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electrical:solar:panels [2023/04/06 21:30] frater_secessus [Panel voltage] |
electrical:solar:panels [2023/09/05 21:44] frater_secessus [efficiency] |
To avoid overcharging,((a bit of an oversimplification, admittedly)) a [[electrical:solar:charge controller|charge controller]] is placed between the PV and the battery bank. | To avoid overcharging,((a bit of an oversimplification, admittedly)) a [[electrical:solar:charge controller|charge controller]] is placed between the PV and the battery bank. |
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[[electrical:solar:output|Many factors]] will affect output; and panels will rarely generate power equal to their laboratory rating. | [[electrical:solar:output|Many factors]] will affect output; and panels will rarely generate power equal to their laboratory rating. As a general rule, expect panels to put out much less than their rated wattage under normal conditions. |
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**As a general rule, expect panels to put out 60% of their rating** under absolutely best-case scenarios. | |
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There are several types of PV widely available on the market, and many more in research stages. PV are described by how each panel's cells are constructed. | There are several types of PV widely available on the market, and many more in research stages. PV are described by how each panel's cells are constructed. |
* **Nominal 12v panels** have 36 cells. They will generally have max power (Vmp) around 18v and open circuit (Voc) around 21v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found on mobile and portable installations. \\ Note: there are some "12v" panels that actually have 40 cells.((nominal 13v?)) Example: [[https://amzn.to/3Pcrcsi|Renogy 200w "12v"]] panels, with Vmp of 22.6v and Voc 27v. The extra voltage //cannot be harvested by PWM// so MPPT is effectively required with these. | * **Nominal 12v panels** have 36 cells. They will generally have max power (Vmp) around 18v and open circuit (Voc) around 21v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found on mobile and portable installations. \\ Note: there are some "12v" panels that actually have 40 cells.((nominal 13v?)) Example: [[https://amzn.to/3Pcrcsi|Renogy 200w "12v"]] panels, with Vmp of 22.6v and Voc 27v. The extra voltage //cannot be harvested by PWM// so MPPT is effectively required with these. |
* **Nominal 20v panels** have 60 cells. They will generally have max power (Vmp) around 30v and open circuit (Voc) around 36v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found in residential rooftop installations. | * **Nominal 20v panels** have 60 cells. They will generally have max power (Vmp) around 30v and open circuit (Voc) around 36v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found in residential rooftop installations. |
* **Nominal 24v panels** have 72 cells. They will generally have max power (Vmp) around 36v and open circuit (Voc) around 42v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found in commercial or residential ground level installations. Due to internal construction (actually 2 36-cell segments in parallel)((https://youtu.be/ofo1HQyGG8s?t=1m22s)) they can be more resistant to partial shading. | * **Nominal 24v panels** have 72 cells. They will generally have max power (Vmp) around 36v and open circuit (Voc) around 42v.((https://www.altestore.com/howto/solar-panels-pv-and-voltages-a98/)) These are commonly found in commercial or residential ground level installations. |
* even higher cell counts (and voltages) can be present in very large panels, like >400w. | * even higher cell counts (and voltages) can be present in very large panels, like >400w. |
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===== Efficiency ===== | ===== efficiency ===== |
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| The forumula for panel efficiency is simply rated watts / square meter. A 20% panel will make 200w per square meter under lab conditions (ie, 20% of the lab's 1000w standard). |
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Higher efficiency doesn't mean the panel makes more power; it means it makes more power from a given area. 100w is 100w, but you might be able to fit a 110w panel high-efficiency panel in the same space as a regular-efficiency panel. | Higher efficiency doesn't mean the panel makes more power; it means it makes more power from a given area. 100w is 100w, but you might be able to fit a 110w panel high-efficiency panel in the same space as a regular-efficiency panel. |
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> At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared radiation, **445 watts is visible light**, and 32 watts is ultraviolet radiation. -- [[https://en.wikipedia.org/wiki/Infrared|wikipedia]] | |
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Mono panels can capture about 15-20% of this visible light energy. Poly panels capture 13-16%, and film panels capture 9%. | ===== longevity ===== |
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| Framed panels are often warranted to make 80% of their rated output for 25+ years. |
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| There is [[https://web.archive.org/web/20220703094223/https://www.sciencedirect.com/science/article/pii/S2211379716301280|some evidence]] that panels with a load connected degrade slower than those stored unconnected (open circuit) |
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===== Specifications ===== | ===== Specifications ===== |
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