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[en] Energy storage must play a crucial role in the widespread adoption of renewable energy sources because they are intermittent. In addition, energy storage is also important in matching the electrical power load with the generation capacity to improve the overall power plant efficiency. This point has been recognized in the recent California state mandate for the electrical utility companies to have energy storage at each power plant in order to utilize their generation capacity more efficiently. While electrochemical energy storage is still very expensive, thermal energy storage can be cost effective even at the present commercial development level, especially for solar CSP plants and conventional thermal power plants. Use of phase change materials for thermal energy storage can increase the storage density, reduce the size and therefore reduce the costs even further. However, it presents certain challenges in terms of poor heat transfer and material compatibility issues. This presentation will describe how these challenges have been overcome by innovative and transformative solutions to develop thermal energy storage using phase change materials at a system cost of less than $15/kWhth as compared to the present commercial thermal energy costs of more than $30/kWhth. (author)
[en] India faces a major challenge in providing a long-term energy security needed for meeting the aspirations of her growing population and, at the same time, in fulfilling her commitments for preventing generation of greenhouse gases. Use of non-fossil energy sources is the solution. There is a need for making a right balance of generation of energy from sources such as solar and wind which are, by nature, distributed and intermittent and from nuclear which is concentrated and continuous. It will be highlighted in this presentation how the solar and nuclear energy – the two primary energy sources can complement each other in supplying energy in a sustainable manner
[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] 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
[en] The present report discusses the renewable energy sources and 21 century (future development, energy revolution and solar radiation in space). The share of renewable energy sources grows normally from 20% to more than 50%. The solar energy from space is the main energy supply in 21 century.
[en] On the one hand energy, respectively electricity based on conventional and renewable, energy sources nationwide, are crucial for economic and social development. Considered globally, they are in continuous progress and the pace of their growth outpaced that of industry and other economic sectors. On the other hand the development of the energy sector in many cases creates problems associated with the environment, which become increasingly relevant, particularly with regard to global warming in recent decades. Subject of this report is an overview of the use of conventional and renewable energy sources concerning the safety and environmental impact. From this point of view is a brief overview is made on the main advantages and disadvantages of conventional power plants and power generation facilities based on solar, wind and biomass, which have high energy potential in Bulgaria. After analysis of selected basic principles of European and national legislation are presented the opportunities and dynamics of the use of various sources of energy in the country, now and in the larger time interval.
[en] Solar cells have huge potential to cost effectively tap the abundant amount of solar energy and supplement the other forms of renewable energy resources. Realizing the importance of solar energy conversion, BARC had initiated the work on solar cells in the decade of 1970 with an objective to fabricate space quality solar cells. The technology for space quality solar cells were developed, modules were fabricated, these were deployed for the intended purpose, and the complete know-how and technology was transferred in 1980s to outside agencies. The developed technology is relevant and useful till date therefore, salient features of that development has been presented in the talk
[en] In recent years, coincidence spectroscopy of photo and Auger electrons helped to investigate the de-excitation of atoms, molecules and solids. These techniques are, for example, used at synchrotrons to analyze the emission of multiple electrons due to Auger processes that follow the excitation or ionization of inner-shell electrons. The total kinetic energy of the emitted electrons allows to obtain information about the spectrum and population of the final states, while the individual electron energies reveal details about the intermediate states, and therefore the decay pathways of an Auger cascade.