Papers by Carlos Portillo
Acta Physica Polonica A, 2001
Remote Sensing, Mar 26, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC), 2018
Metallization of industrial silicon solar cells is evolving towards fine line printing with a lin... more Metallization of industrial silicon solar cells is evolving towards fine line printing with a line width of $30 \mu \mathrm{m}$ and lower. Besides the challenge to keep up a high aspect ratio this might also result in higher contact resistivities. This work investigates the influence of the paste volume on the contact formation for fine line metallization. It is shown that the paste volume has an influence on the contact resistivity. But it depends on the used paste if this influence is detrimental or advantageous for the contact formation on reduction of the paste volume.
Proceedings of the ISES Solar World Congress 2019, 2019
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC), 2018
The implementation of a different approach for the estimation of the maximum photo-generated curr... more The implementation of a different approach for the estimation of the maximum photo-generated current density ($J_{\max}$) regarding internal parameters of the cell and its optical performance was performed introducing an effective optical pathlength enhancement factor, Z($\lambda$). Different PV devices were considered, including dssc, under the world reference and averaged local spectra estimated for the Atacama Desert, under air masses equal to 1.5 and 1.08, respectively. This model was successfully implemented to predict $J_{\max}$ with higher reliability which makes it suitable to be applied to any type of solar cell developed or simulated.
Progress in Photovoltaics: Research and Applications, 2020
Energies, 2021
The Atacama Desert receives the highest levels of solar irradiance in the world with an annual av... more The Atacama Desert receives the highest levels of solar irradiance in the world with an annual average of 2500 kWh/m2 for the global horizontal irradiance and 3500 kWh/m2 for the direct normal irradiance. One of the challenges is the large portion of ultraviolet light. This part of the spectrum be detrimental for the encapsulant materials, reducing their lifetime. To develop a module adapted to the Atacama Desert conditions, it is imperative to have standardized information from first-hand about the typical faults experienced by photovoltaic modules operating in the desert. This work reports on the design and implementation of the Inspection Data Collection Tool to evaluate crystalline silicon-based moules operating in desert climates. The tool brings together novel features of compatibility with current standards, efficient mobile-type instrumentation (equipment and tools), clear procedures/protocols for non-expert users and low development costs. A total of 95 modules were inspect...
Progress in Photovoltaics: Research and Applications, 2020
Bundesministerium fur Wirtschaft und Energie (BMWi) FKZ 0324206 European Solar-Era-Net 038 Comisi... more Bundesministerium fur Wirtschaft und Energie (BMWi) FKZ 0324206 European Solar-Era-Net 038 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT-FONDAP program) 15110019 15130011 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 11160664 11190239 11190289 Fondo de Equipamiento Cientifico y Tecnologico (FONDEQUIP) EQM170111 Corporacion de Fomento de la Produccion (CORFO) 17PTECES-75830 Ministerio de Educacion de Chile (MINEDUC) UA ANT 1755 USM Pi-L-18-21 Millennium Nucleus MULTIMAT-ICM/MINECON
Solar Energy, 2019
Abstract Soiling is an issue that impacts the performance of photovoltaic (PV) technologies as it... more Abstract Soiling is an issue that impacts the performance of photovoltaic (PV) technologies as it attenuates the amount of solar resource reaching the solar cells. The chemical composition of the soil is essential to define cleaning strategies of photovoltaic companies. This paper reports the characterization of the chemical and physical properties of the soiling deposited on photovoltaic modules located in the Atacama Desert. The particle size, shape and chemical composition of dust were studied at 4 different locations (denoted as L1 to L4) with samples taken from the ground and the module surface. It was found that, most deposited material exhibits a diameter between 1 µm and 60 µm. The determination of the particle shape factor shows that smaller particles tend to have a circular appearance, while larger particles exhibit a prismatic form. These small particles show a shape factor close to 1 and occur at the 4 locations with the greatest frequency, 40–70%. The mineral species in both the deposited and ground dust, which were identified by means of X-ray diffraction, were albite, anorthite, calcite, cristobalite, gypsum, halite, quartz, muscovite and orthoclase. The compounds occurring with the highest frequency in both the module and ground dust at all locations were quartz and anorthite. Differences between the locations were found. Calcite was found only at L3. Gypsum was not detected at L1 and L3 but was present in L2 and L4. Similarly, cristobalite was found only at L1 and L3, halite was found at L2 and L3, and muscovite was found at L1 and L2.
Renewable Energy, 2018
Knowledge of the solar spectrum is essential for the design and study of numerous technologies. D... more Knowledge of the solar spectrum is essential for the design and study of numerous technologies. Due to the area considered, the harsh conditions and the difficulty for accessing to some zones, information and measurement on local parameters and spectral resource are scarce. This fact, along with the special atmospheric conditions prevailing in Atacama Desert, has led to increasing interest on the part of the solar industry to ascertain the spectral variation respect to that of other places around the world. Considering the standard spectrum for a typical air mass as 1.5, the evaluation of PV module behaviour or device calibration under real conditions can generate a source of uncertainty where spectra may differ. This preliminary paper aims to study the influence of using the standard or local spectra in photovoltaic technologies in Atacama Desert, in order to highlight the necessity for a long-term ground-based measurement campaign. For that purpose, a first approach to the spatio-temporal average of solar spectrum in the Atacama Desert from satellite databases is estimated. Then, local spectra are compared against the Reference Spectra in order to show the differences in studies on solar energy applications. Long-term satellite database information is used to average the atmospheric parameters, such as Aerosol Optical Depth, Ozone, Precipitable Water Vapour, Albedo and Relative Humidity, for the entire Atacama Desert area and is then used to obtain the mean Global tilted Irradiance and Direct plus Circumsolar Irradiance solar spectrum. Finally, to study the influence that the shape of the local spectrum has on the performance of the different solar technologies, the photo-current density of two different solar cell types were studied under Atacama and standard conditions. The results indicate that there are considerable differences with the ASTM G173-03 reference spectra for short wavelengths, especially in the UV spectral range, which is 55% points higher than the reference, which influences in the performance of the solar technologies.
Renewable Energy, 2019
TYPHABOARD is a sustainable construction and thermal insulation board made of cattail (lat. typha... more TYPHABOARD is a sustainable construction and thermal insulation board made of cattail (lat. typha) and magnesite as a binder. It is characterized by a unique combination of high mechanical strength, highly insulating properties, relatively high diffusion openness, inflammability, and a sustainable lifecycle. The TYPHABOARD concept includes ecological benefits related to the systematic planting of the raw material typha in Bulgaria, the production of TYPHABOARD, and its application as a stabilizing, insulating and passive indoor climate controlling element in the framework structure of the historic typology of the Black Sea House. The entire technological and organizational process provides a sustainable solution for the operation of peat areas by planting typha (which acts as a natural water and ground filter), for the engagement of work forces in structurally underdeveloped regions, for sustainable ecological and social regional development, as well as for the sustainable retrofit of existing historic Black Sea Houses. The building and ecological system TYPHABOARD can be successfully introduced and applied in Bulgaria. In addition to the scientific and the practical study, the political eligibility of this was proved and officially permitted by the relevant public bodies in Bulgaria.
Energy Conversion and Management, 2015
Abstract In the search for new techniques to predict atmospheric features that might be useful to... more Abstract In the search for new techniques to predict atmospheric features that might be useful to solar power plant operators, we have carried out solar irradiance forecasting using emerging sky camera technology. Digital image levels are converted into irradiances and then the maximum cross-correlation method is applied to obtain future predictions. This methodology is a step forward in the study of the solar resource, essential to solar plant operators in adapting a plant’s operating procedures to atmospheric conditions and to improve electricity generation. The results are set out using different statistical parameters, in which beam, diffuse and global irradiances give a constant normalized root-mean-square error value over the time interval for all sky conditions. The average measure is 25.44% for beam irradiance; 11.60% for diffuse irradiance and 11.17% for global irradiance.
IEEE Journal of Photovoltaics, 2017
Ensuring high-quality front contacts in terms of low contact and line resistance while keeping th... more Ensuring high-quality front contacts in terms of low contact and line resistance while keeping the recombination losses low in p-type silicon solar cells has been challenging for the development of silver pastes. In this work, three silver pastes were used to create a contact on a lightly doped emitter of 90 Ω/sq, produced in a tube furnace by POCl<sub>3</sub> diffusion, with an electrically active phosphorus surface concentration of 8 × 10<sup>19</sup> cm<sup>–3</sup>. The peak firing temperature (<italic>T</italic><sub> peak</sub>) and belt speed (<italic>v</italic><sub>belt</sub>) of the firing step were varied to study how the silver pastes performed. No shunting was produced after firing as pseudo fill factor exceeded 83%. Efficiencies up to 19% were measured. When firing at higher <italic>v</italic><sub>belt</sub>, a higher <italic>T</italic><sub> peak</sub> permitted higher efficiencies due to better sintering and contact formation as well as a better passivation. A selective etching procedure was applied in order to investigate the contact interface. It was found that contact imprints were preferably located at pyramid tips for all groups. The paste producing larger and deeper contact imprints led to the lowest contact resistance (4 mΩcm<sup>2</sup>) but higher line resistance (0.46 Ω/cm) and higher saturation current density (30 fA/cm<sup>2</sup> above) compared with the other two pastes.
Energy Procedia, 2017
Abstract The soling can negatively affect the performance of photovoltaic systems. We studied the... more Abstract The soling can negatively affect the performance of photovoltaic systems. We studied the species, which deposit on photovoltaic (PV) modules in northern Chile (Atacama Desert). The environmental conditions are the base for the interaction of dust particles and the module’s surfaces. We considered 4 locations for the study. We determined that the particle size of the dust to deposit on PV modules is smaller than 63 μm for all the selected sites. However, the morphology varies from place to place influencing optical response of the modules. After 4 months dust accumulation the transmittance of PV glass reduced by 55%.
Advances in Quantum Chemistry, 2003
... Following, Mason [1], the Laporte-forbidden f→f electronic transitions of lanthanide systems,... more ... Following, Mason [1], the Laporte-forbidden f→f electronic transitions of lanthanide systems, acquire an electric-dipole probability by two mechanisms in ... a supra-parameterization scheme have worked out vibronic intensity parameters for Er 3+ in Cs 2 NaErCl 6 . Acevedo et al. ...
Energy Conversion and Management, 2015
ABSTRACT Two photovoltaic technologies are compared with regard to the energy yield, performance ... more ABSTRACT Two photovoltaic technologies are compared with regard to the energy yield, performance ratio and their levelized cost of energy. Plants based on amorphous/microcrystalline silicon tandem thin films and multicrystalline silicon solar cells installed at the coastal zone of the Atacama Desert, Chile, were monitored for 21 months. This region can be one of the most suitable places for the use of solar energy due to the high solar radiation levels. However, the coastal desert climate may influence the performance of photovoltaic systems. The global tilted solar irradiation reached mean values of 8.6 kW h/m2 day in summer and 6 kW h/m2 day in winter demonstrating the high irradiation available. It came out that the performance ratio is influenced by the dust accumulation and the temperature associated to this place. The performance ratio of thin films decreased due to the dust accumulation at a rate from −4.2 to −3.7%/month for decreasing temperature and from −4.8 to −4.4%/month for increasing temperature. For multicrystalline silicon modules, the degradation rates were −2.4 to −1.8%/month for decreasing temperature, and −6.2 to −3.7%/month for increasing temperature. It was concluded that the electricity costs were 14.48 cents€/kW h and 15.65 cents€/kW h for thin film and mc-Si, respectively. Thus, the thin films had more benefit after cleaning than multicrystalline modules.
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Papers by Carlos Portillo