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[en] Recent advances in science and technology of materials fabrication, engineering of work functions, and micrometer gap machining between emitter and collector are making thermionic conversion/converter (TEC) of solar energy an emerging technology. As the converter is the lightest of all devices with highest direct power conversion density (per unit area of the converting surface), it has, potential for substituting photovoltaic technology to a large extent and for deployment in space as a power source. This article summarizes the current efforts/technologies in the field, and discusses their inherent merits and demerits towards realizing the goal of achieving high conversion efficiency and simulation of performance evaluation of a solar TEC. We also discuss the use of both metals and nanomaterials, critical roles of work functions of both emitter and collector, collector temperature, absorptivity and emissivity of the surfaces, radiation losses, and use of both metals and nanomaterials in the efficiency of conversion of solar energy. We further deal with the role of correcting thermionic emission current density equation in the simulation of solar TEC performance. We discuss briefly the possible methods of space-charge control in future in a solar TEC. (author)
[en] Photovoltaic effect or phenomenon is the creation of a voltage and corresponding current in a material upon exposure to light energy following the principle that for every excitation there must be a response. The exposition of a solar cell to incident optical radiation excites the dislodgement of electrons hence the creation of holes and subsequent migration of opposite charges. The amount of voltage that can be generated is a function of the intensity of incident optical radiation and the position of the solar cell to such radiation. Measurements of illumination intensity from halogen and tungsten lamps by a digital lux meter and open circuit voltage, short circuit current as output parameters by volt- amp meter LCD display embedded in the solar power device was carried out. The evaluation of fill factor, maximum power and conversion efficiency as other output parameters in relation to illumination from the sources of light at varying angle and distance were carried out in this study also. The variation of the internal resistance of the cell with light intensity was also investigated. The maximum output voltage and current were realized at angle zero degree when the light ray falls at normal to the cell surface. The two 10 Watts halogen lamp gave the highest illumination intensity of 116lx while the 40 Watt and 60 Watt tungsten lamp placed at 10 cm from the solar cell indicated an intensity of 70lx and 25lx each. The results showed the strongly direct dependency of these parameters on illumination intensity and their inverse dependence on the tilt angle and distance of the illumination source. The internal resistance decreases with increasing intensity while the evaluated fill factor, maximum power and efficiency remain fairly constant but at an average value 0.53, 122mW and 55% respectively. (author)
[en] The influence of real operating conditions of the solar modules (solar radiation intensity, ambient temperature, wind speed) on their output performances is analyzed. An analytical expression is proposed, allowing to approximate the temperature of the solar modules. An algorithm for assessing the operating power of solar modules based on their data sheet information has been developed. The MatLab-Simulink simulation has shown that the identification of ambient and solar module temperatures leads to errors of up to 20 percent in estimating the operating power of solar modules
[en] At a time when the world is facing global warming and the burden on natural resources is increasing. Now, the world is switching towards cleaner form of energies. Renewable solar roof top is one of them. Most developed economies of the world have started their solar programmes by targeting household rooftops. Solar power has reached grid parity and is the cheapest source of distributed power across the world
[en] World energy demand is increasing and non-renewable resources are decreasing by exponentially putting a huge burden on the energy sector specifically on the oil and gas industry. To overcome these challenges, renewable energy is the best option with production optimization in the oil and gas sector. However, among all renewable energies, geothermal is the most suitable energy due to its sustainability and presence around the clock. Moreover, there are three types of wells for harnessing geothermal energy such as: producing oil and gas well, abandoned oil and gas wells and geopressured brine well with dissolved gas. In this research study, the author’s considers the technical aspects of electricity generation through oil and gas wells. The power capacity of these wells is determined by the production rate of the well mass flow (m) and temperature (T) of these wells. The main factors that control the wellhead temperature are mass flow rate and formation temperature. Our assessment of gas-producing well in the Kandhkot region showed the wellhead temperature of the produced fluid is too low, compared to ambient temperature for commercial generation of geothermal power. In our work, a conceptual design system to produce power from produced gas by using Solid Works Software is proposed and we have found some positive results. Seven well from the Kandhkot gas field were selected with different mass flow rates and negligible wellhead temperature difference. Author’s found the minimum power net output 21kW at the gas mass flow rate of 0.098504 kg/s with 7.5% thermal efficiency and maximum net output 27.5 kW at gas mass flow rate of 4.102524 kg/s with 10% thermal efficiency. The overall net output power produced from seven well is 174kW and can supply to local communities. (author)
[en] A formal analogy between the Friedmann equation of relativistic cosmology and models of convective–radiative cooling/heating of a body (including Newton’s, Dulong-Petit’s, Newton-Stefan’s laws, and a generalization) is discussed. The analogy highlights Lagrangians, symmetries, and mathematical properties of the solutions of these cooling laws.
[en] Heat leakage is an important parameter to reflect heat insulated performance of cryogenic vessel. According to the current standard requirements, it needs to measure the daily evaporation rate to indicate heat leakage. The test needs-over 24h after cryogenic vessel in heat equilibrium as standard required, therefore test efficiency is poor and new efficient method is required to cut test time. First of all, the volume of instantaneous evaporated gas and heat leakage are calculated by the current standard corresponding to the maximum allowable daily evaporation rate of cryogenic vessel. Depending on the relationship between real daily evaporation rate and maximum allowable daily evaporation rate of cryogenic vessel, we designed a new test method based on the pressure changes over time in cryogenic vessel to determine whether its heat insulated performance meets requirements or not. Secondly, the heat transfer process was analyzed in measurement of cryogenic vessel, and the heat transfer equations of whole system were established. Finally, the test was completed in four hours; meanwhile the heat leakage and daily evaporation rate of cryogenic vessel are calculated basing on test data
[en] Over the last two decades, Pakistan’s energy demand has grown exponentially with very diminutive measures taken by the government to fulfill the needs. The large power plant projects are cumbersome, take years to be completed and require plenty of time to get fully operational. The idea of distributed generation works well in this case. Renewable energy comes well into play when we talk about distributed generation but the dependability of renewable energy resources on back-up such as batteries makes them unappealing. The objective of this paper is to practically implement a backup for the renewable energy resources using a mechanical storage such as CAES (Compressed Air Energy System). The proposed model is a composite technology, which comprises of EES (Electrical Energy Storage) and electrical power supply system. Solar energy driven compressor is used to compress the air in a storage tank, which is used on demand to drive the generator coupled air turbine. The fact that the developed system is solar powered, no other fuel is used with air and it uses mechanical storage instead of conventional storage like batteries, which makes the developed prototype system efficient, economical and durable as compared to the existing CAES. This paper focuses on the thermodynamic investigation, design and finally implementing a prototype CAES for a small load as an un-interrupted power supply system. (author)
[en] The world needs energy to support everyday life and drive human and economic development. In 2019, over 26 000 terawatt-hours of electricity were produced worldwide. This electricity is being produced by a range of energy sources, mostly fossil fuels but also nuclear power and renewables such as solar, hydro and wind. Energy production and use are the largest source of greenhouse gas emissions around the world. As greenhouse gases are a driving force behind climate change, countries worldwide are actively working on a clean energy transition by changing how energy is produced. Here’s a closer look at the clean energy transition and what role nuclear power plays.
[en] The paper provides biographical data on the life and work of Academician of the USSR Academy of Sciences V.I. Subbotin. Academician Valeriy Subbotin was the founder of the scientific school in the field of heat and mass transfer, physical chemistry and technology of heat transfer of fluids in energy systems. The authors of the article present and analyze the key areas of his activity as an outstanding scientist and researcher
[ru]В работе приведены биографические данные о жизни и деятельности академика АН СССР В.И. Субботина, представлены и анализируются ключевые направления деятельности созданной им научной школы «Тепломассоперенос, физическая химия и технология теплоносителей в энергетических системах», руководителем которой он являлся