4161 research outputs found
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Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamount [Resumo]
No full textABSTRACT: Turbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three exceptionally deep cores covering up to 426,000 years in the Tore seamounts area. Here we evaluate the possible role of a number of physical processes that, when combined, may induce sufficiently intense bottom boundary events and likely precondition the recurrence pattern of the observed deep ocean turbidites
Mechanical Performance of Ceria-Coated 3D-Printed Black Zirconia Cellular Structures After Solar Thermochemical CO/H2 Fuel Production Cycles
No full textABSTRACT: Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their suitability in solar thermochemical cycles for CO2 and H2O splitting. Experiments were conducted using a 1.5 kW solar furnace to supply the high-temperature concentrated heat to a windowed reaction chamber to carry out thermal redox cycling under realistic on-sun conditions. The ceria coating on ceramic structures improved the thermal stability and redox efficiency while minimizing the quantity of the redox material involved. Crushing strength measurements showed that samples not directly exposed to the concentrated solar flux retained their mechanical performance after thermal cycling (similar to 10 MPa), while those near the concentrated solar beam focus exhibited significant degradation due to thermal stresses and the formation of CexZr1-xO2 solid solutions (similar to 1.5 MPa). A Weibull modulus of 8.5 was estimated, marking the first report of such a parameter for fused filament fabrication (FFF)-manufactured black zirconia with gyroid architecture. Failure occurred via a damage accumulation mechanism at both micro- and macro-scales. These findings support the viability of ceria-coated cellular ceramics for scalable solar fuel production and highlight the need for optimized reactor designs
Renewable Energy Production in the Mediterranean: Exploring the Potential for Offshore Wind Development [Resumo]
No full textABSTRACT: This study presents an overview of the current state of the Maritime Spatial Planning among the Mediterranean countries, explores the previous studies on evaluating the offshore wind potential of the Mediterranean region along with the criteria for suitable site selection. Based on a review of the current state of offshore renewable energy, the potential locations offshore wind will be explored for the Mediterranean coastline case study area. The research concludes with a set of critical considerations related to the need for proper synergies establishment among different stakeholders and for cultivating social acceptance and community engagement. The analysis aims to support decision-makers evaluating the potential of the Mediterranean coastal area in supporting the energy transition goal.COST Action CA20109 Modenerlands, supported by COST (European Cooperation in Science and Technology
Depositional environment and redox conditions of the Moncorvo Ironstone: Unveiling the evolution of ironstones under Rheic Ocean influence
No full textABSTRACT: Ironstones, as key archives of past marine environments, provide invaluable insights into Paleozoic history. Their mineralogy may reflect the physical-chemical conditions of the environment and the nature of available sediments. This study focuses on the Moncorvo Ironstone, a Lower-Middle Ordovician deposit formed during the opening of the Rheic Ocean. Here, we use an integrated approach combining sedimentology, petrology, and geochemistry to constrain the depositional settings and the redox landscape associated with the ironstone deposition. The Moncorvo Ironstone present some unusual characteristics, such as the lack of ooids, an uncommon mineralogy, and a stratigraphic thickness that can reach over >45 m, a remarkable feature for an ironstone. Our investigation reveals that this iron-rich sequence is distributed in two distinct marine environments: an inner shelf and a middle to distal shelf. Each environment has a unique mineral assemblage. Despite the influence of metamorphism and deformation, evidence suggests that much of the mineralogy and texture of this deposit still preserve characteristics of the original sediments. Finally, our findings, alongside a careful assessment of the mineralogy of other ironstones of similar age, suggest a strong stratification of the Rheic Ocean throughout the Early and Middle Ordovician
Geoconservation initiative for the slabs of the Natural Monument of Dinosaur Footprints in Ourém/Torres Novas and the Dinosaur Footprints Site in Vale de Meios : challenges and achievement
No full textRESUMO: A geoconservação é uma parte essencial da conservação da natureza, especialmente em áreas protegidas possuidoras de património geológico de relevante interesse científico e pedagógico. No âmbito do projeto “Valorização do Património Geológico do Parque Natural das Serras de Aire e Candeeiros”, foram realizados trabalhos de geoconservação nas lajes do Monumento Natural das Pegadas de Dinossáurios de Ourém/Torres Novas (Pedreira do Galinha) e na jazida de Vale de Meios. As principais medidas de geoconservação implementadas incluíram a instalação e reforço das redes de drenagem e a execução de medidas para consolidar adequadamente as pegadas e zonas mais frágeis dos respetivos maciços rochosos. Para eliminar a degradação antropogénica das pegadas, relacionada com o pisoteio resultante das visitas, e para facilitar a visualização e aprendizagem do público, foram instalados passadiços de madeira em ambos os afloramentos, tendo esta intervenção sido realizada pelo ICNF no âmbito de um concurso público autónomo.ABSTRACT: Geoconservation plays a crucial role in the preservation of natural environments, particularly in protected areas that possess significant scientific and educational value due to their geological heritage. In the context of the “Enhancement of the Geological Heritage of the Serras de Aire e Candeeiros Natural Park” project, in Central Portugal, extensive geoconservation efforts were undertaken at the Natural Monument of the Dinosaur Footprints of Ourém/Torres Novas (Galinha’s quarry) and the Dinosaur Footprint Site in Vale de Meios quarry. These efforts primarily focused on implementing various measures to safeguard the footprints and delicate rock formations, such as the installation of drainage networks and consolidation techniques. Additionally, to mitigate the negative impact of human activities, particularly trampling during visits, wooden walkways were constructed at both sites. These walkways not only serve to protect the footprints from anthropogenic
degradation but also enhance the overall visitor experience by providing convenient access and facilitating educational opportunities.POSEUR-03-2215-FC-000116 – Projeto de Valorização do Património Geológico do Parque Natural das Serras de Aire e Candeeiros
Plano de ação do Biometano 2024-2040: Instrumentos para a sua implementação [Comunicação oral]
No full textStrategies to Incentivize the Participation of Variable Renewable Energy Generators in Balancing Markets
No full textABSTRACT: Balancing markets (BMs) play a crucial role in ensuring the real-time equilibrium between electricity demand and supply. The current requirements for participation in BMs often overlook the characteristics and capabilities of variable renewables, limiting their effective integration. The increasing penetration of variable renewables necessitates adjustments in the design of BMs to support the transition toward carbon-neutral power systems. This study examines the levels of active market participation for a wind power producer (WPP) in the Iberian Electricity Market and the Portuguese BMs. In addition to exploring current market dynamics, the study tests one methodology proposed by the Danish Transmission System Operator to support the participation of variable renewables in BMs, the P90, and two new methods based on the full cost balancing concept. These methodologies incentivize WPPs to minimize imbalances by allowing market participation only if imbalances remain within a 10% deadband of annual hours (P90), hourly offers (D90), or both (DP90). The results indicate that participating in the secondary capacity market, particularly for downward capacity, is the most profitable strategy. This participation enhances the value of wind power by over 42%. However, in most methodologies, the WPP failed to deliver nearly 100% of its allocated capacity approximately 1% of the time. In contrast, the D90 approach limited the maximum deviation to 10%, demonstrating the highest reliability among the evaluated methods
Improving Carbon Fixation and Acetate Production from Syngas Fermentation: On-Demand Versus Continuous Feeding
No full textABSTRACT: Syngas fermentation is a promising carbon capture and utilization (CCU) technology for producing carboxylic acids while transforming low-cost waste gas into high-value products. This study evaluates the two bioreactor feeding strategies for synthesis gas (syngas) fermentation by Eubacterium callanderi (formerly Butyribacterium methylotrophicum) strain Marburg-on-demand feeding (ODF) and continuous feeding (CF)-with a synthetic syngas mixture of 23 vol% CO2, 29 vol% CO, 32 vol% H2, and 16 vol% CH4, mimicking the syngas from lignocellulosic gasification. The ODF assay achieved a maximum syngas consumption rate of 112 mL/h, yielding 24.1 g/L acids, namely 22.9 g/L acetate and 1.3 g/L butyrate. CF of syngas at 223 mL/h required more gas (62.9 L) to produce 22.7 g/L total acids, from which 19.0 g/L acetate and 3.7 g/L butyrate were achieved. The CF-specific production rate (gproduct/gdry_cell_weight/hour) reached 0.5 g/gDCW/h (acetate) and 0.17 g/gDCW/h (butyrate), outperforming ODF with 0.3 and 0.02 g/gDCW/h, respectively. ODF minimized gas wastage and enabled CH4 accumulation inside the bioreactor up to approximately 78 vol%, while CF led to CO2 accumulation, indicating a need for more efficient CO2 utilization strategies, such as sequential fermentations. This work highlights the critical impact of the two feeding options studied with regard to scaling up the carbon-efficient production of carboxylic acids, and indicates that both strategies can have potential applications. ODF is ideal for increasing carbon fixation and achieving, simultaneously, gas cleaning, while CF fermentations are better suited to maximizing the acid production rate