Applied Solar Energy最新文献

The possibilities of using single-mirror small solar furnaces (SSFs) with concentrators made of spotlight mirrors in high-temperature materials science are investigated. Calculated estimates of the optical-energy characteristics (OECs) of spotlight mirrors as SSF elements (average concentrations and flux distribution in the focal plane depending on the mirror inaccuracies) are carried out. Experimental studies of SSFs with a spotlight mirror with a diameter of 2 m and an opening angle of 60° showed that they can provide average flux densities of concentrated solar radiation up to 600–700 W/cm² on a working spot with a diameter of up to 10–15 mm and provide heating temperatures above 3000 K. The results of the study show the possibilities of using SSFs with a parabolic spotlight mirror with a diameter of 2 m in high-temperature materials science, both at the research stage and at the stages of developing the technology for obtaining functional materials in the Large Solar Furnace.

Based on the definition of energy security as a state of security of the country, its citizens, society, state, and economy from threats to reliable fuel and energy supply caused by external factors as well as the actual state and functioning of the energy sector of Uzbekistan, the state of energy supply and trends in electricity and heat supply are analyzed. The first part of the article shows the possibilities of hydropower resources of natural and artificial watercourses of Uzbekistan in ensuring energy security for the period up to 2030.

This study examines the electrochemical performance of aluminum dual-ion batteries (ADIBs) using binder-free graphene paper as the cathode and different molar ratios of AlCl₃ to 1-ethyl-3-methylimidazolium chloride [EMIm]Cl as the electrolyte. The graphene paper, with a thickness of 35 µm, offers high electrical conductivity and mechanical strength, making it a strong candidate for scalable energy storage systems. Three electrolyte compositions with AlCl₃ molar ratios of 1.3:1, 1.5:1, and 1.7:1 were tested to assess their effects on battery cell performance. Among these, the 1.7:1 composition exhibited the best electrochemical performance, with faster ion movement, lower charge transfer resistance, and more efficient aluminum-ion intercalation, leading to higher capacity retention. In contrast, the 1.3:1 ratio had limited ion mobility and increased internal resistance, while the 1.5:1 ratio offered a compromise between charge transfer efficiency and capacity retention. Electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic cycling confirmed that the optimized 1.7:1 electrolyte composition, combined with graphene paper, significantly improved the battery’s rate capability and energy efficiency. These findings highlight the promise of binder-free graphene paper and optimized electrolyte compositions in advancing ADIB technology for high-performance and scalable energy storage applications.

Solar power represents a clean and sustainable energy option that boasts widespread accessibility and the potential to drive the establishment of more sustainable systems in the times ahead. The use of solar energy for the use of draying of food, crops, space heating and air ventilation can be consented by a unique device is known as Solar Air Heater (SAH). The utilization of solar energy for activities such as food drying, crop cultivation, space heating, and air ventilation can be facilitated by a unique device known as a SAH. In the present investigation, a compressive investigation of a SAH with right triangular ribs attached to the absorber plate of various orientation with transverse pattern to the flow, investigated numerically. The orientations of the right triangle-shaped ribs are presented individually. Commercially available CFD simulation software, Ansys Fluent, is utilized to solve the equations governing mass, momentum, and energy. The absorber plate is upheld at a heat flux level of 1000 W/m². The effects of various factors on the performance of SAH, such as the inlet velocity of airflow and rib parameters (pitch and height), are examined. The research investigation includes a diverse set of Reynolds numbers, ranging from 3400 to 19 000. Additionally, the rib pitch ratio varies within the range of 7.33 to 20.66. The discussion has covered the pressure drop attributed to the existence of ribs. To elucidate the fluid flow’s physics, temperature, pressure, and velocity contours are presented. Significant improvement is observed, with an optimized case featuring a rib roughness pitch of 7.33 found for the SAH with triangular ribs, resulting in a Thermal Enhancement Ratio (TER) of 1.89. Non-linear regression analysis has been employed to derive the connections between the Nu and friction factor, demonstrating an accuracy within a 6% error margin.

This paper presents an analysis of the thermal performance of a parabolic trough collector (PTC) integrating a secondary reflector. The primary objective is to examine the impact of incorporating fins within the absorber tube, the introduction of nanoparticles to the base fluid, and the combination of fins and a nanofluid as a heat transfer fluid (HTF). The study is divided into two parts: The first part employs a ray-tracing method based on the Monte Carlo technique to determine the heat flux distribution on the lateral surface of the receiver tube. The second part involves simulating the conjugate heat transfer and fluid flow within the absorber tube. The heat transfer fluid used in this study is alumina (Al₂O₃) nanofluid, and the meteorological conditions are representative of Laghouat, a city in southern Algeria. The calculations revealed an average efficiency of approximately 47% for a secondary reflector. In addition, the results demonstrated that the optimal system configuration includes inserting three fins inside the tube, which leads to an efficiency improvement of 11% when using rectangular fins. Furthermore, the addition of 4% alumina nanoparticles (Al₂O₃) to the base fluid (water) increases the system’s efficiency by 12%. Finally, an optimal combination using a secondary reflector, the insertion of fins and the use of a nanofluid as a heat transfer fluid offer an efficiency gain of around 16%.

The measurement of wind resources is essential prior to the construction of wind farms; however, due to the influence of complex terrain and environmental factors, the actual power output of wind turbines often deviates from the predicted values obtained during early-stage measurements. In order to accurately and reliably calibrate wind power in complex terrains, this study employs an improved algorithm combined with large eddy simulation (LES) method to investigate the impact of environmental factors, wake characteristics, and calculation methods on wind power calibration. Within the discrete LES calculation method, the immersion boundary approach is utilized to simulate air flow effects caused by mountainous terrain and surface roughness. The results obtained from LES simulations exhibit excellent agreement with measurements taken from anemometer towers. Furthermore, when simulating wakes in complex terrains, it is observed that mountain wakes deflect downward along their central tracks beneath mountain peaks. For double mountains (complex terrains), variations in airflow acceleration occur within lower portions of wakes resulting in upstream mountain wakes enveloping wind turbines. Consequently, these upstream mountains affect turbine performance whereby a decrease followed by an increase occurs as distance between relief features increases. This paper elucidates how environmental factors impact turbine power output performance under complex terrains while providing valuable insights for constructing wind farms within such challenging environments.

Semi-transparent photovoltaic (STPV) skylights can generate electricity while meeting the needs of indoor lighting, which has an impact on building energy consumption. In this paper, we analyzed a double-layer semi-transparent photovoltaic (DL-STPV) skylight with a light transmittance of 20% in Beijing based on the established and verified model, and compared it with two types of traditional roof glazing. An equivalent electrical method was used to evaluate the energy performance of the DL-STPV skylight. In summer, the total equivalent electricity of the DL-STPV skylight is 7.0 kWh/m², which is 103.3 kWh/m² lower than that of double skin insulating glazing (DSIG) and 83.2 kWh/m² lower than that of DSIG with Low-E, respectively; In winter, the total equivalent electricity of DL-STPV skylight is –44.9 kWh/m², which is 34.7 kWh/m² lower than that of DSIG and 31.3 kWh/m² lower than that of DSIG with Low-E, respectively. The results showed that the DL-STPV skylight in Beijing reduced the air conditioning load in summer and increased the heating load in winter. Although the model used in this paper ignores the heat storage effect of the glazing itself, it is estimated that the loads of air conditioning, refrigeration, and heating are still decreasing, and the annual reduction is significantly reduced.

A one-dimensional non-stationary model of heat losses of a one-story, one-room passive solar house with three-layer walls (including thermal insulation) has been developed, taking into account the fluxes of incident and self-radiation. The one-dimensionality of the model is determined by the uniformity of all enclosing structures and thermal boundary conditions. It was found that heat losses or heating power in passive houses in the Central Asian region on sunny days are almost 50% less than on cloudy days. The influence of thermal insulation on heating output is significant. With thermal insulation of just 5 cm, heating power is reduced by 2.3 times, and with 10 cm, by 3.7 times. The thermal inertia of the walls affects the variation in heating power, as heating power begins to decrease after sunset and continues until nearly sunrise. With an increase in the thermal protection of the house, the amplitude of daily fluctuations in heating power decreases, and the time for heating power and the temperature state of the house enclosures to reach a quasi-stationary (regular) state increases.

This study focuses on optimizing the thermophysical properties of Phase Change Materials (PCMs) integrated into building envelopes to reduce heating and cooling loads. The six key factors analyzed include PCM thickness, melting temperature, latent heat of fusion, density, specific heat capacity, and thermal conductivity. Using Taguchi orthogonal experimental design (OED) and ANOVA analysis, PCM performance was assessed across four climates: the USA, Germany, Uzbekistan, and Egypt. The study revealed that a thinner PCM layer (0.002 m) and higher latent heat of fusion (up to 231 000 J/kg) significantly reduced heating loads, particularly in colder climates like the USA and Germany, with heating load reductions ranging from 65.45 to 80.60 kWh/m² a. In warmer regions, such as Egypt and Uzbekistan, higher melting temperatures (up to 29°C) and greater thermal conductivity (up to 0.5 W/mK) contributed to better energy performance, reducing cooling loads from 207.05 to 124.81 kWh/m² a. The findings demonstrate that optimizing latent heat and density is crucial, with these factors having the highest impact on energy savings across all climates. Specific heat capacity and thermal conductivity, while important, showed less significant effects. Despite these promising results, limitations include the need for further investigation into the long-term durability and cost-effectiveness of PCMs. Future research should focus on large-scale implementation and environmental sustainability. In conclusion, PCM-enhanced building envelopes present a viable solution for improving energy efficiency, and this study highlights the importance of tailoring PCM properties to specific climate conditions to maximize their effectiveness.

The present study is aimed at investigating the process of forming zinc oxide films on macroporous silicon using thermal atomic layer deposition. The macroporous silicon substrate is fabricated by electrochemical etching of a p-type monocrystalline silicon wafer. The ZnO film is deposited at 200°C using diethylzinc (DEZ) and water (H₂O) as precursors. Scanning electron microscopy results confirm uniform coverage of the macroporous silicon surface by the film. Elemental analysis by energy dispersive X-ray spectroscopy shows that the film consists of zinc and oxygen atoms. Raman scattering confirms the structure of the film as the crystalline phase of ZnO. Spectroscopic ellipsometry accurately determined with high precision the film thickness at 46 nm and the surface roughness at 4 nm. In addition, the optical properties of the film, including absorption coefficient, refractive index, and optical bandgap, are investigated. The results indicate a high transparency of the ZnO film in the visible spectrum and its ability to absorb ultraviolet radiation. The optical bandgap of 3.28 eV, Urbach tail in the absorption spectrum, and the detected roughness on the film surface indicate its polycrystalline nature and inhomogeneous crystal growth. The results show that ZnO films obtained by thermal atomic layer deposition can be used as transparent conducting electrodes in photoconverters due to their high transparency in the visible range. In addition, this method has the potential to create finely tunable ZnO/porous Si heterostructures with a large specific surface area.