Panel mismatch refers to a situation in which the electrical parameters of one solar cell within a photovoltaic (PV) module deviate significantly from the parameters of the other cells. The degree of impact and power loss resulting from this mismatch is influenced by several factors:
1. Operating Point of the PV Module: The specific conditions at which the PV module is operating play a role in determining the impact of panel mismatch. Different operating points within the current-voltage (IV) curve can be affected differently by the mismatch.
2. Circuit Configuration: The configuration of the electrical circuit connected to the PV module also influences the consequences of this mismatch. The circuit design interacts with the mismatched cell, potentially amplifying or mitigating the power losses.
3. Different Parameters: Any deviation in the IV curve between one solar cell and the others can contribute to mismatch losses at certain operating points. While mismatches can occur in various parameters, the most common culprits are disparities in the short-circuit current or open-circuit voltage.
Effect of Panel Mismatch
The effect of panel mismatch is contingent upon both the circuit configuration and the type of mismatch present. Large mismatches, particularly in the short-circuit current or open-circuit voltage, tend to have a more pronounced impact. They can result in increased power losses and reduced efficiency.
Reasons for Panel Mismatch
The reasons for this mismatch are as follows-
- Manufacturing discrepancies: Minor variations during the manufacturing process can result in divergent electrical characteristics among solar cells or panels, leading to losses due to mismatch.
- Shading: Partial shading of a solar panel creates an imbalance between shaded and unshaded cells, causing reduced power output due to mismatch.
- Soiling: Accumulation of dirt, dust, or other debris on a solar panel can create a mismatch between soiled and clean cells, leading to decreased power output.
- Temperature effects: Variations in temperature across a solar panel, influenced by factors such as location and orientation, can induce a mismatch between hotter and colder cells, resulting in diminished power output.
- String length disparities: Inconsistent string lengths can contribute to mismatch losses, as the current of a string is limited by the weakest cell’s current.
- Light-induced degradation: Light-induced degradation (LID) can give rise to a mismatch between the initial and degraded performance of solar cells, leading to reduced power output.
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