Physics Cristina L. Pinto Fuste (Olazagutía, 1995) developed nanometric structures, inspired by the leaves of the lotus flower, for the surface of the glass used in photovoltaic modulesThis innovation increases the efficiency of electricity production and reduces maintenance costs.
Specifically, said glass is characterized by “not reflecting light, not getting dirty and, if it does, cleaning itself only with drops of water and, in addition, cooling on the sunniest days, and all this, guaranteeing a useful life, since they have improved resistance to abrasion”, as indicated in its doctoral thesissupported at the Public University of Navarre (UPNA) and developed at the National Center for Renewable Energy (CENER) thanks to an industrial doctorate.
“The different types of photovoltaic technologies share a common element: glass as the facade of the modules,” explains the author of the doctoral thesis. “The glass protects the internal components of the photovoltaic panel by providing a protective barrier against weather phenomena, ensuring the durability and life of the system. The glass also acts as a support by providing rigidity and structural stability to the module. In addition, it offers great transparency, which allows the maximum amount of sunlight to reach the solar cells and thus maximize electrical production,” he emphasizes.
The Glass Problem
But glass too presents a number of challenges that affect the efficiency and performance of photovoltaic modules: reflection of unused light, which the industry is trying to correct by adding anti-reflective coatings; accumulation of dirt on its surface, which can “block light from penetrating the solar cells and require costly and frequent cleaning processes to maintain optimal energy production,” and resistance to abrasion and heat.
“During the three years of the thesis, I designed, simulated, manufactured and tested different types of structures until reaching the optimal ones: hierarchical ones composed of microcylinders and covered with random nanocones, a pattern very similar to that of lotus leaves“, physics emphasizes. “In this way, reflection is minimized, dust adhesion and operating temperature are reduced and its self-cleaning capacity is improved. In addition, by not adding any external coating, the abrasion resistance exceeds commercial solutions,” he adds.
They waste less light
The light reflected by the photovoltaic modules is the one that does not reach the cells of these panels and is therefore not transformed into electricity. “This reflection occurs due to a sudden change in the refractive index, a property of the materials, when going from 1 (air) to 1.5 (glass). The nanocones manufactured in the glass eliminate this sudden change, since they generate a transition of the refractive index. refractive index from air to glass and thus minimize the reflected light,” says Cristina L. Pinto, whose thesis was supervised by Jaione Bengoechea ApezteguíaHead of the Photoelectric and Photovoltaic Technology Innovation and Development Service at CENER, and supervised by Joaquin Seville Moróderprofessor at UPNA and researcher at the Institute of Smart Cities (ISC).
Another important advantage brought by the glass structures designed by the new doctor is the property of anti-dirt. “These nanostructures increase the distance between the base of the glass surface and the surface of the powder and significantly reduce the forces that govern adhesion. In this way, thanks to three different measurement methods, a reduction in the rate of particle fouling of photovoltaic modules of around 50% was achieved, which allows the modules to be kept clean for longer,” he emphasizes.
However, nanostructures cannot completely avoid getting dirty. “However, another advantage discovered is the ability to self-cleaning. When a drop of water falls on the glass, it spreads, collecting all the dirt that may be in the module and, if it is tilted, the drop slides and takes all the dirt with it, thus cleaning the module,” the researcher emphasizes.
Regarding abrasion resistance, the nanoscale structures directly etched into the glass “ensure exceptional durability and avoid the delamination problems common in commercial solutions.” “Abrasion tests show that these structures significantly outperform conventional coatingswith only a slight deterioration of 1% after 500 sand abrasion cycles, compared to between 2.5% and 3% for other commercial coatings,” he says.
In addition, the greenhouse effect produced by glass, as it reflects part of the infrared light and heat, has been eliminated thanks to the microcylinders. “In this way, all the heat generated by the solar cells is absorbed by the glass and this, in turn, emits it in all directions, cooling itself and thus cooling the cells. In this project, it has been possible to reduce the temperature by up to 2.5 ºC on sunny days, which increases the electrical production of the module,” he concludes.
