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electrical:solar:panels [2023/09/05 21:44] frater_secessus [efficiency] |
electrical:solar:panels [2024/05/28 22:01] (current) 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 | ||
+ | |||
+ | |||
+ | |||
==== STC and NOCT ==== | ==== STC and NOCT ==== | ||
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While NOCT may be useful for gauging normal harvests, STC is used for system component((like controllers)) sizing because the panels really can make STC power((or even more)) in some real world conditions. | While NOCT may be useful for gauging normal harvests, STC is used for system component((like controllers)) sizing because the panels really can make STC power((or even more)) in some real world conditions. | ||
+ | |||
+ | >> NOCT is useful for comparing two panels **[that have] the same STC rating**. A panel with a higher rated power at NOCT for example, will generally result in a higher performing panel.((https:// | ||
**PTC** ([[https:// | **PTC** ([[https:// |