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Near-Field Effects on the in situ Estimation of Shear-Wave Velocity and Damping Ratio from MASW Tests
Get PDFMultichannel analysis of surface waves (MASW) is a viable approach for in situ estimation of shear-wave velocity and damping ratio. However, conventional processing techniques assume that the recorded wavefield consists only of surface waves, and the presence of body waves leads to detrimental consequences on the reliability of the estimate, referred to as “near-field effects”. The latter typically induce oscillations in the estimated phase velocity at low frequencies, while little is known about their effect on phase attenuation. This study investigates the influence of near-field effects on the estimated phase velocity and phase attenuation on a synthetic data set. The results show that the phase attenuation is far more sensitive to body waves than the phase velocity. Furthermore, the findings suggest that near-field effects can be mitigated by selecting the experimental data with normalized array center distance (NACD; i.e., the ratio between the average offset of the receivers and the Rayleigh wavelength) greater than 2-3. While phase velocity estimates are reliable at NACD values as low as 1, the requirement for NACD > 2-3 is mainly driven by phase attenuation and its higher sensitivity to near-field effects. However, this threshold should be adjusted based on the noise level, especially when few receivers are used. The proposed criterion has been applied to the characterization of a real site in Italy, demonstrating that the inclusion of data affected by near-field effects leads to an overestimation of the shear-wave damping ratio and significant variability in the estimated profiles
Spatio-Temporal Machine Learning for Ecology and Crisis Management
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Extensive Validation of the Three-Branch Model in Simulating the Static and the Dynamic Behavior of EDLC Supercapacitors
Get PDFThis study demonstrates the response of the three-branch equivalent circuit model in reproducing the terminal voltage of a supercapacitor that undergoes dynamic galvanostatic pulse trains for frequencies from 0.1 Hz to 100 Hz and signal amplitudes of 1 A, significantly wider than the sinusoidal signals used in impedance spectroscopy. Clean and accurate pulse trains were generated at different frequencies using a transconductance power amplifier, and the voltages at the supercapacitor terminals of three different sizes of supercapacitors were successfully compared with the model. The latter was also utilized to check its ability to accurately reproduce charging and self-discharging processes and the ability to simulate voltammetric cycles. This was verified for six supercapacitor sizes from 1 F (rated 1 mWh, 10 W) up to a large 130 F module (rated 70 Wh, 144 kW). In all cases, the relative difference, with respect to the rated voltage, between the terminal voltage provided by the measurements and that yielded by the model simulations did not exceed 3.5%. This extensive multi-level validation demonstrates how the identified three-branch model based on state equations can provide an accurate electrical design tool and a reference for standards
Semi-empirical modeling and experimental evaluation of partial immersive thermal management performance for 21700 cylindrical cells targeted towards automotive battery packs
No full textThermal management of lithium-ion cells in battery packs is of paramount importance, ensuring that their extended service life and safety are guaranteed. This paper explores the potential benefits that partial direct thermal management may offer for automotive battery packs. It presents a systematic modeling and experimentation campaign of a battery pack composed of 21700 cylindrical cells, evaluating its thermal response under six thermal management conditions at the same electrical load. Static air and forced air-cooling are performed, setting a baseline for the analysis. The effectiveness of a single-phase dielectric liquid coolant for direct thermal management is evaluated with varying immersion levels of the cells. The level of the fluid is increased from 25% to 100% of the battery cell height, following 25% increments. For each condition, the pack is tested with a discharge rate of 0.5C, with temperature measurements recorded at the positive terminal, negative terminal and the body of the central cell of the pack. The work presents the development of a multiphysics model considering electrochemical and thermal physics coupling, based on a semi-empirical lumped battery representation. The model results to have a good fit with the experimental data, with a maximum error of 1.4 °C when simulating the partial immersion conditions. The experimental outcomes indicate that an immersion ratio of 50% is an agreeable trade-off between maximum temperature reached, maximum temperature difference between the positive and negative terminals, and coolant volume for the studied battery pack
Deep Learning and Reinforcement Learning for Industrial Microgrid Energy Management
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The potential role of biomethane in the transition towards low-carbon large-scale buildings: the case study of the Torino airport
No full textBiomethane represents an interesting solution for the growing pool of energy-intensive companies that are reducing their greenhouse gas emissions. Biomethane may help in the transition from fossil natural gas. Nonetheless, its inclusion in decarbonisation strategies is hindered by uncertainties around its future availability, price, and net environmental impact. This study aims to assess how these uncertainties affect the potential role of biomethane in the energy transition, investigating the specific case of Torino Airport. To explore the dynamics related to the use of biomethane, an energy system optimisation model is employed, to simulate cost-optimal development pathways under alternative prices and emission factors scenario. The results show that the potential availability of biomethane at an affordable price would significantly accelerate the energy transition of the airport. In particular, biomethane is key for strategies based on fuel cells, smoothing the transition from natural gas to an hydrogen supplied system. Nevertheless, price uncertainties still remain, for mid-terms projections, and these were found to significantly affect the operational expenditures, while the potential unavailability of the supplies could significantly jeopardise the airport environmental commitments. In this regard, pathways relying on a combination of different measures, such as electrification, proved to be more resilient to future potential discontinuities in green energy supplies
Dall'Incapsulazione Minerale alla Genesi della Vita: Un'Analisi Integrata tra Archaea, Clatrati di Metano e Intelligenza Artificiale
Get PDFCavity-Based Approaches to Stochastic Dynamics on Sparse Graphs: From Ecological Systems to Epidemiological Inference
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Technical-environmental assessment of rice husk biochars as renewable adsorbents for hydrogen sulphide removal
Get PDFThis study presents a technical and environmental assessment of H2S removal using four rice husk (RH)–derived
biochars produced by slow pyrolysis. Biochars were obtained under nitrogen (N2) or carbon dioxide (CO2) atmospheres, with and without potassium hydroxide (KOH) activation. The investigated materials included unmodified biochars (RH_N2 and RH_CO2) and biochars activated before (KOH_RH_CO2) or after (RH_CO2_KOH)
CO2-assisted-pyrolysis. Commercial activated carbon (CAC) was used as a reference. Dynamic adsorption experiments were conducted at H2S concentrations between 35 and 700 ppm and gas hourly space velocities
(GHSV) from 3822 to 30,573 h−1 . Compared to N2, CO2-assisted-pyrolysis enhanced carbon content (74.0 vs.
72.0%), reduced H/C and O/C ratios, and improved specific surface area (SSA) (141.0 vs. 55.7 m2/g), and
micropore volume (0.08 vs. 0.02 cm3/g). KOH-activation further enhanced SSA (178.4 m2/g) and micropore
volume (0.60 cm3/g) in pre-activation, while decreasing carbon content due to potassium effects. Among the
tested materials, KOH_RH_CO2 and CAC showed the highest H2S adsorption capacities. Although KOH_RH_CO2
exhibited a lower adsorption capacity than CAC at 700 ppm and GHSV of 3822 h−1 , it demonstrated superior
environmental performance. Life Cycle Assessment results showed that KOH_RH_CO2 achieved a negative global
warming impact, corresponding to approximately 108% of the footprint of CAC but with an opposite sign,
effectively shifting the process from carbon-intensive to carbon-negative. This outcome is attributed to the use of
agricultural waste as feedstock and to carbon sequestration during CO2-assisted pyrolysis. Overall, CO2-pyrolyzed and KOH-activated RH biochars emerge as environmentally advantageous adsorbents for H2S removal in
gas streams