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[en] Highlights: • New Hybrid system coupling photovoltaic and thermoelectric are studied. • Thermal transfer Method. • The effect of coupling types which are direct and indirect are examined. • The Heat Transfer is modeled in Hybrid system. • The indirect coupling significantly improves the overall efficiency. - Abstract: Advanced photovoltaic devices with a high performance/cost ratio is a major concern nowadays. In the present study, we investigate the energetic efficiency of a new concept based on an indirect (instead of direct) photovoltaic and thermoelectric coupling. Using state-of-the-art thermal transfer calculations, we have shown that such an indirect coupling is an interesting alternative to maximize solar energy exploitation. In our model, a concentrator is placed between photovoltaic and thermoelectric systems without any physical contact of the three components. Our major finding showed that the indirect coupling significantly improve the overall efficiency which is very promising for future photovoltaic developments.
[en] The efficiency of materials developed for solar energy and technological applications depends on the interplay between molecular architecture and light-induced electronic energy redistribution. The spatial localization of electronic excitations is very sensitive to molecular distortions. Vibrational nuclear motions can couple to electronic dynamics driving changes in localization. The electronic energy transfer among multiple chromophores arises from several distinct mechanisms that can give rise to experimentally measured signals. Atomistic simulations of coupled electron-vibrational dynamics can help uncover the nuclear motions directing energy flow. Through careful analysis of excited state wave function evolution and a useful fragmenting of multichromophore systems, through-bond transport and exciton hopping (through-space) mechanisms can be distinguished. Such insights are crucial in the interpretation of fluorescence anisotropy measurements and can aid materials design. Finally, this Perspective highlights the interconnected vibrational and electronic motions at the foundation of nonadiabatic dynamics where nuclear motions, including torsional rotations and bond vibrations, drive electronic transitions.
[en] Most of world power plant traditionally use the cooling with water, and the types of cooling system are different from each other. The 85% of cooling system are once-through cooling system and closed cycle wet cooling system. There are two dry cooling system which are direct and indirect cooling system. In direct type, turbine exhaust is directly cooled by air-cooled condenser. In indirect system, turbine steam is cooled by recirculating intermediate cooling water loop, then the loop is cooled by air-cooled heat exchanger in cooling tower. In this paper, the purpose is to remove MMR waste heat, 24 MWth by using newly designed tower. The possibility of enhancing cooling performance by solar energy is analyzed. The simple cooling tower and solar cooling tower are presented and two design should meet the purpose of removing MMR waste heat, 24 MW. In simple cooling tower, as the number of finned tube increase, the required chimney height decreased. In solar cooling tower, as the collector radius increased, the required chimney height is decreased. To optimized the solar cooling tower, the cost analysis was conducted to find low cost tower. To analyze solar cooling tower further, consideration of solar energy performance at night should be analyzed.
[en] A dual-mode thermochemical sorption energy storage system using working pair of expanded graphite/SrCl2-NH3 was proposed for seasonal solar thermal energy storage. The proposed system has two working modes to produce useful heat with an expected temperature during the discharging phase according to the different ambient temperatures, including the direct heating supply and temperature-lift heating supply. Solar thermal energy is transformed into chemical bonds and stored in summer, and the stored energy is released in the form of chemical reaction heat in winter. The direct heating supply mode is adopted at a relatively high ambient temperature in winter. The effective energy storage density is higher than 700 kJ/kg and the corresponding system COP is 0.41 when the heat output temperature and ambient temperature are 35 °C and 15 °C, respectively. The specific heating power increases with the decrease of heat output temperature for a given ambient temperature. The temperature-lift heating supply mode is adopted to upgrade the heat output temperature at a low ambient temperature below 0 °C in winter. It can produce heat with a temperature above 70 °C although the ambient temperature is as low as −15 °C. It is desirable to further improve the system performance using low mass ratio and high global conversion. Experimental results showed the advanced dual-mode thermochemical sorption energy storage technology is feasible and effective for seasonal solar thermal energy storage. - Graphical abstract: Working temperature range of dual-mode thermochemical sorption energy storage system during the discharging phase in winter. - Highlights: • A dual-mode seasonal solar thermochemical sorption energy storage system is developed. • The sorption working pair is strontium chloride/expanded graphite-ammonia. • Two working modes can be performed according to the different heat requirements in winter. • Energy density and COP of direct heating supply mode are 706 kJ/kg and 0.41 respectively. • Temperature-lift heating supply mode can meet heat demand at low ambient temperature.
[en] This paper presented a symmetric prismatic daylight collector to collect daylight for the natural light illumination system. We analyzed the characteristics of the emerging light when the parallel light beam illuminate on the horizontally placed symmetric prismatic daylight collector. The ratio of the relative intensities of collected daylight that emerging from each surface of the daylight collector shown that the ratio is varied with the incident angle during a day. The simulation of the emerging light of the daylight collector shown that the ratio of emerging light is varied with the tilted angle when sunshine illuminated on a symmetric prismatic daylight collector which was not placed horizontally. The integration of normalized intensity is also varied with the tilted angle. The symmetric prismatic daylight collector with the benefits of reducing glare and dividing intensity of incident daylight, it is applicable to using in the natural light illumination system and hybrid system for improving the efficiency of utilizing of solar energy. (paper)
[en] Highlights: • The concept of a thermophysical battery for storing thermal energy is demonstrated. • The battery provides heating and cooling for stationary and mobile applications. • Energy storage mechanisms: adsorption-desorption and evaporation-condensation. • Max. heating: 103 W/l and 65 W/kg; Max. Cooling: 78 W/l and 49 W/kg. • Novel adsorbents further enhance performance for a compact and lightweight system. - Abstract: Climate control applications in the form of heating and cooling account for a significant portion of energy consumption in buildings and transportation. Consequently, improved efficiency of climate control systems can significantly reduce the energy consumption and greenhouse gas emissions. In particular, by leveraging intermittent or continuous sources of waste heat and solar energy, thermally-driven energy storage systems for climate control can play a crucial role. We demonstrate the concept of a thermophysical battery, which operates by storing thermal energy and subsequently releasing it to provide heating and cooling on demand. Taking advantage of the adsorption-desorption and evaporation-condensation mechanisms, the thermophysical battery can be a high-power density and rechargeable energy storage system. We investigated the thermophysical battery in detail to identify critical parameters governing its overall performance. A detailed computational analysis was used to predict its cyclic performance when exposed to different operating conditions and thermodynamic cycles. In addition, an experimental test bed was constructed using a contemporary adsorptive material, NaX-zeolite, to demonstrate this concept and deliver average heating and cooling powers of 900 W and 650 W, respectively. The maximum power densities and specific powers observed were 103 W/l and 65 W/kg for heating, and 78 W/l and 49 W/kg for cooling, respectively, making the thermophysical battery competitive with the state-of-the-art climate control systems that provide relatively lower power densities. Additionally, with further opportunities for development and innovation, especially in synthesizing novel adsorptive materials, the thermophysical battery can achieve significantly higher power densities. With its ability to function using thermal energy input while being compact and lightweight, the thermophysical battery offers an option to address the energy challenges associated with the rising demand for climate control.
[en] Highlights: • Geothermal energy assisted milk powder production line was studied thermodynamically. • The first study on exergy analysis of a milk powder production line. • The overall energy and exergy efficiencies were calculated as 85.4 and 57.45%, respectively. • The evaporator, has the highest exergy destruction rate with 333.6 kW, needs a detailed assessment. - Abstract: Milk has been consumed since time immemorial because of its unique nutritional properties and produced almost 816 million tonnes in the year of 2016. Due to its highly perishable characteristic, milk is processed into more stable milk products such as cheese, yoghurt, and butter and milk powder. Among them, milk powder is distinctive for its longer shelf life and can be stored at ambient temperature. The other advantages of milk powder are less volume requirement during its transportation and higher selling price. Therefore, it is widely used in many food products such as ice cream, bakery products, and sausages. According to a recent study on the statistics from Food and Agriculture Organization, world production of whole dried milk was 3,597,015 tonnes in 2014: Oceania 36.5%, Americas 36.1% and Europe 24.1% of the World production. Milk powder production is a process that requires high energy, especially for evaporation. Recently, reducing energy use has been gaining importance by increasing energy and exergy efficiency. Conventional energy analysis is performed based on the First Law of Thermodynamics. Unlike from the First Law, the Second Law or exergy analysis (defined as useful work) has appeared in the literature, while this analysis not only assesses quantity but also quality of energy. In this study, exergy analysis of a milk powder production system, mainly includes 3 processes (pasteurization, evaporation and spray drying) which will be presented. The aim of the study is to apply a thermodynamic analysis including comprehensive exergy analysis by using different performance parameters such as exergy efficiency, improvement potential rate, sustainability index, relative irreversibility and exergetic factor for the milk powder production system. As a result, exergetic efficiencies of the system components were found in the range of 9–83%. The overall energy and exergy efficiencies of the whole milk powder production system were calculated as 85.4 and 57.45%, respectively. Additionally, it was found that the evaporator and the heater have a higher impact in improvement actions.
[en] Decreasing energy costs from renewable sources could enable many African countries to make the leap into a clean future. This would save the continent the detour via the classic dirty sources.
[de]Sinkende Kosten fuer Energie aus erneuerbaren Quellen koennten vielen afrikanischen Laendern den Sprung in eine saubere Zukunft ermoeglichen. Damit wuerde sich der Kontinent den Umweg ueber die klassischen schmutzigen Quellen sparen.
[en] Decreasing fuel consumption in compressed air energy storage (CAES) system is a general trend for conserving energy and protecting the environment. Waste heat recovery is an interesting technology to compact energy storage system. However, CAES system has a low thermal efficiency when using low grade waste heat as heat source directly. In this paper, an integrated energy system consisting of a CAES system and a precooling system (PC-CAES) is proposed to decrease the energy consumption of compression train in the charging process, and enhance the round trip efficiency (RTE) of the system. Air conditioner is utilized as pre-cooler to precool the inlet air of compressor and five refrigerants are investigated. The thermodynamic analysis is performed by using steady-state mathematical model and thermodynamic laws. The calculation results show that the RTE of the proposed PC-CAES system is improved by more than 3% than that of the conventional CAES system and more economical than CAES with additional compression stages. Meanwhile, a parametric analysis is also carried out to evaluate the effects of several key parameters on the system performance of two CAES systems. - Highlights: • A novel CAES system combined with pre-cooler is introduced. • Proposed PC-CAES is more compact than A-CAES by using free waste heat. • Air conditioner is utilized as pre-cooler to precool the inlet air of compressor. • Efficiency improvement is achieved via cool down the compressor inlet air temperature.