The deployment of electrolysis-based hydrogen technology requires identifying the advantages and disadvantages of scaling hydrogen production plants and determining the limits of the scaling-up process. Until now, experience has been demonstrated with electrolysers of tens and hundreds of kilowatts, but electrolysers in the tens of megawatts range are still closer to being prototypes than commercial products. Additionally, challenges such as maintenance, reliability, long-term operation, and investment recovery time arise in parallel as the scale increases. This raises the question of what is more suitable: installing a single high-power electrolyser or a modular plant composed of multiple smaller electrolysers? This paper addresses that question from both a technical and an economic perspective. Accordingly, it presents a study identifying the degree of modularisation that optimises the technical and economic performance of a large-scale hydrogen production plant. The results show that configurations with a higher degree of modularisation (based on multiple smaller electrolysers) exhibit a better technical performance and lower degradation. However, configurations with a lower degree of modularisation are more competitive in terms of costs. When combining technical and economic criteria, the results show that solutions based on a medium–low degree of modularisation are the most suitable. The advantages are lower replacement costs and uninterrupted hydrogen production. This study also recommends embracing modularisation to prevent a dependence on a single high-power electrolyser.
Icing monitoring and ice detection are critical challenges across many industries where ice formation can severely degrade performance or compromise safety. Conventional ice sensing approaches, such as those based on surface acoustic waves (SAWs), often suffer from limited selectivity, fast saturation, and slow or energy-consuming recovery. In this work, we propose the use of thickness shear mode bulk acoustic waves (TSM AWs) as a selective and robust alternative for monitoring icing phenomena, ranging from frozen sessile droplets to ice accretion in near-real scenarios within aeronautical envelopes. The sensing platform consists of a LiNbO3 plate activated through lateral field excitation electrodes and driven electronically by a Vector or Scalar Network Analyzer. This system reliably detects both freezing conditions and temperature variations. Tracking the evolution of the magnitude of the reflection coefficient, specifically, the resonance peak and shape and frequency of|S11| minimum, of a strongly shear dominant mode provides a reliable means to characterize and extract both qualitative and quantitative information about icing processes. Finite element simulations further elucidate the physical mechanisms governing the ice monitoring capabilities. These results position TSM AW devices as promising candidates for a new generation of simple, light-weight, highly sensitive, and robust acoustic wave icing sensors.
The maritime industry is increasingly adopting wind-assisted ship propulsion (WASP) systems to displace fossil fuel dependency, reduce operational fuel consumption, and curtail greenhouse gas emissions in compliance with international environmental mandates. Among these technologies, rigid wing sails offer exceptional potential for enhancing propulsive efficiency due to their high lift-to-drag characteristics. This work presents a comprehensive experimental investigation exploring the aerodynamic flow patterns generated over a simplified mid-sized cargo ship deck equipped with three rigid wing sails arranged in a tandem configuration. Moving beyond traditional marine geometries, the sails are based on the high-performance Eppler 61 aeronautical airfoil, selected for its advantageous characteristics within low Reynolds number regimes. Experimental data were registered through a Particle Image Velocimetry (PIV) system in the T1 low-speed wind tunnel facility at the National Institute for Aerospace Technology (INTA), Spain, using a 1:150 scaled model. Flow diagnostics were performed at a freestream velocity of 15 m/s. The experimental tests evaluated five apparent wind angles (𝛽= 15°, 30°, 45°, 65°, 80° ) under wing-sails angle of attack (𝛼= 0°, 5°, 10°, 15°). The PIV analysis characterized the non-dimensional velocity fields and turbulence intensity contours to capture sail-to-sail aerodynamic interactions. The results confirmed that the array contributes positively to propulsive generation, generating velocity peaks on the suction side of the wing-sails. However, some aerodynamic interferences have been founded, resulting in a velocity peak reduction between 2.1% and 13.3% for the second sail. At the highest angle of attack (𝛼= 15°), flow detachment and stall were captured on the rear part of the first sail's suction side. These experimental data provide essential information for maximizing multi-sail propulsive efficiency and optimizing future sustainable commercial vessels.
Advances in radar systems have led to the emergence of low observability technologies that minimize target detectability. Among them, metasurfaces and metamaterials appear as promising solutions. In this paper, the analysis and design of a single-layer scattering metasurface with a thickness of lambda(s)/10 is presented for both monostatic and multistatic scenarios, simultaneously. The design achieves -12 dB of radar cross section reduction in the band 9.16 - 11.72 GHz, which means a reduction in the monostatic detection distance of 50%. Due to the symmetry and periodicity of the structure, the metasurface is infinitely replicable and the response has been validated for both polarizations. Moreover, the radar cross section reduction is applicable for an incidence range of theta=[-60,60](degrees) . Several prototypes have been fabricated and measured, and the results have been experimentally validated. For the measurement process, the vector background subtraction technique was used, as well as time gating and cylindrical mode expansion to transform from near-field to far-field.
This work presents a modification to the ASTM D4935-18 shielding effectiveness test method for planar materials. The proposed variation of said standard method employs time-domain techniques and instrumentation for instantaneous measurements over a broad frequency range extending from 30 MHz to 1 GHz. For an accurate broadband determination of the attenuation levels provided by the test samples, a large dynamic range is required. This is achieved by a multitone excitation signal adapted through time and frequency multiplexing, enabling full coverage of the target frequency band while improving the signal-to-noise ratio and detection sensitivity. Using the proposed methodology, shielding effectiveness values up to 90 dB were measured and validated with respect to frequency swept based methods for four different material samples. The results demonstrate that the proposed approach provides performance comparable to the reference method, while offering increased flexibility in instrumentation and almost halving the measurement time.
