Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
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Life Cycle Assessment and Soil Nitrogen Balance of different N fertilizers for top dressing rye as energy crop for electricity generation
No full textNitrogen fertilizers have been identified in energy crops LCAs as the main contributors to global warming, as well as to many other environmental impacts. The distinct production process and application emissions of nitrogen fertilizer types for top dressing produce different GHG savings when energy crops value chains are compared to fossil energy alternatives. In this study, three types of fertilizers (calcium ammonium nitrate, urea and ammonium sulphate) at N top dressing rates of 80 kg N/ha are used to grow rye for electricity generation under the conditions of the Continental Mediterranean climate of central-northern Spain. Complete LCAs for the whole value chain based on real data were performed in conjunction with soil nitrogen balances (SNBs) to assess the accomplishment of European Union (EU) GHG savings sustainability criteria, as well as the sustainability of fertilization practices for soil nitrogen stocks. The results obtained can provide interesting insights for policy making, since calcium ammonium nitrate, the most common fertilizer for rye crops, led to 66% GHG savings, as opposed to the 69% achieved when applying urea and 77% when ammonium sulphate was used. Nevertheless, the three fertilizers produced annual soil deficits greater than 50 kg N/ha. In order to ensure savings above 80%, as required by the EU sustainability criteria, and sustainable SNBs, additional optimization measures should be taken at key points of the value chain
Role of Hydrogen in the Preparation of Amorphous Silicon Nanowires by Metal Assisted Chemical Etching
No full textHydrogenated amorphous silicon (a-Si:H) has recently proved to be a suitable base material for the synthesis of silicon nanowires (SiNWs) by metal-assisted chemical etching (MACE). The etching procedure on this material shows an extraordinary sensitivity to slight compositional changes and, although dopant influence on the process has been previously addressed, little is known on the role of hydrogen. In this article, we have studied the behavior of MACE on a-Si:H films with different hydrogen contents and bond configurations. As-grown films were studied by Raman spectroscopy, Fourier transform infrared spectroscopy, and ion beam analysis to obtain a complete description of the material composition. Additionally, these results were further correlated with the morphology and characteristics of the obtained SiNWs, showing that the material stability under MACE is reduced as the bond configuration is shifted from monohydrides to polyhydrides. The effect of bond configuration has an extraordinary importance regarding the material application, as it is intrinsically related to the content of hydrogen, which simultaneously controls the optical properties of the material. This study proves that bond configuration also affects the nanostructuration, which should be considered in future devices based on this material
High-performance Ag-NWs doped graphene/ITO hybrid transparent conductive electrode
No full textIndium tin oxide (ITO) is a commonly used material for transparent conductive
electrodes (TCE) in optoelectronic applications. On the other hand, graphene has superior
electrical conductivity and exceptional mechanical flexibility, which makes it a promising
candidate as a TCE material. This work proposes a CVD graphene/ITO hybrid electrode
enhanced by doping with silver nanowires (Ag-NWs). The study aims to improve the
performance of the electrode by optimizing two key parameters during the fabrication
process: the thermal annealing time after the transfer of graphene on ITO and the Ag-NWs
doping conditions. The annealing treatment is fundamental to reducing the residues on the
surface of graphene and increasing the interface contact between graphene and ITO. The
correct coverage and distribution of the dopant on graphene is obtained by controlling the
concentration of the Ag-NWs and the spin coating speeds. The results indicate a substantial
improvement in the optical and electrical performance of the Ag-NWs/graphene/ITO
hybrid electrode. A remarkably low sheet resistance of 42.4 ??/sq (??2 ??/sq) has been
achieved while maintaining a high optical transmittance of 87.3% (??0.5%)
High-pressure sputtering deposition and in situ plasma oxidation of TiOx thin films as electron selective contact for photovoltaic applications
No full textAbstract: In this article, we show the structural, optical, and electrical characterization of TiOx deposited by the unconventional technique of High-Pressure Sputtering (HPS). This technique has the potential to reduce the plasma-induced damage of the samples. To fabricate the TiOx, a 2-step process was used. Firstly, a thin Ti film was deposited in an Ar atmosphere. Secondly, O2 was introduced into the HPS chamber to create an Ar/O2 plasma that, along with low temperatures (150????C or 200????C), induces the oxidation of the deposited Ti film. With this approach, the Ti film is expected to behave as a capping layer that will reduce the oxidation of the Si substrate. This study aims to obtain a TiOx layer with low specific contact resistivity (??c) and high minority carrier lifetime. These are crucial characteristics for obtaining high-quality selective contact. It was found that the 2-step process can oxidize the Ti layer. These HPS TiOx layers show a resistivity in the order of 0.3???10 ??cm and a ratio Ti/O of ???1.9. Moreover, the SiOx regrowth is minimal since this is comparable to the native oxide. This was confirmed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The samples fabricated with a Ti layer (???4??nm) plus an oxidation temperature of 200????C (duration of less than 2??h) show a low ??c of 0.02 ??cm2, an excellent transmittance (>87??%) in the visible region and an optical bandgap of 2.8??eV. These TiOx layers are amorphous, although some anatase phase crystalline clusters appear for the 200????C processes. However, the minority carrier lifetime results of Si passivated by TiOx were inadequate for fabricating efficient solar cells. We also found that using the RCA oxide improved lifetime. This indicates that introducing alternative low-temperature passivating layers can solve this issue
Mechanical Properties of Dense Cordierite Discs Sintered by Solar Radiation Heating
No full textConsolidation of cordierite disc specimens was undertaken under concentrated solar beam in a solar furnace at PSA (Plataforma Solar de Almer??a). Satisfactory extent of densification was achieved by the present solar-sintering experiment. The mechanical properties measured for the solar-sintered cordierite test pieces were; density ??=2.45??0.02 g/cm3, Vickers microhardness HV=7.31??0.29 GPa, Young???s modulus E=97??5 GPa, shear modulus G=38??2 GPa, Poisson ratio ??=0.27??0.01, fracture toughness KIC=1.50??0.15 MPa??m1???2 and modulus of rupture evaluated by ring-on-ring test MORROR=57.8??13.7 MPa which were comparable to those of the counterparts sintered by conventional industrial gas urnace
Development of Sustainable Hydrophobic Coatings for Textiles Based on Nitrogen Deposition.
No full textThis study investigates the use of copper nitride (
Cu3N) thin films as a hydrophobic coating for acrylic textiles, offering a
safer and more sustainable alternative to conventional fluorocarbon-based treatments. Copper nitride is a non-toxic, abundant,
and cost-effective semiconductor material with tunable properties, yet its application in textiles remains largely unexplored.
In this work, Cu3N
coatings were deposited on acrylic fabric using reactive sputtering at room temperature, 50W of power
and 3.5 Pa of working pressure, under two different gas atmospheres: pure nitrogen (
N2) and a nitrogen-argon (
N2 + Ar)
mixture. Deposition times were varied at 60, 90, and 120 min to evaluate the influence of process duration on hydrophobic
performance. Hydrophobicity was assessed by measuring the water contact angle on coated samples, both in their initial
state and after mechanical stress tests including washing and folding. The results demonstrated strong hydrophobic behavior
across all samples, with contact angles ranging from 96.30?? to 113.68??. Notably, coatings deposited under N2
+ Ar showed
slightly enhanced performance and durability compared to those deposited under pure N???. The entire process was conducted
at room temperature and generated no chemical waste, highlighting its environmental advantages. These findings
suggest that copper nitride coatings can effectively impart hydrophobicity to textiles without relying on harmful fluorinated
compounds. The combination of performance, safety, and sustainability positions Cu3N
as a promising candidate for future
textile finishing technologies
Projections of the start of the airborne pollen season in Barcelona (NE Iberian Peninsula) over the 21st century
No full textThe effects of global warming are numerous and recent studies reveal that they can affect the timing of pollination. Temperature is the meteorological variable that presents a clearer relationship with the start of the pollination season of most of the observed airborne pollen taxa. In Catalonia, in the last fifty years, the average annual air temperature has increased by +0.23 ???C/decade, and the local warming has been slightly higher than the one on a global scale. Projections point to an increase in temperature in the coming decades, which would be more marked towards the middle of the century. To analyse the effect of the increase in temperature due to global warming on the starting date of pollen season in Barcelona, a forecasting model has been applied to a set of projected future temperatures estimated by the European RESCCUE project. This model, largely used in the literature, is based on determining the thermal needs of the plant for the pollen season to begin. The model calibration to obtain the initial parameters has been made by using 20 years of pollen data (2000???2019), and the model effectiveness has subsequently been tested through an internal evaluation over the period of the calibration and an external evaluation on 4 years not included in the calibration (2020???? 2023). The mean bias error in the internal calibration ranged between ???? 0.4 and ???? 0.6 days, and between +0.5 and ???? 8.3 in the external one, depending on the taxon. The results of the application of the model to the temperature projections over the 21st century point to a progressive advancement in the pollination dates of several pollen types abundant in the city, allergenic most of them. These advances ranged, at the end of the century, between 15 and 27 days, depending on the climate model, for the scenario of the highest concentrations
(RCP8.5) and between 7 and 12 days for the emissions stabilization scenario (RCP4.5)
Concentrating PV: An Alternative to Calorimeters for Measuring High Solar Flux Densities
No full textGardon calorimetric transducers are widely used to measure concentrated solar radiation flux on solar thermal areas. These measurements need some correction to adapt their response from thermal to solar irradiance measurement. The authors propose the use of concentrating photovoltaic PV-cells to measure concentrated solar radiation flux. This paper shows the results obtained from a comparative test carried out in a solar furnace measuring concentrated solar irradiance with calorimetric and photovoltaic sensors, Gardon, and PV-Cells, respectively
Evaluating Assisted Gene Flow in Marginal Populations of a High Mountain Species
No full textMany species cannot either migrate or adapt at the rate of temperature increases due to
climate warming. Therefore, they need active conservation strategies to avoid extinction.
Facilitated adaptation actions, such assisted gene flow, aim at the increase of the
evolutionary resilience of species affected by global change. In elevational gradients,
marginal populations at the lower elevation edges are experiencing earlier snowmelt
and higher temperatures, which force them to adapt to the new conditions by modifying
their phenology. In this context, advancing the onset of flowering and seed germination
times are crucial to ensure reproductive success and increase seedling survival prior to
summer drought. Assisted gene flow may bring adaptive alleles and increase genetic
diversity that can help throughout ontogeny. The main aim of this work is to assess
the effects that different gene flow treatments could have on the desired trait changes
in marginal populations. Accordingly, we established a common garden experiment
in which we assayed four different gene flow treatments between Silene ciliata Pourr.
(Caryophyllaceae) populations located in similar and different elevation edges, belonging
to the same and different mountains. As a control treatment, within-population crosses
of low elevation edge populations were performed. The resulting seeds were sown and
the germination and flowering onset dates of the resulting plants recorded, as well as
the seedling survival. Gene flow between populations falling on the same mountain and
same elevation and gene flow from high-elevation populations from a different mountain
to low-elevation populations advanced seed germination time with respect to control
crosses. No significant effects of gene flow on seedling survival were found. All the gene
flow treatments delayed the onset of flowering with respect to control crosses and this
effect was more pronounced in among-mountain gene flows. The results of this study
highlight two important issues that should be thoroughly studied before attempting to
apply assisted gene flow in practical conservation situations. Firstly, among-populations
gene flow can trigger different responses in crucial traits throughout the ontogeny of
plant species. Secondly, the population provenance of gene flow is determinant and
plays a significant role on the effects of gene flow
Empirical scaling of the L-H threshold power for metal wall tokamaks using a multi-device database
No full textThe empirical scaling for the H-mode power threshold in tokamaks has been revisited using a database with threshold data from machines with a metallic first wall as part of International Tokamak Physics Activity (ITPA) task TC-26. The database contains discharges from ASDEX Upgrade (W), JET (Be/W) and Alcator C-Mod (Mo). This was motivated by reports that in like-for-like discharges the power threshold was reduced by approximately 30% after the change from carbon based to metallic first wall materials on AUG [F. Ryter et al., Nuclear Fusion, 53(11):113003 (2013)] and JET [C.F. Maggi et al., Nuclear Fusion, 54(2):023007 (2014)]. The database contains L-H transition data for all hydrogen isotopes and mixtures, including T and DT from the recent JET campaigns. Compared to the ITPA 2008 scaling [Y R Martin et al., Journal of Physics: Conference Series, 123(1):012033 (2008)], the metal wall scaling has a smaller magnetic field exponent but a larger density exponent. We present an additional parameter to capture the strong dependence of the L-H power threshold (approx. factor 2) on the magnetic configuration in the divertor on JET. The scaling recovers the approximate inverse isotope mass scaling of the threshold power. Alternative scalings involving the plasma current and poloidal magnetic field are explored. Despite the reduction in threshold observed earlier, the scalings based on the metal wall database do not necessarily extrapolate to a lower threshold fo