Browsing by Issue Date, starting with "2025-07"
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- Techno-economic analysis of a renewable energy based multigeneration system for zero energy buildingsPublication . Aelenei, Laura Elena; Rodrigues, Carlos; Brites, Maria João de Sousa; Viana, SusanaABSTRACT: The present study explores the contribution and benefits of a renewable energy based multigeneration prototype integrating a luminescent compound parabolic concentrator, a photovoltaic/thermal system and thermal storage using phase change materials. A numerical model was developed for assessing the energy performance of the prototype and the results are presented for three different European locations. A simplified economic analysis was also developed and presented for two different scenarios and the same European locations. The results reveal that the installation of the IDEAS system in Lisbon, with a total estimated yearly use of solar energy of 1215 kWh and an amount of energy sold to the grid of 40.6 kWh, results in savings of 266 (26 % of energy bill). For the Ferrara location, with a total estimated yearly use of solar energy of 967 kWh and 19.8 kWh of energy sold to the grid of, results on 229 (16 % of energy bill) of annual savings. In Dublin, with a total estimated yearly use of solar energy of 862 kWh and an amount of energy sold to the grid of 20.5 kWh, results on annual savings of 257 (14 % of energy bill).
- Industrial Off-Gas Fermentation for Acetic Acid Production: A Carbon Footprint Assessment in the Context of Energy TransitionPublication . Pacheco, Marta; Brac de la Perrière, Adrien; Moura, Patrícia; silva, carlaABSTRACT: Most industrial processes depend on heat, electricity, demineralized water, and chemical inputs, which themselves are produced through energy- and resource-intensive industrial activities. In this work, acetic acid (AA) production from syngas (CO, CO2, and H2) fermentation is explored and compared against a thermochemical fossil benchmark and other thermochemical/biological processes across four main Key Performance Indicators (KPI)—electricity use, heat use, water consumption, and carbon footprint (CF)—for the years 2023 and 2050 in Portugal and France. CF was evaluated through transparent and public inventories for all the processes involved in chemical production and utilities. Spreadsheet-traceable matrices for hotspot identification were also developed. The fossil benchmark, with all the necessary cascade processes, was 0.64 kg CO2-eq/kg AA, 1.53 kWh/kg AA, 22.02 MJ/kg AA, and 1.62 L water/kg AA for the Portuguese 2023 energy mix, with a reduction of 162% of the CO2-eq in the 2050 energy transition context. The results demonstrated that industrial practices would benefit greatly from the transition from fossil to renewable energy and from more sustainable chemical sources. For carbon-intensive sectors like steel or cement, the acetogenic syngas fermentation appears as a scalable bridge technology, converting the flue gas waste stream into marketable products and accelerating the transition towards a circular economy.
- Oceanos e continentes: no fim dos séculos XV e XX, e no início do século XXIPublication . Ribeiro, AntónioRESUMO: Durante os séculos XV e XVI, os descobridores portugueses substituíram a geografia Mediterrânica pela Atlântica. De algum modo, é possível estabelecer um paralelo com a perspetiva atual da Tectónica de Placas Macias, em que a litosfera oceânica arrasta a litosfera rígida dos escudos pré-câmbricos.
- Comparison of the corrosion of ferritic and austenitic stainless steel (AISI 430 and AISI 316L) with LiNaK carbonate salts for thermal energy storage in CSP/CST applicationsPublication . Gil, Mafalda; Pedrosa, Fátima; Paiva Luís, Teresa; Figueira Vasques, Isabel; Oliveira, Fernando; Cunha Diamantino, TeresaABSTRACT: This study focuses on the corrosion rates and mechanisms of two stainless steels, austenitic AISI 316L and ferritic AISI 430, in contact with a eutectic mixture of LiNaK carbonates in long-term tests at 650 degrees C. The selection of these two stainless steels was based on their differences, both in their intrinsic characteristics and in the cost associated with each one. The research also underscores the importance of optimizing the descaling methods used to evaluate the corrosion rate. Corrosion rates were measured gravimetrically according to ISO 17245:2015, revealing an asymptotic behavior for both steels, with AISI 430 with a corrosion rate of 237 f 21 mu m and AISI 316L of 151 f 13 mu m after 2000 h of testing. Corrosion mechanisms were analyzed using SEM/EDS, GDOES, and XRD techniques, which identified well-defined oxide layers with varying compositions. Given the observed corrosion mechanisms and its lower cost, AISI 430 steel seems to have great applicability in CSP/CST plants, provided it is paired with an appropriate protective coating.
- Editorial: The biorefineries and application of green technologies for recovering bioactive compounds from microalgaePublication . Vladic, Jelena; Gouveia, LuisaABSTRACT: Microalgae are attracting growing scientific and industrial interest as a renewable and versatile source of high-value bioactive compounds, including pigments, fatty acids, proteins, and antioxidants. Their rapid growth, ability to adapt to extreme conditions, and rich biochemical composition make them a promising resource for sustainable development across a range of applications. From cosmetics to food supplements, their potential spans multiple industries. Still, the considerable gap between encouraging laboratory research and commercially viable production remains. One of the major challenges lies in developing methods for extracting and preserving these compounds in ways that are both efficient and environmentally responsible.
- Consortium of microalgae/nitrogen-fixing bacteria as a next-generation biofertilizer, biostimulant and biopesticidePublication . Gouveia, Luisa; Ferreira, Alice; Bastos, Carolina R. V.; Avetisova, Gayane; Karapetyan, Zh.; Toplaghaltsyan, A.; Melkonyan, LusineABSTRACT: This study aims to provide insights into a new consortium of a microalga, twelve nitrogen-fixing (N-fixing) bacteria and a cyanobacterium. The microalga Tetradesmus obliquus (T), in conjunction with various N-fixing bacteria and the cyanobacterium Synechocystis sp. PCC 6803 (S), the N-fixing bacterium Sphingobacterium sp. L13G8 (5), cultivated in complete Bristol medium and in Bristol-NaNO3 free conditions, were examined. The study encompassed the analysis of their consortia, including evaluation of their growth, and potential as a biostimulant, biofertilizer and biopesticide, and assessed for sedimentation performance for targeted applications. The T and N-fixing bacteria consortia had higher growth in Bristol NaNO3-free media. The triple culture TS5 had the highest growth parameter (2.4 OD540) in the same medium, followed by T5. The consortia were employed to ascertain the efficacy of their biostimulants and biofertilizers on watercress (Lepidium sativum) and to determine the potency of their biopesticides against the fungal pathogens Fusarium oxysporum and Rhizoctonia solani (in certain consortia). Consortium T5 demonstrated the most significant impact on the seeds germination index (212.7%) and root length (6.0 cm) of L. sativum. The same consortium had a significant impact on the shoot length (4.4 cm) of L. sativum. Among all consortia that were examined, T5 exhibited significant inhibitory effects on the growth of F. oxysporum (60.6%) and R. solani (69.2%). In the same consortium, the rate of microalgal biomass sedimentation was enhanced by the N-fixing bacterium (0.4 cm h-1). Consortium T5 was the most effective in relation to growth and biomass sedimentation efficiency, in addition to its use as a biostimulant, biofertilizer and biopesticide. The created combination of microalga and N-fixing bacterium represents significant progress in the field of microalga cultivation, with notable benefits including improved biomass sedimentation and enhanced agricultural practices, as well as environmental friendliness and safety.
- Monitoring C. vulgaris Cultivations Grown on Winery Wastewater Using Flow CytometryPublication . Lopes da Silva, Teresa; Silva, Thiago; França, Bruna Thomazinho; Ribeiro, Belina; Reis, AlbertoABSTRACT: Winery wastewater (WWW), if released untreated, poses a serious environmental threat due to its high organic load. In this study, Chlorella vulgaris was cultivated in diluted WWW to assess its suitability as a culture medium. Two outdoor cultivation systems-a 270 L raceway and a 40 L bubble column-were operated over 33 days using synthetic medium (control) and WWW. A flow cytometry (FC) protocol was implemented to monitor key physiological parameters in near-real time, including cell concentration, membrane integrity, chlorophyll content, cell size, and internal complexity. At the end of cultivation, the bubble column yielded the highest cell concentrations: 2.85 x 106 cells/mL (control) and 2.30 x 106 cells/mL (WWW), though with lower proportions of intact cells (25% and 31%, respectively). Raceway cultures showed lower cell concentrations: 1.64 x 106 (control) and 1.54 x 106 cells/mL (WWW), but higher membrane integrity (76% and 36% for control and WWW cultures, respectively). On average, cells grown in the bubble column had a 22% larger radius than those in the raceway, favouring sedimentation. Heterotrophic cells were more abundant in WWW cultures, due to the presence of organic carbon, indicating its potential for use as animal feed. This study demonstrates that FC is a powerful, real-time tool for monitoring microalgae physiology and optimising cultivation in complex effluents like WWW.
- Fractionation of macroalgae carbohydrates using hydrothermal and dilute inorganic salt pretreatments to produce oligosaccharides and furansPublication . Martins, Pedro L.; Andrade, Cristiana; Duarte, Luís; Reis, Alberto; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: Furans are among the most important compounds derived from biomass, providing conversion pathways for sustainable alternatives to petroleum-based fuels and materials. Furfural, 5-hydroxymethylfurfural (5-HMF), and 5-methylfurfural (5-MF) are furans that can be obtained by carbohydrate dehydration under acidic conditions at elevated temperature and pressure. One of the mechanisms to produce these compounds from lignocellulosic materials relies on prior fractionation of biomass carbohydrates and further dehydration catalysis. However, this is a costly and technically challenging method and it would be advantageous to develop a one-pot conversion mechanism that facilitates simultaneous biomass fractionation and conversion to furans. Ulva lactuca is an alga that has the advantage of being lignin-free and rich in glucose, rhamnose, and xylose, which are ideal for producing 5-HMF, 5-MF, and furfural, respectively. The high diversity of sugar constituents is also relevant for the production of added-value oligosaccharides. Catalysis with inorganic salts has been reported as a successful tool for biomass upgrading to furans when combined with hydrothermal pretreatments, and could provide a cheap and environmentally friendly one-step methodology for furan production. This study therefore aimed to investigate the effect of hydrothermal and dilute acid pretreatments, as well as treatment with inorganic salt solutions (ferric chloride, ferric nitrate, and aluminium nitrate) on U. lactuca biomass to produce oligosaccharides, monosaccharides, and furans (furfural, 5-HMF, and 5-MF). These methods resulted in a maximum sugar solubilization of 65% in non-salt-assisted hydrothermal pretreatments and 84% in salt-assisted hydrothermal pretreatments, with inorganic salt catalysis also resulting in 100% xylose, 36% glucose, and 46% rhamnose conversion to the respective furans.
- Mechanical Performance of Ceria-Coated 3D-Printed Black Zirconia Cellular Structures After Solar Thermochemical CO/H2 Fuel Production CyclesPublication . Oliveira, Fernando; Sardinha, Manuel; Justino Netto, Joaquim Manoel; Leite, Marco; Farinha, Miguel; Barreiros, Maria Alexandra; Abanades, Stéphane; Fernandes, JorgeABSTRACT: 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.
- The Role of Demand and Vres Flexibility in Carbon-Neutral Power Systems: Insights from Portugal and Spain in Prospective 2050 ScenariosPublication . Algarvio, Hugo; Couto, António; Lopes, Fernando; Estanqueiro, Ana; Faia, Ricardo; Santos, Gabriel; Carvalho, Rui; Faria, Pedro; Vale, ZitaABSTRACT: The goal of a carbon-neutral society by 2050 is speeding up the integration of variable renewable energy sources (vRES) in European power systems. For the expected levels of vRES, the adaptation of the demand will be crucial to manage the stochastic behaviour of these technologies. This work evaluates the impact of four prospective 2050 energy mix scenarios in the Iberian electricity market. All scenarios consider near 100% vRES shares. Scenarios that incentivize demand flexibility (S2 and S4) result in the lowest wholesale prices and costs for society. Peak load reduction using demand response occurred in the two scenarios (S1 and S3) with low demand flexibility and high share of renewable generation. S3 is the most unstable leading to the higher wholesale prices. The results highlight that an equilibrium between demand flexibility and investments in the generation side is essential for reducing costs and ensuring stability.