PHOTOVOLTAICS

Solar modules

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Solar modules for individual locations

There are now a lot of photovoltaic modules from different manufacturers on the market, where the functionality mostly works according to the same principle, but the different solar PV modules find their individual place of use depending on the intended use. Therefore, the question of a very good or the "best" PV module is not so easy to answer and should be planned individually with an expert for PV systems depending on the building project or location. The majority of all solar modules consist of monocrystalline or polycrystalline cell material. So-called thin-film modules are also offered.

In addition to the known crystalline cell technology, a new variant can now be found, namely quasi-monocrystalline. The module technology is sometimes also called mono-multi, virtus wafer, baby maple or quasimono.

All variants also differ in efficiency. The higher the efficiency of a module, the more power can be mounted on an available area. However, this does not mean that a module with a lower degree of efficiency must also have lower prospects of yield per kWp.

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What kind of solar modules are there?

Monocrystalline

Monocrystalline PV modules are solar modules that are very complex to manufacture.

The cells of the monocrystalline modules are sawn from a melt of high-purity silicon grown monocrystalline rod into 0.2 to 0.3 mm thick silicon wafers. The manufacturing process of the solar cell is completed by further chemical processes, such as doping the top and bottom of the cells and applying the anti-reflective layer as well as the front and rear contacts.

Due to the very high silicon content and the same (homogeneous) alignment of the crystal structure, the cells or modules have a high degree of efficiency compared to other types.

Due to the high production costs, the monocrystalline modules are also the most expensive.

Polycrystalline

Polycrystalline PV modules can be recognized by their mostly bluish color and crystalline structure. The use of polycrystalline solar cells or solar modules is currently one of the most frequently used PV modules in PV module production worldwide.

For the production of polycrystalline silicon cells, raw silicon is heated very strongly, cooled in a controlled manner in a mold and then cut into silicon wafers, 0.2 to 0.3 mm thick.

The crystal structure is inhomogeneous due to the irregular arrangement of the many crystals and is easily recognizable due to the pattern. Further chemical processes and the application of the contact tracks complete the manufacturing process of the solar cell.

The efficiency of poly- or multicrystalline modules is lower than that of monocrystalline modules. However, compared to monocrystalline modules, the yield prospects of polycrystalline modules per installed kWp are not lower.

Quasi-monokrystallin

In addition to the well-known crystalline cell technologies (monocrystalline & polycrystalline cells), there is now a new variant, namely quasi-monocrystalline. The module technology is sometimes also called mono-multi, virtus wafer, baby maple or quasimono.

The advantages of both known methods are combined here. A largely monocrystalline ingot is produced in a crucible that is actually intended for the production of polycrystalline ingots. A plate made of monocrystalline silicon is placed in the bottom of the furnace. The polycrystalline silicon that is melted over it is now based on this monocrystalline "template". So you get a uniform structure like with monocrystalline wafers.

But compromises have to be made. Only a relatively small percentage of 10% can be described as purely monocrystalline. This part is inside the block. The closer the material is to the outer wall, the more polycrystalline grains there are. These still have a monocrystalline expression. The material on the outside of the crucible wall is then again purely polycrystalline. That’s the remaining 10%.

The block is then processed or sawed in such a way that mono-, poly- and mixed wafers are created.

The efficiency of quasi-monocrystalline modules lies between that of monocrystalline modules

and polycrystalline modules.

Thin film

When assessing an overall system, the ratio of costs to total return is important. Thin-film modules are less efficient than crystalline modules. This means that for the same kWp output, a larger module area and thus higher costs for the substructure and assembly are necessary. The lower specific module price can currently no longer exceed these higher costs to such an extent that a thin-film variant is recommended. A thin-film module can only be of interest for optical reasons (e.g. facades).

Recycling carbon footprint

Old or broken solar modules can be recycled, which means that valuable raw materials such as glass, aluminum and semiconductor materials can be reused. This contributes to a positive environmental balance by avoiding waste and at the same time saving energy in the production of modules. A completely recycled system can recycle 95 percent of the materials used.

The claim that the production of solar power systems consumes more energy than can ever be generated with it is repeatedly brought up to us. Independent research results such as For example, the Institute for Energy Systems at ETH Zurich has shown that, on average, modern solar systems already produce more energy after around two years than is necessary for their production and recycling. Everything that is produced in terms of energy after this time is pure energy gain.