DESAFIO

Artículos científicos

• Ángel Andueza; Cristina Pinto; David Navajas; Joaquín Sevilla (2021): “Enhanced thermal performance of photovoltaic panels based on glass surface texturization”, Optical Materials, Volume 121, November 2021, 111511 (https://doi.org/10.1016/j.optmat.2021.111511)

PROJECT SCOPE AND RESULTS:
The goal of the DESAFIO project is to improve the efficiency of photovoltaic modules by developing photonic structures. The goal is to have the photonic structure improve catching solar radiation falling on photovoltaic solar cells and that they are cooled passively, such that the operating temperature of the photovoltaic modules is lowered, which increases their efficiency and durability (figure 1). In this collaborative project the consortium was made up of ADItech, as the coordinator, CENER as the technical leader and the UPNA as a collaboration partner.

In the second phase of the project, the developments were applied from previous years in bifacial technology, which are currently on the rise because of the production improvement they provide. The bifacial technology usually manufactured in a glass/glass configuration will make it possible to also add the advantage of passive cooling on the back face. In that way, the goal of the project applied to bifacial technology contributes to lowering the LCOE of photovoltaic mediums to promote the transition to a sustainable energy model and replace the consumption of fossil fuels.

More specifically, in this phase of the project albedo models were developed for different surfaces that was used to evaluate the energy gain (UPNA, see figure 2 below), provided by the back face when the bifacial panel is placed in different
settings in terms of albedo. The conclusion was drawn that the texturization on the bottom face hardly affects what happens on the front face. The models covered the entire optical-radiation spectrum, wavelengths from 300 nm up to 15 micras, and included all the components of the photovoltaic modules, cells, polymer materials and glass.

Likewise, a thermal model of the bifacial solar panels that operated outside was developed, with which the real thermal effect derived from the variations in the radiative power obtained was evaluated (see figure 3 of the experimental field, CENER). To validate the results of the thermal model, an improved differential calorimeter was built and fine-tuned with which the cooling capacity of different samples (designed and fabricated to optimise radiative cooling) could be obtained experimentally. The UPNA finished the version 2.0 prototype and a multitude of measurements were done both inside and outside that were extremely useful for characterising the cooling capacity of the samples. The results obtained with the calorimeter made it possible to adjust the parameters of the models to make it more realistic.

As a result of the work done, it was concluded that the functionality of catching light with random pyramids is hard to improve, even by using regularly placed pyramids, to which the difficulty of manufacturing them has to be added. Nevertheless, mini-modules with an improved bifacial response were fabricated using structured glass. The current produced increased approximately 3% at a normal incidence, and at 80º incidence the improvement was more than 6%. This parameter is directly related with bifacial performance, because the reflectance of the albedo is usually diffuse.

In regard to passive cooling, glass with improved radiative cooling was fabricated (CENER) that in a characterisation with the differential calorimeter 2.0, a 4º C temperature reduction and 12 W/m2 cooling power were determined. Likewise, even though the samples showed better absorption, an increase in their absorbance in the visible spectrum was also detected, which is a negative effect that could counteract the effect of the increase in radiative cooling. Likewise, it should be highlighted that in August 2021 an article was published about passive cooling in the journal Optical Materials (Elsevier, Q1, impact index 3.06): Enhanced thermal performance of photovoltaic panels based on glass surface texturization, https://doi.org/10.1016/j.optmat.2021.111511), in which a study and optimisation of the design of structures with passive cooling capabilities were done.