Browsing by Author "Machado, Maider"
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Item Accelerated aging test of solar reflectors according to the new AENOR standard – results of a round Robin test(American Institute of Physics Inc., 2018-11-08) Fernández-García, Aránzazu; Martínez-Arcos, Lucía; Sutter, Florian; Wette, Johannes; Sallaberry, Fabienne; Erice, Raquel; Diamantino, Teresa; Carvalho, M. João; Raccurt, Olivier; Pescheux, Anne-Claire; Imbuluzqueta, Gorka; Machado, Maider; Mancilla, Rodrigo; Richter, Christoph; SISTEMAS FOTOVOLTAICOS; Tecnalia Research & InnovationDurability tests of reflector materials for concentrating solar applications are crucial to guarantee the profitability of the plants and to ensure a proper efficiency during their lifetime. A standard including a set of five accelerated aging tests is close to be published by the Spanish standardization entity AENOR, within the sub-committee AEN/CTN 206/SC117. Under the framework of the STAGE-STE project, a Round Robin Test was organized by six partners to evaluate the comparability of results obtained in their respective laboratories after performing these durability tests. According to the results, in general a good agreement among the partners was found, with negligible to slight reflectance losses. In addition, it was noticed that the reference standard used in the reflectance measurements is of high importance. The conclusions of this work will help to improve the standard in future versions.Item Antireflective mesoporous silica coatings by optimization of water content in acid-catalyzed sol-gel method for application in glass covers of concentrated photovoltaic modules(2019-01-15) Agustín-Sáenz, Cecilia; Machado, Maider; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSPorous silica layers with outstanding antireflective properties have been prepared by acid-catalyzed sol-gel process in presence of organic phases as structure directing agents (SDA) and excess water, with the aim of offering a cost-competitive, easy up-scaling and high efficiency process that contributes to reduce current levelized cost of energy (LCOE) of concentrating photovoltaics (CPV). The process has been optimized by controlling the water/alkoxide ratio, which is an important structure-regulating tool, having a strong influence in the structural properties of sol-gel synthesized materials. Hydrolysis of the inorganic precursor has been accomplished in high water/alkoxide conditions and in the presence of SDAs. Evaporation induced self-assembly (EISA) during coating deposition and the scanning of four types of SDAs have permitted to select the coating that fulfilled specific thickness and refractive index values with, in parallel, excellent results on sol stability. The final optimization has produced mesoporous coatings with ∼9 nm mean pore size, leading to an enhancement in transmittance up to 7.4% over bare glass in the 300–1500 nm wavelength range. The transmittance spectra have been used as inputs for the theoretical calculation of the short-circuit current density of a commercially available multijunction solar cell for CPV applications.Item Broadband antireflective coating stack based on mesoporous silica by acid-catalyzed sol-gel method for concentrated photovoltaic application(2018-11) Agustín-Sáenz, Cecilia; Sánchez-García, José Ángel; Machado, Maider; Brizuela, Marta; Zubillaga, Oihana; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; INGENIERÍA DE SUPERFICIES; SISTEMAS FOTOVOLTAICOSSilica multi-layer stacks have been designed with the aim to provide broadband antireflective (AR) properties for glass components in concentrated photovoltaic (CPV) application. Silica porous coatings were grown by combining acid-catalyzed sol-gel route and evaporation induced self-assembly (EISA) method with four types of organic/inorganic systems. Sols were prepared using tetraethylorthosilicate (TEOS) as inorganic precursor assembled with two di-block copolymers, one tri-block copolymer and one cationic surfactant as organic templates. Optical properties were characterized by ellipsometry and spectrophotometry while the material structure was analyzed by environmental ellipsometric porosimetry (EEP) and atomic force microscopy (AFM). The concentration of inorganic and organic phases was optimized and a broadband AR bi-layer stack was obtained providing a 7.2% (under the reference AM1.5 solar spectral irradiance) increase in transmittance over bare glass in the wavelength range 300–2000 nm when coated on both sides.Item Hydrophobic and spectrally broadband antireflective methyl-silylated silica coatings with high performance stability for concentrated solar applications(2019-09-15) Agustín-Sáenz, Cecilia; Machado, Maider; Zubillaga, Oihana; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; SISTEMAS FOTOVOLTAICOSAn efficient and environment-friendly process, consisting of acid-catalyzed sol-gel process combined with evaporation induced self-assembly, was conducted to build antireflective (AR) layer stacks for concentrated solar applications. Considering the external factors that may alter the optical properties of the system when operating outdoors, such as soiling, harsh climate conditions and alkali ions diffusion from glass, several stack configurations were proposed. Particularly, the effect of a methyl-silylating post-treatment, the presence of the inner layer and the optimization of sintering temperature have been devised in order to minimize soiling adherence and alkali diffusion from the glass substrate and to assure the required robustness to comply with the durability requirements. The assessment consisted of (i) an analysis of the optical transmittance, reflectance and refractive index and (ii) hydrophobicity and effect of water absorption on the external porous coatings in relation to the results of accelerated aging tests following photovoltaics standards. The main goal was to achieve the most rational design, based on a proper trade-off between cost efficiency, processability, optical properties and reliability during real life operation.Item On the analytical calculation of the solar heat gain coefficient of a BIPV module(2017-09-15) Baenas, Tomás; Machado, Maider; Tecnalia Research & InnovationA closed-analytical expression for the solar heat gain coefficient (SHGC) of a glass-glass photovoltaic module forbuilding-integration is constructed ab initio, from the thermal study of the general case of any number of planarparallel layers with homogeneous absorption of solar radiation. By introducing the optical model of Baenas andMachado, the expressions for the SHGC of the opaque and transparent parts of the module will be provided. Thescope of the calculation and the assumed working hypothesis are in line with those of international standards formultiple glazing systems and building-integrated photovoltaic modules. The proposed model has been applied to a real case of study, showing an excellent agreement with the numerical and experimental related data.Item Optical model for multilayer glazing systems: Application to laminated glass and photovoltaic modules: Application to laminated glass and photovoltaic modules(2016-02-01) Baenas, Tomás; Machado, Maider; Tecnalia Research & InnovationThis article provides theoretical developments broadening the scope of previous optical simulation models for multilayer glazing systems. The applicability of existing models will be extended through additional characterization of the multilayer optical components from global spectrophotometric (UV–vis–NIR) measurements. A more complete interlayer film characterization, including reflectivity in the film–glass interface, will be provided. Singular solutions of the related equation systems will be derived for situations involving components with very low or null transmissivity. As a contribution to the fundamentals of the formalism, the condition relating the symmetry of the transmittance of the system with the symmetry of the transmissivity of its optical components will be studied. Finally, with the extension for the calculation of energy fluxes through the components of a multilayer system, analytical expressions for the components absorptivity will be derived. These results are particularly useful to quantify differences in energy absorption of the constituents of a laminated glass, as a tool to define, from the glazing design phase, the thermal and mechanical processing needed for each glazing component. Additionally, the model provides a procedure for the calculation of the absorptivity of encapsulated photovoltaic cells, which is directly related to cell efficiency in each particular configuration.Item Optical model for multilayer glazing systems: Experimental validation through the analytical prediction of encapsulation-induced variation of PV modules efficiency: Experimental validation through the analytical prediction of encapsulation-induced variation of PV modules efficiency(2016-10-01) Machado, Maider; Baenas, Tomás; Yurrita, Naiara; Tecnalia Research & Innovation; SISTEMAS FOTOVOLTAICOSA simple analytical calculation based on a transfer matrix method for incoherent optics, allowing the prediction of photovoltaic module efficiencies in different encapsulation conditions is presented. This approach is used for the experimental validation of the main features of the optical model for multilayer glazing systems considered, through the relation between the external quantum efficiency of the module and its optical modeling. The theoretical procedure avoids the need to manufacture and characterize by solar simulator or external quantum efficiency measurements all the variety of photovoltaic module configurations, which is of interest at research and manufacturing levels, especially for building-integrated photovoltaics. The absorptivity of encapsulated solar cells is not directly accessible from direct air-bare cell or airencapsulated cell optical measurements, and therefore analytical or numerical methods are generally needed. The calculations presented in this work provide closed analytical expressions for the layer-bylayer absorption of the different components of a photovoltaic module. From a small set of experimental measurements of a particular encapsulation configuration, and the theoretical expressions for spectral absorptivities, the short-circuit current of a module can be predicted for any other encapsulation scheme. It will be proved that the method accurately matches short-circuit current density of the modules as obtained from experimental measurements. Results will be presented for crystalline silicon and CIGS thin film cell technologies with several glass and encapsulation material combinations.Item Polyfluoroalkyl-silica porous coatings with high antireflection properties and low surface free energy for glass in solar energy application(2020-04-15) Agustín-Sáenz, Cecilia; Machado, Maider; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSPolyfluoroalkyl-silica porous coating stacks with durable antireflection (AR) properties have been obtained for photovoltaic (PV) application. An acid-catalyzed sol-gel process combined with evaporation induced self-assembly and the presence of a non-hydrolyzable polyfluoroalkyl group linked to the central atom of the silicon alkoxide was conducted. The aim was to obtain a low surface energy coating, devised to mitigate soiling adherence, without losing the AR properties of a baseline coating. In particular, the influence of polyfluoroalkyl chain length on the thickness, the water contact angle and optical transmission properties was first analyzed. The optimized polyfluoroalkyl-silica porous coating presented low surface energy < 20 mJ/m2, even with the desired low roughness values required for obtaining a negligible scattering of the incoming solar radiation. This coating was studied as an AR mono-layer and as an external coating in an AR bi-layer stack, with the presence of an inner dense-structured silica layer, that contributed to both the optical performance and durability, acting as an alkali diffusion preventing layer. The AR bi-layer stack deposited on two sides of glass provided a transmittance gain of 7.1%. Those optical properties were inalterable after accelerated aging tests, which sustains the reliability of the materials for solar energy applications.Item PVSITES: Building-Integrated Photovoltaic Technologies and Systems for Large-Scale Market Deployment(MDPI, 2017) Espeche, Juan Manuel; Noris, Federico; Lennard, Zia; Challet, Simon; Machado, MaiderThe large potential for energy savings in buildings led the EU Commission to adopt the 2010/31/EU Directive on the energy performance of buildings with the objective that all new buildings are Nearly Zero Energy Buildings (NZEB) by 2020. Renewable energy technologies, and in particular the integration of photovoltaic systems in the building environment offer many possibilities to play a key role within the NZEB scenario. The objective of PVSITES project is to drive BIPV technology to a large market deployment by demonstrating an ambitious portfolio of building-integrated solar technologies and systems, giving a forceful, reliable answer to the market requirements identified by the industrial members of the consortium in their day-to-day activity.Item Round robin performance testing of organic photovoltaic devices(2014-03) Gevorgyan, Suren A.; Zubillaga, Oihana; Vega de Seoane, José María; Machado, Maider; Parlak, Elif Alturk; Tore, Nesrin; Voroshazi, Eszter; Aernouts, Tom; Müllejans, Harald; Bardizza, Giorgio; Taylor, Nigel; Verhees, Wiljan; Kroon, Jan M.; Morvillo, Pasquale; Minarini, Carla; Roca, Francesco; Castro, Fernando A.; Cros, Stéphane; Lechêne, Balthazar; Trigo, Juan F.; Guillén, Cecilia; Herrero, José; Zimmermann, Birger; Sapkota, Subarna Babu; Veit, Clemens; Würfel, Uli; Tuladhar, Pabitra S.; Durrant, James R.; Winter, Stefan; Rousu, Sanna; Välimäki, Marja; Hinrichs, Volker; Cowan, Sarah R.; Olson, Dana C.; Sommer-Larsen, Peter; Krebs, Frederik C.; SISTEMAS FOTOVOLTAICOS; Tecnalia Research & InnovationThis study addresses the issue of poor intercomparability of measurements of organic photovoltaic (OPV) devices among different laboratories. We present a round robin performance testing of novel OPV devices among 16 laboratories, organized within the framework of European Research Infrastructure Project (SOPHIA) and European Energy Research Alliance (EERA). Three types of OPVs with different structures, dimensions and encapsulations are studied and compared with reference Si solar cells certified by accredited laboratories. The agreement of the measurements of these among different laboratories is analyzed by focusing on testing procedures, testing equipment and sample designs. A number of deviations and pitfalls are revealed and based on the analyses, a set of recommendations are suggested for improving the agreement among the measurements of such OPV technologies.Item Thermal analysis of a BIPV system by various modelling approaches(2017-10) Assoa, Ya Brigitte; Mongibello, Luigi; Carr, Anna; Kubicek, Bernhard; Machado, Maider; Merten, Jens; Misara, Siwanand; Roca, Francesco; Sprenger, Wendelin; Wagner, Martin; Zamini, Shokufeh; Baenas, Tomás; Malbranche, Philippe; Tecnalia Research & InnovationThis work presents various models developed and implemented within the SOPHIA European project in order to thermally characterize PV modules in a rooftop BIPV configuration. Different approaches have been considered, including a linear model, lumped elements models and models that make use of commercial software solvers. The validation of the models performed by comparing the results of simulations with experimental data recorded on a test bench over an entire year is presented and discussed on a seasonal basis. The results have shown that all the models implemented allow achieving a good prediction of the PV modules back surface temperature, with the minimum value of the coefficient of determination R2 around 95% on a yearly basis. Moreover, the influence of season weather conditions and of the incident solar irradiance magnitude on the accuracy of the considered thermal models is highlighted. The major result of the present study is represented by the fact that it has been possible to perform a better thermal characterization of the BIPV module by tuning some of the heat transfer coefficients, such as those relative to the effects of the wind velocity, and to the evaluation of sky temperature.