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Posted: May 14, 2010

Mapping system for photovoltaic surfaces will help to improve the performance of solar panels

(Nanowerk News) A group of researchers of the University of Cádiz has designed a new mapping system for the study of photovoltaic surfaces. The system can detect, at the micrometric level, all the defects existing in a solar panel. This should have a significant influence on the overall performance of these photovoltaic cells. The team headed by Professor Joaquín Martín Calleja has developed the methodology for detecting faults in photovoltaic solar panels resulting from manufacturing errors. The defects identified can then be made good and the overall performance of the panel will be enhanced.
This device, which has now been patented by the University of Cádiz, determines whether or not the cells mapped present irregularities in their functioning, according to the particular zone of the surface that is analyzed. These defects have a negative effect on the overall performance of the panel, since the defective cell will generate photoconversion values that are lower than the maximum theoretically possible.
The mapping of the photosensitive surfaces allows the possible causes of the reduced performance of the panel to be determined. Although devices that make point-to-point measurements of the cell by laser currently exist, none of these has achieved the accurate emulation of solar light. The majority of these systems are not available on the market, and they suffer from evident limitations through utilizing only monochromatic light as the source of irradiation. This represents a serious limitation since the photoconversion panels function when exposed to sunlight; therefore measurements obtained with laser beams are not true to the real conditions to which these solar panels are subjected.
Faced with this situation, the research group on the Simulation, Characterization and Evolution of Materials (FQM-166) has developed a system based on “trying to adapt the theories of vision to this system by mixing three laser beams (one red, one green and another blue). We perform the same scanning with each laser, having adjusted their strength in such a way that a species of light is generated whose chromatic composition is similar to that of solar light”, explains Professor Martín Calleja.
“The objective is to study how the surface behaves by analyzing it point-to-point, at the micrometric level of the solar cells, under conditions as close as possible to actual sunlight”, according to the head of the research group. And, he stresses, “This system can detect all the defects that there may be in a solar panel at the micrometric level. In the overall performance of such a panel, the reduced efficiency of the bad points is compensated by the high efficiency of the good points. However, if we can identify precisely which are the bad points and detect the causes giving rise to their negative functioning, this deficiency can be made good”.
This work therefore offers three clear advantages over previously developed systems:
1. It provides the simulation of a source of white light that matches the specifications of a solar emission.
2. It enables high resolution maps of photoconvertor efficiency to be obtained.
3. It allows possible manufacturing defects in photoconvertor surfaces to be detected.
“This new mapping equipment has not been designed with a direct commercial objective; rather, it is a scientific development that will facilitate our research work for future studies. However, this advance may be of interest to those universities working with energy conversion systems, and who may be doing research in this field. It could similarly be made available commercially to laboratories of companies engaged in the design and manufacture of solar energy equipment and who may be carrying out their own research work”, states Professor Joaquín Martín Calleja.
He also wants to emphasize that “the studies we have carried out in these cells were made possible by our collaboration with the department of Environmental Sciences of the University of Pablo de Olavide. In fact, we are also studying jointly with researchers of the UPO a non-commercial type of cell that is being developed fundamentally for research purposes, and is designated DSSC. These cells are based on a technology different from that of silicon: titanium oxide activated with a colorant. We make these cells utilising not only synthetic but also natural colorants, from petals of bougainvillea and other flowers, as activators. Obviously the output obtained with them is much less than that obtainable with commercial silicon cells; but they are a good system to study since their fabrication does not require very substantial technological resources, to which universities do not usually have access”.
After outlining the advances made, it only remains to say that “our most immediate future task is to improve the system patented and, to this end, we are already working on some modifications”.
Source: Universidad de Cádiz
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