• Energy Research
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Solar energy is a natural source that provides clean and renewable energy, which supplies two types of energy: thermal energy and photovoltaic energy. Whereas, the most effective way to exploit this energy is photovoltaic cells. However, for all the incident solar radiation, the solar panels can absorb a limited quantity of energy. While, the rest of radiation energy gets lost as heat, that increases the temperature of the photovoltaic cells, this is the reason why the productivity of electricity is decreased. Therefore, to exceed this issue and benefit from the two sources of sun radiation, a hybrid thermo-electrical system is proposed. The system is a solar panel surrounded by the phase change material that can absorb the temperature to increase the efficiency of solar system and use this energy to produce a hot water.

Thermal energy storage (TES) systems are much preferred in many engineering applications, which have the ability to overcome the mismatch between energy supply and energy demand. TES can be used to store thermo-chemical, sensible, or latent heat or a combination of these. Among the three forms, latent heat thermal energy storage (LHTES) has grown considerably in importance over recent years as a promising alternative to traditional systems. These systems use phase change materials (PCM), in simple or cascade configuration, and store the latent heat of melting (charging process) and release it during solidification (discharging process). Among different configurations of LHTES systems, tube and shell heat exchangers represent a promising and simple design in high temperature PCM. In this paper, we present a new numerical study involving a tube and shell heat exchanger to evaluate the heat storage phenomena. A case study and numerical results are provided using the Lattice Boltzmann Method.

This paper focuses on the design of an optimized thermal interface for a thermoelectric energy harvesting system mounted at endothermic animals. In this application scenario the mammal’s fur reduces the heat flux from the animal’s body through a thermoelectric generator (TEG) to the ambient air. This requires an adapted design of the thermal interface between TEG and body surface, to increase its thermal conductivity without harming the animal. For this purpose the thermal conductivity through a mammal’s fur is determined with a specially designed heatsink. An analytical model is built to predict the resulting thermal resistances and is validated with experimental results for two different fur lengths. We show that an optimized design of the thermal interface reduces its thermal resistance up to 38% compared to a trivial design while lowering its weight for about 23%. It is found that the most important design parameter of such a thermal connector is the ability to slide into the fur.

An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned‐tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned‐tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises.

Abstract This paper deals with an investigation of a thermal energy harvester based on the coupling of a piezoelectric membrane and a bimetallic strip heat engine. The general working principle of the device consists of a double conversion mechanism: the thermal energy is first converted into mechanical energy by means of a bimetallic strip, then the mechanical energy is converted into electricity with a piezoelectric membrane. This paper deals with the study and optimization of the harvester’s design. First, the piezoelectric membrane configuration is studied to find the most efficient way to convert mechanical energy into electricity. A benchmark of various piezoelectric materials is then presented to point out the most efficient materials. Finally, our study focuses on the bimetallic strip’s properties: the effect of its dimensions of its thermal hysteresis on the harvester’s performances are studied and compared. Thanks to these different steps, we were able to point out the best configuration to convert efficiently thermal heat flux into electricity.

Currently the climate computer offers many benefits and solves problems related to the regulation, monitoring and controls. Greenhouse growers remain vigilant and attentive, facing this technological development. They ensure competitiveness and optimize their investments / production cost which continues to grow. The application of artificial intelligence in the industry known for considerable growth, which is not the case in the field of agricultural greenhouses, where enforcement remains timid. It is from this fact, we undertake research work in this area and conduct a simulation based on meteorological data through MATLAB Simulink to finally analyze the thermal behavior greenhouse microclimate energy. In this paper we present comparison of modeling and simulation management of the greenhouse microclimate by fuzzy logic between a wetland (Dar El Beida Algeria) and the other arid (Biskra Algeria).

AbstractConventional analyses suggest that the metabolism of heterotrophs is thermally more sensitive than that of autotrophs, implying that warming leads to pronounced trophodynamic imbalances. However, these analyses inappropriately combine within- and across-taxa trends. Our new analysis separates these, revealing that 92% of the difference in the apparent thermal sensitivity between autotrophic and heterotrophic protists does indeed arise from within-taxa responses. Fitness differences among taxa adapted to different temperature regimes only partially compensate for the positive biochemical relationship between temperature and growth rate within taxa, supporting the hotter-is-partially-better hypothesis. Our work highlights the importance of separating within- and across-taxa responses when comparing temperature sensitivities between groups, which is relevant to how trophic imbalances and carbon fluxes respond to warming.