A solar panel datasheet provides valuable information regarding the technical aspects of the solar panel which is very useful for engineers and designers to determine how to configure the whole system.
The panel data sheet gives information on things like material characteristics, packaging information, and the electrical specifications which we will go through in this article one by one.
Material characteristics
This part of the datasheet provides information on how large the panel is. The standard dimensions will be given in millimetres. In addition to this, there will also be a diagram of the pane with more measurements. This is important for the solar installers as it also gives information regarding the mounting holes. Information like the number of cells in series/parallel and the type of junction box, connector type, and output cable will also be mentioned.
Figure 1: Illustration of Mechanical specification
Figure 2: Material Characteristics
Solar panels are manufactured to be robust and weather resistant. The standard wind load value is 2400 Pa, but there are best solar panel manufacturers, who increase the mechanical load limit of the solar panels to 5400 P as you can find from figure 1.
Electrical specifications
The electrical data values are calculated concerning the standard testing conditions (STC) with an irradiance of 1000 W/m2 with AM spectrum of 1.5 and test temperature condition of 25 °C.
Nominal Operating Cell Temperature (NOCT)
Unlike the standard testing conditions (STC), Nominal operating cell conditions are defined as the temperature of the open-circuited solar cells in a module under the given conditions of Irradiation 800 W/m2 the ambient temperature is 20 °C. Module design, including module materials and packing density, have a major impact on the NOCT. So, both convective and
conductive heat transfer is affected by the mounting of the modules. A rear surface has infinite thermal resistance and won’t be able to conductively transfer heat as effectively as the front surface. Thus, Roof integrated mounting causes higher operating temperature.
Temperature coefficient (%/ °C)
The temperature coefficient of solar panels is one of the main criteria to consider when buying solar panels. On a hot summer day, a module will quickly reach 60°C or maybe even 70°C. The temperature coefficient specifies just how this heating affects the module power. It provides a number showing how much the module power is reduced if the ambient temperature is increased by 1°C. The lower the temperature coefficient, the better. The relation between the module temperature and the power output i.e., the temperature coefficient is becoming more important because of extremely hot summers occurring frequently.
Maximum Power Point (Pmax)
Pmax refers to the maximum power that the panel can produce. It is a product of the maximum current and voltage combined.
Minimum Power Point Voltage (Vmp)
Vmp refers to the maximum voltage that you want to see when it is connected to a maximum power point tracker (MPPT) equipment under standard conditions when the power output is the greatest.
Maximum Power Point Current (Imp)
Similar to Vmp , Imp refers to the maximum current that you want to see when connected to MPPT equipment when the power output is the greatest.
Open Circuit Voltage (Voc)
The open-circuit voltage is the given volts when the panels have no output load connected to them. This is a very important number, as it is the maximum voltage that the solar panel can produce under standard test conditions, so this is the number to use when determining how many solar panels you can wire in series going into your charge controller.
Short Circuit Current (Isc)
Short circuit current is the current produced by the panels when they are not connected to any load. i.e., when the positive and negative terminals of the panels are short-circuited. When determining how many amps a connected device can handle, like a solar charge controller or inverter, the short circuit current is used.
Figure 3: I-V cure of solar cell
Figure 4: Electrical specification
Figure 4 illustrates the electric specifications of a solar panel found in a typical datasheet. Different variety of panel models are shown in the sheet. The model numbers are not indicated in the figure.
Power tolerance
Power tolerance refers to how close to the specified power will be in real-world conditions. For example, from the datasheet in figure 2, the nominal power is 165 Wp with + 4.99 power tolerance which means it could go up to 170 Wp for that particular model.
As the technology behind solar panels continues to advance, it’s becoming more common for panels to have a 0% or 0W negative power tolerance. This means the solar panel will always have a rated STC Max Power equal or greater than what’s been specified. So, when choosing the panels always go for low negative or positive only values.
Module efficiency (%)
The efficiency of a panel is expressed as a percentage of the solar irradiation that the panel can transform into usable electricity at standard test conditions. One benefit of this is highly efficient panels take slightly less space to produce the same amount of power.
Certifications
While reviewing a solar panel datasheet, you’ll likely notice a bunch of acronyms and random numbers listed under safety and rating certifications like the ones seen in Figure 3. When comparing different panels, it is important to look for these standard testing certifications. IEC 61215 is one of the core testing standards for crystalline solar modules. If a solar panel module successfully meets IEC 61215 standards, that means it completed several stress tests and performed well in regards to quality, performance, and safety. IEC 61739 tests make sure that the panels pass the thermal, fire, electrical, and mechanical safety and possess a low risk for these hazards.
Figure 4: Different types of certifications in a datasheet
For salt mist corrosion testing, the panels are salt-sprayed in a controlled environment and later is inspected for damage. Frequent exposure to abrasive sand can wear a panel down, leading to physical or mechanical defects over time. If you’re installing solar in an area that sees frequent sand or dust storms, try choosing a panel that successfully passed these tests to maximize the durability of your system. Other testing conditions include Ammonia corrosion which can accelerate degradation in a panel, leading to lower overall electricity production over the lifetime of your system.
By keeping the above-mentioned points in mind, you can choose the panel that best fits tour budget and system. As a solar system owner, you are not required to interpret each and every technical aspect mentioned in the data sheet but is required to have a little understanding.