The effect of inclination angle in fixed photovoltaic system applications

Solar energy is a clean and renewable source of energy that can help reduce our dependency on fossil fuels and solve a part of the climate change problem. As solar technology advances and becomes more affordable, it is critical to ensure that solar panel systems, such as our rooftop PV panels, operate as efficiently as possible. This study focuses on optimizing and maximizing the efficiency of the solar energy systems which built on the roof of the Electric and Electronics Engineering at Sakarya University, Turkey. Regarding the region's expanding solar potential, there is limited measured and observed data on solar irradiance and PV panels output under the impact of soiling. The first method used to understand the effect of inclination on solar panel performance is to estimate and calculate the optimal tilt angle. This optimal angle is critical because it directly affects the quantity of solar radiation a panel can collect throughout the year. The optimum tilt angle is the angle at which a solar panel should be tilted in order to receive the most total solar energy on its surface. Achieving this optimal orientation is critical for increasing energy efficiency and maximizing the utilization of solar resources. To determine the optimum tilt angle, it is necessary to conduct a detailed analysis of the total solar radiation incident on the panel. This involves evaluating the mathematical model of total solar radiation, which consists of three major components which are direct or beam radiation, diffuse radiation, and ground-reflected radiation. Among these, diffuse solar radiation is particularly important, especially in areas or seasons with higher cloud cover or air scatter. Unlike direct radiation, which travels in a straight line from the Sun, diffuse radiation is scattered by molecules and particles in the atmosphere and strikes the panel from many angles. The best method to estimate the total solar radiation is to use specialized tools and sensors to take direct measurements. For every aspect of solar radiation, including diffuse radiation, these measurements offer reliable and accurate information. Unfortunately, the measurement tools are not available. Therefore, a different approach that is based on existing equations and models that through the study develop new diffuse solar radiation equations depending on pervious researches has been used. These models offer a close approximation to actual conditions because they are based on observed or computed data. The study takes a comprehensive strategy by choosing 34 models from previous studies in order to improve reliability and accuracy. The variety of equations that estimate diffuse solar radiation under different circumstances. Give us a variety of results by computing diffused solar radiation using each model, capturing variances across various approaches and assumptions. The study calculates the average of these 34 models to further improve the estimation. Our presumed "measured value" for diffuse solar radiation in Sakarya city be this averaged value, which presumed as measured value. To organize this, 34 equations have been divided into five distinct groups based on their characteristics, data requirements or mathematical structure. These groups help categorize the models, facilitating analysis, and enabling us to compare the performance and accuracy of different approaches. The five groups are diffuse fraction (H_d/H) calculated by clearness index (H/ H_0), diffuse fraction (H_d/H) calculated by sunshine fraction (S/S_0), diffuse fraction (H_d/H)calculated by sunshine fraction (S/S_0) and clearness index (H/ H_0),diffuse coefficient (H_d/H_0)\ calculated by clearness index (H/H_0)\ and diffuse coefficient (H_d/H_0)\ calculated by sunshine fraction (S/S_0).H_0 and S_0 are extraterrestrial solar radiation and is maximum sunshine hours respectively. Extraterrestrial solar radiation and maximum sunshine hours are the main components in our diffuse solar radiation calculation. We have calculated monthly average daily extraterrestrial solar radiation (H_0) the availability of extraterrestrial solar radiation energy varies by month. January's give a value of 4.11 kWh/m²/day shows low solar irradiation at the start of the year. H₀ levels steadily rise over time, peaking at 7.52 kWh/m²/day in March and 5.51 kWh/m²/day in February, respectively. By April, the number increases to 9.56 kWh/m²/day, showing great solar energy potential. Solar irradiance peaks in June at 11.60 kWh/m²/day, then decreases slightly in July to 11.28 kWh/m²/day during the winter. The values continued decreasing in the second half of the year, dropping to 8.20kWh/m²/day in September and gradually decreasing to 3.68 kWh/m²/day in December. This pattern emphasizes the seasonal nature of solar energy availability, with the highest values occurring during the summer months and the lowest during winter. The monthly average maximum sunshine hours (S_0) have calculated in this study. The results numbers show the theoretical maximum amount of daylight accessible at a specific place on a clear day. The maximum value is in June with 14.88 hours, while the lowest is in December with 9.12 hours. This variation reflects the changing length of the day caused by the Earth's axial tilt and orbit around the Sun. The data is critical for understanding seasonal variations in Sun availability. Maximum sunshine hours are affected by geographical location, particularly latitude. After obtaining the values of extraterrestrial solar radiation and maximum sunshine hours, the next step was calculated the diffuse solar radiation using 34 models. The average value of 34 models has been used as our estimated measured value and by using MATLAB the regression methods have been applied to create our new diffuse solar radiation model for Sakarya. In the monthly average daily of new model diffuse solar radiation, seasonal variation can be observed, with the lowest value in December (0.79 kWh/m²/day) and the highest in June (2.39 kWh/m²/day). Diffuse radiation gradually increases from winter to early summer, peaking during the sunniest months when atmospheric scattering is greatest. By using the values of the new model diffuse solar radiation, the values have been used to calculate total solar radiation in inclined surface. In January, the average daily total solar radiation is 2.15 kWh/m²/day, and the optimum tilt angle is 57.16 degrees. During February, the solar radiation increases to 3.20 kWh/m²/day with an optimum tilt angle of 51.04 degrees. In March, the value increases more to 3.86 kWh/m²/day at a tilt angle of 36.94 degrees. By April, the average daily solar radiation reaches 4.63 kWh/m²/day with an optimum tilt angle of 20.83 degrees. The highest solar radiation occurs in June at 6.01 kWh/m²/day with a minimal tilt angle of only 0.10 degrees. After June, the values begin to decrease gradually; for instance, in July it is 5.85 kWh/m²/day at 3.19 degrees, and August records 5.44 kWh/m²/day at 16.65 degrees. In September, it is 4.81 kWh/m²/day with an optimum tilt angle of 33.47 degrees. October sees it decrease to 3.91 kWh/m²/day at 48.65 degrees, and November drops further to 2.61 kWh/m²/day at 57.20 degrees. Finally, December has the lowest solar radiation at 2.10 kWh/m²/day with the steepest tilt angle of 60.42 degrees. The yearly average optimum tilt angle is 32.64 degrees. Using PV*SOL, PV imulation software, it shows that the optimal tilt angle for a panel facing south throughout the year is 32 degrees. The optimum tilt angle for east and west-facing panels is from 8 to 9 degrees. This result is very similar to our determined optimum tilt angle of 32.64 degrees, showing a significant agreement between simulation results and our analytical approach. According to the PV*SOL software the PV system exports energy to the grid with a value of 5660 kWh/Year. The comparison between PV*SOL simulation results and real site measurements shows a similar pattern throughout the year. The smallest errors appear in May and June with about 0.34% difference, showing very close agreement. The largest differences occur in February with a 52.13% error and in December with a 29.94% error. The highest energy production happens in summer months like June, July, and August, which is expected due to stronger sunlight. Overall, PV*SOL provides reliable results with a total error of just 0.68%. A comparison between south, east, west, and horizontal panels based on real site data shows that east and west-facing panels can produce similar energy to horizontal panels. In some months, east and west-facing panels can even produce more than horizontal panels. This means east or west-facing panels with a small tilt like 8° to 9° as PV*SOL suggested or even the east and west site facing panels in the site can be a better choice than flat ones, as they need less cleaning efforts and cost less to maintain.PV*SOL shows that the panels facing south produced the best results between different orientations and horizontal panels. South oriented panels received the most Sun radiation with 1645.69 kWh/m², had the best performance ratio 82.56%, and produced the most electricity in a year 1632.53 kWh yearly. Zero degrees tilt angle generates 1421.22 kWh of energy each year, with a specific output of 1184.35 kWh/kWp. East-facing panels produced a little less energy than flat panels, with 1371.92 kWh/year, 1143.27 kWh/kWp, and an 81.90% performance ratio. The west-facing panels produced the lowest results. They produced only 1234.60 kWh per year and the lowest performance ratio of 79.89%. These findings indicate that orienting panels to the south is the greatest option for capturing the most energy from the Sun. An experiment in Istanbul indicated that uncleaned panels lost approximately 0.4% of their power after 3 days, but up to 3.0% after 24 days without rain, in our PV roof system, the tilt angle of the panels has a considerable impact on decreasing soiling. Horizontal panels tend to collect more dust and have a slower snow-melting rate, increasing the amount of effort to clean. The panels set at an appropriate tilt angle require less care, especially as Sakarya sees heavy rains from November to May, which naturally helps keep the panels cleaner. However, during the summer, all panels require a regular cleaning routine to reduce the impacts of soiling.