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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 portable solar panels have dropped in price and have some advantages.+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://www.amazon.com/portable-solar-panel/s?k=portable+solar+panel|Amazon search]] [[https://www.amazon.com/portable-solar-panel/s?k=portable+solar+panel|Amazon search]]
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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.  To make storage/placement easier they are usually 100x times however many you need. 
 ==== half-cut ==== ==== half-cut ====
  
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 ===== efficiency ===== ===== efficiency =====
  
-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).+The formula for panel efficiency is simply rated kW / square meter ].  A 20% efficient panel will make 200w per square meter under lab conditionsie, 20% of the lab's 1000w standard. (0.20kW per square meter) 
  
  
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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.  If you are tight for space and need the power then pony up the cash and enjoy the premium product+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.  If you are tight for space and need the power then higher efficiency panels might be worth the premium.
  
  
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   * **Maximum Power Voltage (Vmp)**: 28.60 Vmp <- voltage at which max power is generated in lab conditions   * **Maximum Power Voltage (Vmp)**: 28.60 Vmp <- voltage at which max power is generated in lab conditions
   * **Maximum Power Current (Imp)**: 6.64 Imp <- Amps at Vmp in lab conditions   * **Maximum Power Current (Imp)**: 6.64 Imp <- Amps at Vmp in lab conditions
 +  * **Temperature coefficient**; see below.
  
 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:solar:output|power output will likely be less]] than under optimal lab conditions and the Vmp may not be at the voltage given on the label.  Vmp will vary due to local conditions like temperature, shade, and sunshine.  An [[electrical:solar:charge_controller|MPPT charge controller]], if present, will sweep the range of voltages regularly to find Vmp under the existing conditions. In real world conditions [[electrical:solar:output|power output will likely be less]] than under optimal lab conditions and the Vmp may not be at the voltage given on the label.  Vmp will vary due to local conditions like temperature, shade, and sunshine.  An [[electrical:solar:charge_controller|MPPT charge controller]], if present, will sweep the range of voltages regularly to find Vmp under the existing conditions.
  
-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://digivation.com.au/solar/tempderate.php))+==== temperature coefficient ==== 
 + 
 +Panel voltage //decreases// as cell temperature //increases// Ramifications:   
 + 
 +  - 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:  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://digivation.com.au/solar/tempderate.php)) 
 + 
 +The actual amount of drop is dictated by the **temperature coefficient**, expressed as -0.X%/ºC.  In other words, the Vmp will go down by X% per degree celsius of cell temp above 25C.  Since  
 + 
 +This coeffcient ranges from 0.3% to -0.5%.  Crystalline panels average around -0.44% and thin-film lower (in the thirties).  The general pattern seems to be that cell chemistries with higher Vmp tend to experience greater heat-related losses.  "Mind the [air]gap".  
 + 
 +Let's consider three different panels in 80F ambients: 
 + 
 +  * 100w mono, rated 19Vmp, -0.445%/ºC((https://www.researchgate.net/profile/Abdelhamid-Rabhi/publication/274373712/figure/fig3/AS:667621221478403@1536184711417/MPP-thermal-coefficient-for-mono-and-poly-crystalline-PV-module-varying-with-power.png)) == **14.65w** lost @ 16.22Vmp 
 +  * 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.  The system needs to be sized to deal with high-output situations, particularly overly high panel voltages.  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.  The system needs to be sized to deal with high-output situations, particularly overly high panel voltages. 
 +
 +>> 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://solardesignguide.com/stc-and-noct-solar-panel-test-conditions-explained/))
  
 **PTC** ([[https://www.osti.gov/servlets/purl/93997-mpCvkV/webviewable/|PVUSA]] Test Conditions)((https://solarmazd.com/stc-ptc-noct-what-do-they-mean-and-how-to-use-them/)) is a rarer standard. **PTC** ([[https://www.osti.gov/servlets/purl/93997-mpCvkV/webviewable/|PVUSA]] Test Conditions)((https://solarmazd.com/stc-ptc-noct-what-do-they-mean-and-how-to-use-them/)) is a rarer standard.
electrical/solar/panels.1693964644.txt.gz · Last modified: 2023/09/05 21:44 by frater_secessus