Repositório do LNEG
Repositório Científico do Laboratório Nacional de Energia e Geologia
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Enhancing microalgal biohydrogen production: Unlocking higher yields with hydrothermal pretreatment with niobium phosphate
Publication . Silva, Thiago; Jesus Junior, Maurino Magno; Neves de Araujo, Matheus; Castro, Laressa Santos; Fuess, Lucas Tadeu; Rodrigues, Fábio de Ávila; Zaiat, Marcelo; Reis, Alberto; Calijuri, Maria Lucia
ABSTRACT: Microalgae cultivated in wastewater hold promise as a substrate for biohydrogen (bioH2) production. However, their rigid cell walls pose a challenge to fermentability. In this context, this study evaluated hydrothermal pretreatment with niobium phosphate (NbP) at 100-180 degrees C for 0-70 min, using up to 75 % NbP (relative to the dry weight of microalgal biomass). The hydrothermal pretreatment at 180 degrees C for 10 min with 75 % NbP released 7431 mg total carbohydrates (CHt) L-1, increasing the availability of fermentable substrates in subsequent dark fermentation (DF). When this pretreated biomass was subsequently fermented at pH 5.0 (sample PB5), bioH2 production reached 1.03 mmol H2 mol-1 CHt, with a maximum cumulative output of 0.17 mmol H2 and a CHt conversion efficiency of 83.6 %. In contrast, pH 5.5 and 6.0 reduced bioH2 yields and promoted methanogenic activity, while no pH control resulted in negligible bioH2 evolution. In conclusion, hydrothermal pretreatment with niobium phosphate and pH improvement synergize to enhance hydrogenogenesis, integrating wastewater treatment and renewable biohydrogen production.
Mid-Neoproterozoic extensional tectonics in the Larsemann Hills, East Antarctica: Implications for Indo-Antarctic correlation in Rodinia
Publication . Chatterjee, Sandro; Dev, J. Amal; Debnath, Aishi; Ghosh, Anuj; Dey, Soham; Mukherjee, Anik; Arora, Devsamridhi; Tomson, Joseph Kallukalam; Guimarães, Fernanda; Pant, Naresh Chandra; Gupta, Saibal
ABSTRACT: The supercontinents Rodinia and Gondwana are believed to have assembled through orogenic events at similar to 1000 Ma and similar to 550 Ma, respectively. The Larsemann Hills, part of the extended Rayner Complex of East Antarctica, is a Neoproterozoic granulite terrane that was a part of both supercontinents. The tectonic evolution of the terrane in the Rodinia to Gondwana interval remains uncertain. This study integrates new field, microstructural, metamorphic and geochronological information to unveil a previously undocumented mid-Neoproterozoic thermo-tectonic event in the Larsemann Hills. Granulite facies metamorphism (M-1), synchronous with the deformation, D-1, is interpreted to have occurred in the Larsemann Hills at similar to 1000 Ma, followed by a crustal shortening (D-2) event that continued from similar to 990-900 Ma, signifying the incorporation of the Rayner crustal unit into Rodinia. Subsequent mid-Neoproterozoic extensional deformation (D-3), characterized by NW-SE trending S-3 shear zones, reoriented pre-existing structural fabrics. The extensional deformation operated under amphibolite facies metamorphic conditions (M-2) and resulted in a post-peak decompressive P-T trajectory. UPb LA-ICPMS dates on zircons separated from metapelites within high D-3 strain zone yield clusters at similar to 700 Ma; zircons immediately adjacent to the shear zone yield ages around similar to 990-900 Ma. A thermal overprint at similar to 550 Ma is evident but weakly manifested in the western Larsemann Hills, with no unambiguously correlatable structural or metamorphic evidence, suggesting distance from the Gondwana orogenic front. The extensional deformation documented here is contemporaneous with extension in the northern Eastern Ghats Province, India that was contiguous with the Rayner Complex in the Neoproterozoic. This suggests that a major terrane-wide extensional event was associated with the disintegration of Rodinia. In the Neoproterozoic, the EGP-Rayner unit was therefore a tectonic entity distinct from cratonic India, with only the former being an integral component of Rodinia.
Unit Sizing and Feasibility Analysis of Green Hydrogen Storage Utilizing Excess Energy for Energy Islands
Publication . Koca, Kemal; Dursun, Erkan; Bekçi, Eyüp; Uçar, Suat; AKPOLAT, Alper Nabi; Tsami, Maria; Simões, Teresa; Tesch, Luana; AKSÖZ, Ahmet; Borg, Ruben Paul
ABSTRACT: This study examines whether green hydrogen production using combined wind and solar energy on Marmara Island can meet the island's electricity demand and fuel the fuel needs of a hydrogen-powered ferry. A hybrid system consisting of a 10 MW wind farm, a 3 MW solar PV system, and a PEM electrolyzer sized to meet the island's hydrogen demand was modeled for the island, located in the southwestern Sea of Marmara. The hydrogen production potential, energy flows, and techno-economic performance were evaluated using HOMER-Pro 3.18.4 version. According to the simulation results, the hybrid system generates approximately 62.6 GWh of electricity annually, achieving an 82.8% renewable energy share. A significant portion of the produced energy is transferred to the electrolyzer, producing approximately 729 tons of green hydrogen annually. The economic analysis demonstrates that the system is financially viable, with a net present cost of USD 61.53 million and a levelized energy cost of USD 0.175/kWh. Additionally, the design has the potential to reduce approximately 2637 tons of CO2 emissions over a 25-year period. The results demonstrate that integrating renewable energy sources with hydrogen production can provide a cost-effective and low-carbon solution for isolated communities such as islands, strengthening energy independence and supporting sustainable transportation options. It has been demonstrated that hydrogen produced by PEM electrolyzers powered by excess energy from the hybrid system could provide a reliable fuel source for hydrogen-fueled ferries operating between Marmara Island and the mainland. Overall, the findings indicate that pairing renewable energy generation with hydrogen production offers a realistic pathway for islands seeking cleaner transportation options and greater energy independence.
Enhanced borohydride oxidation kinetics with Au@MOF-808 nanocomposite electrocatalysts with ultra-low Au loading
Publication . Belhaj, Ines; Becker, J. Alexander; Viana, Alexandre M.; Gusmão, Filipe M. B.; Chaves, Miguel; Pereira, Eulália; Sljukic, Biljana; Balula, Salete S.; Silva, Luis Cunha; Santos, Diogo M. F.
ABSTRACT: The highly stable metal-organic framework (MOF) composed of[Zr6O4(mu 3-OH)4(OH)6(H2O)6(BTC)2]& sdot;nH2O units (MOF-808) was modified by incorporating gold (Au) nanoparticles and functional groups to enhance electrocatalytic activity for the borohydride oxidation reaction (BOR). Three composite materials (Au@MOF-808, Au@MOF-808-NH2, and Au@MOF-808-SH) were prepared by the incorporation of Au in structurally related MOFs, MOF-808, MOF-808-NH2, and MOF-808-SH, respectively. These composite materials were evaluated as anodic electrocatalysts for BOR in alkaline media using cyclic voltammetry and chronoamperometry. Among the prepared materials, Au@MOF-808-NH2 exhibited the highest BOR activity, with an apparent activation energy of 15.3 kJ mol-1, a reaction order of 0.6, an anodic charge transfer coefficient of 0.63, and a number of exchanged electrons of 4.4. The latter was significantly below the theoretical eight-electron value, indicating the presence of alternative reaction pathways. Notably, this material achieved a high mass-specific BOR peak current of 4.23 A mu gAu-1, demonstrating outstanding electrocatalytic efficiency despite the ultralow noble metal loading. These results underscore the potential of Au@MOF-808-NH2 as a cost-effective and scalable anodic electrocatalyst for high-performance direct borohydride fuel cells.
Novel approach to location planning of hydrogen refueling stations: How market drivers and existing infrastructure impact the hydrogen economy
Publication . Espinha, Maria; Portillo, Juan C. C.; Simoes, Sofia; Barbosa, Juliana Pacheco
ABSTRACT: This study aims to present a novel methodology to assess future potential location of hydrogen refueling stations (HRS), involving geospatial and levelized costs of hydrogen (LCOH) analyses. This methodology entails five stages and was developed and applied to mainland Portugal. It can be used in other regions or countries. In this study, a total of 708 potential locations for different HRS were identified and studied for five scenarios. The results indicate that LCOH varies between a minimum of 6.5 €/kg H and a maximum of 11.2 €/kg H. Moreover, 3 574 routes were analyzed considering four hydrogen production sites and the five scenarios, of which 2 395, or 67% of the routes, have a LCOH of between 6 - 9 €/kg H. The main conclusions of the study indicate that there are significant regional disparities in Portugal and that the adoption of hydrogen as an alternative fuel still presents challenges, especially in regions with limited hydrogen refueling infrastructure. The uneven distribution of hydrogen infrastructure and the high associated costs are likely to further exacerbate these economic and technological disparities. Addressing these imbalances requires the development of regional strategies that encourage, for example, hydrogen production in remote and underserved regions.