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electrical:solar:shading [2020/01/07 23:32] frater_secessus [partial shading] |
electrical:solar:shading [2022/08/06 15:18] frater_secessus [Partial shading] |
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+ | Words of Wisdom: | ||
+ | |||
====== Partial shading ====== | ====== Partial shading ====== | ||
- | Partial shading can have surprisingly dramatic effects on panel output. | + | Partial shading can have surprisingly dramatic effects on [[electrical: |
+ | ===== reminder: | ||
+ | **Before we begin:** solar panels are " | ||
+ | Partial shading in this context means: | ||
+ | * light is falling on the panel | ||
+ | * but not evenly on the panel -- it is different on some cells | ||
+ | To prevent power from rushing into the shaded string and overheating them, panels have bypass diodes between the strings. | ||
- | It works this way: | ||
- | - partial shade causes //voltage differences// | + | ===== panel configuration for partial shade ===== |
- | - electricity flows from higher-voltage areas to lower-voltage ones, so voltage differences would cause power to rush into the lower-voltage (shaded) cells | + | |
- | - overheating the shaded cell and possibly damaging it | + | |
- | To prevent damage panel manufacturer' | + | The way to avoid the problems associated with partial shade is to avoid partial shade. |
- | ===== panel configuration for partial shade ===== | ||
+ | * **avoiding shade** is best | ||
+ | * a **dedicated controller for each panel** is the next best thing | ||
+ | * [[electrical: | ||
+ | * With **PWM controllers, | ||
+ | * With **MPPT controllers** and **low-ish voltage** serial panel configurations (where the total Vmp is <=2x battery bank voltage) **parallel will probably still yield more**. | ||
+ | |||
+ | |||
+ | |||
+ | ===== exception: | ||
+ | |||
+ | There is another approach, which is to **bring the shaded cells/ | ||
- | * With PWM controllers **parallel panel configurations typically yield more power** in partial shade than serial. | + | This occurs because the MPPT has a broader range of voltages to sweep and can find [[https:// |
- | * With MPPT controllers and **low-ish voltage** serial panel configurations (where the total Vmp is <=2x battery bank voltage) it's close but **parallel will probably still yield more**. | + | |
- | * With MPPT controllers and **higher voltage** serial configs (say Vmp is >=3x bank voltage) we see **an increasing serial advantage over parallel in partial shade**. | + | |
+ | ===== examples ===== | ||
+ | * [[https:// | ||
+ | * [[https:// | ||
+ | * [[https:// |