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electrical:solar:overpaneling [2019/02/11 12:08]
frater_secessus [Overpaneling] |
electrical:solar:overpaneling [2024/12/22 11:23] (current)
frater_secessus [vs. charge controller] |
| **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. |
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| * [[#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. This is the most common meaning. | * 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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| **Note:** overpaneling is not //overvolting//, which would be exceeding the maximum input voltage of the charge controller. Overvolting often results in damage to the controller; it can be caused by linking too many panels in series, or running too close to the voltage max in conditions that raise the panels' Voc.((http://www.cheaprvliving.com/forums/Thread-36-volt-solar-panel?pid=144154#pid144154)) | **Note:** overpaneling is not //overvolting//, which would be exceeding the maximum input voltage of the charge controller. Overvolting often results in damage to the controller; it can be caused by linking too many panels in series, or running too close to the voltage max in conditions that raise the panels' Voc.((http://www.cheaprvliving.com/forums/Thread-36-volt-solar-panel?pid=144154#pid144154)) |
| ===== vs. charge controller ===== | ===== vs. charge controller ===== |
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| | **TL;DR**: overpaneling the controller means sizing MPPT for //actual// incoming solar power rather than //rated// panel wattage. |
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| {{ http://www.nacleanenergy.com/images/articles/NovemberDecember2014/Solar/advancedenergy_figure1.jpg?200}} | {{ http://www.nacleanenergy.com/images/articles/NovemberDecember2014/Solar/advancedenergy_figure1.jpg?200}} |
| **Overpaneling**, or having "too much" panel for the rating of your MPPT charge controller, can be desirable in some situations. It is a **trade-off that biases the setup** to get more power out of normal and marginal conditions at the expense of the peak output during optimal conditions.((sun overhead, clear sky, low temps)) | **Overpaneling**, or having "too much" panel for the rating of your MPPT charge controller, can be desirable in some situations. It is a **trade-off that biases the setup** to get more power out of normal and marginal conditions at the possible expense of the peak output during optimal conditions.((sun overhead, clear sky, low temps)) |
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| >In car terms, the overpaneled system trades away some of the panels' top-end output for more low- and mid-range grunt. -- secessus | >In car terms, the overpaneled system trades away some of the panels' top-end output for more low- and mid-range grunt. -- secessus |
| 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. |
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| **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: |
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| | >> 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]] |
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| | ==== theory ==== |
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| | 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. \\ |
| * you spend time in partial shade | * 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. |
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| | ==== example ==== |
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| | 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. |
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| | * 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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| 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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| 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. |
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| | Further reading: |
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| | * [[electrical:solar:slim_reserve|slim reserves]] |
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