Photovoltaic Concentrators

The photovoltaic (FV) systems today in use are still too much expensive and for this reason they are not competitive from an economical point of you with the traditional energetic sources.
The main problem is related to the high cost of the raw material (silicon) in comparison with the value of the energy produced.

That determines that photovoltaic market is increasing in those countries where there is a favorable legislation which encourages the development of this technology.

To reach the economical competitiveness with the other renewable sources a primary necessity is the rise of investments in research & development. This could increase the use of the photovoltaic technology in specific fields, in which its employment is considered already today technically valid.
A promising approach in order to accelerate the process of cost reduction of the photovoltaic systems is to develop innovative technologies.

Among these, at international level, concentration photovoltaic (CPV) technology is considered a promising application for an important reduction of investment costs.

There are fundamentally two constructive philosophies to realize a solar concentrator:

1. The use of lenses in order to refract the sun light on the photovoltaic cell
2. The use of mirrors or paraboloids in order to reflect the sun light in the focal point

 
The approach to lowering the cost of electricity generated by solar photovoltaics is, therefore, to use suitable optics to focus, or "concentrate", sunlight from a large area onto a small solar cell receiver, which represent, as we said, the more expensive part of the photovoltaic system.
In order to obtain this result we have to track the sun with a high precision.

The system is constituted by a support structure which tracks the sun on the two aces with respect to its position during the day. The alt-azimuth movement is assured from a mechanical system, controlled by a specific control system, able to assure the tracking accuracy.

Arrays of PV concentrator modules constitute the generator.

PV concentrator module components include solar cells, an electrically isolating and thermally conducting housing for mounting and interconnecting the cells, and optical concentrators These optics allow the cells to work under a solar concentration ratio equal to 100-500X.
It is possible to summarize the expected advantages of this technology in the following way:

• Cost reduction per power unit in comparison with flat photovoltaic panels;
• Higher electrical energy output per power unit with respect to flat photovoltaic panels;
• Great potentialities to further increase the electrical yield;
• Lower need of semiconductor matter (e.g. silicon);
• Scale up of the production process;

Pirelli Labs is testing different CPV prototypes based on various technologies on the roof of a telephonic station roof in Naples, in order to directly estimate in field the efficiency of the new systems compared with the conventional crystal silicon flat panels.