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electrical:solar:overpaneling [2018/05/10 22:06]
frater_secessus [clipping is relatively uncommon] 		electrical:solar:overpaneling [2023/11/22 10:31] (current)
frater_secessus [vs. charge controller]
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 **Overpaneling** has two related meanings;  both refer to having more solar panel output than a system might otherwise require. **Overpaneling** has two related meanings;  both refer to having more solar panel output than a system might otherwise require.
  
-  * [[#vs._charge_controller|overpaneled charge controller]] - battery bank and charge controller are evenly matched;  panel nominal or actual output is  more than the controller's rating. +  * Most common meaning:  [[#vs._charge_controller|overpaneled charge controller]] - battery bank and charge controller are evenly matched;  panel nominal or actual output is  more than the MPPT controller's rating.  This is the most common meaning. Note:  PWM controllers should not be overpaneled as they have no way to limit incoming current to protect themselves.  
-  * [[#vs._battery_bank|overpaneled battery bank]] - solar panels and charge controller are evenly matched; both are oversized compared to battery bank.+  * Less common meaning:  [[#vs._battery_bank|overpaneled battery bank]] - solar panels and charge controller are evenly matched; both are oversized compared to battery bank.  
    
  
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 The overpaneled system's power output bell curve is //shifted upwards// and cut off by the controller when it reaches its limits.  This is known as clipping, trimming, or clamping due to the "flat top" appearance of the overpaneled output curve. The overpaneled system's power output bell curve is //shifted upwards// and cut off by the controller when it reaches its limits.  This is known as clipping, trimming, or clamping due to the "flat top" appearance of the overpaneled output curve.
  
-**Example:**  Consider the image to the right.((The image is that of a different PV-related configuration but it works for our purposes.)) The smaller/interior bell curve is the normally paneled configuration. \\ +With appropriate overpaneling the clipping is relatively minor.  Victron notes that: 
 + 
 +>> Generally total energy harvested from a 130% panel oversizing results in less than 1% annual energy loss. -- [[https://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/|source]] 
 + 
 + 
 +==== theory ==== 
 + 
 +Consider the image to the right.((The image is that of a different PV-related configuration but it works for our purposes.)) The smaller/interior bell curve is the normally paneled configuration. \\ 
 The larger/exterior curve is the overpaneled configuration. \\   The larger/exterior curve is the overpaneled configuration. \\  
 The striped area is the peak power "clipped" by the controller when the controller is overpaneled.  \\  The striped area is the peak power "clipped" by the controller when the controller is overpaneled.  \\ 
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   * you want to get deeply cycled batteries charging as early as possible in the morning   * you want to get deeply cycled batteries charging as early as possible in the morning
   * you spend most of your time in areas with [[electrical:solar#weather-related_issues|marginal insolation]], like the Pacific Northwest   * you spend most of your time in areas with [[electrical:solar#weather-related_issues|marginal insolation]], like the Pacific Northwest
 +  * you spend time in partial shade
   * you want to use a smaller controller instead of jumping up to the next size.  Example, 43A max output and your choices are 40A or 60A controllers.   * you want to use a smaller controller instead of jumping up to the next size.  Example, 43A max output and your choices are 40A or 60A controllers.
 +
 +
 +==== example ====
 +
 +Let's say you want to adhere to Victron's 10-30% overpaneling approach.  Working backwards, their model appears to use 14.2v Vbatt as a constant.  
 +
 +  * 500w / 14.2v = 35.2A. 
 +  * 35.2A on a 30A MPPT is    17.3% overpaneled:  ( (35.2 - 30) / 30 = 0.173)
 +
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   -  when there is very little load being used   -  when there is very little load being used
  
-This occurs because the PPT controller moves Vpanel toward Voc to reduce current when less is needed but battery voltage is high, as in late Absorption .  Counterintuitively, some load to the system can drop PV voltage (and therefore CC temps) to lower levels.((http://forum.solar-electric.com/discussion/comment/256896#Comment_256896))+This occurs because the PPT controller moves Vpanel toward Voc to reduce current when less is needed but battery voltage is high, as in late Absorption.  For this reason adding some load to the system in Absorption can //reduce// PV voltage (and therefore CC temps) to lower levels.((http://forum.solar-electric.com/discussion/comment/256896#Comment_256896))
  
  
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 [This section is based on [[https://www.cheaprvliving.com/forums/showthread.php?tid=30236&pid=378960#pid378960|a forum post]] - secessus] [This section is based on [[https://www.cheaprvliving.com/forums/showthread.php?tid=30236&pid=378960#pid378960|a forum post]] - secessus]
  
-Perhaps counterintuiitively, in overpaneled systems in normal((non-optimal)) conditions don't need to constrain power that often.  A couple reasons for this:+Perhaps counterintuiitively, overpaneled systems in normal((non-optimal)) conditions don't need to constrain power that often.  A couple reasons for this:
  
   - Overpaneled systems start collecting usable power earlier in marginal light.  Secessus observes that by the time the sun is high enough to theoretically max out the controller, it has already completed Bulk and the bank's current acceptance is dropping.     - Overpaneled systems start collecting usable power earlier in marginal light.  Secessus observes that by the time the sun is high enough to theoretically max out the controller, it has already completed Bulk and the bank's current acceptance is dropping.  
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 The heavy vertical black line((also added by secessus)) comes down from that intersection at 21v.((It also crosses at ~11v but most MPPT downconvert rather than boost, so 11v is not useful.)) The heavy vertical black line((also added by secessus)) comes down from that intersection at 21v.((It also crosses at ~11v but most MPPT downconvert rather than boost, so 11v is not useful.))
  
-In this case the controller wants to limit panel output to 65w So it runs the panel at 21v.  Then it downconverts the excess voltage to amps:  it charges the battery((or runs loads)) 5A @ 13v.((this same mechanism is used to reduce power in Absorption and Float stages))+In this case the controller wants to limit panel output to 65w So it runs the panel at 21v, which is a far cry from Vmp.  Then it downconverts the excess voltage to amps:  it charges the battery((or runs loads)) 5A @ 13v.  This same mechanism is used to reduce power in Absorption and Float stages. 
  
 === corollaries === === corollaries ===
 If you have the curve and Vpanel you can derive the power output. \\ If you have the curve and Vpanel you can derive the power output. \\
 If you have the curve and you know Wpanel you can derive Vpanel. \\ If you have the curve and you know Wpanel you can derive Vpanel. \\
-If you have a lot of time and patience, you can plot Vpanel and Wpanel to draw the curve yourself. +If you have a lot of time and patience, you can plot Vpanel and Wpanel to draw the curve yourself. \\ 
- +An MPPT controller is //always// **T**racking and using powerpoints, not just when the **M**aximum **P**ower **P**oint is required.
 ===== vs. battery bank ===== ===== vs. battery bank =====
  
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-Overpaneling the bank gets lead-acid batteries charged faster and keeps them charged longer than other approaches.  This minimizes [[electrical:depth_of_discharge#partial_state_of_charge|battery murdering partial state of charge conditions]] found in [[electrical:solar:overbanking|overbanking]].+Overpaneling the bank gets lead-acid batteries charged faster((faster/shorter Bulk charging stages -  Absorption duration will not be affected)) and keeps them charged longer than other approaches.  This minimizes [[electrical:depth_of_discharge#partial_state_of_charge|battery murdering partial state of charge conditions]] found in [[electrical:solar:overbanking|overbanking]].
  
  
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   * you want your lead-chemistry batteries to stay as charged as much as possible   * you want your lead-chemistry batteries to stay as charged as much as possible
 +  * you are in an area with relatively little sunshine
   * you want to save battery weight   * you want to save battery weight
   * you want to reduce battery investment and complexity   * you want to reduce battery investment and complexity
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 Since the underbanked system has less capacity will reduce your actual [[electrical:solar:sizing#your_reserve_needs|reserve days of power]] to some extent.  But during daytime there is //some// solar power coming in and an overpaneled configuration will harvest relatively more power in sub-optimal conditions.  The smaller bank will get through Bulk and well into Absorption faster, too. This will help extend the //effective// reserve days of power. Since the underbanked system has less capacity will reduce your actual [[electrical:solar:sizing#your_reserve_needs|reserve days of power]] to some extent.  But during daytime there is //some// solar power coming in and an overpaneled configuration will harvest relatively more power in sub-optimal conditions.  The smaller bank will get through Bulk and well into Absorption faster, too. This will help extend the //effective// reserve days of power.
 +
 +Further reading:
 +
 +  * [[electrical:solar:slim_reserve|slim reserves]]
  
electrical/solar/overpaneling.1526004413.txt.gz · Last modified: 2020/10/11 19:48 (external edit)

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