The Solar Energy

A photovoltaic system is an electrical system that uses solar energy   to produce electricity by the photovoltaic effect.   When an electromagnetic radiation invests a material can, under certain conditions, transfer energy to the outer electrons of the atoms of the material and, if this is sufficient,   the electron is free to move away from the atom of origin.   The absence of the electron is called in this case gap.   The minimum energy required for the electron away from '   atom (then pass from the valence band which corresponds to the bound state   outermost to the conduction band where it is no longer linked) must be greater than the band gap of the material.

Currently the photovoltaic cells produced at an industrial level have an efficiency (Percentage of solar radiation converted into electrical energy)   between 5% and 17%, cells with higher efficiency are under development.   For example, with the technology of tandem cells,   that uses cells based on gallium arsenide and gallium antimonide superimposed in layers,   one day will be possible to obtain an efficiency of 31%. Parallel to the research addressed   improving the efficiency of the cells, they are trying to develop methods of production cheaper.   The materials in this sense are more efficient when the copper and indium diselenide (CIS),   the cadmium telluride (CdTe), and lately the microcrystalline + amorphous silicon (mc-Si thin film micromorph), all three have already been used in the production of photovoltaic panels.

The solar radiation that reaches the Earth can be converted into electrical energy by means of:

- photovoltaic conversion, which allows the direct conversion of solar energy into electricity by exploiting the photovoltaic effect the physical phenomenon that occurs when light hits certain materials;
- The thermal conversion (thermodynamics), which uses different technology systems to collect and concentrate the solar radiation on a heat transfer fluid; the heat stored by the fluid is subsequently transferred to the circuit of a conventional plant for the production of electricity. The elementary device that is the basis of photovoltaic technology is the photovoltaic cell comprises a semiconductor material (silicon, copper, indium, cadmium, gallium, etc.) suitably treated. A set of photovoltaic cells connected together in series or in parallel constitutes the photovoltaic module, the base component commercially available. More modules connected together electrically and mechanically installed in their place of operation, make up a photovoltaic field.
A photovoltaic system consists of one or more photovoltaic fields, the converters DC AC said inverter, and protection components, and control to be placed in accordance with relevant legislation.

The positive aspects of photovoltaic technology can be summarized as follows:
1. absence of any type of pollutant emissions during operation of the plant;
2. saving of fossil fuels;
3. extreme reliability since, in most cases, there are no moving parts (useful life of more than 30 years);
4. costs of operating and maintenance costs;
5. modularity of the system (to increase the size just increase the number of modules and, where appropriate inverter).

Given these advantages, we must take into account the main aspect penalizing epresented by the cost of the plants currently high, although the trend is a steep drop, due to a market that has not yet reached full maturity technical and economic.

That is why in many countries (Italy, Germany, France, Spain, Greece) the development of this technology is guided and supported by programs and incentive mechanisms government, which triggered strong growth in the market is currently characterized by the highest annual growth rate of the entire electricity sector (30-40%).


The silicon is constituted by a set of atoms (or molecules) linked together in a rigid manner. In crystalline silicon atoms are arranged regularly. Since different types of silicon and machining are two types of ingots: one in the shape of parallelepiped from which are obtained polycrystalline cells, recognizable by their color iridescent blue and square-shaped, one cylindrical and from which are obtained monocrystalline cells recognizable by the dark color and hexagonal or circular. Into Normally the DC voltage obtained from a cell is about 0.5 volts. The cells may have different sizes depending on their use. The technology to reduce costs is oriented to increase the efficiency of the cell and reduce the thickness of the wafer. When it comes to efficiency is necessary to distinguish the efficiency of the cells, the panels and the system. Reducing the thickness of the cells will produce more cells with less amount of silicon. Today, the amount of silicon is less than the market demand. The producers are technologically more advanced, therefore, reducing the thickness by the current 230μ/300μ to 160μ.

panels monocrystalline silicon

With a more complex production process, from the molten silicon, are obtained of the cylindrical ingots of monocrystalline silicon. The cylinder is given a hexagonal shape and then cut into thin slices (wafers) from 200μ/300μ, which have a silver finish. These, also, are shaped in a more or less square in order to decrease the unused spaces and increase the number of cells hosted by the panels. To be avoided, even if with reasoned exceptions, to the more southern latitudes for their low tolerance to high temperatures.

amorphous silicon panels

The amorphous silicon is characterized by a disorderly manner in which the atoms or molecules are bound to each other. Using the amorphous silicon can not speak of cells, as it is of thin layers of amorphous silicon applied to surfaces larger than the normal cells. Excellent at more southern latitudes for their high tolerance to high temperatures.

panels monocrystalline silicon + amorphous silicon layers.

products matching the two materials in the same panel. Amorphous silicon, monocrystalline wafers positioned outside of, limits and compensates for losses of that with the high temperatures and improves its performance under unfavorable orientation, tilt and low irradiance. Have the highest efficiency, at the present time on the market, corresponding to less than 6mq. of panels for 1kWp. Very good for the more southern latitudes and in case of poor surfaces that are available.

Thin Film

Among the many advantages of the use of thin film should be especially noted that:

1. production decreases to a lesser extent at high temperatures;
2. degrades immediately after the entry in production and remains stable over time;
3. was affected to a lesser extent of shading;
4. is not very sensitive to the inclination not optimal (in contrast to the crystalline lens) by activating the 100% of its productive potentiality between 5 ° and 10 ° of inclination, thus adapting itself without losses in coplanar to the mounting of any type of pitched;
5. produces more hours of sunlight (starts earlier in the morning and ends later in the evening);
6. uses diffused and reflected light, producing much better than the crystalline a cloudy day;
7. the appearance is much more attractive, black (or red) uniform, with a mirror effect, with no obvious white lines.

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