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electrical:solar:panels [2021/07/19 21:57] frater_secessus [Specifications] |
electrical:solar:panels [2023/09/05 21:45] frater_secessus [efficiency] |
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To avoid overcharging, | To avoid overcharging, | ||
- | [[electrical: | + | [[electrical: |
There are several types of PV widely available on the market, and many more in research stages. | There are several types of PV widely available on the market, and many more in research stages. | ||
+ | ---- | ||
- | ===== types of panels ===== | + | ===== Types of panels ===== |
- | ==== monocrystalline | + | ==== Monocrystalline |
//Mono// or //single crystal// cells are made from complete slices of silicon crystal. | //Mono// or //single crystal// cells are made from complete slices of silicon crystal. | ||
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* slightly better than poly in uniform low light | * slightly better than poly in uniform low light | ||
* theoretically greater longevity than poly, much better longevity than thin film | * theoretically greater longevity than poly, much better longevity than thin film | ||
- | * slightly higher [[electrical: | + | * slightly higher [[electrical: |
* slightly better performance in higher temps than poly, possibly due to higher Vmp | * slightly better performance in higher temps than poly, possibly due to higher Vmp | ||
* CON | * CON | ||
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- | ==== polycrystalline | + | ==== Polycrystalline |
//Poly// cells are made up of smaller pieces of slices. | //Poly// cells are made up of smaller pieces of slices. | ||
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- | ==== flexible | + | ==== Flexible |
Flexible panel configurations place unusual demands on the materials. | Flexible panel configurations place unusual demands on the materials. | ||
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The other challenge is to make solar cells that can slightly flex. | The other challenge is to make solar cells that can slightly flex. | ||
- | === crystalline | + | === Crystalline |
While the flex panel market has largely gone to poly/mono crystalline, | While the flex panel market has largely gone to poly/mono crystalline, | ||
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Handle with care, and bend as little as possible. | Handle with care, and bend as little as possible. | ||
- | === thin film === | + | === Thin film === |
[Note: | [Note: | ||
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* semi-flexible so it can be applied to curved shapes | * semi-flexible so it can be applied to curved shapes | ||
* least affected by high temps | * least affected by high temps | ||
- | * least affected by shading | + | * least affected by shading |
+ | * least affected by cloudy/hazy conditions, due to increased sensitivity at the blue end of the light spectrum((https:// | ||
* very light | * very light | ||
* CON | * CON | ||
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* lower Vmp | * lower Vmp | ||
- | ===== portable ===== | + | ==== Portable |
- | While most panels are hard mounted horizontally, | + | While most panels are hard mounted horizontally |
- | PRO | + | [[https:// |
+ | |||
+ | * **PRO** | ||
* no mounting costs | * no mounting costs | ||
* can be stored securely in the camper | * can be stored securely in the camper | ||
* can collect sunlight while the camper stays in the shade | * can collect sunlight while the camper stays in the shade | ||
+ | * Can be angled and moved follow the sun and collect maximum power | ||
+ | * Sometimes have USB charging ports directly on the back of them, allowing charging of small devices directly without the use of a charge controller and battery setup. | ||
- | CON | + | * **CON** |
* animals may damage or pee on the panels((http:// | * animals may damage or pee on the panels((http:// | ||
* long wiring runs can cause voltage drop | * long wiring runs can cause voltage drop | ||
* deployed panels can make [[camping: | * deployed panels can make [[camping: | ||
* it is easy to get lazy and not put out the panels every time | * it is easy to get lazy and not put out the panels every time | ||
+ | * Questions exist about long-term durability | ||
+ | * Possibility of panels getting stolen | ||
+ | ==== half-cut ==== | ||
+ | Some panels are " | ||
+ | {Secessus reminds us we should avoid [[electrical: | ||
- | ===== panel voltage ===== | + | |
+ | ===== Panel voltage ===== | ||
12V panels are not really 12V; they are called that because they charge 12V battery banks (which aren't really 12v either!). | 12V panels are not really 12V; they are called that because they charge 12V battery banks (which aren't really 12v either!). | ||
- | * **Nominal 12v panels** have 36 cells. | + | * **Nominal 12v panels** have 36 cells. |
* **Nominal 20v panels** have 60 cells. | * **Nominal 20v panels** have 60 cells. | ||
- | * **Nominal 24v panels** have 72 cells. | + | * **Nominal 24v panels** have 72 cells. |
+ | * even higher | ||
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higher voltage panels are more common on the used market, as people upgrade residential/ | higher voltage panels are more common on the used market, as people upgrade residential/ | ||
- | MPPT [[electrical: | + | MPPT [[electrical: |
Higher voltage panels can reduce wire costs; amps are cut in half for the same amount of wattage. | Higher voltage panels can reduce wire costs; amps are cut in half for the same amount of wattage. | ||
- | They more likely to stay above charging setpoints in poor insolation or high heat. | + | They are more likely to stay above charging setpoints in poor insolation or high heat. |
+ | |||
+ | Panel voltage((more precisely, the relationship between panel voltage and battery voltage)) is an important factor when [[electrical: | ||
===== efficiency ===== | ===== efficiency ===== | ||
+ | |||
+ | The formula for panel efficiency is simply rated watts / square meter. | ||
+ | |||
Higher efficiency doesn' | Higher efficiency doesn' | ||
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In general, mono has higher efficiency than poly, and poly has higher efficiency than thin film. | In general, mono has higher efficiency than poly, and poly has higher efficiency than thin film. | ||
- | The cost of higher efficiency panels typically outstrips the increase power, so unless you are tight for space they typically aren't a good value for money. | + | The cost of higher efficiency panels typically outstrips the increase power, so unless you are tight for space they typically aren't a good value for money. |
+ | |||
+ | ===== longevity ===== | ||
+ | |||
+ | Framed panels are often warranted to make 80% of their rated output for 25+ years. | ||
+ | |||
+ | There is [[https:// | ||
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PV are generally rated by several criteria((http:// | PV are generally rated by several criteria((http:// | ||
- | * **Power (W)**: 190 Watts. | + | * **Power (W, or Pmax)**: 190 Watts. |
* **Open Circuit Voltage (Voc)**: | * **Open Circuit Voltage (Voc)**: | ||
* **Short Circuit Current (Isc)**: | * **Short Circuit Current (Isc)**: | ||
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Panels will get closest to their rated output at ambient temperatures around 32f/0f when the panels will be running about 85F. By the time ambient temperatures are 90F panel temps will rise to 145F and power output will drop about 18.45%.((http:// | Panels will get closest to their rated output at ambient temperatures around 32f/0f when the panels will be running about 85F. By the time ambient temperatures are 90F panel temps will rise to 145F and power output will drop about 18.45%.((http:// | ||
+ | ==== STC and NOCT ==== | ||
+ | |||
+ | To help consumers understand output outside the lab (Standard Test Conditions - STC) some producers also publish specs for conditions that might be more applicable to actual use (Normal Operating Cell Temperature - NOCT). | ||
+ | |||
+ | ^ ^ STC | **NOCT** | ||
+ | | **Irradience** | ||
+ | | **temperature** | ||
+ | | **wind speed** | ||
+ | |||
+ | |||
+ | We can see that with NOCT the sunlight is not as strong, and the panels are assumed to be much warmer((therefore Vmp and Pmax reduced)) though some cooling from ambient breezes is present.((panels are installed with an airgap to let breezes cool the underside)) | ||
+ | |||
+ | 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. | ||
- | ===== diodes | + | **PTC** ([[https:// |
+ | ===== Diodes | ||
+ | > A diode is designed to let current flow in one direction.... [it] is the electrical equivalent of a [plumbing] check valve. -- Amy@AltE((https:// | ||
> **Bypass Diodes** are inside the panel junction box, wired parallel to each cell group. It conducts when the cell is shaded and has reverse polarity due to other cells producing. **Blocking Diodes** are external to the panels. It blocks reverse current from other panels. It must handle the full voltage of system (series panels). -- Pappion((https:// | > **Bypass Diodes** are inside the panel junction box, wired parallel to each cell group. It conducts when the cell is shaded and has reverse polarity due to other cells producing. **Blocking Diodes** are external to the panels. It blocks reverse current from other panels. It must handle the full voltage of system (series panels). -- Pappion((https:// |