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Item type:Publication, Genetic algorithms-based size optimization of directly and indirectly coupled photovoltaic-electrolyzer systems(Elsevier Ltd, 2022-10-15)Since relatively high costs and low efficiencies are usually associated with photovoltaic-electrolyzer (PV-EL) systems, the coupling of a PV system to an EL one is a critical aspect when sizing PV-EL systems. Accordingly, using a genetic algorithms-based optimization approach and considering a hydrogen production target of 100 g per day, the size of different directly and indirectly coupled PV-EL systems is optimized in this work. The referred optimization processes are carried out for five PV-EL system configurations, one related to directly coupled systems and four (one per each DC/DC converter topology accounted for) to indirectly coupled ones. In addition, seeking to maximize hydrogen production, minimize losses, and increase system efficiency, four objective functions are assessed. Some of the results highlight that, when using system cost and overall efficiency as objective functions, properly sized indirectly coupled PV-EL systems feature lower implementation costs than directly coupled ones. In addition, the differences in the overall efficiencies characterizing the optimum directly and indirectly coupled PV-EL systems so determined are relatively small (>1%). One of the original contributions of this work relates to the fact that this is one of the first works dealing with optimization processes of both directly and indirectly coupled PV-EL systems, where optimum system configurations are compared with each other. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, On the application of sliding mode control to indirectly coupled photovoltaic-electrolyzer systems used in the production of clean energy(Elsevier B.V., 2024-08-01)To improve the performance of photovoltaic-electrolyzer (PV-EL) systems, it is key to operate them at the right operating conditions, not only at design point but also at off-design. In addition, when directly coupling a PV system to an EL one, an ideal sizing of the resulting PV-EL coupled system ensuring the best interaction between the PV system and the EL stack is not always possible. Coupling indirectly PV systems to EL ones, through DC/DC converters for instance, results thus advantageous. Accordingly, this work discusses the application of sliding mode control (SMC) to indirectly coupled PV-EL systems, which allows them to operate as efficient as possible. The control scheme employed here includes mathematical models for both the PV system and the EL stack, and for the DC/DC converter and the sliding mode control algorithm utilized. To determine their influence on the obtained results, two different converter topologies are assessed here. Some of the results obtained emphasize that using a DC/DC converter can significantly increase the hydrogen produced by PV-EL systems, especially when it is paired with a control algorithm like SMC. This effort represents one of the first works involving the application of sliding mode control to indirectly coupled PV-EL systems. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Effective Thermal-Electric Control System for Hydrogen Production Based on Renewable Solar Energy(Elsevier BV, 2023-12-14)This paper focuses on the design and use of a control system for a renewable energy production plant based on hydrogen. The proposed control system aims at ensuring the stability and smooth functionality of the plant, which consists of a (i) photovoltaic... - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Phase stability and tunable structural, hyperfine, and magnetic properties of Sol–Gel FeNi nanoparticles(Elsevier, 2026)In this study, Fe50Ni50 powder alloys were synthesized successfully using the sol–gel method, followed by systematic thermal treatments up to 1000 °C in a reducing atmosphere (Ar-H). Synchrotron X-ray diffraction patterns indicate that the data are well modeled by face-centered cubic (FCC) FeNi phase. The stability of this phase was studied, revealing that as the temperature is increased, the unit cell volume changes, suggesting an enhancement in the migration of iron atoms. This migration alters the stoichiometry of the FeNi alloy, potentially shifting it beyond its nominal 50/50 composition. High resolution TEM demonstrated the formation of the FeNi phase, which is in good agreement with the results obtained by XRD. Additionally, only a slight increase in crystalline particle size was observed. Magnetic characterization shows that thermal annealing strongly influences the magnetization. In particular, the sample annealed at 700 °C exhibits the highest magnetization and a Curie temperature 805 K, highlighting the role of thermal treatments in tuning the magnetic response. Zero-field cooling and field cooling measurements in the range 5–380 K further reveal irreversibilities above room temperature, attributed to the small particle size and strong interparticle interactions, which significantly affect the coercive field and overall magnetic behavior. These FeNi nanoparticles were characterized as magnetically soft materials. Mössbauer spectroscopy confirms the ferromagnetic behavior of the cubic FeNi phase as shown by XRD. Increasing the treatment temperature produces an increase in the hyperfine magnetic field, while the IS becomes more negative, which is primarily attributed to modifications in the s-electron density at the iron nuclei resulting from thermally induced electronic redistribution.