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electrical:solar:panels [2022/04/19 14:56]
frater_secessus [STC and NOCT] |
electrical:solar:panels [2022/07/10 16:56]
frater_secessus [Panel voltage] |
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| * **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. | * **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. 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. |
| higher voltage panels are more common on the used market, as people upgrade residential/commercial installations | higher voltage panels are more common on the used market, as people upgrade residential/commercial installations |
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| MPPT [[electrical:solar:charge_controller|controllers]] do a DC-DC downconversion that is quite efficient. If Vmp isn't required most will move PV voltage away from Vmp to prevent power from ever getting to the CC. | MPPT [[electrical:solar:charge_controller|controllers]] do a DC-DC downconversion that is quite efficient. If Vmp isn't required they will move PV voltage away from Vmp to prevent power from ever getting to the CC. |
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| 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. |
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| Panel voltage((more precisely, the relationship between panel voltage and battery voltage)) is an important factor when [[electrical:solar:charge_controller#how_to_choose|selecting a solar charge controller]]. | Panel voltage((more precisely, the relationship between panel voltage and battery voltage)) is an important factor when [[electrical:solar:charge_controller#how_to_choose|selecting a solar charge controller]]. |
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| ===== Efficiency ===== | ===== Efficiency ===== |
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| PV are generally rated by several criteria((http://www.kg4cyx.net/solar-panel-specifications-explained/)) | PV are generally rated by several criteria((http://www.kg4cyx.net/solar-panel-specifications-explained/)) |
| * **Power (W)**: 190 Watts. <- rated power in Watts under lab conditions. You can derive **price-per-watt** by dividing $/watts. | * **Power (W, or Pmax)**: 190 Watts. <- rated power in Watts under lab conditions. You can derive **price-per-watt** by dividing $/watts. |
| * **Open Circuit Voltage (Voc)**: 36.00 Voc <- Volts in full sun with no load. In practice you will likely not see Voc when hooked to the controller, but **all parts of your solar installation need to be able to cope with the theoretical Voc**. In serial arrays the Voc ratings are added. | * **Open Circuit Voltage (Voc)**: 36.00 Voc <- Volts in full sun with no load. In practice you will likely not see Voc when hooked to the controller, but **all parts of your solar installation need to be able to cope with the theoretical Voc**. In serial arrays the Voc ratings are added. |
| * **Short Circuit Current (Isc)**: 7.42 Isc <- Amps in full sun when shorted. Also theoretical, but **connectors and cables need to be sized to handle Isc**. | * **Short Circuit Current (Isc)**: 7.42 Isc <- Amps in full sun when shorted. Also theoretical, but **connectors and cables need to be sized to handle Isc**. |
