Thermodynamic Optimization of Electrical and Thermal Energy Production of PV Panels and Potential for Valorization of the PV Low-Grade Thermal Energy into Cold

In the present study, the evaluation of potential improvement of the overall efficiency of a common PV panel, valorizing the heat extracted by a heat exchanger that is integrated on its back side, either into work using an endoreversible Carnot engine or into cold by using an endoreversible tri-thermal machine consisting of a heat-driven refrigeration machine operating between three temperature sources and sink (such as a liquid/gas absorption machine), was carried out. A simplified thermodynamic analysis of the PV/thermal collector shows that there are two optimal operating temperatures and of the panels, which maximize either the thermal exergy or the overall exergy of the PV panel, respectively. The cold produced by the endoreversible tri-thermal machine during the operating conditions of the PV/thermal collector at is higher with a coefficient of performance (COP) of 0.24 thanks to the higher heat recovery potential. In the case of using the cold produced by a tri-thermal machine to actively cool of an additional PV panel in order to increase its electrical performances, the operating conditions at the optimal temperature provide a larger and more stable gain: the gain is about 12.2% compared with the conventional PV panel when the operating temperature of the second cooled panel varies from 15 to 35 °C.

The bows and rings of dawn and dusk

The arcs of dawn and dusk are natural phenomena that define the boundary of the border between day and night. They are associated with the refraction of solar rays at high angles of incidence that converge to project an arc of light onto the back side of the earth's atmosphere. The rings of dawn and dusk, in turn, are associated with rays, also at large angles of incidence, which converge to project the image of the Sun. Arcs and rings become visible by scattering light by clouds or particles suspended in atmospheric air in the region in which they occur. Here we show a model that describes these natural phenomena and report the first-time record image produced in July of this year.

Computational Studies of Coinage Metal Anion M− + CH3X (X = F, Cl, Br, I) Reactions in Gas Phase

We characterized the stationary points along the nucleophilic substitution (SN2), oxidative insertion (OI), halogen abstraction (XA), and proton transfer (PT) product channels of M− + CH3X (M = Cu, Ag, Au; X = F, Cl, Br, I) reactions using the CCSD(T)/aug-cc-pVTZ level of theory. In general, the reaction energies follow the order of PT > XA > SN2 > OI. The OI channel that results in oxidative insertion complex [CH3–M–X]− is most exothermic, and can be formed through a front-side attack of M on the C-X bond via a high transition state OxTS or through a SN2-mediated halogen rearrangement path via a much lower transition state invTS. The order of OxTS > invTS is inverted when changing M− to Pd, a d10 metal, because the symmetry of their HOMO orbital is different. The back-side attack SN2 pathway proceeds via typical Walden-inversion transition state that connects to pre- and post-reaction complexes. For X = Cl/Br/I, the invSN2-TS’s are, in general, submerged. The shape of this M− + CH3X SN2 PES is flatter as compared to that of a main-group base like F− + CH3X, whose PES has a double-well shape. When X = Br/I, a linear halogen-bonded complex [CH3−X∙··M]− can be formed as an intermediate upon the front-side attachment of M on the halogen atom X, and it either dissociates to CH3 + MX− through halogen abstraction or bends the C-X-M angle to continue the back-side SN2 path. Natural bond orbital analysis shows a polar covalent M−X bond is formed within oxidative insertion complex [CH3–M–X]−, whereas a noncovalent M–X halogen-bond interaction exists for the [CH3–X∙··M]− complex. This work explores competing channels of the M− + CH3X reaction in the gas phase and the potential energy surface is useful in understanding the dynamic behavior of the title and analogous reactions.

Single-shot experiments at the soft X-FEL FERMI using a back-side-illuminated scientific CMOS detector

The latest Complementary Metal Oxide Semiconductor (CMOS) 2D sensors now rival the performance of state-of-the-art photon detectors for optical application, combining a high-frame-rate speed with a wide dynamic range. While the advent of high-repetition-rate hard X-ray free-electron lasers (FELs) has boosted the development of complex large-area fast CCD detectors in the extreme ultraviolet (EUV) and soft X-ray domains, scientists lacked such high-performance 2D detectors, principally due to the very poor efficiency limited by the sensor processing. Recently, a new generation of large back-side-illuminated scientific CMOS sensors (CMOS-BSI) has been developed and commercialized. One of these cost-efficient and competitive sensors, the GSENSE400BSI, has been implemented and characterized, and the proof of concept has been carried out at a synchrotron or laser-based X-ray source. In this article, we explore the feasibility of single-shot ultra-fast experiments at FEL sources operating in the EUV/soft X-ray regime with an AXIS-SXR camera equipped with the GSENSE400BSI-TVISB sensor. We illustrate the detector capabilities by performing a soft X-ray magnetic scattering experiment at the DiProi end-station of the FERMI FEL. These measurements show the possibility of integrating this camera for collecting single-shot images at the 50 Hz operation mode of FERMI with a cropped image size of 700 × 700 pixels. The efficiency of the sensor at a working photon energy of 58 eV and the linearity over the large FEL intensity have been verified. Moreover, on-the-fly time-resolved single-shot X-ray resonant magnetic scattering imaging from prototype Co/Pt multilayer films has been carried out with a time collection gain of 30 compared to the classical start-and-stop acquisition method performed with the conventional CCD-BSI detector available at the end-station.

Isothermal Air Flow Investigation in Industrial Baking Oven of Different Impeller Locations using Computational Fluid Dynamics (CFD) Approach

Computational fluid dynamics (CFD) modelling was performed on a forced convection oven to investigate the isothermal airflow. Three oven design configurations based on their impeller location (back, side, and top wall) were compared with respect to their Turbulence Kinetic Energy (TKE) profile to determine the optimal configuration design for quick uniform baking. The air velocity was estimated from both experimental and modelling approaches at specific points in an oven with the back walled impeller. The CFD model was validated resulting in a calculation error of 30.34% of actual velocity which was mainly due to limitation in grid density and the turbulence modelling. The other two oven configurations were simulated and their average TKE data were extracted and compared. The third configuration (impeller at the top wall) was found to have the highest average TKE of 3.55 m2/s2 followed by the first configuration (impeller at the back wall) with 3.30 m2/s2 which provides a relatively uniform TKE distribution across the cavity. The findings show the significance of impeller placement in oven performance.

A Thermopile Detector Based on Micro-Bridges for Heat Transfer

A thermopile detector with their thermocouples distributed in micro-bridges is designed and investigated in this work. The thermopile detector consists of 16 pairs of n-poly-Si/p-poly-Si thermocouples, which are fabricated using a low-cost, high-throughput CMOS process. The micro-bridges are realized by forming micro trenches at the front side first and then releasing the silicon substrate at the back side. Compared with a thermopile device using a continuous membrane, the micro-bridge-based one can achieve an improvement of the output voltage by 13.8% due to a higher temperature difference between the hot and cold junctions as there is a decrease in thermal conduction loss in the partially hollowed structure. This technique provides an effective way for developing high-performance thermopile detectors and other thermal devices.

A Rare Belt Plaque in Zoomorphic Style from the Inner Tien Shan

The article publishes a very rare for Saka culture of the Tien Shan region belt plaque, made with the Scythian-Siberian animal motif. It was accidentally found at an altitude of 2300 m. in the northern part of the Inner Tien Shan, and, most likely, it was lost there in antique time. The plaque has a butterfly-shaped shape, and a relief paired heads of a snow leopard was depicted on its outer surface in a realistic manner. On its reverse side there are two small loops indicating the construction of the combat belt on which it was fixed. Apart from the main belt there were additional leather straps which also were used as laces in the front. Belts of a similar construction with plaques of similar shape were previously found only in an elite burial of the Issyk kurgan in Tien Shan region. Nevertheless, outside this region, this belt plaque has close analogies in the synchronous cultures of the Scythian type in the Forest-steppe Altay, Tuva, Ordos and Northern China, as well as in the forest-steppe part of the Urals region. Based on stylistics and analogies, this belt plaque can be dated back to the turn of the 5th and 4th centuries BC. But in these regions, with the exception of the Urals, all similar plaques have one central loop on the back side. This indicates an independent line of development of these belt garment items on the territory of Saka culture of the Tien Shan region, although the origins of this line, undoubtedly, were initially outside its distribution area.

Performance Analysis of Photovoltaic Module with Different Passive Cooling Methods

This paper analyses the difference in terms of performance of passive cooling systems for photovoltaic (PV) modules. The objective of this paper is to identify which passive cooling systems offers the best results in reducing the operating temperature and improving the generation of output power. The performance of photovoltaic (PV) module will gradually decrease as the operating temperature increases. The energy from the sun’s photons are not enough to knock out the electrons from the atom to generate more electricity. That being the case, two passive cooling systems is developed which is the cotton wick structures with water and aluminium fins were attached to the back side of the photovoltaic (PV) module. The cotton wick structures with water utilises the capillary action of the water to extract excess heat from the module while the aluminium fins act as a heat sink that can remove heat from module to the adjacent air. Results showed that the cooling systems managed to enhance the output power by an average of 3.94% for the module with cotton wick structures with water while an average of 2.67% increment for the module under aluminium fin mounted as the cooling system.

Tillage unit with new design working bodies for minimal tillage

The design of the tillage unit is presented, with new working bodies made in the form of a holder with rectilinear and oval parts, the rectilinear part is made in the form of a bar made at an acute angle to the horizontal surface and rigidly fixed on a rack with the possibility of dismantling. The lower part of the holder is shaped like an elongated ellipse, the upper oval part of which is a ripper, the lower-a slitter. The height of the ripper and the slitter is the same, on their butt line on the side of the toe, a groove is made for the pointed paw of the cultivator. On the back side of the paw, a groove is made for the holder, while the ratio of the length of the grooves of the paw and the holder is 1:3. The new design of the working body will improve the quality of tillage and water-air balance, increase crop yields and reduce fuel consumption.