What does it say on the label of a solar panel?
In many occasions doubts arise about certain technical aspects of a solar panel, such as: what voltage it has, its power or its short-circuit current. Here we will review some of the concepts that appear on the labels and data sheets of solar panels.
PMAX (Maximum Power): is the maximum power that the solar panelcan generate. It can be calculated by multiplying the VMP by the IMP. Its unit of measurement is the Watt (W).
VMP (Maximum Power Voltage): is the nominal voltage of the solar panel at maximum power. It is the voltage value that, combined with its current, makes the panel produce the maximum power. Its unit of measurement is the volt (V).
MVS (Maximum Voltage System): is the maximum voltage that cannot be exceeded by the set of panels that make up the string. Its unit of measurement is the volt (V).
VOC (Open Circuit Voltage): is the voltage in volts that the photovoltaic panel delivers when it is without load. It would be the value that would be measured if a multimeter were used to measure the voltage between the connectors when the panel is disconnected from everything. It is an important data to obtain the maximum number of panels in series without exceeding the maximum of the equipment where they will be connected. Its unit of measurement is the volt (V).
IMP (Maximum Power Current): is the current produced by the panel when it is connected to the installation producing the maximum power of the panel indicated in the data sheet. Its unit of measurement is the ampere (A).
ISC (Short Circuit Current): is the current intensity that the panel can produce when it is short-circuited. It would be the value that would be measured with an ammeter clamp when connecting the male and female of the same panel. It is an important value when defining the maximum number of strings per input that can be connected. Its unit of measurement is the ampere (A).
Temperature Coefficient of Pmax: is the percentage of power loss due to temperature variation in degrees.
Temperature Coefficient of Voc: is the percentage of voltage loss due to temperature variation in degrees.
Temperature Coefficient of Isc: is the percentage of current losses due to temperature variation in degrees.
Cell Type: indicates the photovoltaic cell technology.
Cell number: indicates the number of cells per module.
Module Efficiency: is the ratio between the power of the photovoltaic panels and the radiation incident on its surface. It does not indicate the effectiveness of the panel. For the same power, the larger the size, the lower the efficiency.
Product Warranty: is the time the manufacturer assures that the product will not suffer any failure due to faulty manufacture.
Performance Warranty: is the percentage of maximum power that the manufacturer claims the panel will have after a certain period of time.
All values indicated by the manufacturers are based on standard measurement conditions (STC), normally defined as 1000W/m2 irradiance, AM1.5G spectral distribution and 25°C temperature. On the sticker on the solar panel you can also find the exact temperature and irradiance conditions where the measurements were made. The weight, dimensions and the manufacturer's technical certifications are also included in the data.
It should be noted that some names may vary from one manufacturer's data sheets and labels to another.