Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
Repositorio Institucional del CIEMAT (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas)Not a member yet
1694 research outputs found
Sort by
Texturization of silicon wafers with Na2CO3 and Na2CO3/NaHCO3 solutions for heterojunction solar-cell applications
No full textTheformationofpyramidalstructuresbyanisotropicetchingof/100S-orientedmono
crystalline siliconwafer surfaces is an effectivemethod to reduce reflection losses
originatingonthefrontsideofconventionalsiliconsolarcellsandsilicon-heterojunction
(SHJ)solarcells.Oneofthemostcommonmethodsoftexturizationusedinthesolar-cell
industry isbasedonaqueous solutionsofNaOHorKOHand isopropyl alcohol (IPA).
However, IPAis toxicandrelativelyexpensive, soeffortsarebeingmadetoreplace it.
Among the potential alternatives, solutions based on Na2CO3 and Na2CO3/NaHCO3
mixtureshavebeenproposed. Inthepresent study, solutionsofNa2CO3 andNa2CO3/
NaHCO3mixtureswerepreparedinordertoformpyramidalstructuresonsiliconwafer
surfaces. Itwasnotpossibletoobtainuniformandcompletelytexturedsurfacesbyusing
aqueoussolutionsconsistingonlyofNa2CO3.NaHCO3mustbeaddedinordertoachieve
uniformtexturedsurfaceswithlowhemispherical reflectancesuitableforSHJ solar-cell
applications. Textured surfaceswithgooduniformity and lowaveragehemispherical
reflectance (15.4%)wereprepared from/100Ssiliconsubstrateswithrelatively low
etchingtimes (25min).Goodsurfacepassivation(lifetime4600msandimplicitopen
circuitvoltageof690710mV)onthesep-typetexturedwaferswereachieved
PROTOCOLO DE MANEJO DE INFORMACI??N CONFIDENCIAL
No full textEl presente documento describe el manejo de datos sensibles y confidenciales que residen en los sistemas de informaci??n de la Unidad de Innovaci??n Nuclear para el debido control y acceso
Calibration of high-heat-flux sensors in a solar furnace
No full textThe most common sensors used for the measurement of high solar
irradiance are the Gardon gauges, which are usually calibrated using a black
body at a certain temperature as the radiant source. This calibration
procedure is assumed to produce a systematic error when solar irradiance
measurements are taken using these sensors. This paper demonstrates a
calorimetric method for calibrating these high-heat-flux gauges in a solar
furnace. This procedure has enabled these sensors to be calibrated under
concentrated solar radiation at higher irradiances under non-laboratory
conditions in the CIEMAT solar furnace at the Plataforma Solar de Almer????a.
Working at higher irradiances has allowed the uncertainty in the calibration
constant of these sensors to be reduced. This work experimentally confirms
the predicted systematic errors committed when measuring high
solar irradiances using Gardon sensors calibrated with a black body
Study of the Effect of Different Atmospheric Conditions on the Temporal Evolution of the Mixing Layer over Madrid during the Year 2020 by Means of Two Different Methods: Ceilometer Signals and the ECMWF-IFS Meteorological Model
No full textAbstract: Atmospheric aerosols are one of the main factors that contribute to poor air quality. These aerosols are mostly concentrated within the atmospheric boundary layer (ABL) and mixing layer (ML).
The ABL extends from ground level to the lowest level of the troposphere directly affected by surface temperature, solar irradiance, the orography and its proximity to coastal areas, causing turbulence in
a daily cycle. This turbulence controls the vertical mixing of aerosols and pollutants and their dispersion in the ML. Therefore, proper characterization of these layers is of crucial importance in numerical weather forecasting and climate models; however, their estimation nowadays presents some spatial and temporal limitations. In order to deal with these limitations and to assess the influence of different meteorological conditions on the temporal evolution of the aforementioned layers, the evolution of the ML over Madrid (Spain) has been studied for the year 2020 by means of ceilometer profiles fed into the STRATfinder algorithm. This algorithm is able to give reliable estimates of the height of the ABL (ABLH) and ML (MLH). The results are compared with the ECMWF-IFS model predictions, which is able to compute the MLH under any meteorological condition. Then, the influence of the meteorology in the estimation of MLHs was established by classifying data based on the season and
six different prevalent synoptic meteorological situations defined using ground-level pressure fields, as well as by splitting the days into four periods (morning, daytime, evening and nighttime). Our results show that both datasets, the STRATfinder values and the ECMWF-IFS model computations, are very sensitive to the meteorological conditions that play a main role in the MLH temporal evolution. For instance, high solar irradiance and ground radiation cause high turbulence and convection that lead to a well-developed ML. In cases in which the ML is well developed, both methods show similar results, and there are therefore better correlations between them. On the contrary, the results
presented here show that the presence of high relative humidity and low temperatures hamper the growth of the ML, causing different errors in both MLH estimations and poor correlations between them. Furthermore, the ECMWF-IFS model has shown a sharp decrease, identified as an artificial behavior
from 16:00 UTC, because of the influence of low solar zenith angles and the temporal interpolation. The STRATfinder algorithm also shows a sharp decrease just before the sunset because of the way the algorithm distinguishes between the ML and the residual layer. Thus, this study concludes that the MLH temporal evolution still needs to be characterized using complementary tools, since the methods presented here are strongly affected by the meteorological conditions and do not show enough reliability to work individually. However, ceilometer measurements offer great potential as a correction tool for ABL heights derived from models involved in air pollution dispersion assessments
Influence of synoptic meteorology on airborne allergenic pollen and spores in an urban environment in Northeastern Iberian Peninsula
No full textThe influence of the most frequent patterns of synoptic circulation on the dynamics of airborne pollen/spores recorded
at the Barcelona Aerobiological Station (BCN) was analysed. Six pollen types (Platanus, Cupressaceae, Olea, Poaceae, Urticaceae and Amaranthaceae), and one fungal spore (Alternaria) were selected for their high allergenic effect in sensitive people. Six synoptic meteorological patterns were identified through cluster analysis of sea level pressure fields as the main responsible of the weather conditions in the Iberian Peninsula. The local meteorological conditions in Barcelona associated with each one of the synoptic types were also stablished. Different statistical methods were applied to analyse possible relationships between concentrations and timing of the recorded aerobiological particles and specific synoptic types. The study, focused in the 19-year period 2001???2019, shows that one of the scenarios, frequent in winter and linked to high stability and air-mass blockage, registered the highest mean and median values for Platanus and Cupressaceae, but it was not very relevant for the other taxa. It was also this scenario that turned out to be the most
influent on the pollination timing showing a significant influence on the start occurrence of Urticaceae flowering and on the peak date of Platanus. On the other hand, the most frequent synoptic type in the period, relevant in spring and summer, was linked to sporadic episodes of levels considered to be of high risk of allergy to Platanus, Poaceae, and Urticaceae pollen, and Alternaria fungal spore. This synoptic pattern, characterized by the presence of the Azores anticyclone
and the Atlantic low located in the north of the United Kingdom, was associated with high temperature
BIPV Market Development: International Technological Innovation System Analysis
No full textLa integraci??n de fotovoltaica en edificios (BIPV) est?? llamada a desempe??ar un papel importante en la descarbonizaci??n de las ciudades, tanto en edificios nuevos como en proyectos de rehabilitaci??n, al hacerlos m??s sostenibles, resilientes y atractivos. Sin embargo, sigue siendo un nicho de mercado. Para comprender las razones y fomentar su desarrollo, el art??culo analiza la BIPV de forma hol??stica y sistem??tica, teniendo en cuenta su doble naturaleza como tecnolog??a fotovoltaica y producto de construcci??n. La metodolog??a se basa en el estudio de varios sistemas de innovaci??n tecnol??gica (TIS) de BIPV en seis pa??ses, junto con evaluaciones comparativas para identificar caracter??sticas comunes y diferenciadoras. El an??lisis aborda aspectos sociales, el estado y las previsiones del mercado, las perspectivas de los sectores fotovoltaico y de la construcci??n, as?? como la regulaci??n y la normalizaci??n, con el fin de formular recomendaciones para los responsables pol??ticos.
Entre los resultados destacan una aceptaci??n baja a moderada de la BIPV por parte de los propietarios de edificios ???quienes suelen optar por la fotovoltaica a??adida al edificio (BAPV) por motivos de coste??? y la necesidad de mayor informaci??n, directrices oficiales, personal cualificado, mejor colaboraci??n entre sectores, mayor disponibilidad de productos BIPV, herramientas digitales adecuadas y una regulaci??n espec??fica que refuerce la legitimidad de la BIPV en el sector de la construcci??n.
En conclusi??n, es fundamental desarrollar pol??ticas que impulsen la adopci??n de la BIPV, incluyendo normalizaci??n, promoci??n y financiaci??n.Building-integrated photovoltaics (BIPV) is expected to play a relevant role in decarbonising our cities, both in new buildings and retrofit projects, making them more sustainable, resilient and pleasant. However, BIPV remains a niche market. To understand the reasons and help boost its development, this paper provides insights into BIPV through a holistic and systematic analysis that considers BIPV???s dual nature as both photovoltaic and building product. The methodology is based on the analyses of several BIPV technological innovation systems (TISs) developed in six countries, as well as extensive comparative assessments and investigations to identify key global features of BIPV. Social aspects, market status and forecast, perspectives from the photovoltaic and building sectors, and related regulations and standardisation are key aspects analysed to develop recommendations for policymakers. Outcome examples are low to moderate acceptance of BIPV among building owners, who give cost reasons for choosing building-added photovoltaics (BAPV) over BIPV, as well as a need for information, official guidance, skilled personnel, improved cross-sector collaboration, availability of BIPV products, proper digital tools and specific regulation to improve BIPV???s legitimacy in the construction sector. Essential is developing policies that encourage the adoption of BIPV, including standardisation, promotion and financing
Volatile fission products transfer from hot sodium pools
No full textAnnals of Nuclear Energy
Volume 212, March 2025, 111059This study focuses on the release of the most relevant volatile fission products from the hot sodium pools. From an exhaustive review of the open literature, a critical review of a model based on the film theory and its estimates in comparison to data from the NALA experimental program has been conducted. Due to certain assumptions embedded in the approach, the fitting-to-data transport coefficients derived and some inconsistencies found between its formulation and the reported estimates, an alternate approach including other phenomena anticipated in the scenario is here proposed. Based on diffusive and convective mechanisms in the gas phase, the assumption of the analogy between heat and mass transport (HMT) and the ideal-dilute solutions laws to set the fission products concentration at the Na pool interface, a good agreement has been found with experimental data, which mean a substantial enhancement of qualitative and quantitative predictability while maintaining a conservative nature
Impact of Saharan Dust Intrusions on Atmospheric Boundary Layer Height over Madrid
No full textAbstract: Atmospheric pollution caused by aerosols deteriorates air quality, increasing public health risks. Anthropogenic aerosols are usually located within the atmospheric boundary layer (ABL), which presents a daytime evolution that determines the air pollutants??? vertical mixing of those
produced near the surface and, therefore, their ground-level concentration from local sources. Precise and complete characterization of the mixing layer is of crucial importance for numerical weather
forecasting and climate models, but traditional methods such as radiosounding present some spatial and temporal limitations. Better resolutions have been obtained using lidar, which provides the
aerosol vertical distribution. A particular type of lidar, the ceilometer, has demonstrated continuous measurement capabilities, providing vertical profiles with sub-minute time resolution and severalmeter spatial resolution. Advanced methods, such as the recently developed STRATfinder algorithm, are required to estimate the ABL height in the presence of residual layers. More complex situations
occur due to the advection of aerosols (e.g., due to long-range transport of desert dust, volcanic eruptions, or pyrocloud convection), producing a lofted layer in the free troposphere that may remain decoupled from the local ABL but can also be mixed. Aerosol-based methods for determination of the
ABL height are challenging in those situations. The main objective of this research is the assessment of the impact of Saharan dust intrusions on the ABL using ceilometer signals, over a period of four
years, 2020???2023. The ABL height database, obtained from ceilometer measurements every hour, is analyzed based on the most frequent synoptic patterns. A reduction in the ABL height was obtained from high dust load days (1576 ?? 876 m) with respect to low dust load days (1857 ?? 914 m), although it was still higher than clean days (1423 ?? 772 m). This behavior is further studied discriminating by season and synoptic patterns. These results are relevant for health advice during Saharan dust intrusion days
Synthesis report on C/E validation and nuclear data trends
No full textThis deliverable of the EC SANDA project ???Supplying Accurate Nuclear Data for Energy and non-Energy Applications??? (H2020 Grant Agreement number 847552) addresses Task 5.2 ???Validation studies using existing experiments???, Subtask 5.2.2 ???????????/???????? validation and trends???.
It compiles the findings of Deliverables 5.7 and 5.8 on validation of JEFF nuclear data files across reactor, shielding and criticality benchmarks as well as a validation of fission product nuclear data against MINERVE/CERES pile oscillation experiments, that was also envisaged in the task. As a result of the systematic benchmark calculations performed for each JEFF release, the needs for nuclear data improvement or reconsideration are synthesized, with particular indication of the benchmarks identified as useful for checking the performance of specific isotopes, reactions and energy ranges. Finally, new applications that should be addressed in future validation suites are proposed
Viabilidad del uso de la radiaci??n solar concentrada al proceso de sinterizaci??n de cobre
No full textEn la actualidad, el proceso de sinterizado, as?? como la pr??ctica totalidad de los procesos que se llevan a cabo en la industria, depende de las energ??as convencionales. Este trabajo pretende demostrar la viabilidad del uso de una fuente de energ??a renovable como es la Energ??a Solar T??rmica en el sinterizado de cobre. Con objeto de realizar en el futuro una evaluaci??n de las fuerzas conductoras y de la trayectoria del material transportado en funci??n de las caracter??sticas del sistema y de la radicaci??n incidente, se opta por dise??ar distintos dispositivos experimentales de empaquetamiento basados en modelos de part??culas ideales, en este caso cilindros, con los que se pretende simplificar la geometr??a del sistema real basado en part??culas compactadas, siendo evaluados experimentalmente en el Homo Solar de la Plataforma Solar de Almer??a. Las muestras tratadas en atm??sferas ligeramente reductoras, desarrollan cuellos bien definidos y muestran una reducci??n de porosidad, lo que permite demostrar la viabilidad del proceso