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Planning of electrical energy for the Galapagos Islands using different renewable energy technologies
(Elsevier, 2021-10-30) Arévalo, Paul; Eras-Almeida, Andrea; Cano-Ortega, Antonio; Jurado-Melguizo, Francisco; Egido-Aguilera, Miguel Ángel
The present study focuses on the planning of electrical energy for the Galapagos islands using different renewable energy technologies for the year 2031 in order to reduce diesel consumption and achieve 100% renewable energy share. To do that, a long-term load demand forecast study on the Santa Cruz and Baltra islands (Galapagos), applying Artificial Neural Networks, is done. Then, to optimize the islands’ power system, mostly based on diesel generation, different renewable energy technologies together with energy storage systems, such as batteries and hydraulic pumping, have been analyzed through the application of the HOMER Pro software. For this purpose, two energy control models have been developed to gradually reduce the operating hours of the diesel power plant. The results show that these islands can achieve 100% renewable penetration with the following configuration: photovoltaic/wind turbines/batteries/pumping hydroelectric storage system/diesel generators (only as back-up). This implies increasing the photovoltaic capacity by 26 MWp and installing a pumped hydraulic storage of 374 MWh. In this way, the electricity generation cost would be reduced from $ 0.32/kWh to $ 0.23/kWh, and the CO2 emissions would decrease by 16,000 tons of CO2 into the environment.
Comparative analysis of HESS (battery/supercapacitor) for power smoothing of PV/HKT, simulation and experimental analysis
(Elsevier, 2022-09-17) Cano-Ortega, Antonio; Arévalo, Paul; Benavides, Darío; Jurado-Melguizo, Francisco
Photovoltaic and hydrokinetic systems are increasing their penetration in electrical distribution systems. This leads to problems of power fluctuations due to the intermittence of renewable sources that could compromise the stability and quality of the power grid. To address this issue, this paper presents a feasibility study of three power smoothing methods for a photovoltaic-hydrokinetic system using laboratory equipment to optimally replicate the real behavior of this type of hybrid system. The proposed algorithms are based on a hybrid storage system with supercapacitors and lithium-ion batteries, several analyzes are presented based on technical and economic parameters.
The results demonstrate the feasibility of power smoothing methods for real systems, the comparison between the algorithms highlights the characteristics of the Enhanced Linear Exponential Smoothing Method, reducing the energy cost and regulating the point of common coupling voltage. Moreover, the sensitivity studies show that the energy exchange with the utility grid is affected according to the variations in the capacity of the batteries and the response to power smoothing can decrease or improve depending on the size of the supercapacitors.
A comparison of sizing methods for a long-term renewable hybrid system. Case study: Galapagos Islands 2031
(The Royal Society of Chemistry, 2021-02-04) Cano-Ortega, Antonio; Arévalo, Paul; Jurado-Melguizo, Francisco
This research compares different sizing methods to improve the current autonomous hybrid system in the Galapagos Islands in the year 2031, analyzing the loss of power supply probability (LPSP). In the first place, the energy consumed in the islands for the year 2031 has been obtained, using ANN artificial neural networks with Matlab, from fundamental parameters in the design of a multilayer perceptron neural network model. Second, the methods used for sizing the system are HOMER Pro and Simulink Design Optimization (SDO). The dynamic models of the different components of the hybrid system have been made in MATLAB/Simulink. The proposed hybrid system is composed of PV photovoltaic and WT wind, and lead-acid batteries, hydraulic pumping, and diesel generator as storage and support systems. Then, in order to design a sustainable system, a hybrid system has been dimensioned with renewable energy sources of an appropriate size. The LPSP values obtained are below 0.09% and 0.22%, which shows that the system has been optimally dimensioned. In addition, a cost analysis has been carried out, the values obtained from NPC and COE according to HOMER Pro are $ 183,810,067 and 0.26 $/kWh, and $ 233,385,656 and 0.25 $/kWh and using SDO are $ 148,523,110 and 0.25 $/kWh, $ 189,576,556 and 0.24 $/kWh for strategies I and II respectively of the proposed hybrid system. The data obtained shows that SDO's Latin Hypercube algorithm achieves a better optimization compared to HOMER Pro.Abstract text goes here. The abstract should be a single paragraph that summarises the content of the article.
Determination of the power smoothing effect in a photovoltaic-hydrokinetic system by experimental analysis and pattern search
(Elsevier, 2023-03-26) Arévalo , Paul; Cano-Ortega, Antonio; Jurado-Melguizo, Francisco
Sizing optimization and power smoothing methodology in highly fluctuating grid-connected renewable systems represent important challenges nowadays, the total cost and energy quality depend on the effective balance between source and load with certain restrictions to increase reliability and enhance the use of renewable sources at all scales. This article presents a novel power smoothing effect and sizing optimization methodology for a grid-connected photovoltaic-hydrokinetic system by pattern search method comparatively with three optimization algorithms encompassing a multi-objective optimization. In this context, the method considers the reduction of power fluctuations using supercapacitors, where the objective function considers technical and economic indexes. The main contribution of the research is that the objective function decreases the fluctuation suppression ratio to sizing optimization of renewable system through three pattern search size optimization algorithms. Experiments have shown that pattern search method can find the global optimum by reducing the computational effort; the Latin hypercube algorithm reduces the photovoltaic capacity by approximately 5% and 2.3% with respect to the Nelder Mead and genetic algorithm respectively. The influence of the supercapacitor successfully reduces power fluctuations and causes an increase in self-consumption of 32.32%, this result represents an annual cost savings of 42% on energy purchased from the grid. Furthermore, this paper goes further by calculating the optimal location of a hydrokinetic turbine in a river using the HEC-RAS software to determine with high precision the HKT power fluctuations as input signal to novel proposed method.
Anxiety in young university students: the mediating role of sense of coherence and self-esteem
(BMC, 2025-10-03) da-Silva-Domingues, Henrique; Palomino-Moral, Pedro Ángel; del-Pino-Casado, Rafael
Background: Anxiety is a frequent mental health concern among university students, shaped by psychological, social, academic, and economic influences. While previous studies have linked anxiety to factors such as social support, family functioning, sense of coherence, and self-esteem, the mediating role of sense of coherence and self-esteem remains unclear. This study investigates these relationships, with particular attention to the potential mediating effects. The present study aimed to investigate the relationships between social support, family functioning, sense of coherence, self-esteem, and anxiety, with an emphasis on the mediating role of sense of coherence and self-esteem.
Methods: The study included 530 university students from public universities in Andalusia (Spain), selected through stratified multistage cluster sampling. Analyses included descriptive statistics, Pearson correlations, t-tests, and path analysis.
Results:The mean age of university students was 20.11 years. The majority of participants in the study were women (56.6%). More than 60% of university students considered themselves anxious. Anxiety was strongly and negatively associated with sense of coherence and self-esteem, and moderately negatively associated with social support and family functioning. Path analysis indicated that the model explained 69% of the variance in anxiety and 49% of self-esteem.
Conclusions: Our findings suggest that social support and family functioning influence anxiety levels in university students, with sense of coherence and self-esteem acting as key mediators. Higher levels of both are linked to lower anxiety and better student well-being.