Applied Solar Energy最新文献

In recent advancements within the realm of Parabolic Trough Collectors (PTC), a noteworthy stride has been made through the adoption of novel thermal fluids known as nanofluids. This study specifically delves into the numerical investigation of the impact of Multi-Walled Carbon Nanotube (MWCNT) nanofluid as a heat transfer medium on the performance of an indigenously developed parabolic trough collector. In the evaluation, water and MWCNT nanofluid were employed as heat carriers within the PTC tube. The investigation considered variations in flow velocities at the tube entrance, ranging from 0.1, 0.08, and 0.05 m/s. The resulting temperature change differences along the length of the PTC tube were observed to be 1.3, 1.7, and 2.7 K, respectively. Given the absence of specific studies addressing the essential three-dimensional distribution of absorber tube temperatures in parabolic trough collectors, our investigation sought to fill this gap through Computational Fluid Dynamics (CFD) analysis. The study aims to contribute insights into the nuanced temperature distribution within the absorber tube, shedding light on the potential benefits of employing MWCNT nanofluids in enhancing the thermal performance of parabolic trough collectors.

An analysis of the level of technical solutions for solar heating systems constructed in Uzbekistan was carried out. The importance of organizing statistical monitoring of facilities equipped with such systems in the republic was noted. The introduction of solar power plants in the climatic conditions of Uzbekistan requires solving problems related to protecting solar collectors from freezing of the coolant in winter and boiling in summer, removing dust from glass surfaces, and ensuring effective heat accumulation. However, the technical solutions used to solve these problems in most cases do not meet the basic efficiency and reliability requirements of the building codes and regulations for solar power plants currently in force in the republic. The analysis also took into account the latest scientific achievements aimed at improving the efficiency of solar collectors under real operating conditions. It was noted that during the construction and installation of solar heating systems, in most cases, individual design solutions tailored to each facility’s specific features are not developed; instead, ready-made factory-produced modules are installed. This leads to higher costs for heat storage systems and significant heat losses due to the use of numerous small individual storage tanks, which collectively have a large surface area of heat exchange with the environment. It has been shown that for solar water heaters with a five-section accumulator, heat losses to the environment and material consumption for manufacturing increase by 2 to 2.63 times compared to a compact accumulator with minimal surface area. It is recommended that for solar collectors operating with natural circulation, a five-section accumulator should be considered the maximum permissible configuration for solar water heating systems with horizontal cylindrical accumulators, where the ratio of their dimensions L/D > 1.5.

The results of computer modeling of temperature distribution in the layers of a solar panel, obtained using global climate databases, are presented. The non-stationary mathematical model for determining temperatures in the solar panel included approximation functions for solar flux density, wind speed, and ambient temperature. The approximation functions corresponded to the selected day of the year and the geographic data. These approximation functions were constructed in the program code based on regression analysis of data from global climate databases, both in real-time and archived. The adequacy of the mathematical model, numerical algorithm, and computer simulation results was confirmed through comparison with experimental data. The proposed approach allows determining the impact of real climate data on the temperature of the solar panel, identifying the errors when using average climate data for the solar panel’s location, finding the correlation between changes in climate data during daylight and the temperature regime of the solar panel, and calculating changes in the solar panel’s efficiency based on its temperature. Computer modeling was performed for a solar panel in which polycrystalline silicon solar cells were positioned between two glass surfaces. However, the proposed approach is universal and, with minor modifications, can be used to determine the thermal and energy characteristics of a solar panel with any design and any type of solar cells.

Central tower concentrated solar power (CSP) systems are considered the most mature clean technology to substitute conventional power plants. This work incorporates a simulation and optimization study on a 100 MW central tower CSP plant with 15 h of thermal energy storage in Dubai, UAE. The main performance indicators studied are the capacity factor (CF) and the levelized cost of electricity (LCOE). At first, a parametric study was conducted by varying 10 different operational and geometrical parameters to observe their impact on CF and LCOE using System Advisor Model (SAM) software. The 4 most significant parameters included were hot and cold HTF temperatures, tower height and the heliostat area. A total number of 81 SAM simulations were performed and obtained data sets were used for data regression to find the coefficients of the decision variables in the objective functions to either minimize LCOE or maximize CF. Results showed that the data regression performed accurately with an error of less than 1% compared to the simulated results. The maximum CF was found to be 48.3% where the minimum obtained LCOE value was 13.22 c/kWh. The optimized parameter values can lead to a substantial performance enhancement of 17.8% in the CF and 19.3% compared to the base case scenario obtained by SAM.

Adsorption cooling system (ACS) is one of the promising alternatives to the conventional vapor compression refrigeration system (VCRS) due to its advantage of driven by low grade thermal energy instead of electric power. However due to its lower efficiency, a significant research works is in progress worldwide. In view of this, the presented paper proposes a methodology to predict the required optimum heat source temperature of two different ACSs based on novel environment friendly pairs of activated carbon-methanol and silica gel-water for the ice-making and water chiller applications, respectively and their performance analysis. Performance parameters, cooling capacity, thermal efficiency, and coefficient of performance (COP) have been used to derive the limits of source temperature and applied to two different ACS. Further feasibility study has been carried out integrating economic and environmental perceptions for the El Oued city, Algeria. The performance analysis of CarboTech A35/1/CH₃OH showed the maximum ice production of 16.17 kg/day for the generator temperatures of 358–378 K with a COP of 0.65. The analysis of S40/H₂O application showed the maximum chilled water of 7.88 kg/day for the generator temperatures of 348–37 K having COP of 0.74. The economic analysis suggests that hot water generation with solar energy is a better option as compared to geothermal resource.

A computer simulation of antireflective gradient coatings for a transparent substrate of a photovoltaic battery and a silicon solar cell has been performed. The simulation results have shown that porous and gradient porous films deposited on glass increase the relative efficiency of a silicon solar cell by 8.0%. The influence of precipitation on the antireflection effect of glass is considered. It has been shown that filling the entire pore volume with water does not influence the antireflection effect: the relative efficiency of the solar cell increases by 6.8%. If we assume that the pores are completely filled with soot, then the relative efficiency of the solar cell will decrease by 50%. A gradient antireflection coating based on a mixture of MgF₂–CaF₂ is of practical interest since it may increase the relative efficiency of the solar cell by 6.2%. The simulation has established that the short-circuit current density can be increased to 40.0 mA/cm² if a gradient antireflective coating based on a SiO₂–Si mixture is deposited on the surface of a silicon solar cell.

It is known that the deposited dust prevents the passage of sunlight and reduces the transmission coefficient of solar energy, which, in turn, affects the efficiency of solar panels. This study estimated the effect of dust particles on power losses in a photovoltaic module by measuring electrical characteristics such as voltage, current, and power under standard conditions. It is shown that at a dust density of 0.427 mg/cm², the panel performance decreases to 36%. The analysis of the effect of dust accumulation on the performance of a solar photovoltaic plant in the conditions of the city of Dushanbe showed that the non-proportional dependence of the output power of photovoltaic modules on the intensity of solar radiation in summer is a consequence of the accumulation of dust on the surface of photovoltaic modules. It is shown that in the conditions of the city of Dushanbe, during the study period of June–July 2023, three dust storms were recorded, which reduced the efficiency of solar photovoltaic power plants (SPPPs) by 22%, i.e., each dust storm led to a decrease of 7–9%. The most effective time to clean the panels is 3–4 days after a dust storm, since during this period the dust settles on the surface of the solar panels. Knowing the nature of dust deposition allows you to find possible solutions and methods for cleaning solar panels to mitigate the effects of dust.

The processes of hydrogen absorption in porous ceramic materials have been studied. The results of the synthesis of porous materials for use in hydrogen absorbers are presented. The dependences of the degree of hydrogen absorption on the composition of the absorber, as well as on the temperature of hydrogen sorption, are obtained. It is shown that aluminosilicate materials synthesized from raw materials fused in a solar furnace with a specific surface area of 2500 cm²/g can be used as hydrogen absorbers for the physical binding of hydrogen in pores by Van der Waltz forces at high (30–50 atm) pressures. It was revealed that the aspect number, i.e., the ability of the material to absorb hydrogen at 200°C, varies from composition to composition. The maximum value of the aspect number (4.3 wt %) corresponds to a material with a diatomite content of 70 wt % and burnout additives of 20% by weight. It is shown that a porous material based on AlSiNaO sodium aluminosilicate with lattice parameter a = 4.056 А is a good hydrogen absorber. With an increase in the temperature of the sorption process from 100 to 190°C, the value of the aspect number increases from 3 wt % up to 13 wt %.

This study tries to analysis the thermal performance of the newly fabricated compact hybrid double pass collector-solar dryer using a wavy absorber. Energy and exergy efficiencies of the solar collector, drying chamber and drying process were performed during drying of tomato slices and compared with the open sun drying in the same conditions. The experiments were performed during spring seasons with the least available amount of solar energy. Mathematical modelling of drying kinetics was tested and used to evaluate the effective moisture diffusivity. The results show that a tomato slice reaches the equilibrium moisture content of 8.9% (wet basis) after just 7–8 h of operating time, depending to the trays positions. The average effective diffusivity of tomato reaches 1.657 × 10^–10 and 1.518 × 10^–10 m²/s for open sun and hybrid solar dryer, respectively. The average exergy efficiencies reach 2.32, 49 and 27% for solar collector, drying chamber and drying process, respectively. Low exergy efficiency is therefore observed in the solar collector which requires more efficient insulation. Exergy efficiencies of drying chamber and drying process decreases significantly during the operating periods of auxiliary system. The thermal energy input becomes important and thermal losses increase.

Considering the global fuel crisis, countries have made it imperative to exploit solar energy correctly, which has emerged as the most significant renewable energy source in recent times. Utilizing solar energy to heat the water appropriately to reduce global energy consumption is a challenge most countries face. Research has, therefore, been done extensively to maximize the performance of solar water heating through various applications. Several methods were enumerated and applied in this review study to determine how to enhance the performance of solar water heaters. Eleven techniques for improvement were identified. They are as follows: using nanofluid with phase change material; improving the collector design; coating; lowering the inlet water temperature; switching to a combined system in place of the conventional gas heating system; utilizing a dual glass cover; utilizing the upstream delta wing; utilizing the evacuated tube collector; utilizing the heat exchanger; utilizing the photovoltaic glass unit; and integrating the solar water heater and tubular lighting device into one unit. According to the essential results, using an absorption cooling system with solar power resulted in 34% electricity savings. The absorption system was enhanced, and the COP was raised to 2.75 by implementing the solar water heating system. Solar heating systems combined with PCM achieved the highest efficiency rating of 65%. The dryer system’s CO₂ emissions were lowered by about 34% when adding a solar collector. The solar water heater’s thermal efficiency was increased by 22.53% by a CuO/H₂O nanofluid.