Solar energy has recently become a significant renewable energy source because of its sustainability and favourable effects on the environment, the solar modules or solar photovoltaic (PV) systems are frequently utilized to collect sunlight and generate the electrical power. The estimated life span of the solar PV system is 30-35 years but efficiency will be reduced during the time span spends due to the material degradation. The average life of these modules is approximately 25 years for which it can efficiently work – as claimed by all the manufacturers in India. In the coming decades, more systems will reach the end of their useful lives even if currently there aren’t many systems entering the waste stream. By minimizing waste, energy use, detrimental impacts on human health, and pollution, innovative materials, designs, and production techniques can also assist to lessen the environmental impact of PV manufacture.
India’s geographical surface receives around 5,000 trillion kWh of incident energy annually, with the majority of areas receiving 4–7 kWh per square metre every day. Solar photovoltaic energy may be effectively harnessed in India, offering enormous scalability. Additionally, solar energy offers the option of distributed power generation and permits quick capacity expansion with minimal lead periods. India currently ranks fourth globally in the deployment of solar PV as of the end of 2021. As of the 30th of November 2022, the installed capacity of solar energy was approximately 61.97 GW. India’s solar tariffs are currently extremely competitive and have reached grid parity. The India’s installed capacity on 31st March 2023 was estimated by 66.78 GW. Reverse auctions’ average bid in April 2017 is $3.15 (3.9 US cents) per kWh, compared to $12.16 (15 US cents) per kWh in 2010. This is a 73% decrease throughout the time range. The minimum levelised tariff was discovered by `3.99 (5.0¢ US) per kWh in April 2023 for the round-the-clock for the hybrid solar power supply with or without storage.
The PV modules deteriorate or affect the power generation due to number of causes like including changes in temperature, moisture, mechanical stress, and material ageing. The degradation of solar modules may lead to the financial losses of manufacturers as well as it will reduce the efficiency of the PV module.
Thermal cameras or infrared photography can be used as valuable tools for detecting solar module degradation and optimizing the performance of solar energy systems. Through their non-invasive and comprehensive inspection capabilities, thermal cameras enable early detection of degradation mechanisms, proactive maintenance, and improved safety. While thermal imaging technology has challenges and limitations, ongoing advancements in algorithms, integration with AI, and miniaturization will further enhance its capabilities and accessibility. By leveraging the benefits of thermal cameras and continuously improving their performance, solar energy system operators can effectively monitor and maintain their installations, maximize energy generation, and achieve a higher return on investment.
Detecting and addressing solar module degradation in a timely manner is essential to ensure optimal performance and maximize the return on investment for solar PV systems. Various factors, including cell defects, module cracks, dirt accumulation, and electrical failures, can cause degradation. Traditional visual inspections and electrical performance tests may not be sufficient to identify subtle issues that can impact module efficiency. The primary objective of this research is to highlight the importance of thermal cameras as a reliable tool for detecting solar module degradation.
This article deals with the type of various defects in solar panel and its causes; impacts of these factors on PV energy system; various thermal imaging technologies and types of thermal cameras; the experimental work is also presented and analyzed in this communication. The work is very useful to the researchers, manufacturers and energy auditors of photovoltaic energy management fields.
Solar Module Degradation
The types of module degradation: The module degradation may occur due to various effects of related to environmental and other reasons. The various degradations of effects are shown in figure 1 and these degradation defects are cracks, dust, hotspot, thermal and humidity effect, delamination dislocations.
Causes of solar module degradation: Solar module degradation refers to the gradual deterioration of the performance and efficiency of photovoltaic (PV) modules over time. Several factors contribute to the degradation of solar modules: (a) PID degradation: This degradation mechanism, also known as Potential-Induced Degradation (PID), occurs due to high voltage stress and exposure to humidity. PID can lead to significant power losses in solar modules. (b) Thermal stress: Exposure to high temperatures can cause thermal stress, leading to the degradation of materials used in solar modules. The expansion and contraction of materials over repeated thermal cycles can result in cracks, delamination, and other forms of damage. (c) Moisture ingress: Water penetration into the solar module’s encapsulated or back sheet can accelerate the degradation process. Moisture ingress can cause corrosion, delamination, and electrical failures. (d) Mechanical stress: Environmental factors such as wind, hail, and snow can subject solar modules to mechanical stress, resulting in microcracks, cell fractures, and module failure. (e) UV exposure: Continuous exposure to ultraviolet (UV) radiation can cause the deterioration of encapsulated materials, leading to yellowing, discoloration, and reduced module performance.
Impact of degradation on solar energy systems: The degradation of solar modules has significant implications for solar energy systems: (a) Reduced Energy Production: Degraded modules exhibit lower power output, reducing energy generation. This reduction directly impacts the overall performance and energy yield of the solar system. (b) Financial implications: Decreased energy production due to module degradation decreases revenue and Return on Investment (ROI) for solar system owners and operators. It may also impact the feasibility and profitability of solar energy projects. (c) System reliability and safety concerns: Degraded modules may experience electrical failures, hot spots, and potential safety hazards. Module degradation compromises solar energy systems’ long-term reliability and safety, requiring proactive monitoring and maintenance.
Need for detection and monitoring: The need for accurate and timely detection and monitoring of solar module degradation arises from several factors:
(a) Performance optimization: Identifying and addressing degradation issues early allows for timely maintenance, repair, or replacement of affected modules. Proactive detection enables the optimization of energy production and system performance. (b) Warranty compliance: Solar module manufacturers typically offer performance and power output warranties. Regular monitoring and detecting degradation help ensure warranty compliance and facilitate necessary replacements or repairs. (c) Asset management: Solar module degradation affects solar energy systems’ overall value and lifespan. Effective detection and monitoring strategies enable efficient asset management, including planning for module replacements and evaluating the system’s long-term financial viability. (d) Safety and fire risk mitigation: Certain degradation mechanisms, such as hot spots and electrical failures, can pose safety risks and increase the likelihood of module fires. Timely detection and monitoring allow for preventive measures, reducing the risk of accidents and property damage.
Thermal Imaging Technology
Principles of thermal imaging: Thermal imaging technology is based on the principle of capturing and visualizing the infrared radiation emitted by objects. The following key principles govern thermal imaging: (a) Infrared radiation: All objects emit infrared radiation based on temperature. This radiation falls within the electromagnetic spectrum, specifically in the range of 9,000 to 14,000 nanometers (9-14 µm) for thermal imaging purposes. (b) Temperature measurement: Thermal cameras use special sensors called microbolometers to detect and measure the intensity of infrared radiation emitted by objects. The temperature of an object can be determined based on its emitted radiation. (c) Heat distribution visualization: Thermal cameras convert the detected infrared radiation into a visible image, representing heat distribution across an object or scene. The resulting thermal image, also known as a thermogram, displays varying colors or grayscale shades to indicate different temperature levels. (d) Thermal contrast: By detecting and displaying temperature differences, thermal imaging technology enables the identification of anomalies, patterns, and areas of interest, facilitating the detection of solar module degradation.
Types of thermal cameras: Thermal cameras come in different types, each offering specific features and capabilities. The two primary types of thermal cameras commonly used for solar module inspection are: (a) Uncooled thermal cameras: Uncooled thermal cameras are the most common types used in various applications, including solar module inspection. They use microbolometer sensors that do not require cooling. Uncooled cameras offer lower costs, smaller sizes, and increased portability, making them suitable for on-site inspections and routine maintenance activities. (b) Cooled thermal cameras: Cooled thermal cameras employ more advanced technology, using a cryogenic cooling system to cool the detector element. Cooled cameras provide higher thermal sensitivity and better image quality, enabling the detection of more minor temperature variations. However, these cameras are generally larger, more expensive, and less portable, often utilized in specialized research or high-precision applications.
Advantages of thermal cameras for solar module inspection: Thermal cameras offer numerous advantages when applied to solar module inspection and monitoring: (a) Non-invasiveness: Thermal cameras enable non-contact and non-intrusive inspection of solar modules. They do not require physical contact with the modules, eliminating any potential damage or interference during the inspection process. (b) High-resolution imaging: Modern thermal cameras provide high-resolution imaging capabilities, allowing for detailed visualization of temperature variations across the solar modules – this high level of detail aids in accurately identifying potential degradation issues. (c) Real-time monitoring: Thermal cameras can capture and display thermal images in real time, providing instant feedback on the temperature distribution of solar modules. This real-time monitoring immediately identifies hot spots, anomalies, and other temperature-related irregularities. (d) Wide area coverage: Thermal cameras can capture a wide field of view, allowing for the simultaneous inspection of multiple solar modules or large-scale solar arrays. This feature enhances the efficiency and speed of inspections, enabling comprehensive monitoring of solar systems. (e) Cost-effectiveness: Thermal cameras offer cost-effective solutions for solar module inspection compared to traditional manual inspection methods. They can help reduce labour costs, minimize downtime, and optimize maintenance efforts by detecting issues before they escalate. (f) Early detection of degradation: By visualizing temperature variations, thermal cameras facilitate the early detection of degradation mechanisms such as hot spots, cell cracks, delamination, and moisture ingress. Early detection enables timely intervention, reducing further damage and maximizing the overall performance of solar modules. (g) Safety enhancement: Thermal cameras enable the detection of electrical anomalies, potential fire hazards, and safety risks. By promptly identifying and addressing these issues, thermal cameras contribute to improved safety standards and risk mitigation in solar energy systems.
Experimental Methodology and Data Analysis
Selection of test site: The Kota University {Kota (25.11677 N, 75.82304 E)}, India is selected for the experiment for this work. The experimental study requires carefully selecting a representative test site and solar modules. The selected single PV panel is 300W of make Vikram Solar of 100kW total plant capacity which is connected with the grid. The solar modules should have different ages, technologies, and degradation levels to ensure a comprehensive analysis.
Thermal imaging equipment and result analysis: A high-quality thermal camera capable of capturing detailed thermographic images is necessary to conduct the experiment. The camera should have a suitable temperature range and resolution for detecting temperature variations in solar modules. Additionally, the camera should be calibrated before data collection to ensure accurate temperature measurements.
Data collection involves capturing thermal images of the selected solar modules using the thermal camera. Images should be taken under consistent environmental conditions, preferably during clear sky conditions to minimize the impact of ambient temperature variations. Multiple images should be captured from various angles to view each module comprehensively.
The experiments were carried out on May 22, 2022. The minimum, maximum and average temperature of PV module is shown in figure 2. It is evaluated that the minimum temperature was observed by 51°C and maximum by 54°C as well as average temperature was 52.5°C. The reason of higher temperature accumulation is the dust which expressed by dark red patches on the module surface and it is not feasible to collect the high temperature at the module. On the other hand, the hotspots on the surface are presented by the red colour dots in figure 3. The three dimensional temperature variation for both the conditions are shown in figure 4 and 5 respectively. Quantitative assessment of the thermal imaging results is crucial to obtain objective and measurable data. This assessment involves analyzing the thermal data and correlating it with other measurements or performance metrics of the solar modules.
Temperature differentials and thermal patterns captured in the thermal images can be quantitatively analyzed to determine the severity and extent of degradation. For example, the temperature difference between a hot spot and the surrounding areas can be measured, providing a quantifiable indicator of the severity of localized degradation.
In addition to temperature analysis, other ancillary measurements, such as electrical parameters (e.g., shunt resistance and open-circuit voltage), can be correlated with the thermal imaging results. This correlation helps establish a more comprehensive understanding of the impact of degradation on module performance and efficiency.
By quantitatively assessing the thermal imaging results, it is possible to track the progression of degradation over time and compare the effectiveness of different mitigation strategies. This data-driven approach aids in making informed decisions regarding maintenance interventions, module replacement, or system optimization.
Furthermore, statistical analysis techniques can be employed to establish correlations between the solar energy system’s thermal imaging data and performance metrics. This analysis can provide valuable insights into the relationship between degradation indicators detected through thermal imaging and the overall energy generation and system efficiency.
In conclusion, discussing and interpreting experimental data obtained through thermal imaging involve a comparative analysis of degradation mechanisms and a quantitative assessment of the thermal imaging results. By examining the prevalence and severity of different degradation indicators and correlating the thermal data with other measurements, it is possible to prioritize maintenance strategies and make data-driven decisions to optimize the performance and longevity of solar modules.
Benefits and Limitations of Thermal Cameras for Solar Energy Systems
The various benefits have been observed of thermal cameras for solar energy PV systems and its management these are expressed as follows:
- Proactive Maintenance and Reduced Downtime
- Enhanced Performance Monitoring and Optimization
- Improved Return on Investment (ROI)
- Safety and Fire Risk Mitigation
The following limitations and challenges have been considered for the future study in this area of research:
- Accuracy and Interpretation of Thermal Data
- Cost Considerations and Accessibility
- Weather Conditions and Limitations
Future Research Scope in Thermal Imaging
The present experimental small study is being carried out in Kota India and found that there is lot of work required for complete study of PV system degradation and energy management system. The some of the research gaps are presented as follows:
- Development of Advanced Algorithms
- Integration with Artificial Intelligence (AI)
- Miniaturization and Portability
- Higher Spatial and Temporal Resolution
- Integration with Other Sensing Technologies
Conclusion
In this article, we have explored the importance of thermal cameras for detecting solar module degradation. Through experimental data analysis, we have highlighted the benefits and limitations of thermal imaging technology in identifying various degradation mechanisms in solar modules.
Key findings from the research include:
- Thermal cameras provide valuable insights into solar module degradation by detecting hot spots, temperature variations, cell cracks, bypass diode malfunctions, Potential-Induced Degradation (PID), back sheet degradation, and corrosion/moisture ingress.
- Thermal imaging technology enables proactive maintenance and reduces downtime by facilitating early detection of degradation issues. In turn, it enhances the performance and longevity of solar energy systems.
- Thermal cameras offer several advantages over traditional inspection methods, including comprehensive inspections, non-invasiveness, speed, objectivity, and reliability in adverse environmental conditions.
- Comparative analysis of degradation mechanisms helps prioritize maintenance and mitigation strategies, ensuring efficient allocation of resources and efforts.
- Quantitative assessment of thermal imaging results and other performance metrics allows for data-driven decision-making, monitoring of degradation progression, and evaluation of mitigation strategies’ effectiveness.
Sumit Verma currently works as PhD Research Scholar in Department of Renewable Energy, Rajasthan Technical University of Kota. He has professional interest in renewable energy technologies, solar energy data analysis, performance ratio, fluency on PVSYST software, PVSol software, solar PV degradation analysis, climate change, performance analysis of solar power plant, sustainable development, PV technologies, and economic empowerment.
Dr. D. K. Yadav is an Associate Professor in Electrical engineering department, Rajasthan Technical University, Kota, India. He has PhD degree from IIT Delhi and expertise in power quality issue in RES, Power Electronics application in Renewable Energy, renewable energy power generation sources, Grid integration with renewable energy source.
Dr. Shiv Lal is an Associate Professor in the Mechanical Engineering Department, Rajasthan Technical University, Kota, India. He did his PhD degree from IIT Delhi and expertise in Energy Assessment, buildings passive heating and cooling, energy and exergy analysis, solar chimney power plant, Renewable Energy, Design of thermal systems, heat transfer, IC engine, solar refrigeration etc.
