Papers by Keyword: Solar Radiation

Abstract: The increase in the temperature of photovoltaic (PV) cells is a critical factor that negatively affects the efficiency of converting solar radiation into electrical energy. This phenomenon not only reduces energy conversion efficiency but also causes damage to PV components, thereby preventing the achievement of the intended energy production goals. Moreover, the heating of PV modules has two significant impacts: first, a reduction in energy efficiency, and second, a decrease in the lifespan of the solar cells. Therefore, projects aimed at producing clean electrical energy using PV solar panels must consider the study of installation sites for PV solar plants and the impact of environmental conditions on panel performance. Given that an increase in PV cell temperature reduces their productivity, this study examines the impact of ambient temperature on the maximum temperature reached by a PV solar panel and analyzes the results. The results show that installing solar panels in harsh environments characterized by high temperatures, such as Ouarzazate in Morocco, can cause these panels to reach critical temperature thresholds of up to 115°C under high solar flux, which can lead to solar system failure and thus the failure of the entire project. In addition, the heating of photovoltaic modules has two major impacts: firstly, energy efficiency is reduced by around 0.44% for every 1°C increase, and overall efficiency is reduced from 16% to less than 10% under extreme conditions; secondly, solar cell life is shortened. Finally, this study highlights the importance of carrying out thorough climatic and environmental assessments before establishing solar photovoltaic power plants. It also highlights the importance of employing high-performance cooling systems or innovative technologies to reduce the impact of heat on photovoltaic panels. This approach is essential to ensure the longevity and efficiency of solar photovoltaic installations, and to achieve our ambitions for sustainable, green energy production.

Abstract: Heat and mass transfer performance of Casson nanofluid for both non-conducting (m=0), electrically conducting (m≠0) fluids with solar radiation effects in stagnation point flow is considered. In this model, entropy, irreversibility, and multi slip impacts over a shrinking, static, and stretching sheet are investigated. To minimize the energy used in the solar system, it is important to monitor the processes of heat and mass transfer in the solar radiation process. The slips boundary conditions acts as a closure of the fluid velocity, mass, and heat transfer differential equations. The equations obtained are solved numerically via Galerkin Weighted Residual Method (GWRM). In the limiting sense, the present results conform with the existing work. The Behaviors of the flow physical quantities, temperature, concentration, and velocity for distinct values of the applicable dimensionless numbers are demonstrated with tables and graphs. The results reveal that, for a theoretical account of thermal boundary layers, Prandtl number serves as a variable. Furthermore, higher values of variable thermal conductivity have a significant influence on the skin friction coefficient than the case of constant variable thermal conductivity even when the fluid viscosity is assumed to be variable. The structure of the new method can be applied to the development of oil production.

Abstract: Only a small number of Ethiopia’s rural population has access to electricity. These rural areas can be electrified using different electrification approaches. One of the prime challenges in the decision making process is to obtain reliable information about the energy potential of the region under consideration. In this paper, an assessment of the solar energy potential of East Gojjam Zone in Ethiopia is presented. In the study area, there are only four meteorological measurement stations, namely: Debre Markos, Debrewerk, Mota, and Yetnora. The data for the hours of sunshine for these sites is collected from the National Meteorological Agency, Bahir Dar Branch Office. The data is prepared and used to calculate the mean global horizontal solar radiation using Angestrom-Prescott (AP) Model. An AP model for the four study sites was developed. The model regression coefficients, a and b, are estimated for each study site for respective latitudes, average hours of sunshine and day length. According to the models, the annual mean daily global horizontal radiation for Debre Markos, Debrewerk, Mota, and Yetnora is 5.88, 6.52, 6.28, and 6.31 kWh/m²/day, respectively, and 6.30kWh/m²/day for East Gojjam Zone, which is actually a very good solar energy potential. According to the monthly average global horizontal solar radiation profiles, the study sites receive the highest solar radiation in April and lowest solar radiation in July and August. The radiation in Debre Markos varies between 3.97 and 5.88kWh/m²/day, but Debrewerk receives more uniform solar radiation throughout the year. By considering intermittency and average solar energy potential of the four sites, Debrewerq and Debre Markos are the best and the worst sites, respectively, for large solar energy projects.

Abstract: In the literature, several correlation models have been developed to predict solar radiation on horizontal surfaces. In this paper, the daily solar radiation data and sunshine duration data measured during the period of 2006-2010, were used to calculate the monthly mean values of daily total solar radiation using five modified Angstrom–Prescott model and three day of the year based empirical models of Oran city (35°42 N and 00°36 W) in Algeria. Furthermore, those modified models are compared with three existing models. In order to evaluate the accuracy of the models, the statistical testing error such as R², RMSE, rRMSE, MAPE and MBE are used. According to statistical test results and from the sunshine duration models, the polynomial model (#4) showed the best estimation results with a coefficient of determination R²=0.991, rRMSE=4.129%, and MAPE=3.635%. Furthermore, the accurate model from the day of the year models is the model (7), with R²=0.987, rRMSE=4.067%, and MAPE=3.5194%. Moreover, this paper finds that the best accuracy model to estimate the monthly mean daily solar radiation on horizontal surfaces in Oran city is the sine and cosine wave trigonometric model (#7).

Abstract: Nowadays, shading net is widely use in Thailand, especially for vegetable production. Many colors of shading net can be found in the market. In this experiment, we set up three net houses for lettuce by using three colors of 50% transparent shading net, black, red and green. Ten of 15 days after planting (DAP) lettuces were moved to each color net house and control (direct sun). Total 40 lettuces were used for 10 days experiment. The result showed that the leave length and width of lettuce under red shading net respectively were significantly bigger than those under green shading net and control treatment without significant difference with the black shading net. The lettuce under red shading net had a highest stem diameter, fresh weight and dry weight comparing with others color shading net. The spectra of the solar radiations that transmitted through the red shading net were suitable for the photosynthesis of the lettuce leaves that could promote lettuce growth and yield.

Abstract: Titanium dioxide (TiO₂) is one of popular semiconductor materials that usually used for photocatalytic application. Recent studies show the improvement of TiO₂ photocatalytic activity through nitrogen doping (N-doped TiO₂). In this study, we focused on the synthesis and characterization of N-doped TiO₂. Ultrasonic assisted synthesis or sonochemical method was used to prepare N-doped TiO₂ polycrystalline powder under room temperature. X-ray diffractometer (XRD), and diffuse reflectance ultraviolet-visible spectrophotometer (DR-UV) were employed to evaluate physical properties of N-doped TiO₂. XRD pattern exhibited that all samples have anatase crystalline phase and crystallite size decrease with increase of N dopant concentration. The absorbance spectra showed the slight shift toward higher wavelength (red shift) and from Kubelka-Munk function the band gaps were getting smaller with increase of N content. The increase of photocatalytic activity under solar radiation was achieved by N-doped TiO₂ samples with highest efficiency about 81 % for 5% of N doping concentration.

Abstract: Many building performance applications (energy use, solar gains, thermal comfort, renewable energy systems, daylight, etc.) require information about both direct and diffuse components of the incident solar radiation. However, most meteorological stations only monitor global horizontal irradiance. Consequently, multiple methods have been proposed in the past to derive from measured global horizontal irradiance data the diffuse fraction. Thereby, additional data regarding other parameters such as clearness index, solar altitude, air mass, and turbidity are used. Given the importance of this procedure for the down the line tools, its reliability represents a critical issue. To address this point, we pursued an empirical approach. A number of existing methods for the computation of the diffuse fraction were selected. Actual measurements of global and diffuse irradiance were obtained for seven locations in USA and one location in Austria. The measured global irradiance data for these locations were fed to the aforementioned diffuse fraction models. The calculation results were then compared with the corresponding empirical data. The comparative assessment yielded a number of findings. The relative performance ("ranking") of the models was found to be more or less consistent across the different locations. However, none of the models can be said to be performing wholly satisfactory. For instance, the best performing model displayed only in 45 to 65 percentage of the cases relative errors less than 20%. In case of the worst performing model, the percentage of the cases for which relative errors were less than 20% was even smaller, namely 30% to 60%.

Abstract: The article deals with analysis of the heat balance and temperature microclimate of indoor space of a four-storey building atrium. With regard to the anticipated thermal loads in all functionally connected rooms, investor made a request to verify the thermal stability of the atrium before the implementation stage. Atrium and adjacent rooms are a geometrically complicated inner space which cannot be solved by analytical methods to ensure the required temperature conditions in occupied zone. This led to the creation of a mathematical model of the atrium with the current project solution. The result of the simulation of the existing solutions is that there is not complied desired air temperature in the occupied zone. For this reason, it was developed optimization of existing variant. Optimization was performed in steps as changing temperature of the central air conditioning system, changing number of units and performance of local refrigeration air conditioning. The conclusion of this paper is to evaluate the thermal profiles of temperature stratification in the atrium area and request the required cooling performance of the ventilation system. The article attempts to use computer modelling as a tool for the placement and performance design of ventilation equipment.

Abstract: Solar radiation exposure and its monitoring does have not only the importance for climate science and meteorology however is equally of highly relevant use for the field of Building Science as primarily those of analyzing thermal aspects in building physics. Here the measuring of solar irradiance by means of well-established solar instruments can be applied whose advances have been undergoing steep progress. Currently, a silicon photodiode element, as a truly obtainable form, may have a feasible exploitation in the field of building applications concerning the solar radiant flux quantifying. It represents a small optoelectronic element and has a several exploitable advantages. The paper presents a perspective alternative to monitor solar irradiance. Own measurement assembly is proposed and introduced. Initial in-situ measurements are performed and final comparability with existing commercial solar instruments is presented. An obtained correlation with existing types demonstrates its applicability to the field of building science and solar energy.

Abstract: The constant evolution of the energy industry, has introduced the need for ongoing research studies about climate change due to its direct action on the production of alternative energies. Thus, they have focused on developing predictive algorithms in order to resolve, in an early way, the climate action on each point of energy production. In the development of this work, the ANFIS algorithm and information from the NASA Langley research center virtual database were implemented. They being oriented to the analysis and prediction of solar radiation over the geographic area of the Nueva Granada Military University campus, Cajicá, Colombia, with the purpose of making appropriate use of the power generating system located in the zone. The development of such systems, would allow the early identification of solar radiation that can be present in different geographical areas of Colombia, in order to provide the necessary power to cover the electricity demand required in each region, achieving as results an approximation error less than 1%.