What Factors Affect Solar PV System Efficiency?
It’s possible that after the installation of your solar PV module, you have noticed a decline in its efficiency. There are several factors contributing to this, one of which is the accumulation of dust on the surface of the panels. However, there are other losses that also play a role in reducing the performance of your solar panels.
The two most common losses associated with solar panels are heat loss and the difference in ambient temperature. These factors can cause degradation over time. Other reasons for a decrease in efficiency include shading by trees or other obstacles and dust accumulation.
In this article, we will explore all the losses that occur in a Solar PV module, helping you understand the reasons for reduced efficiency.
Here are 7 types of losses in Solar PV Module
1. Losses in Solar PV Module due to Hotspot Effect
A hotspot is an area of high temperature that can result in energy loss, reduced output efficiency, and accelerated degradation of the panel due to overheating. It occurs when shaded cells in a solar panel cause a large reverse bias, leading to excessive power dissipation in a small area, causing local overheating.
Hotspots can occur due to several reasons such as:
- Partial shading due to trees or vegetation
- Mechanical damage to the solar PV module like broken glass, collisions, improper fixturing
- Internal module failures such as cell material defects, cracks, poor solder joints to prevent hotspots, it is important to consider shading and other shadow-causing objects during the design of the solar PV plant. Regular cleaning and maintenance can also minimize soiling. A strong O&M program can help prevent hotspots and maintain the life and performance of the plant.
2. Losses in Solar PV Module due to Snail Trail effect
Snail trails, also referred to as snail tracks or worm marks, are discolouration lines that appear on solar panels after extended usage. These lines, which are typically dark or brown, can be found near busbars, at the edges of the panel, or near microcracks. Snail trails are a result of physical defects, such as microcracks, on the solar panels that allow for unwanted chemical reactions. This common but often overlooked defect can lead to reduced efficiency and the formation of hotspots. To prevent snail trails, it’s crucial to handle solar panels with care to avoid microcracks and regularly monitor their health through thermal imaging.
3. Potential Induced Degradation Losses in solar PV Module
Potential Induced Degradation (PID) in photovoltaic (PV) modules occurs when the PN junction of solar cells is damaged, resulting in a leakage current. This is caused by a large potential difference between the PV module frame and the module circuit, leading to decreased conductivity in the solar cells.
This causes electrical charges to be deposited on the Aluminum frame instead of flowing to the inverter, resulting in reduced efficiency and power generation. Although PID has no noticeable visual effects on the module, it can be detected through various photovoltaic analysis techniques, such as the IV curve method and infrared thermography.
4. Light-Induced Degradation Losses in Solar PV Module
Crystalline modules can experience a decline in performance known as Light Induced Degradation (LID) when exposed to sunlight for the first time. This loss can negatively impact the actual performance of some PV modules as reported by their manufacturer’s factory flash test data. The degree of LID loss is related to the quality of wafer manufacturing and can range from 1% to 3% or higher.
The cause of LID is the diffusion of positive-charged oxygen dimers across silicon lattices, forming complexes with boron dopant acceptors under the influence of light. These boron-oxygen complexes create energy levels in the silicon lattice, which allows them to capture electrons and holes lost in the photovoltaic process. Only conventional p-type boron-doped wafers are affected by LID, while technologies utilizing n-type doped wafers are not impacted.
5. Losses in Solar PV Module Due to Accumulation of Dirt and Dust
In solar photovoltaic (PV) systems, the build-up of dirt and dust on the modules can significantly reduce efficiency as it interferes with the incoming sunlight by absorbing, scattering, and reflecting it. This soiling, consisting of mineral dust, soot particles, aerosols, pollen, fungi, and other contaminants, has become a growing concern for PV systems worldwide as it reduces the intensity of light reaching the active part of the solar cells. With a yearly increase of more than 25%, soiling and dust accumulation on PV modules is becoming a major challenge in the technology. Additionally, debris or longer particles can penetrate the PV cell layer, blocking light absorption and potentially causing damage to the panel’s protective cover or other components in the PV system. This loss can be prevented by regularly cleaning the modules and monitoring the plant’s performance using an O&M software platform.
6. Module Quality Losses
Module quality loss, also known as module rating loss or module nameplate rating loss, refers to the discrepancy between the stated power of a solar PV module and its performance in standard testing conditions. This loss is indicated in the module’s datasheet, which lists the power tolerance, including both a (+) and (-) tolerance. The power tolerance represents the range of electrical power the module can generate above or below its rated capacity. For example, a power tolerance of -5%/+5% on a 200-W panel means the panel can produce between 190 W and 210 W under normal atmospheric conditions.
7. Module Degradation Losses
The output of solar panels decreases over time due to degradation. Research from NREL shows that the average degradation rate for solar panels is 0.5% annually, but this rate can be higher in warmer climates. It is important to choose high-quality panels with low degradation rates to minimize the impact on your system.
To prevent losses in your solar PV module, regular monitoring and following standard operation and maintenance procedures is crucial. Futr Energy offers O&M services, including detailed analysis of PV modules through drone-based technology and AI-powered cloud-based asset management solutions. Their Futr OS system uses IV Testing & EL data to provide insights for asset performance optimization, helping industries meet their goals for improvement.
Originally published at futr.energy/knowledge