4161 research outputs found
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Exploring the offshore wind and wave generation complementarity in Portugal for a sustainable and resilient power system
No full textABSTRACT: Exploring variable energy sources generation complementarity can, among several benefits, help in the reduction of the negative impacts of variability from individual sources, and lower the system’s flexibility requirements. This study focuses on the complementarity between offshore wind and wave energy aiming to identify its overall value to the power system. Using Portugal as a case study, this work examines two offshore regions of the Plan for the Allocation of Offshore Renewable Energy in Portugal using standard approaches to assess the level of complementarity. The findings show a clear seasonal mismatch in the summer between wind and wave energy, which supports their complementary nature and helps smooth out seasonal fluctuations in offshore renewable generation. The results indicate that wave energy brings value to diversifying the offshore energy mix. When compared with onshore renewable generation, the combined use of offshore wind and wave power significantly enhances the stability of energy supply, reduces extreme events, which can contribute to decrease the need for additional system flexibility in future nearly 100% renewable-based power systems
Pilot-Scale cultivation of microalgae in blended effluents: C/N ratio management to boost biomass and biofuel precursors
No full textABSTRACT: Algal biotechnology offers a sustainable pathway for wastewater treatment and resource recovery. However, the low carbon-to-nitrogen (C/N) ratio in domestic wastewater often limits microalgal productivity, which may compromise process viability and, consequently, limit its application in bioproduct valorization routes. This study evaluated the effects of blending municipal wastewater (MW) with industrial wastewater from juice processing (IWJ) at different ratios on biomass production, biochemical composition, and pollutant removal. Pilot-scale experiments in outdoor high-rate algal ponds, operated without external carbon dioxide (CO2) supply (relying on inorganic carbon present in the wastewater and passive diffusion from air). These experiments tested three blends: T1 (60 % MW + 40 % IWJ, C/N 9.25), T2 (40 % MW + 60 % IWJ, C/N 25.31), and T3 (20 % MW + 80 % IWJ, C/N 52.71). T1 achieved the highest biomass productivity and lipid content (14.44 %, p < 0.05), while T3 presented the highest levels of saturated fatty acids C16:0 (40.39 %) and C18:0 (10.08 %), supporting its biodiesel potential. Carbohydrate accumulation was enhanced in T2 (18.44 %) and T3 (21.09 %) under nitrogen-limited conditions. Microalgal species composition varied significantly with the C/N ratio, indicating selective adaptation. Additionally, dissolved organic carbon removal followed first-order kinetics across treatments, confirming model applicability. These findings underscore the effectiveness of effluent blending and C/N adjustment to enhance biomass quality, pollutant removal, and suitability for biofuel production in integrated algal-based wastewater treatment systems
Scale-up of a clean hydrogen production system through the hydrolysis of sodium borohydride for off-grid applications
No full textABSTRACT: Hydrogen is considered a promising energy vector with the potential to replace fossil fuels, and sodium borohydride serves as an effective energy carrier capable of releasing hydrogen (H2) for off-grid applications. However, the hydrolysis of sodium borohydride has only matured at laboratory-scale. Therefore, the scale-up of a laboratory reactor was designed and manufactured to study the effect of larger H2 production. For that, the effect of inhibitor NaOH concentration and water quality were studied. Experiments using 3 wt% NaOH showed overall better performance than those using 1 wt%. Additionally, experiments using tap water - scarcely reported in the literature - demonstrated performance equal to or better than that achieved with distilled water. These results are indicative of a possible significant reduction in the H2 production cost through this method
Application of the electrical resistivity method in the characterization of limestone in a quarry of ornamental rock
No full textRESUMO: O principal objetivo deste trabalho foi a caracterização do maciço calcário explorado na pedreira “EM&R nº 6478”, com base na aplicação do método geofísico de resistividade elétrica, tendo em vista a otimização da operação extrativa de calcário para fins ornamentais. Pretende-se identificar as zonas do maciço com coloração acinzentada, que apresentam menor interesse económico. Verificou-se que os valores de resistividade elétrica sofrem variações significativas nas zonas de contato entre as zonas de coloração bege e as zonas de coloração acinzentada do calcário. Constatou-se que a tonalidade acinzentada se deve à presença de uma fração argilosa na sua composição, que pode explicar os valores mais baixos de resistividade elétrica. A metodologia utilizada revelou-se bastante eficaz no planeamento futuro da exploração, permitindo uma melhor orientação das frentes de desmonte, tornando a exploração ainda mais rentável.ABSTRACT: The main objective of this work was to characterize the limestone massif exploited in the “EM&R nº 6478” quarry, based on the application of the geophysical method of electrical resistivity, with a view to optimizing the limestone extraction operation for ornamental purposes. The aim is to identify the areas of the massif with a greyish
color that are of less economic interest. It was found that the electrical resistivity values vary significantly in the contact zones between the beige and grey areas of the limestone. It was found that the greyish hue is due to the presence of a clay fraction in its composition, which may explain the lower electrical resistivity values. The methodology used proved to be highly effective in the future planning of quarrying, allowing for better orientation of the blasting fronts, making quarrying even more profitable
Strategic Bidding to Increase the Market Value of Variable Renewable Generators in New Electricity Market Designs
No full textABSTRACT: Electricity markets with a high share of variable renewable energy require significant balancing reserves to ensure stability by preserving the balance of supply and demand. However, they were originally conceived for dispatchable technologies, which operate with predictable and controllable generation. As a result, adapting market mechanisms to accommodate the characteristics of variable renewables is essential for enhancing grid reliability and efficiency. This work studies the strategic behavior of a wind power producer (WPP) in the Iberian electricity market (MIBEL) and the Portuguese balancing markets (BMs), where wind farms are economically responsible for deviations and do not have support schemes. In addition to exploring current market dynamics, the study proposes new market designs for the balancing markets, with separate procurement of upward and downward secondary balancing capacity, aligning with European Electricity Regulation guidelines. The difference between market designs considers that the wind farm can hourly bid in both (New 1) or only one (New 2) balancing direction. The study considers seven strategies (S1-S7) for the participation of a wind farm in the past (S1), actual (S2 and S3), New 1 (S4) and New 2 (S5-S7) market designs. The results demonstrate that new market designs can increase the wind market value by 2% compared to the optimal scenario and by 31% compared to the operational scenario. Among the tested approaches, New 2 delivers the best operational and economic outcomes. In S7, the wind farm achieves the lowest imbalance and curtailment while maintaining the same remuneration of S4. Additionally, the difference between the optimal and operational remuneration of the WPP under the New 2 design is only 22%, indicating that this design enables the WPP to achieve remuneration levels close to the optimal case
Integrating social aspects in microalgal biorefineries: a Product Social Impact Life Cycle Assessment (PSILCA) approach
No full textABSTRACT: The ongoing climate change phenomenon requires the reduction of atmospheric CO2 concentrations. Microalgal biorefineries, which convert atmospheric CO2 into chemical energy, offer a viable alternative to fossil fuel-based industrial systems. This study assesses the social impacts of microalgal biorefineries using the Product Social Impact Life Cycle Assessment database approach, focusing on an industrial facility located in P & oacute;voa de Santa Iria, Vila Franca de Xira, Portugal. The foreground system involves the production of microalgae in cascade raceway systems, followed by their refinement into protein, lipid and carbohydrate fractions. Dedicated surveys were distributed to the local community to collect social data, which was then analyzed using the Product Social Impact Life Cycle Assessment (PSILCA) database and a newly designed evaluation schema. Preliminary data from approximately 300 valid responses indicated that the local community faces a medium risk of being unfamiliar with the concept of microalgae or its benefits but acknowledged the high probability of local economic benefits and job creation upon implementation. The study highlights a general lack of familiarity with microalgae among the local community, which could affect the acceptance of the biorefinery. Although the PSILCA approach identifies social hotspots effectively, reliance on generic data may not accurately represent the local context. The study underscores the need for enhanced information dissemination to improve community acceptance and support for microalgal biorefineries. Preliminary data collection and analysis highlight the potential for social benefits, but further research is required to address the identified limitations
Ediacaran and early-palaeozoic bimodal volcanism in the Ossa-Morena Zone, SW Iberian Massif: New clues for intraplate rifting shortly after the Cadomian Orogeny
No full textABSTRACT: This study focuses on bimodal meta-volcanic rocks present in the Iberian Massif, in the Evora-Aracena Metamorphic Belt of the Ossa-Morena Zone (OMZ), near the boundary with the South Portuguese Zone. New petrological, geochemical (whole-rock and Sr-Nd isotopes) and LA-ICP-MS U-Pb zircon geochronology data are presented to track the magmatic evolution of both felsic and mafic rocks and their respective geodynamic setting during the transition between the Cadomian Orogeny and subsequent Palaeozoic rifting events. Our research shows that the Evora-Aracena Metamorphic Belt (EAMB) in the southwestern OMZ possesses a significant record of the transition between the Cadomian and Variscan cycles. U-Pb geochronological data confirm the existence of both felsic and mafic Ediacaran igneous rocks (546 and 556 Ma, respectively), a novelty in the region. The Cadomian-related felsic rocks show geochemical similarities to meta-felsic rocks formed during the initial phases of the Cambrian rifting event, namely very negative epsilon Nd values (-10.1 to -11.8), depleted HREE patterns and orogenic signatures. Such similarities imply that meta-felsic rocks formed in the earliest stages of the Cambrian Rift-to-Drift event resulted from a shallower melting. Moreover, meta-felsic rocks formed in the early stages of the Cambrian rifting (525 Ma) present a significant amount of Ediacaran aged zircons, whereas the Cadomian-related counterparts display a few discordant Cambrian ages, likely a consequence of Pb-loss. This indicates that the convergent, subduction-related regime that prevailed during most of the Cryogenian-Ediacaran times along the boundaries of NW Gondwana was swiftly supplanted by a rift-dominated regime during the Cambrian, with no substantial gap between these two thermal events. Meanwhile, meta-felsic rocks formed during the Rift-to-Drift (525-480 Ma) event exhibit progressively higher epsilon Nd values (-5.0 to +3.0), HREE-enrichment, as well as anorogenic signatures, denoting an increasing contribution of mantle-derived melts. This increasing mantle contribution eventually led to the occurrence of bimodal magmatism in the Middle Cambrian Main Rift event. Such Cambrian mafic rocks, unlike the Ediacaran mafic rocks that present flat REE patterns and continental arc signatures, display varying degrees of LREE enrichment and N-MORB to E-MORB signatures
A primeira ocorrência do atum Thunnus sp. (Família Scombridae) no registo fóssil Miocénico de Portugal
No full textABSTRACT: The fossil record of tunas (tribe Thunnini, family Scombridae) is sparse due to their pelagic lifestyle. Yet such finds are essential for reconstructing evolutionary and biogeographic patterns of these marine apex predators. We report the first occurrence of Thunnus sp. in Portugal, based on a well-preserved caudal vertebra from Burdigalian (Lower Miocene) deposits at Praia da Foz da Fonte (Baixo Tejo Basin, Setúbal Peninsula). The specimen, although recovered ex situ, is confidently attributed to the Lower Miocene shallow-marine succession of the locality. Morphological features—including an amphicoelous centrum, paired lateral foramina, and distinct growth rings—support its assignment to a large scombrid, consistent with the taxon Thunnus. Estimated body length exceeds 284 cm, indicating the presence of large pelagic predators from this genus in Miocene seas of western Iberia. This find represents the earliest tuna record from Portugal and supports a widespread Miocene distribution and diversification of the genus Thunnus across Europe and the Americas.RESUMO: O registo fóssil dos atuns (tribo Thunnini, família Scombridae) é relativamente escasso devido ao seu modo de vida pelágico, que limita o potencial de preservação. Ainda assim, esses registos são fundamentais para compreender a história evolutiva e a paleobiogeografia de um dos grupos de peixes mais importantes do ponto de vista ecológico e económico. Neste trabalho reporta-se a primeira ocorrência de Thunnus sp. no registo fóssil de Portugal, com base numa única vértebra bem preservada proveniente de depósitos do Burdigaliano (Miocénico Inferior) na Praia da Foz da Fonte, localizada na Bacia do Baixo Tejo (Península de Setúbal). O espécime foi encontrado ex situ na base de uma arriba, mas é atribuído com confiança à sucessão marinha miocénica local, caracterizada por biocalcarenitos, calcarenitos e margas interestratificadas, representativos de ambientes deposicionais marinhos pouco profundos. A análise morfológica da vértebra caudal revela características diagnósticas de grandes escombrídeos, incluindo o centro anficélico, centrum robusto, pares de forâmenes laterais e anéis de crescimento bem definidos, consistentes com um indivíduo de tamanho médio a grande do género Thunnus. Com um comprimento corporal estimado superior a 284 cm, este fóssil evidencia a presença de predadores pelágicos altamente adaptados nos mares miocénicos do oeste da Ibéria. Comparações com outros registos miocénicos de Thunnus da Europa, América do Norte e do Sul, sugerem uma distribuição mais ampla e a diversificação do grupo neste período. Embora vértebras isoladas sejam geralmente não diagnósticas ao nível específico, o espécime enquadra-se na morfologia “tipo-Thunnus” reconhecida noutros depósitos miocénicos a nível mundial. Este achado não só amplia o registo fóssil português de Scombridae, anteriormente pouco documentado, como também constitui a evidência mais antiga de espécies de atum na região. A presença de Thunnus nestes depósitos reflete tanto a importância ecológica dos atuns nos ecossistemas marinhos de idade Miocénico, como o seu papel de predadores pelágicos de topo durante uma fase crítica da evolução oceânica do período Neogénico
Mapping Critical Raw Materials (CRM) hard rock deposits in Europe
No full textABSTRACT: This article presents the new version of the map of critical raw materials hard rock deposits that has been produced in the frame of the GSEU project (Geological Service for Europe). The map displays over 800 medium to very large deposits for 30 Critical Raw Materials (CRM) from the 2023 list of the European Commission, in 33 European countries. We explain the objective of this work and the process and methodology for collecting, compiling and harmonizing CRM data from multiple providers. We also describe the map itself, the information it carries and its availability. As an example of added-value output, we present a pan-European assessment of CRM potential, classified in 4 categories of confidence from “historical or non-compliant resource estimates” to “mineral reserves”. This assessment provides an image of the current known potential for CRM in Europe. Based on this exercise, we discuss the challenges and barriers of compiling and harmonizing mineral resources data at continental scale, and the future perspectives of this work we envision through the EGDI (European Geological Data Infrastructure). We also discuss the limitations of the map and dataset to raise awareness on their proper interpretation and use
Decarbonization Transition Pathways and Regional Trends: Insights from One Million Studies
No full textABSTRACT: As global temperatures near critical thresholds and emissions continue to rise, the urgency for strategic, accelerated decarbonization grows. Despite a vast climate mitigation literature, a systematic understanding of actionable pathways remains limited. Here, we apply artificial intelligence to analyze over one million scientific papers (2011–2021), generating a data-driven typology of six archetypal decarbonization pathways: Technology Breakthrough, Electrification of Uses, Integrated Policy, Decarbonization of Electricity, Demand Reduction & Co-benefits, and Land Use & Circularity. Regional patterns show Electrification of Uses prevailing in Europe (EU27), while Technology Breakthrough dominates in China, the US, and Japan. Increasing political and societal resistance to mitigation makes the strategic selection and combination of pathways even more critical. Our analysis highlights key synergies between pathways, the scientific competencies required to support them, and persistent gaps—particularly in Land Use and Circularity. We also compare current climate policy directions with the typology, revealing alignment gaps that may weaken policy effectiveness. This framework enables policymakers to better match strategies with regional capacities and research strengths, offering a more coherent approach to decarbonization. Strengthening the integration of science, technology, and policy is essential to overcome fragmentation and deliver the emissions reductions needed to meet the net-zero climate targets