. Thus it is concluded that the neutron pair is broken and it eventually lead to shape transition. (author)
[en] A brief summary of data collection and the creation of an actinometric database necessary for estimation of the solar energy potential of the Republic of Uzbekistan is provided. The results of the processing of four-year data from six meteorological stations of the Republic are presented in a graph form.
[en] Harnessing renewable solar energy through different technologies is greatly dependent on the advancement of solar grade materials’ science and engineering. In this article, the prominent solar energy technologies, namely solar photovoltaic and concentrated solar power and other relevant technologies, and aspects related to various solar grade materials, influence of nanomaterials on enhancement of solar energy harvest, technology–market relations, development of hybrid systems etc., are discussed. The inspiration to write this article is not only to review the existing technologies to harvest solar energy but also to highlight the pertinent and possible solutions thereof, especially from materials perspective.
[en] Highlights: • A 3D model couples flow and heat transfer processes of DHE, wellbore and reservoir. • The model is validated against experimental data with a maximum error of 8.3%. • The entire temperature and flow fields of DHE system is analyzed comprehensively. • Performances of single U-tube, double U-tube and spiral tube are compared. • Effects of key factors on heat extraction performance of DHE system are studied. - Abstract: The downhole heat exchanger (DHE) geothermal system is commonly used to exploit geothermal energy for space heating. In this paper, a 3D unsteady state numerical model is established to couple fluid flow and heat transfer processes of DHE system. The model is validated by field experimental data. Temperature and velocity fields are analyzed to understand thermal process of DHE system. Heat extraction performances of three different DHE structures, including single U-tube, double U-tube and spiral tube, are compared. Subsequently, cases are studied to investigate how key parameters affect DHE performance. Simulation results depict that spiral-tube has the best heat extraction performance. As working fluid mass flow rate rises, outlet temperature declines and thermal power increases. When inlet temperature ascends, outlet temperature rises while thermal power decreases. Effects of reservoir porosity and tube wall heat conductivity on DHE performance are minor. Higher subsurface water velocity and larger rock heat conductivity can improve DHE performance, but the former has a more significant influence. Besides, subsurface water flow direction has neglected influence on performances of single and double U-tube, but appreciable impact on that of spiral tube. Key findings of this work are beneficial for optimal design and optimization of DHE geothermal system.
[en] The optical response of ZnAl2X4 (X = S, Se, Te) compounds to photon energy as well as to temperature variations has been studied by using self consistent full potential linearized augmented plane wave (FP-LAPW) method with Wu-Cohen generalized gradient approximation (WC-GGA) and mBJ potential. From the energy band structures, a direct bandgap is observed in all the zinc aluminides compounds, which reduces in the order S>Se>Te. The mBJ potential brings the calculated energy band gap close to the experimental one. From the density of states, it is observed that there is a strong hybridization of Zn-d, Al-p and X-p states. The optical nature of the compounds is described in terms of the absorption coefficient, reflectivity etc. The peaks observed in the photocurrent spectra of ZnAl2Se4 corresponds to the various structures at 3.52, 3.61 and 3.717 eV observed in the calculated conductivity and absorbance spectra