ESTiG - Artigos em Revistas Indexados à WoS/Scopus
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Percorrer ESTiG - Artigos em Revistas Indexados à WoS/Scopus por Objetivos de Desenvolvimento Sustentável (ODS) "07:Energias Renováveis e Acessíveis"
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- Accessible power for medical equipment in remote healthcare: a solution for single-phase power generation using three-phase induction machinesPublication . Romeiro, Bruno; Oliveira, Carlos; Hildenberg, Cicero; Ferreira, Ângela P.; Filho, FranciscoThis work was motivated by the urgent need for reliable electricity in remote areas where conventional power distribution, and consequently access to healthcare, remains impractical. The proposed system is a practical alternative to conventional synchronous generators commonly used in off-grid applications, which have high implementation and maintenance costs and potential risks in healthcare applications due to the spark generated by the brushes. We propose the use of a self-excited single-phase generator, derived from a three-phase induction machine, as a robust, low-cost, highly reliable and safe solution for supplying electrical power to medical applications in remote locations. The work presents a mathematical model based on the theory of symmetrical components, which incorporates frequency variation and unbalanced system operation, along with an analytical methodology to determine the capacitance values required for this application and all system elements, including the definition of the sizing factors KE and KM. The proposed approach allows for rigorous design without relying on empirical procedures as commonly presented in the literature, and is experimentally validated using real medical loads. Our experimental setup incorporates current medical devices, including three infusion pumps, a cardioverter-defibrillator, and a patient monitoring device. Despite modest voltage imbalances observed during steady-state operation, all medical devices maintained adequate functionality during testing. The transient response during load switching showed damped oscillations before returning to steady-state operation, demonstrating stable voltage and frequency behavior without the use of active electronic control. The generator demonstrated satisfactory voltage regulation and short-circuit self-protection capabilities without the need for complex systems, making it economically viable for deployment in resource-constrained environments. These results suggest that the proposed configuration offers a practical solution for the electrification of medical facilities in regions where grid extension remains challenging or prohibitively expensive.
- Harnessing geothermal energy in kazakhstan: techno-economic assessment of organic rankine cycle application in the almaty regionPublication . Abdlakhatova, Nazym; Ribeiro, Luís Frölén; Savosh, Larysa; Orynbayev, Seitzhan; Tokmoldayev, Amanzhol; Zhussip, TalgatThis study assesses the feasibility of geothermal electricity generation in Kazakhstan using Organic Rankine Cycle (ORC) systems to exploit low-to medium-temperature geothermal resources. ORC systems efficiently convert heat from moderate-temperature sources into electricity using organic fluids with boiling points lower than that of water. Globally, ORC systems contribute over 3 GW of installed capacity, accounting for 25.1 % of geothermal power production. Kazakhstan's electricity generation rose from 85.3 TWh in 2013 to 98.4 TWh in 2023, with associated COQ emissions increasing from 67.4 to 77.0 million tonnes. Despite known geothermal reserves, the country has not yet developed geothermal power capacity. This study identifies the geothermal potential of the Mangystau-Ustyurt and Almaty Artesian basins, with a focus on the Zharkent field. Among the wells evaluated, Well 5539, with a wellhead temperature of 103 degrees C, is estimated to generate 5.467 TWh of electricity annually, accounting for 51.9 % of the regional potential. Wells 1-RT and 2-TP also show strong promise, with annual outputs of 2.471 and 2.598 TWh, respectively. Thermal power availability ranges from 5.1 to 8.3 MW, and the combined yearly potential of 10.5 TWh could offset 82.1 % of the Almaty region's electricity deficit and avoid 5.47 million tonnes of COQ emissions annually. The methodology includes thermodynamic modelling and well data analysis to estimate geothermal electricity potential. This study represents the first assessment of ORC-based geothermal power in Kazakhstan for low-temperature wells in a specific region.
- On-site power generation using biogas in sewage treatment plants: a techno-economic assessment of a brazilian uasb facilityPublication . Pérez, Nestor Proenza; Adrião Cabral, Edilson; Bimestre, Thiago Averaldo; Loures, Carla Almeida; Yepes Maya, Diego M.; Ribeiro, Luís FrölénSmall sewage treatment plants (STPs) in developing regions often flare the biogas produced in their upflow anaerobic sludge blanket (UASB) reactors, giving away a cost-effective energy source. This study tests whether on-site biogas-to-energy can pay for itself in approximately 2 years, even in plants treating less than 30 l s(-1). A small-scale STP in Angra dos Reis, Brazil (25 L/s), was studied, with an average biogas flow of 9.7 m(3)/h; electricity generation was modeled for an engine generator unit with an efficiency of 30%. The techno-economic results show that the actual system would generate 125 MWh/year at a levelized cost of 0.017-0.023 USD/kWh, covering 47% of the plant's electricity demand. At a discount rate of 8%, the net present value was + 9.3 k US$, and the simple payback period was 2 years for the initial investment. Additionally, extrapolating the results to account for future expansion of the sewage treatment plant based on the total population in the region served by the system reveals even more promising results, with a suggested payback period of 1 year and 1 month of operation, covering approximately 57% of electricity demand. Scaling this retrofit to the approximately 18,000 comparable UASB-based STPs worldwide at low capital cost could reduce electricity bills by approximately 40% and avoid similar to 450 tons of CO2-eq. per plant per year through methane capture and displacement of electricity from the grid. These results confirm that decentralized biogas power generation on a small scale is not only technically feasible, but also financially attractive and ecologically beneficial for operators of sewage and wastewater treatment plants and municipalities.
- On‐site power generation using biogas in sewage treatment plants: a techno‐economic assessment of a brazilian UASB facilityPublication . Pérez, Nestor; Cabral, Edilson; Bimestre, Thiago; Loures, Carla; Maya, Diego; Ribeiro, Luís FrölénSmall sewage treatment plants (STPs) in developing regions often flare the biogas produced in their upflow anaerobic sludge blanket (UASB) reactors, giving away a cost-effective energy source. This study tests whether on-site biogas-to-energy can pay for itself in approximately 2 years, even in plants treating less than 30 l s−1. A small-scale STP in Angra dos Reis, Brazil (25 L/s), was studied, with an average biogas flow of 9.7 m3/h; electricity generation was modeled for an engine generator unit with an efficiency of 30%. The techno-economic results show that the actual system would generate 125 MWh/year at a levelized cost of 0.017–0.023 USD/kWh, covering 47% of the plant’s electricity demand. At a discount rate of 8%, the net present value was + 9.3 k US$, and the simple payback period was 2 years for the initial investment. Additionally, extrapolating the results to account for future expansion of the sewage treatment plant based on the total population in the region served by the system reveals even more promising results, with a suggested payback period of 1 year and 1 month of operation, covering approximately 57% of electricity demand. Scaling this retrofit to the approximately 18,000 comparable UASB-based STPs worldwide at low capital cost could reduce electricity bills by approximately 40% and avoid ~ 450 tons of CO2-eq. per plant per year through methane capture and displacement of electricity from the grid. These results confirm that decentralized biogas power generation on a small scale is not only technically feasible, but also financially attractive and ecologically beneficial for operators of sewage and wastewater treatment plants and municipalities.
- Optimization approaches in electric machine design: insights from a bibliometric analysisPublication . Nascimento, Cecilia Pagnozzi do; Silvério, Ana Cristina; Baptista, Bruno; Carvalho, José Augusto; Bazzo, Thiago; Ferreira, Ângela P.Optimizing the design of electric machines is a complex task due to the large number of interrelated geometric and physical parameters that influence performance, efficiency, cost, and sustainability. Numerous deterministic and stochastic optimization techniques have been developed to address these challenges, each presenting distinct advantages and limitations. Deterministic approaches, though computationally efficient, often converge to local minima, while stochastic methods provide broader search capabilities at the expense of higher computational effort. Despite the growing application of optimization in electric machine design, a comprehensive bibliometric overview of this research area is lacking. This study aims to fill that gap by conducting a bibliometric analysis of optimization methods applied to electric machine design. Using data retrieved from the Web of Science (WoS) and analyzed through co-citation mapping with VOSviewer, 246 relevant articles were examined, resulting in a focused sample of 73 key studies. The analysis identifies the most frequently optimized machine types, the main optimization objectives, and the predominant methodologies employed in recent years. By addressing these dimensions, this work provides a conceptual reference framework to guide both academic researchers and industry professionals in selecting appropriate optimization strategies. The results also highlight emerging trends and future research opportunities, contributing to a deeper understanding of the evolution and intellectual structure of optimization in electric machine design.
- Pressure-loss coefficients of Newtonian fluid flows in axisymmetric diffusersPublication . Rosa, Sérgio; Cavadas, AdelioA comprehensive numerical investigation was conducted on the flow of Newtonian fluids in axisymmetric diffusers across laminar, transitional, and turbulent regimes to quantify the pressure-loss coefficient as a function of Reynolds number, diffuser angle, and diameter expansion ratio. Simulations were performed using ANSYS Fluent software for Reynolds numbers ranging from 2 to 4 x 10(6), diffuser angles varying from 5 degrees to 90 degrees, and expansion ratios of 1.15, 1.5, and 2. The pressure-loss results are systematically presented in graphics and tables, offering detailed insight into the influence of geometric and flow characteristics on axisymmetric diffuser pressure drop. The complete dataset and a Python interpolation tool are provided as supplementary material to facilitate direct application in engineering analysis.