How to determine the quality of solar panels

The properties of materials used for the production of heliopanels are most determined by their functionality, durability, and compliance with the characteristics of the manufacturer. The quality of solar batteries manufactured from secondary or low-grade raw materials leaves much to be desired. The low purchase value of such equipment does not bring benefits due to insufficient performance and short service life.

How do I determine the quality level of solar panels?

The parameters used to determine the quality of solar panels are easily evaluated.

Volt-ampere characterization factor (VA)

The factor of filling the WHH is the main indicator of the quality of products and is defined as the result of the ratio of the real power of the panel to the hypothetical. The higher it is, the less performance loss due to the internal resistance of the material.

Assessment of the appearance of the solar battery

The appearance of the solar panels also provides an indication of their quality and performance. The idea is to use homogeneous solar cells without any visible defects such as chips, cracks, or scratches. They are the cause of losses in the conversion of solar energy into electrical energy.

Damage reduces the life span of the solar panel because it allows the harsh UV radiation to destroy its microstructure faster. The number and shape of elements in a module can also tell you about its performance.

Evaluating the appearance of the solar panel
  • Systems of 90 watts or more, designed to operate at a base voltage of 12 V, must consist of 36 identical modules of at least 12.5×12.5 cm in size. The use of a larger number of parts of a different shape than a square usually indicates that scrap solar cells have been used to make the battery.
  • Systems characterized by a voltage of 24 V are a kind of exception since they must have in their structure parts in the form of half elements of 12.5×12.5 cm.
  • Systems from 140 to 170 watts with a rated voltage of 12 V, should consist of 36 elements 15.6×15.6 cm.

The number of solar cells in a design that exceeds the recommended number implies a large amount of soldering, which increases the risk of short circuits. Systems made of low-grade components are not of high quality, and together with the above-mentioned assembly feature, they lose a lot of reliability.

Quality categories of solar cell components

The modules for converting incoming solar energy during daylight hours are complex structures in which every detail counts for efficient operation.

Classification of solar cells

Assessing the quality of solar cells helps to find out the class of solar cells used for their production. It is their microstructure that determines their lifetime and influences their efficiency.

Grades A, B, C, D

Классификация солнечных элементов
  • Grade A cells have the best quality indicators: no chips, scratches, or cracks. Smooth surface and homogeneity of crystal layer and color ensure a low degradation rate and a high coefficient of VAR filling – over 0.7. Models of this type are usually characterized by higher than specified in the passport power values and a reduced temperature coefficient.
  • Grade B solar cells have a BAC fill factor of 0.4 to 0.7 due to the presence of visual surface defects. Disturbances in the structure are also the reason for the accelerated aging of equipment made of this type of raw material. In some cases, it still allows to obtain a comparable performance with the previous category, so it is widely used in the production of solar panels.
  • Grade C solar cells have serious structural and surface defects: cracks, chips, and loss of structural parts. They are sold at a low cost and do not allow the production of solar equipment with high efficiency, because their efficiency does not exceed the figure of 15%. In a professional production, such modules are acceptable only for the manufacture of systems with low voltage to charge batteries from 12 to 48 V.
  • The Grade D category includes solar cell waste. Officially, they are considered unsuitable for the manufacture of solar cells and must be melted down. In practice, they are widely used by unscrupulous manufacturers who cut out entire parts of products and use them to produce low-power equipment.

Grade C and D solar cells are relatively large and heavy with a low efficiency of less than 14%. They are especially dangerous to use in systems with series-connected components and high DC-side voltages from the modules (100 V or more).

The micro-cracks in these categories can cause a module to “hot spot” and fail completely. The temperature in the damaged area can rise to 300°C or more in a very short time (just 60 seconds).

Some manufacturers of solar equipment can use their own options for dividing cells into groups, depending on their quality. For example, Suntech uses a system consisting of Perfect Grade, A and B Grade. In fact, these categories meet the requirements described for the first three positions of the conventional classification.

Many factories in China are guided in the division of goods into just two groups according to their quality indicators, A and B Grade, so the second category includes not only solar cells with significant defects in surface and structure but even waste to be recycled.

EVA laminating film

EVA laminating film is located on the front and back sides of the solar panel, it is designed to ensure complete sealing of the equipment without delaying sunlight. Its properties directly determine the longevity of the equipment:

  • cheap varieties have a lifespan of 5-10 years;
  • quality products work without complaint for 25 years and more.

After the declared period of uninterrupted operation, the material begins to decay under the influence of atmospheric influences and ultraviolet radiation. They are expressed in the formation of delamination, clouding, and the appearance of yellowing. These disturbances lead to loss of tightness and a general decrease in module efficiency.

Gradual decline in performance can go up to the complete failure of the equipment. It is impossible to distinguish a poor-quality film from a good one by its appearance, so it is necessary to be guided by the cost of the finished module. Unusually low prices are often caused by the use of unstable and short-lived varieties of EVA.

PET Backsheet (PET)

Photocells based on amorphous silicon

PET, which is usually white or black in color, is used to protect the underside of solar panels and seal them. It is a thermoplastic polymer highly valued in manufacturing for its transparency, durability, chemical inertness, and plasticity.

Good quality material retains its properties over a wide temperature range (-40°C to +75°C). According to the thickness of the applied layer of insulation polyethylene terephthalate provides the highest voltage values of the structure (600 or 1000 V). Its technical description must contain the necessary data on the applied PET film.

The cheaper the material, the shorter its service life will be. Its lifetime will be marked by the inevitable peeling, cracking, and yellowing of the film. Damage to PET leads to a breach of the tightness of the solar panel and a complete loss of performance of the modules.

Manufacturer’s Level Assessment

Confidence in the product is also largely determined by the reputation of the manufacturer.

  1. The largest factories with extensive experience in the solar equipment market usually have an annual volume of at least 1 GW and their own production of components. Plants of this type support scientific research and make extensive use of automated systems.
  2. The middle category is represented by manufacturers who produce solar cells themselves but do not make sufficient use of innovative robotic technologies. The manufacturers in this group in Russia include the Hevel plant, which, however, does not sell components on the domestic market.
  3. Small assembly companies represent the main segment of the market. They do not make investments and produce solar panels from off-the-shelf components purchased on the side.

Thus, the quality of solar panels produced in Russia is determined only by the integrity of manufacturers and their care in selecting suppliers of components and parts. They must undergo strict control and selection before assembly.

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