Panels photovoltaic solar energy

Types Of Photovoltaic Cells

Types Of Photovoltaic Cells

The photovoltaic cells are responsible for converting solar radiation into electrical energy in the form of direct current. Photoelectric cells are an indispensable element for this type of renewable energy.

There are different types of photoelectric cells depending on the nature and characteristics of the materials used. The most common type is the crystalline silicon cell (Si). This material is cut into very thin disc-shaped, monocrystalline or polycrystalline sheets, depending on the manufacturing process of the silicon bar.

The first crystalline cell that was manufactured in the industrial field is that of pure monocrystalline silicon. These types of solar cells have a good energy efficiency, but they cost more than other types. For this reason, they currently have a moderate level of implementation.

The set of photovoltaic cells connected in series form a solar panel. In this case, a photovoltaic solar panel.

Monocrystalline and polycrystalline solar cells

Monocrystalline solar cells usually have a square shape, with rounded corners. Formerly they had a circular shape. This is due to the growth process of the monocrystalline silicon crystal that has a cylindrical shape.

Monocrystalline and polycrystalline photovoltaic cells

In the manufacturing process of polycrystalline silicon, the silicon is allowed to solidify slowly in a rectangular mold and a rectangular solid with many crystals is obtained, which gives rise to the polycrystalline cells. This type of cells have a lower yield than monocrystalline cells, but currently have a strong implantation because they have a lower economic cost than monocrystalline.

With less implementation, we can find on the market photovoltaic panels called "thin layer". These are not manufactured with individual cells, but in the form of continuous bands in which a thin layer of amorphous silicon (a-Si), 1 or 2 microns thick, is deposited on an appropriate substrate (glass or synthetic resins), making a continuous panel that does not need interior interconnections.

A characteristic of these cells is that photons that do not collide with any electron pass through them thanks to their small thickness, which makes it possible to design panels with different layers superimposed and which are called tandem (two layers) or triple union (three layers). ).

The cells with amorphous silicon have a yield of about half that of crystalline cells, and therefore, in the manufacture of thin-film cells are beginning to use other types of semiconductors, essentially copper and indium selenur (CIS) ) or cadmium telluride (CdTe).

Silicon As innovative technologies in the manufacture of photovoltaic cells, we will highlight the so-called "HIT cells" (Heterojunction with Intrinsic Thin Layer). This term refers to a technique based on the superposition of semiconductor layers of different "gap" such as amorphous silicon combined with crystalline silicon cells or cadmium tellurium, etc.

This improves the energy efficiency of solar cells and broadens the usable solar radiation spectrum, since each of the semiconductors is especially sensitive to some of the bands of the electromagnetic spectrum.

Solar concentration systems

Another of the lines of technological innovation developed in recent years is the so-called solar concentration technique.

This technology is based on the concentration of solar radiation on a small surface (the photovoltaic cell) by means of an optical concentrator. For example, through a Fresnel lens (magnifying effect) or a reflector, such as a simple mirror with which a significant increase in the incident solar radiation can be achieved and, consequently, a greater energy efficiency of the system. This technique is also known as a solar oven.

In any case, concentration systems have the disadvantage that they take advantage of almost only direct solar radiation. Therefore, with the concentration panels it is essential to use precise tracking systems.

Currently, the market offers some photovoltaic panels with point Fresnel concentrator systems and other parabolic trough concentrators integrated in the same panel, which can increase the radiation incident in the cell up to 500 times, and thus significantly increases the energy production per cell surface unit.

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References

Last review: February 12, 2016