I recently set up a pv system for home (24V) using a 2 string arrays (3 panels 345w, 37V, 9.1A in series) for a total after combining of 112V @ 18.2A. My controller is rated @ 150V @ 60A with a 2kW inverter. I am wondering if it would be better to have 3 string array (2 panels 345w, 37V, 9.1A) to produce ~74V @ 27.3A instead? My average compsumption is ~10kWh a day, I am fine covering 80% (why I got a 2kW pv system). I will appreciate any help.
High volts vs Amps
- Thread starter LRH_pv
- Start date
Welcome to the forum.
You are wired 3S2P with 6 total panels based on my interpretation of your setup.
First, the 150V limit is based on the Voc of the panels, not Vmp. You need to confirm that the 3S Voc does not exceed 150V AND it has a cushion for cold temperature voltage increases. If your Voc is around 45V, most SCC manufacturers recommend only going 2S unless you live in a climate that never sees even mildly chilly temps.
Given the product of your stated voltage and currents, you are using Vmp numbers, and your Voc is closer to 45V: 37V*9.1A = 333W vs. 345W
You seem to perceive that changing from 3S2P to 2S3P will incur some 20% penalty. It will not. It will have negligible impact. Note the math:
3S2P: 112V * 18.2A = 2038.4W
2S3P: 74V * 27.3A = 2020.2W
vs. 6*345W = 2070W
The difference between the two calculations and rated is rounding error.
In most climates, the default configuration would be 2S3P. If it NEVER gets below 10°C/50°F, 3S is likely fine.
You are wired 3S2P with 6 total panels based on my interpretation of your setup.
First, the 150V limit is based on the Voc of the panels, not Vmp. You need to confirm that the 3S Voc does not exceed 150V AND it has a cushion for cold temperature voltage increases. If your Voc is around 45V, most SCC manufacturers recommend only going 2S unless you live in a climate that never sees even mildly chilly temps.
Given the product of your stated voltage and currents, you are using Vmp numbers, and your Voc is closer to 45V: 37V*9.1A = 333W vs. 345W
You seem to perceive that changing from 3S2P to 2S3P will incur some 20% penalty. It will not. It will have negligible impact. Note the math:
3S2P: 112V * 18.2A = 2038.4W
2S3P: 74V * 27.3A = 2020.2W
vs. 6*345W = 2070W
The difference between the two calculations and rated is rounding error.
In most climates, the default configuration would be 2S3P. If it NEVER gets below 10°C/50°F, 3S is likely fine.
Thanks for your comments, I still have to learn the differences and mening of the new vocabulary, but I get the main idea. I am located in the Caribbean at latitud 18, thanks again.
If your climate never drops below 10°C/50°F, then 3S is probably fine.
3S2P means you have two strings of 3 panels in series, and those two strings are in parallel with each other. I believe this is how you described your array.
Vmp and Voc are listed on the back of your panel.
Voc is the open circuit voltage, i.e., no current is flowing. if the panel is put in the sun, and you check the leads with a voltmeter, you will measure something close to that voltage.
Vmp is the voltage where the panel will deliver the maximum power while in operation with current flowing.
3S2P means you have two strings of 3 panels in series, and those two strings are in parallel with each other. I believe this is how you described your array.
Vmp and Voc are listed on the back of your panel.
Voc is the open circuit voltage, i.e., no current is flowing. if the panel is put in the sun, and you check the leads with a voltmeter, you will measure something close to that voltage.
Vmp is the voltage where the panel will deliver the maximum power while in operation with current flowing.
