Performance evaluation and degradation analysis of grid connected photovoltaic systems for energy efficient buildings in tropical climates – Nature

Performance and Degradation Analysis of a Grid-Connected Photovoltaic System in a Tropical Climate

Executive Summary

In alignment with the United Nations Sustainable Development Goals (SDGs), particularly SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action), the global adoption of photovoltaic (PV) systems is accelerating. This report presents a comprehensive analysis of a 3.575 kWp grid-connected PV system to evaluate its long-term reliability and contribution to sustainable energy infrastructure. The system, operated by the Power Electronics and Renewable Energy Laboratory (PEARL), was monitored over 36 months (January 2020 – December 2022). It comprises two technologies: Poly-Crystalline (Array 1) and Mono-Crystalline silicon (Array 2). Performance was assessed using eleven parameters based on IEC 61724 guidelines. The Modified Akima cubic Hermite (MAKIMA) method was employed to forecast degradation rates, providing critical data for promoting SDG 12 (Responsible Consumption and Production) through enhanced material longevity. Results showed average AC energy outputs of 3881.67 kWh for Array 1 and 1120.48 kWh for Array 2, with performance ratios of 86.74% and 56.30%, respectively. Forecasted degradation rates for 2023 were 10.58% for Array 1 and 11.99% for Array 2. These findings offer crucial insights into PV material durability in tropical climates, supporting the optimization of renewable energy systems to achieve global sustainability targets.

1.0 Introduction: Aligning Photovoltaic Systems with Sustainable Development Goals

The global transition towards renewable energy (RE) is a cornerstone of the international effort to achieve SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action). Solar energy, particularly through photovoltaic (PV) systems, has emerged as a highly reliable and scalable solution. The adaptability of PV technology, from residential installations to large-scale power plants, is crucial for developing sustainable cities and communities (SDG 11). According to the International Energy Agency (IEA), global solar PV capacity is experiencing sustained growth, reflecting a worldwide commitment to decarbonization.

In Southeast Asia, Malaysia is actively contributing to the RE agenda, with national policies like the Malaysia Renewable Energy Roadmap (MyRER) aiming to increase the RE share to 31% by 2025. This strategy directly supports Malaysia’s Nationally Determined Contributions (NDC) under the Paris Agreement, targeting a 45% reduction in greenhouse gas (GHG) emissions intensity by 2030. The expansion of solar PV is central to achieving these climate and energy goals.

1.1 Literature Review and Research Gap

Extensive research has evaluated the performance of PV systems in various tropical climates. Studies have analyzed different configurations, including Building-Integrated Photovoltaics (BIPV), which offer a strategic solution for urban energy generation and contribute to SDG 11. Previous research in Malaysia has demonstrated the potential of PV systems to generate significant energy and reduce CO₂ emissions. However, a critical gap exists in long-term, field-based assessments that comprehensively evaluate system degradation and operational efficiency over time. Many studies lack integrated forecasting models to predict performance decline, limiting their utility for long-term planning and investment, which are essential for the sustained success of SDG 7.

1.2 Report Objectives and Contributions

This report bridges this gap by conducting a rigorous 36-month field evaluation of a grid-connected PV installation in Malaysia, comparing Mono-crystalline and Poly-crystalline technologies. The study provides novel insights that support the advancement of several SDGs. The key contributions are:

1. A direct comparative analysis of two PV technologies under identical environmental conditions, providing an unbiased assessment to inform technology selection for sustainable energy projects.
2. A thorough evaluation using eleven core performance metrics as defined by the IEC 61724 standard, ensuring robust and internationally comparable results to guide global PV implementation.
3. Utilization of the Modified Akima Cubic Hermite Interpolation (MAKIMA) algorithm to forecast PV degradation, offering an innovative approach to asset management that supports the long-term viability of clean energy infrastructure (SDG 7) and promotes responsible production and consumption patterns (SDG 12).
4. Rigorous quantitative validation of the degradation forecasts, strengthening the credibility of the predictive model as a practical tool for strategic decision-making in the renewable energy sector.

2.0 Methodology: Performance and Degradation Analysis Framework

This section details the technical specifications of the PV system, the data collection process, and the analytical methods used to evaluate performance and degradation in the context of promoting sustainable energy solutions.

2.1 System Description and SDG Alignment

The research was conducted on the PEARL grid-connected PV system, installed in October 2015 on the rooftop of the Engineering Tower Building at Universiti Malaya, Kuala Lumpur. The system’s operation as a research platform directly contributes to advancing knowledge for SDG 7.

• Array 1: Poly-Crystalline silicon with a total capacity of 2 kWp.
• Array 2: Mono-Crystalline silicon with a total capacity of 1.875 kWp.
• Total System Capacity: 3.875 kWp.

Both arrays are fixed in a south-facing orientation with an inclination angle of 10°. This setup allows for a direct comparison of two leading PV technologies under identical tropical climate conditions.

2.2 Data Collection and Monitoring

System performance and meteorological data (solar irradiance, ambient temperature, module temperature, wind speed) were continuously monitored using an SMA Sunny Sensor Box. Data was collected at 15-minute intervals between 07:00 and 19:00 to correspond with daylight hours. To ensure the scientific validity and integrity of the analysis, no data imputation or interpolation was performed on the raw dataset. This rigorous approach ensures the findings provide a reliable benchmark for future sustainable energy research.

2.3 Performance Evaluation Criteria (IEC 61724)

The system’s performance was evaluated using standardized indicators defined in IEC 61724-1:2017. This standardized methodology ensures that the results are robust and comparable, providing valuable data for global efforts to scale up clean energy infrastructure. The key performance parameters analyzed include:

• Energy Output (AC and DC): The total energy generated by the system.
• Yields (Reference, Array, and Final): Metrics representing the productivity of the PV system relative to its capacity and available solar resources.
• Performance Ratio (PR): A critical metric quantifying the overall efficiency of the PV system, independent of location, reflecting the quality of components and installation.
• Capacity Factor (CF): A measure of how much energy the system produces relative to its maximum potential output.
• Efficiencies (Array, System, and Inverter): Indicators of the conversion efficiency at different stages of the system.
• Losses (Array and System): Quantification of energy losses within the PV array and during the DC-to-AC conversion process.

2.4 Degradation Forecasting Model (MAKIMA)

To assess the long-term sustainability and material durability of the PV technologies, a critical aspect of SDG 12, the Modified AKIMA Interpolation (MAKIMA) method was used to forecast the degradation rate for 2023. This advanced interpolation technique is effective for handling the nonlinear trends often observed in PV efficiency data. The relative degradation rate was calculated based on the change in system efficiency over time, with 2019 serving as the baseline year. The accuracy of the forecast was validated using standard performance error metrics (RMSE, MAE, MAPE).

3.0 Analysis of Performance and Contribution to SDGs

This section presents the results of the performance analysis, with a focus on how the findings contribute to the broader objectives of sustainable development.

3.1 AC Energy Output and Climatic Impact

The average annual AC energy output was 2.24 MWh for Array 1 and 1.18 MWh for Array 2. Energy generation was highest between January and March and lowest in August and September. This seasonal variation directly correlates with Malaysia’s monsoon seasons, where increased cloud cover and rainfall reduce solar irradiation. The observed decline in energy output from 2020 to 2022 underscores the impact of climatic variability on renewable energy generation. Understanding these patterns is essential for developing resilient and reliable clean energy systems (SDG 7, SDG 11) that can withstand the challenges posed by climate change (SDG 13).

3.2 System Yields, Capacity Factor, and Performance Ratio

The system’s yields and capacity factor mirrored the seasonal trends of energy output. Array 1 consistently demonstrated higher yields and a higher average capacity factor (12.79%) compared to Array 2 (7.16%), indicating superior performance of the Poly-crystalline technology in this specific tropical environment.

Critically, the Performance Ratio (PR) for Array 1 was 86.74%, a high value indicating excellent internal system efficiency relative to the available solar energy. This result is significant because it demonstrates that despite challenging climatic conditions that may lower absolute energy output, a well-designed PV system can operate with minimal internal losses. A high PR is a key indicator of quality and reliability, aligning with the principles of responsible production (SDG 12) and ensuring that investments in clean energy (SDG 7) deliver maximum value.

3.3 System Efficiency and Losses

The analysis of array, system, and inverter efficiencies revealed that Array 1 consistently outperformed Array 2. The overall system efficiency was highest during months with optimal sunlight and moderate temperatures. System losses were primarily influenced by environmental factors, with Array 2 exhibiting significantly higher array losses, potentially due to material aging and manufacturing mismatches. Minimizing these losses through better technology and maintenance is crucial for maximizing the output of clean energy assets.

3.4 Degradation Analysis and Long-Term Sustainability

The degradation analysis provides critical insights into the long-term viability of PV investments, a key consideration for achieving SDG 7. Both arrays showed a clear decline in efficiency from 2019 to 2022.

• Array 1 (Poly-crystalline): Average annual degradation rate of 2.22%.
• Array 2 (Mono-crystalline): Average annual degradation rate of 2.54%.

The MAKIMA forecast predicted a continued increase in degradation for 2023, with rates reaching 10.58% for Array 1 and 11.99% for Array 2. These rates are higher than the industry average, highlighting the accelerated aging of PV materials in harsh tropical climates. This finding underscores the need for developing more durable materials and effective maintenance strategies to ensure the longevity of renewable energy infrastructure, thereby supporting SDG 12 (Responsible Consumption and Production) and ensuring the long-term success of SDG 13 (Climate Action).

4.0 Conclusion and Recommendations for Sustainable Energy Policy

This report provides a comprehensive 36-month performance and degradation analysis of a grid-connected PV system in a tropical climate, offering valuable data to support the achievement of the Sustainable Development Goals.

4.1 Summary of Key Findings

• Superior Technology: The Poly-crystalline system (Array 1) consistently outperformed the Mono-crystalline system (Array 2) across all performance metrics, making it a more suitable technology for the specific environmental conditions of the study location.
• Energy Generation: The system demonstrated significant potential for clean energy generation, directly contributing to SDG 7, though output is heavily influenced by seasonal monsoon patterns.
• Performance Ratio: Array 1 achieved a high performance ratio of 86.74%, indicating excellent system design and operational efficiency despite challenging climatic conditions.
• Degradation Rates: The observed degradation rates (2.22% and 2.54% annually) are higher than global averages, highlighting the accelerated aging of PV materials in tropical environments. The MAKIMA model accurately forecasted this trend.

4.2 Recommendations

The findings from this study confirm that while PV technology is a cornerstone for achieving SDG 7 and SDG 13, its long-term performance in tropical climates requires careful consideration. It is recommended that policymakers and project developers:

1. Prioritize the selection of PV technologies and materials specifically proven to be resilient in high-temperature, high-humidity environments to ensure the long-term viability of clean energy investments.
2. Integrate long-term degradation analysis and forecasting into the planning and financial modeling of renewable energy projects to create more accurate lifecycle cost assessments.
3. Develop and implement robust maintenance schedules to mitigate the impacts of environmental stressors and slow the degradation process, thereby maximizing the contribution of PV systems to climate action and sustainable energy goals.

Future work will include a techno-economic analysis to identify the most cost-effective PV solutions for Malaysia and other tropical regions, further supporting the global transition to affordable and clean energy.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The article addresses and connects to several Sustainable Development Goals (SDGs) through its focus on renewable energy technology, climate action, and sustainable infrastructure. The primary SDGs identified are:

• SDG 7: Affordable and Clean Energy: The entire article is centered on solar photovoltaic (PV) systems, a key source of clean and renewable energy. It discusses the global shift to renewable energy, the performance of PV systems, and their role in reducing energy costs, directly aligning with the goal of ensuring access to affordable, reliable, sustainable, and modern energy.
• SDG 9: Industry, Innovation, and Infrastructure: The study represents scientific research and innovation aimed at improving renewable energy infrastructure. By analyzing the performance, durability, and degradation of different PV technologies (Poly-Crystalline and Mono-Crystalline), the research contributes to optimizing system performance and material selection. This supports the goal of building resilient infrastructure and fostering innovation.
• SDG 11: Sustainable Cities and Communities: The article highlights the integration of PV systems into buildings, known as Building-Integrated Photovoltaics (BIPV), as a solution for urban energy generation. This directly addresses the challenge of spatial limitations in densely populated urban areas and contributes to making cities and buildings more sustainable and resilient.
• SDG 13: Climate Action: The article explicitly links the adoption of solar PV to climate change mitigation. It mentions Malaysia’s national targets for reducing greenhouse gas (GHG) emissions under the Paris Agreement and cites studies where PV systems have led to significant reductions in CO₂ emissions. This demonstrates a direct contribution to taking urgent action to combat climate change and its impacts.

2. What specific targets under those SDGs can be identified based on the article’s content?

Based on the article’s discussion, the following specific SDG targets can be identified:

1. Target 7.2: By 2030, increase substantially the share of renewable energy in the global energy mix.
   • Explanation: The article directly supports this target by analyzing the performance of solar PV systems, which are a crucial component of the renewable energy mix. It references Malaysia’s national goal “of achieving a 31% RE share in the total installed capacity by 2025,” which is a clear national strategy to increase the renewable energy share.
2. Target 9.4: By 2030, upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes.
   • Explanation: The study’s focus on evaluating the efficiency, durability, and degradation of PV materials contributes to the adoption of cleaner technologies. The analysis of Building-Integrated Photovoltaics (BIPV) is a direct example of upgrading infrastructure (buildings) to be more sustainable and energy-efficient.
3. Target 9.5: Enhance scientific research, upgrade the technological capabilities of industrial sectors in all countries, in particular developing countries, including, by 2030, encouraging innovation.
   • Explanation: The study is conducted by the “Power Electronics and Renewable Energy Laboratory (PEARL) for research purposes.” Its rigorous analysis of eleven performance parameters, comparison of PV technologies, and use of forecasting models like MAKIMA represent an effort to enhance scientific research and upgrade technological understanding of PV systems in a tropical climate.
4. Target 11.6: By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.
   • Explanation: By promoting solar energy in urban settings through BIPV, the article advocates for a technology that reduces reliance on fossil fuels, thereby lowering greenhouse gas emissions and improving urban air quality. The article cites a study where a PV system led to a “carbon emission reduction of 177 metric tons of carbon dioxide (CO₂),” directly contributing to reducing the environmental impact of cities.
5. Target 13.2: Integrate climate change measures into national policies, strategies and planning.
   • Explanation: The article explicitly mentions Malaysia’s national climate policies, stating that the country “aims to achieve significant emissions reductions by 2030 and 2035 in alignment with its Nationally Determined Contributions (NDC) under the Paris Agreement, specifically a 45% reduction in greenhouse gas (GHG) emissions intensity by 2030.” The promotion and analysis of solar PV technology are presented as a means to achieve these integrated national goals.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, the article mentions or implies several indicators that can be used to measure progress towards the identified targets:

• For Target 7.2: The official indicator is 7.2.1 (Renewable energy share in the total final energy consumption). The article provides a direct example of this indicator by citing “Malaysia’s Ministry of Natural Resources, Environment, and Climate Change (NRECC) has set a target of achieving a 31% RE share in the total installed capacity by 2025.”
• For Target 9.4: The official indicator is 9.4.1 (CO₂ emission per unit of value added). The article provides data that directly measures this concept, citing studies that quantified “a carbon emission reduction of 177 metric tons of carbon dioxide (CO₂)” and the potential to “mitigate over 28,000 kg of CO₂ emissions.” These figures measure the environmental performance and cleanliness of the technology.
• For Target 9.5: The official indicator is 9.5.1 (Research and development expenditure as a proportion of GDP). While not providing expenditure figures, the article itself is a product of scientific research. The entire study, with its detailed analysis of performance metrics (Performance Ratio, Capacity Factor, system efficiency) and the development of a forecasting model (MAKIMA), serves as a qualitative indicator of ongoing R&D activities aimed at enhancing PV technology.
• For Target 13.2: The official indicator is 13.2.1 (Number of countries that have established national climate change plans). The article directly refers to such a plan by mentioning Malaysia’s “Nationally Determined Contributions (NDC) under the Paris Agreement” and the “Malaysia Renewable Energy Roadmap (MyRER),” which are national strategies to combat climate change.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com