How to read Solar Panel specifications?

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All solar panels come with their specifications and these are mentioned on the back side of solar panels. This article is all about how to read solar panel specifications and choose the best solar panel according to your needs.

solar panel specifications
Solar Panel specifications as mentioned on a Tata module at our site
Standard Test Conditions (STC)

STC are set of conditions in which solar panels are tested. Since, the output voltage and current depend highly on ambient temperature and intensity of light, among various other criterion, all solar panels are tested at the same Standard Test Conditions. These conditions include,the cells temperature to be 25℃, light intensity/irradiation of 1000 watts per square meter and the atmospheric density (or, air mass) of 1.5. As you can see in the picture above, STC is mentioned on all solar panels.

Aricle: Solar Panel Specifications

Peak Power (Pmax)

Peak Power is the power output you’ll get when all the solar panels are generating to its fullest. Here, the output voltage and current from the panels are Vmpp and Impp respectively. In other words, Pmax is the maximum power output one can get from that solar panel.

Since, Power = Voltage X Current

So, Pmax = Vmpp X Impp

where, mpp = Maximum Power Point

Pmax is always mentioned on the solar panels. When Maximum Power Point Tracking (MPPT) charge controllers or inverters are employed, this is the point where it tries to keep the voltage and current to maximize the power output.

Aricle: Solar Panel Specifications

Voltage @ Pmax (Vmpp)

This is the voltage a solar panel will generate when power output is maximum. This is the value one desires when solar panels are connected to charge controllers and inverters. This value is also, always mentioned on the solar panels.

Aricle: Solar Panel Specifications

Current @ Pmax (Impp)

This is the current a solar panel can generate when power output is maximum. This is the value one desires when solar panels are connected to charge controllers and inverters in order to get peak power. This value is also, always mentioned on the solar panels.

Aricle: Solar Panel Specifications

Open Circuit Voltage (Voc)

This is the voltage generated by solar panels when no load is connected to it. This means, if you just connect a voltmeter across positive and negative terminals of a solar panel, you will get the reading, Voc. Since the solar panel isn’t connected to anything (there is no load on it), no current will be produced in it.

This is the maximum voltage a solar panel can generate under Standard Test Conditions (STC).

Aricle: Solar Panel Specifications

Short Circuit Current (Isc)

This is the current generated by solar panels when no load is connected to it. This will be the current rating when the positive and negative terminals of the panels are connected with each other.

This is the maximum current the solar panels will produce under Standard Test Conditions (STC).

Aricle: Solar Panel Specifications

Maximum Series Fuse

Modules are built to withstand only a small amount of current and can fail if they are exposed to a higher current. Back feeding of current from parallel strings can happen if one string stops producing power due to some reasons.

To avoid this, a protection fuse is installed in solar panels. This rating can be seen in the picture of specifications above.

Aricle: Solar Panel Specifications

Power Tolerance

Power Tolerance is the actual range, a solar panel can deviate from its specified maximum power, that is, Pmax at Standard Test Conditions (STC).

Example, The panel mentioned above has Pmax of 295 Wp and power tolerance of (0 to +5)W. This means solar panel can actually have an STC maximum power anywhere between (295 to 300)W.

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