Portion Of Energy Research Articles

Numerical and experimental investigation of negative stiffness beams and honeycomb structures

Metamaterial structures that exhibit negative stiffness (MSNS) behavior have shown the potential to be used as energy dissipation systems in different applications. Negative stiffness honeycomb structures consist of multiple pre-buckled beams that snapping through from one pre-buckled mode to another buckled mode, when subjected to transverse loads, displaying negative stiffness, and dissipating a significant portion of the input energy. This paper presents finite element models (FEMs) developed to investigate the performance of negative stiffness pre-buckled beams and honeycombs. The FEMs were validated using experimental results of single pre-buckled beams and honeycomb structures. The experimental testing of the pre-buckled beams was presented in the current study while the results of the honeycomb were available in the literature. The FEMs have the ability to capture the transition of the elements from one mode of buckling to another mode as well as the force thresholds, energy dissipation values, and residual displacements. The FEMs were extended to investigate the effect of different parameters such as boundary condition, apex height-to-beam thickness ratio, and constraining the second mode of buckling on the behavior of negative stiffness honeycombs.

Integrated device for multiscale series vibration reduction and energy harvesting

A multi-degree-of-freedom device is proposed, which can achieve efficient vibration reduction as the main objective and energy harvesting as the secondary purpose. The device comprises a multiscale nonlinear vibration absorber (NVA) and piezoelectric components. Energy conversion and energy measurement methods are used to evaluate the device performance from multiple perspectives. Research has shown that this device can efficiently transfer transient energy from the main structure and convert a portion of transient energy into electrical energy. Main resonance and higher-order resonance are the main reasons for efficient energy transfer. The device can maintain high vibration reduction performance even when the excitation amplitude changes over a large range. Compared with the single structures with and without precompression, the multiscale NVA-piezoelectric device offers significant vibration reduction advantages. In addition, there are significant differences in the parameter settings of the two substructures for vibration reduction and energy harvesting.

Scheduling of the HVAC system in a real commercial building considering equipment cycling and rebound effects

Commercial buildings consume a large portion of energy and the heating, ventilation, and air conditioning (HVAC) system is the major contributor to this high consumption. Though there are many reported works on the optimal scheduling of HVAC systems, practical considerations such as equipment cycling and possible rebound effects are rarely considered. This paper provides insights into the optimal scheduling of the HVAC system in an actual 3-floor commercial building where the cycling and rebound effects are addressed in the optimization. The experimental results prove that energy cost reduction can be achieved while ensuring temperature comfort and longer life expectancy of the HVAC. The results also show that considering the cycling and rebounds will affect the potential cost reduction.

Offshore near-fault pulse-like ground motions: An insight into the DONET1 seafloor ground motions from the 2016 Mw6.0 Off-Mie earthquake in Japan

Offshore near-fault ground motions were obtained by the DONET1 seafloor seismic network during the 2016 Off-Mie Mw6.0 earthquake that occurred in the Nankai Trough of Japan. These data provide an opportunity for exploring the characteristics of offshore near-fault ground motions, especially pulse-like ground motions. A comparison of the offshore and onshore near-fault ground motions indicates that the recorded offshore spectral acceleration (SA) in the period of 0.5–5.0 s and peak ground velocity (PGV) for this earthquake are higher than those of the onshore values, and the observed maximum spectral value (βmax) of the offshore near-fault ground motions in this event is underestimated by the design spectra in the seismic codes of China, the United States, and Japan. Based on the Hilbert-Huang transform method, eight offshore pulse-like ground motion records are identified and extracted in the Off-Mie earthquake. The primary analysis indicates that the pulse-like ground motion may be caused by the directivity effect and the radiation pattern. Comparing the pulse parameters, time-frequency parameters, and response spectra of offshore and onshore pulse-like ground motions, the findings demonstrate that within the context of this earthquake event, approximately half of the offshore pulse amplitude (Vp) exceeds the predicted values of onshore models; the low-frequency components of offshore pulse-like ground motions of this event are more pronounced, constituting a larger portion of the total ground motion energy; offshore pulse-like ground motions exhibit a tendency to possess higher maximum instantaneous energy (Einst) compared to onshore pulse-like ground motions with similar rupture distances. Moreover, the βmax of offshore pulse-like ground motions is found to be greater than that of onshore pulse-like ground motions in medium to long periods (>0.5 s). The identified and characteristic recognition of offshore near fault pulse-like ground motion revealed by this earthquake event raises new concerns about seismic design for offshore engineering.

Recent Progress on the Tribological Applications of Solid Lubricants

Abstract Nonrenewable energy has produced abundant waste during tribological applications because a large portion of energy has been consumed to overcome friction and wear. Solid lubricants have recently aroused significant interest due to their defined friction and wear properties. Despite enormous efforts on solid lubricants, their important contributions to coatings, bulk materials, oil/grease, and super-lubricity have not yet been fully evaluated. This paper discusses in detail the present status of solid lubricants as effective reinforcements in tribology. It begins with the introduction of various descriptions and advanced structures of solid lubricants. Afterwards, it discussed their applications on improving friction properties in coatings and bulk materials. Additionally, lubrication mechanisms of solid lubricants in oil/grease are highlighted, followed by the detailed discussion of super-lubricity for solid lubricants. Finally, this review concludes final outlooks on the main challenges and future directions in this key area.

A novel method to evaluate phase change materials' impact on buildings' energy, economic, and environmental performance via controlled natural ventilation

The construction industry consumes a significant portion of global energy, with space conditioning in buildings accounting for a substantial 34% of energy usage. Notably, the energy consumption of a building is significantly influenced by its envelope. Researchers widely acknowledge that incorporating phase change materials (PCM) into the building envelope is a promising way to enhance energy efficiency and mitigate CO2 emissions in the building sector, owing to their high latent heat capacity. However, PCM must be completely charged after each cycle to exploit its full potential. Natural ventilation is a viable technique to facilitate the charging and discharging cycle of PCM within a 24-h period. To this end, the present study utilized EnergyPlus simulations to optimize the cooling energy savings of a residential building incorporating PCM into its envelope for PCM melting temperatures, considering various ventilation strategies across 45 cities in 15 climate zones worldwide. In order to evaluate the latent heat utilization of PCM and its improvement facilitated by natural ventilation, two novel indicators, namely HS and HR, were formulated to represent the heat stored and released by PCM during a 24-h cycle, respectively. In addition, following an economic analysis of PCM integration, a comprehensive environmental evaluation was carried out, which included the carbon intensities (CI) of all fuel sources contributing to power generation. The study's findings reveal substantial energy savings across all climate zones when controlled natural ventilation is coupled with PCM, and the newly proposed indicators precisely quantify the performance of PCM in all scenarios evaluated. In the arid climate zone (A), combining PCM and natural ventilation enhances energy savings, albeit to a similar extent as using ventilation alone. However, the integration of PCM with temperature-controlled ventilation yields striking energy reductions of up to 72.8%, 85.3%, and 61% in arid (B), warm temperate (C), and snow (D) climate zones, respectively. The cost-benefit analysis reveals a minimal return period of as short as five years in climate zone C. In the same climate zone C, the in-depth environmental analysis reveals a maximal reduction of 42,004 CO2-e kg/year in carbon emissions. In conclusion, this research study demonstrated that integrating PCM with controlled natural ventilation offers a practical, sustainable, and cost-effective solution with eco-friendly and energy-efficient outcomes.

A novel frame-type crashworthy device for protecting bridge piers from vehicle collisions

The development of different types of crashworthy devices that can alleviate the damage of bridge piers under vehicle collisions has attracted the attention of many researchers. However, the existing crashworthy devices often suffer from problems such as high cost, difficulty involved in maintenance, uneconomical expenditure for structural retrofitting after an impact event, etc. This paper develops a novel frame-type crashworthy device using relatively cost-effective steel material. Beam segments with reduced cross-sections are employed to concentrate the plasticity in certain structural components during vehicle collisions, which may facilitate structural repair after impact. Non-linear finite-element (FE) models of a colliding vehicle, of the device and of a protected reinforced concrete (RC) pier column are developed with detailed model validations to assess the effectiveness of the device for pier protection. Numerical results show that the device can absorb a large portion of the impact energy during a vehicle collision and can reduce the magnitude of the impact force and the dynamic response of a protected RC pier column very markedly.

Broadband unidirectional surface plasmon polaritons with low loss.

Unidirectional surface plasmon polaritons (SPPs) have been proven to truly exist at an interface between a magnetized semiconductor and an opaque isotropic material, however, they suffer rather serious leakage loss (with propagation length shorter than two wavelengths) caused by nonlocality. In this work, we investigate an alternative category of unidirectional SPPs existing on a nonreciprocal plasmonic platform with a cladding composed of a dielectric heterostructure transversely terminated by metal. This unidirectional SPP mode exists for small wavenumbers within the entire upper bulk-mode bandgap of the magnetized semiconductor, hence it is robust against nonlocal effects over a broad band. In contrast to previous unidirectional SPPs, the leakage loss of the present unidirectional SPPs is significantly reduced by more than five times, since the portion of modal energy distributed in the cladding is substantially increased. A similar reduction in absorption losses associated with semiconductor dissipation is observed. Though the nonlocality induces a backward-propagating SPP with extremely large wavenumbers, it can be suppressed even at very small level of dissipation. Therefore, our proposed plasmonic waveguide actually exhibits exceptional unidirectional characteristics.

Multiobjective optimization of heat recovery steam generator in a combined cycle power using genetic algorithm

AbstractDue to the increasing demand for electrical energy, efforts to increase the thermal efficiency of the steam and gas power plants have led to extensive reform in these cycles. One of these common reforms is employing a conventional combined gas‐steam cycle. In combined cycle power plants that are built to produce power, a significant portion of the input energy is lost. In this research to achieve the thermodynamic properties of a combined cycle power plant after modeling the cycle and determining the cycle potential independent variables, multiobjective optimization by imposing restrictions on cost functions and changing them concerning exergy efficiency has been analyzed. The results show that increasing the parameters of superheated temperature, pinch point temperature difference, pump exhaust pressure, and condenser inlet flow rate improves the system performance and increases exergy efficiency. It is shown by two‐objective optimization that when costs are increased up to 40%, exergy efficiency is increased, and when an increase is more than 40% repeated results would be obtained. Applying costs lower than 5% is not considered according to software limitations. Also, the results show that it is possible to increase exergy efficiency up to 79.7% with a 40% investment cost.

Engineering of heat sources in laser precision machining

Requirement towards the enhancement of the results of technological operations of laser processing, their transformation into precise technological operations is solved, in general, by the choice of optimal technological schemes of laser processing and characteristics of a tool that is formed from laser beam characteristics. The main goal of these attempts is to minimize portions of energy that destroys and removes the material from the cavity of element being formed utilizing ultra-short pulses of electro-magnetic energy with high intensity that can bring balance to the instability of technological process, manage it outcome and maintain the quality of processing. On the other hand, it leads to a decrease in the efficiency of technological operations of laser processing. For example, linear speed of laser cutting of stent with nanosecond pulses are used is within the range of 25 to 30 millimeters per minute, whereas in the case of microsecond pulses - the processing speed can reach up to 250 mm/min and slight striation of side surface of the cutting kerf could be eliminated by means of post processing. Since the process of material destruction at laser beam processing is of a thermal nature in terms of heat dissipation and its propagation into the body of the work piece (especially the metal one), it is possible to control and modify the absorption of radiation by the surface of the work piece, the spatial shape of the heat source and thermal an physical properties of the work piece. This paper discusses perspective solutions for the successful engineering of laser beam irradiation process.

Archetype-based energy and material use estimation for the residential buildings in Arab Gulf countries

Residential buildings account for a significant portion of global energy and material use, particularly in developing countries such as those in the Gulf Cooperation Council (GCC) where rising income, urbanization, and construction material use have led to increased energy use. To reduce greenhouse gas emissions, resource efficiency strategies in residential buildings are crucial. To better capture and reduce regional CO2 emissions rooted in residential building stocks in the developing world, country-specific studies are crucial and should consider building-specific factors and their effects on the environment. This paper explores the characteristics of residential buildings in all GCC countries, where arid climatic conditions and urbanization create a high energy demand, particularly for cooling. Using a five-stage bottom-up archetype development methodology, the authors created 153 multi-scale archetype models for the GCC region considering each residential building stocks’ cultural, historical, technological, climatic, and economic conditions. The simulations conducted using the BuildME tool revealed the energy and material intensity of six typology groups of buildings, including apartments, villas, skyscraper flats, Arabic-traditional houses, vernacular houses, and informal houses. The archetypes were used to investigate resource use rates across various administrative levels, climate regions, typologies, cohorts, and countries. The findings were discussed in the nexus of occupant behaviors, cultural lifestyles, demographics, extreme climate conditions, and building standards across various administrative levels, typologies, cohorts, and countries in the GCC. According to the results, residential buildings in Kuwait have the highest energy use per capita, and Saudi Arabia has the highest energy use overall. Also, the cooling loads represent the largest energy demand in all GCC countries, ranging from 58% in Oman to 75% in Bahrain, and 63% for the entire region. The study’s insights into the high residential material use patterns and trends across the GCC countries, with SAU leading other GCC countries in residential material demand, and Oman having the highest material use per capita. The results can help identify opportunities to cut emissions and develop resource-efficient construction practices and tailored policies targeting the resource efficiency of buildings in regions with high energy burdens caused by residential buildings.

Failure characteristics and brittleness index establishment based on marble energy evolution mechanism

The “carbon peak” and “carbon neutrality” require a continuous increase of clean energy supply, and hydropower shares a big portion of clean energy in China. The Jinping II Hydropower station is the biggest one and its main surrounding rock is marble. Thus, the failure characteristics of its marble holds great significance in safely and economically devising support measures of tunnel groups in this station. In this study, triaxial compression tests were conducted on the deep-buried marble to elucidate their formation mechanism and failure characteristics. Further, the 3D CT reconstruction was conducted for the evolution of microstructures. Finally, a new brittleness evaluation index (BNew) was formulated based on the pre-peak energy evolution and the post-peak stress drop to accurately evaluate the influence of confining pressure (σ3) on rock brittleness. The test results indicate that the strength values (σP and σeh) at segment points increase linearly with the increase of σ3, while the corresponding axial strains (ɛP and ɛeh) at these strength points also show a linear increase. The 3D CT reconstruction results reveal that the failure characteristics of the marble mainly have four types: ‘I’ type shear, ‘II’ type tensile–shear, ‘III’ type tensile–shear, and ‘y’ type conjugate shear. With the increase of σ3, the spatial distribution of crack characteristics in samples gradually shifts from complexity to simplicity and then back to complexity. The accumulated volume of cracks first decreases and then increases.

Investigation of diffraction grating in photothermal cavity

The photothermal effects in an optical cavity driven by a strong control field and a weak probe field have recently been shown to generate an induced transparency phenomenon (Ma et al., 2020). This phenomenon, referred to as photothermally induced transparency (PTIT), arises from the nonlinear behavior of an optical resonator caused by optical heating of the its mirrors. In this study, we investigate the manipulation of PTIT by substituting the strong coupling field in the PTIT scheme with a spatially periodic standing wave (SW) coupling field, resulting in the diffraction of the weak probe field into high-order diffractions. The resulting structure, termed the photothermally induced grating (PTIG), can be effectively controlled by adjusting various system parameters, including the coupling strength, effective detuning, interaction length, and photothermal coefficient. By carefully optimizing the coupling strength, we demonstrate that a significant portion of the probe field energy can be efficiently transferred to the third-order diffraction grating. The introduction of a spatially periodic standing wave coupling field opens up new possibilities for designing and manipulating photothermally induced gratings with enhanced functionalities.

Experimental analysis of patterned floating absorbers integrated thermal storage facilitating interfacial evaporation

Conventional solar-driven desalination methods yield low water productivity as a portion of the available energy is wasted for bulk heating. Furthermore, like any solar device, desalination is restricted by the availability (i.e., during night-time) and intermittent nature of solar flux. As a remedy, in this work, (a) interfacial evaporation, which is one of the best emerging energy-efficient technology that can help rectify the drawback of the conventional methods, and (b) the inclusion of thermal energy storage materials, which can supplement the energy needed for evaporation during the off-sunshine hours are selected for further investigations. The cumulative impact of the Solar Interfacial Evaporation (SIE) system incorporated with Phase Change Material (PCM) and different patterned floating absorbers is presented. As an extension, the system is introduced with Thermoelectric Generator (TEG) modules for cogeneration (i.e., desalination and open circuit voltage (OCV)). Primarily, under a controlled environment, this system is subjected to three different solar flux conditions, and the resulting water production is determined. Under 2-Sun conditions, the SIE-PCM approach yielded a higher evaporation rate of 2.3 kg/m2-h, 59 % higher than the SIE system without PCM. Also, under off-sunshine conditions, the SIE-PCM system yielded the highest evaporation rate of 0.5 kg/m2-h. Energy and exergy analysis indicated that the 36 square patterned absorbers yielded higher efficiencies than other tested configurations. The findings revealed that the cogeneration strategy yielded a low OCV showing its lack of potential in the proposed system.

Shake-off effect on the portions of energy reemitted by gold atom upon the cascade decay of vacancies in its K to O shells

Abstract Cascade decays of single vacancies in K to O shells of the gold atom are simulated by straightforward construction and analysis of the cascade decay trees. Portions of energies (a) absorbed by initially ionized Au atom, (b) reemitted by cascade-produced electrons, and (c) reemitted by cascade-produced photons are calculated with taking into account the shake-off processes caused by the change of atomic core potential during cascade transitions. Au atom absorbs noticeable amount of energy acquired in photoionization act only when ionized in its N and O shells, 33%–45% and 41%–54%, respectively. Except for the case of K-ionization, most of the energy is reemitted by cascade electrons: 57%–64%, 77%–85%, 55%–67%, and 46%–59% during the decay of vacancies in L, M, N, and O shells. Energies carried away by the cascade photons are only important for initial vacancies in K (89%) and L (29%–39%) shells. Inclusion of the shake-off branches in the decay trees increase substantially their complexity, however it leads to comparatively small corrections to calculated portions of energy redistributed through channels a, b, and c. This supports earlier qualitative prediction of small possible effect of the SO processes on the cascades in heavy atoms.

A new look at China’s environmental quality: how does environmental sustainability respond to the asymmetrical behavior of the competitive industrial sector?

ABSTRACT This research aims to expand the existing literature by bringing a new perspective to China’s environmental quality. Existing literature concerning China’s environmental sustainability disregards competitive industrial performance, which allows the analysis of Sustainable Development Goal-9. The study investigates the impact of competitive industrial performance, economic growth, and renewable energy consumption on the environmental quality (represented by load capacity factor) within the load capacity curve framework. Considering the positive and negative shocks in industrial competitiveness, the study runs the novel asymmetric ARDL with Fourier terms method to examine the non-linear connection between competitiveness and the environment. Empirical analysis shows that industrial competitiveness asymmetrically affects environmental quality and that the load capacity curve hypothesis is invalid in China. It is also evident that renewable energy contributes to environmental quality. Based on these findings, the study presents sustainable development policies for China within the framework of SDG targets. In this context, country’s rapid growth and higher-order industrial competitiveness strategies need to be redesigned in order to increase the share of high-tech activities in total manufacturing and the portion of renewable energy in total energy use. Accordingly, the Chinese policymakers’ primary objectives should be regulations that guide fundamental principles for enhancing environmental quality while preserving the country’s rapid growth and competitive advantage in the industrial process.

Novel design of thermo-electric air conditioning system integrated with PV panel for electric vehicles: Performance evaluation

Traditional air conditioning may be inappropriate for electric vehicles due to its moving parts noise besides using chlorofluorocarbons that harm the environment. In addition, it consumes a significant portion of the stored energy in batteries, reducing the vehicle's driving range. So, in this paper, a novel design of thermo-electric cooling (TEC) system coupled with a photovoltaic (PV) panel replacing the vehicle roof is studied. This system consists of a sandwich of PV panel outside the vehicle and TEC inside with a heat sink system integrated between them. The air temperature variation in the cabin during the daytime is predicted by solving a complete mathematical transient thermal model of the whole system before and after mounting the cooling system. The air streams through the vehicle moving are exploited to improve the TEC and PV system performance. The system performance is investigated for different cases during the day with and without including the PV output power and for the vehicle parks inside or outside. The results indicate that, for each scenario, the number of used TEC modules influences the system performance where the best number varies between 128 and 98. Coupling the PV panel with the TEC system reduces the daily required energy from batteries by about 19%. Running the TEC system during parking from 8 to 10 am decreases the cabin air temperature from 47.5 to 34°C while the input power declines by about 45%, which reduces the interior temperature to 25°C in 10 min (transition time). The contribution of the PV panel based on the studied conditions can increase the range of the vehicle by 10.4 km/day and about 160kWh/year energy saving. The reduction in the input power during transition time reaches 27.8% when the vehicle speed increases from 30 to 60 km/h, while this ratio declines to 10.8% as the vehicle speed rises from 60 to 90 km/h. During vehicle moving, powering the TEC system by the PV panel only can prevent the cabin temperature from rising over 40°C, whereas during parking, there is an optimum fan air velocity that gives the maximum reduction of the cabin temperature.

Utilization of Distinct HVAC Operation Modes to Improve Demand Response Flexibility in the Pharmaceutical Industry and Economic Analysis for Optimization by HOMER Software

Abstract In the pharmaceutical industry (PMI), the major portion of energy is consumed in heat ventilation air conditioning (HVAC) system; therefore, building energy management systems (BEMS) primarily focus on optimizing the energy consumption in HVAC systems. The two operation modes of HVAC, function mode (FM) and non-function mode (NFM), are descriptively explained with their role in improving the flexibility of demanded energy. Both modes are also exposed to hybrid optimization of multiple electric renewables (HOMER) software analysis from an economic perspective. Concerning net present cost (NPC) and cost of energy (COE) constraints, the FM/NFM of HVAC is preferable to the FM. This paper recognizes a comparative evaluation of several demand response (DR) alliances to deliver a comprehensive image of the suitability of DR alliances for different PMIs. Further, the paper also explores an innovative concept in the form of a control algorithm and discusses the relevant challenges and future opportunities. Moreover, the use of renewable energy systems (RESs) for enhancing energy management (EM) flexibility with the economy in the PMI or other industries is emphasized through DR alliances. This review study could be helpful to the PMI in terms of managing energy demand and also incorporating DR as an essential aspect of EM.

Explosion of high pressure hydrogen tank in fire: Mechanism, criterion, and consequence assessment

This study published experimental data on the catastrophic rupture consequences of high-pressure hydrogen storage tanks in fire environments. It made up for the lack of actual explosion data for verification of the traditional theoretical prediction models and numerical simulations. To reveal the mechanism of high-pressure tank explosion and corresponding characteristics of hydrogen explosion, the fireball parameters, fragment characteristics, and blast wave attenuation patterns resulting from tank rupture were analyzed. The results indicated that the hazard of hydrogen storage tank explosion was coupled with the combined contribution of physical and chemical explosion energies. The failure pressure of a 6.8 L – 30 MPa tank under fire conditions decreased by 60.3 % compared to that at room temperature. Following tank explosion, the duration of hydrogen-air deflagration was only about 2 s, and the maximum diameter of the fireball was nearly 4.48 m. A portion of the mechanical energy generated by tank explosion was converted into the kinetic energy of projectile fragments, with the farthest discovered fragment distance reaching 46.0 m. Additionally, the measured peak overpressure decreased from 875.33 kPa to 7.52 kPa at distances ranging from 2 m to 15 m from the explosion source. To evaluate blast wave overpressure in high-pressure hydrogen tanks for engineering applications, a standardized and generalized procedure was innovatively proposed, and its effectiveness was validated by experimental data. Furthermore, the hazardous distances defined by the peak overpressure were utilized to delineate risk zones. The distances of 61.6 m and 17.3 m from the explosion source were identified as zones without injury to human and without damage to structures, respectively. The proposed methodology and the results of the experiments were of practical importance for ensuring the safety of high-pressure hydrogen storage systems in various applications.

Direct Numerical Simulation of Bubble Cluster Collapse: Shape Evolution and Energy Transfer Mechanisms

This study employs the VOF method to conduct the direct numerical simulation of the collapse progress of the near-wall bubble cluster. Factors such as viscosity, compressibility, and surface tension are taken into account, with an emphasis on the flow field energy evolution. Firstly, the collapse of a cubic bubble cluster comprising 64 bubbles is simulated, validating previous research regarding the morphological evolution and energy release mechanisms during cluster collapse. Overall, the cubic bubble cluster collapse exhibits a layer-by-layer phenomenon, where the outer layer bubbles collapse first, converting a portion of bubble potential energy into fluid kinetic energy, which then contributes to the inner layer bubble collapse. The pressure wave energy is primarily released when the whole bubble cluster completely collapses. Secondly, we investigate the collapse process of columnar bubble clusters, which closely resemble realistic cloud cavitation. By comparing the collapse behavior of bubble clusters with different heights, we reveal the non-linear delay effect of the cluster height on the collapse time. Additionally, we consolidate our long-term research on the bubble cluster and conclude that both the scale and shape of the bubble clusters have a limited impact on the conversion rate η of bubble potential energy to pressure wave energy η. For instance, when the stand-off distance η=1.5 and the inter-bubble distance D=2.5, the conversion rate η remains consistently 9–15% for various bubble clusters of different scales and shapes.