Cell microcracks, hot spots, and PID effects were once three major problems influencing the performance of crystalline silicon PV modules. With the rapid advancement of process technology, equipment, and materials in recent years, these issues in the solar panel production process have been significantly improved, and the quality of the solar panels leaving the plant is guaranteed.
The problem of microcracks caused by improper external forces in storage, transport, and installation of modules has become a new problem in recent years, along with the rapid development of the distributed market, due to large and small installation teams of mixed quality, or without systematic training, after the modules leave the factory and before and after installation. In this section, we will look at the causes of microcracks in solar panels during transit, installation, and use, as well as the negative impacts of microcracks and the major treatments.
Microcracks are invisible cracks that can form in the cell unit and are not visible to the human eye when the cell (modules) is subjected to high mechanical or thermal stresses.
What causes the formation of microcracks?
Cell fractures are a common issue for both solar panel manufacturers and system owners, both before and after installation. Microcracks in solar panels are caused by mechanical pressures during transit and installation, as well as harsh weather variables.
Mechanical stress is an internal force that interacts between the parts of an object to try to resist the external cause and return the object from its post-deformation position to its pre-deformation position when an object deforms due to an external cause (force, change in humidity and temperature, etc.).
Mechanical stress can be caused in the logistics and supply chain processes by:
(1)Inadequate packing
(2)Inappropriate forms of transportation
(3)Inadequate handling methods
Mechanical stress can be caused during the installation of a solar PV system by:
(1)Using modules as a platform for other equipment or for stepping;
(2)Modules crashing or falling as they are elevated to the roof;
(3)Installation on a non-flat surface may result in the mounting frame twisting and putting stress on the module.
Microcracks in solar PV systems can also be caused by the following environmental factors:
(1)Thermal cycling, or the temperature difference between day and night;
(2)freezing and humidity
(3)Wind and cyclic (or dynamic) pressure stresses
(4)Ample snowfall
(5)Hail
How are microcracks discovered after installation?
The most successful method for locating faults in solar panels on-site is to use infrared cameras to measure temperature differences on the solar panel surface. When exposed to sunlight, cracked solar panel cells create a high resistance zone with a higher temperature than nearby cells.
An infrared camera can successfully identify places with large temperature swings and alert the maintenance personnel so that the dubious panels may be investigated straight away.
DISSEM, an Allied Vision Korean partner, has assisted a prominent supplier of solar cell inspection systems in developing a low-cost imaging solution based on near-infrared spectrum electroluminescence.
What are the harmful consequences of microcracks?
Microcracks might induce loss and hot spots effects
Microcracks, according to the study, may induce an electrical disconnection, leaving some cell components inert. However, because microcracks can have a variety of effects, including no influence at all, quantifying the power loss caused by these microcracks is difficult. Rejecting every module with a microcrack can pose issues, particularly when it comes to warranty, but it is not necessary for all of them to work at the level of power that is guaranteed for the duration of the module. According to certain studies, a module with several cracks that do not separate specific parts of the cell can experience losses of up to 2.5%. More losses may occur for a module with microcracks that isolate areas of the cell. Microcracks can also cause hot spots to emerge. These occur when the internal resistance of a damaged cell increases and current flows through it, elevating the temperature of the cell. Hot spots have been shown to exacerbate cell damage.
Microcracks can cause power outages in solar panels and even flames.
Some microcracks on the solar panel are not obvious, and a direct look is also unable to see them. Many people will believe that there is no problem and that they can continue to use. However, microcracks will cause a direct factor is to cause a decline in solar panel power. There may be some very slight, at this stage of the test power will not be much change, but after a few months, a year of thermal expansion and contraction, the power of the solar panels will drop sharply. Even a severe internal short-circuit will develop, resulting in fire and other problems.
How are microcracks repaired?
Micro-fractures form within cells and cannot be healed without the replacement of a module. However, if the microcracks have little effect on the normal performance of the solar panels, they can be utilised. As a result, installers and end users should concentrate on how to handle, install, and utilize solar panels in a scientific manner to avoid microcracks.
How can microcracks be avoided?
To effectively avoid solar panel microcracks, three critical areas must be addressed: manufacture, transportation and installation, and operating environment. A critical component of the strategy is selecting a solar panel manufacturer who understands the need of preventing microcracks.
A competent solar panel provider must meet the following requirements:
(1)A well-organized supply chain
(2)A customer warranty program based on guarantees
(3)A testing method that ensures each module is exposed to EL testing
(4)A favorable reputation
How can microcracks be avoided when solar panels are stored in a warehouse?
1. To facilitate transport operations while avoiding slanted components caused by hidden fractures or damage, the complete box of components should be put on a level, open position.
2. The total height of the box stacking cannot exceed the height of two boxes. Pay great attention to how the pallet is gently moved up and down to avoid having the pallet corners in the air.
3. The components should be carried to the building site with as little handling or movement as possible after being set in place, as this increases the chance of hidden cracks in the components.
4. Once the components have been carefully organized, they should be covered with materials such as colorful striped cloth to prevent visible damage or concealed cracks caused by the components tilting or overturning after the site has been subjected to continual rainstorm washout.
5. When temporarily put, the components must be properly stacked and placed on a pallet or flat surface, with the middle components facing upward on the back side and the first and last components facing upward on the glass side. The flat components can only be placed on a maximum of 18 pieces.
6.They must be carefully arranged and temporarily set diagonally against columns or other objects; the supporting objects must be level, without protrusions, and no more than 10 pieces in number.
7.When installing solar panels, the temporary panels should be loaded on the same day, and the remaining panels should be positioned neatly and flatly or well-protected to avoid collapsing when left unattended.
How can microcracks in secondary handling be avoided?
1. Two individuals are required to transport each component to the installation place after they have been unpacked. This eliminates the need for one person to carry one or more components, reduces the chance of the components slipping out of the hand, and reduces the risk of hidden cracks or damage to the components caused by bumps or shocks.
2. Be aware of your surrounds as you handle the components to avoid collapsing and producing hidden fissures or exploding panels.
3. When the pieces are complete, lean on the bracket beams rather than placing them flat on the floor.
4. To avoid component damage during the transfer process, only forklift trucks and cranes should be used, and uncommon machinery (excavators, loaders, etc.) should be avoided.
5.It is critical to cover the components well when they are on the roof to avoid unintended collisions with the walls or their corners, which could result in internal fractures or outwardly visible scars.
How can microcracks be avoided during installation?
1. Install the components from top to bottom using a top-to-bottom installation technique. When mounting the components, avoid using bricks, wood plugs, or other temporary fastening methods; at the very least, use the upper two bolts for temporary attachment.
2. Installation workers should avoid stepping, sitting, kneeling, pressing, knocking, squeezing, or physically touching the components when installing them. Because of the confined tension on the internal battery cells, this might produce hidden cracks in the components.
3. The spring pads must be leveled, and the component mounting bolts must be appropriately adjusted.
4. When using the pressure block to secure the components, the horizontal surface of the pressure block should be firmly in contact with the component frame to avoid the appearance of a pinch angle.
Since 2008, Maysun Solar has specialized on developing high-quality solar modules. Choose from our extensive selection of half-cut, MBB, IBC, and Shingled solar panels in full black, black frame, silver, and glass-glass. These panels provide outstanding performance as well as beautiful designs that mix in with any building. Maysun Solar has effectively created offices, warehouses, and long-term relationships with great installers across the globe! Please contact us for the most recent module quotations or for other PV-related questions. We are delighted to help you.
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