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electrical:solar:panels [2024/01/04 16:54] frater_secessus [STC and NOCT] compare |
electrical:solar:panels [2024/05/28 22:01] frater_secessus [efficiency] |
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==== Portable ==== | ==== Portable ==== | ||
- | While most panels are hard mounted horizontally on the roof of the van, portable folding | + | While most panels are hard mounted horizontally on the roof of the van, portable solar panels((folding, briefcase, framed or otherwise)) may have some advantages. |
[[https:// | [[https:// | ||
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* Questions exist about long-term durability | * Questions exist about long-term durability | ||
* Possibility of panels getting stolen | * Possibility of panels getting stolen | ||
+ | * not all portables are weatherproof | ||
+ | * can be blown over by wind | ||
+ | Note that regular framed panels can also be carried as portables. | ||
==== half-cut ==== | ==== half-cut ==== | ||
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===== efficiency ===== | ===== efficiency ===== | ||
- | The formula for panel efficiency is simply rated watts / square meter. | + | The formula for panel efficiency is simply |
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* **Maximum Power Voltage (Vmp)**: | * **Maximum Power Voltage (Vmp)**: | ||
* **Maximum Power Current (Imp)**: | * **Maximum Power Current (Imp)**: | ||
+ | * **Temperature coefficient**; | ||
Note that in this example the Power (W) rating is 190, which is the Vmp x Imp (28.60 x 6.64 = 189.904W). | Note that in this example the Power (W) rating is 190, which is the Vmp x Imp (28.60 x 6.64 = 189.904W). | ||
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In real world conditions [[electrical: | In real world conditions [[electrical: | ||
- | Panels | + | ==== temperature coefficient ==== |
+ | |||
+ | Panel voltage // | ||
+ | |||
+ | - since panels are rated by Vmp x Imp, anything that reduces voltage will reduce power.((PWM are generally not affected since they are not using that higher voltage anyhow)) | ||
+ | - the Vmp your MPPT controller finds in human-comfortable temps will likely be lower than rated Vmp | ||
+ | |||
+ | Example: | ||
+ | |||
+ | The actual amount of drop is dictated by the **temperature coefficient**, | ||
+ | |||
+ | This coeffcient ranges from 0.3% to -0.5%. | ||
+ | |||
+ | Let's consider three different panels in 80F ambients: | ||
+ | |||
+ | * 100w mono, rated 19Vmp, -0.445%/ | ||
+ | * 100w poly, rated 18Vmp, -0.440%/ºC == **14.48w** lost @ 15.39Vmp | ||
+ | * 100w CIGS((not really, trying for apples-to-apples here)), rated 18.66Vmp, -0.36%/ºC == **11.85w** lost @ 16.45Vmp | ||
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==== STC and NOCT ==== | ==== STC and NOCT ==== |