Energy Recovery Efficiency Research Articles

Designing green chemicals by predicting vaporization properties using explainable graph attention networks

Computational predictions of vaporization properties aid the de novo design of green chemicals, including clean alternative fuels, working fluids for efficient thermal energy recovery, and polymers that are easily degradable and recyclable.

Equilibrium Modelling and Optimization of the Co-gasification of E-waste and Petcoke

Addressing the critical issues of Electronic waste (E-waste) with its low recycling and environmental impacts, this study highlights the necessity for efficient waste management and energy recovery. Leveraging petroleum coke's rich carbon content, co-gasification presents a viable method to transform E-waste into syngas. Using response surface methodology (RSM), the research analyzes various E-waste and petroleum coke blends, focusing on how gasification temperatures and pressures affect cold gas efficiency (CGE). Results highlight that the 25% printed circuit board (PCB) socket blend achieves an optimal CGE of 66.03% at 1,171.27°C and 1.95 bar via RSM and attains 64.10% CGE at 1,150°C and 1 bar as per the equilibrium model, in contrast to the 75% blend's CGE of 49.96% at 1,256°C and 1.57 bar, and 47% at 1,250°C and 1 bar. These findings reveal significant optimization opportunities in co-gasification processes, providing key insights for efficient E-waste handling and syngas generation.

Weak electrostimulation to enhance planktonic and biofilm microbial interactions on complex carbon degradation for biogas recovery

Electrode biofilm and planktonic microorganisms are two important parts in bioelectrochemical system, but the mechanism of planktonic microorganisms affect biofilms is not clear. Waste sludge lysate produced from sludge pyrolysis contains melanoidins as complex carbon source that are refractory. Anaerobic digestion companied with weak electrostimulation is adopted to treat the wastewater and explore the mechanism in electron transfer, biofilm activity and microbial community structure. In the presence of planktonic microorganisms, electrode biofilm still plays a major role that about 70% of organics was removed by biofilm, the energy recovery efficiency increased by 10.81%, and the main electron transfer mechanism of biofilm is unchanged, but extra electron transfer pathway (Ef = 0.404 V vs Ag/AgCl) is generated. More cytochrome is produced in biofilm and charge transfer resistance decreases to facilitate electron transfer. The planktonic microorganisms cause more electrochemically active microorganisms and methanogens enrich in the electrode biofilm to enhance the direct interspecies electron transfer.

Effect of the Guide Vane on the Hydraulic Stability of a Low-head, Large-discharge Industrial Hydraulic Turbine

The hydraulic turbine has been used extensively in the field of energy conservation. For turbines that have low heads and large discharge, improving recovery efficiency and stability is crucial due to their significant hydraulic impact. This paper provides a detailed analysis of the correlation between the influence of radial guide vanes on the stability of low-head, large-discharge turbines focusing on hydraulic performance and energy dissipation before and after the implementation of guide vanes. Moreover, in this paper, two types of turbines, with and without guide vanes, were designed considering the desulfurization scenario. Hydraulic efficiency, radial force, and internal flow field mechanics were numerically studied, and validated through experiments. The results reveal that the working range of the hydraulic turbine could be widened and the energy recovery efficiency improved by a maximum of 3.11% in the small flow rate under the action of guide vanes. Furthermore, it results in a substantial reduction in the radial force of the impeller. Subsequently, the variation in entropy production of different components under full flow rate conditions was compared between the models with and without guide vanes. The total energy consumption decreases sharply under overall working conditions due to the flow control ability of guide vanes affecting the flow state. The entropy production rate of the impeller remains the largest regardless of the presence of a guide vane in the turbine. The vortices inside the guide vanes increase obviously with the flow rate increase.

Hydrothermal pre-treatment of hospital food waste for efficient bio-methane generation

Municipal solid waste management (MWM) in Malaysia has become a challenging task in recent years due to the growth of population, industrialization and an increase in quantity and variation in the types of waste generated. Major solid waste generated in Malaysia is organic waste which includes mainly food waste from households, food processing facilities, markets, food and beverages industry and hospitals. Therefore, it is crucial to identify ways to manage food waste (FW) properly and improve the energy recovery efficiency. This paper is aimed to study the impact of pre-treatment on food waste from Hospital Pakar Sultanah Fatimah (HPSF) as a method to decompose FW faster and to determine the potential of bio-methane generation. A compositional study showed that total solid waste generated was 2,301 kg with 67% waste from lunch followed by 31% from breakfast sessions daily. Hydrothermal pre-treatment was done using a Multipurpose Recycling Machine (MRM) at 1.6MPa for 15 minutes followed by anaerobic digestion with and without the inoculum addition. Un-treated FW with inoculum was used as control in this experiment. It was found out that at a controlled pH of 7, hydrothermal pre-treatment and addition of inoculum i.e. cow manure played an important role in anaerobic digestion process for enhancement of bio-methane production. It significantly reduced the lag phase by 4 days and produced biogas faster compared to nontreated FW and hence, increased the biogas volume up to 638.53 mL compared to 504.08 mL in non-treated FW at the same experimental conditions. Therefore, this study signified that hydrothermal pretreatment is an effective and a beneficial technique added to the waste through the generation of biogas energy.

Improving Renewable Energy Recovery Efficiency in Variable Pressure Source Systems Through BP Neural Network Optimization

Improving Renewable Energy Recovery Efficiency in Variable Pressure Source Systems Through BP Neural Network Optimization

The role of bionic tubercle leading-edge in a centrifugal pump as turbines(PATs)

The structure of the blade's leading edge significantly affects the centrifugal pump as turbines (PATs) performance. This paper has attempted to investigate the hydraulic performance and pressure pulsations characteristics of PATs with bionic tubercle leading edge impellers by numerical calculation and experiment methods. The results showed that the bionic tubercles structure at the leading edge of the blade does not change the PAT's best efficiency point and helps improve the energy recovery efficiency under all operating conditions, especially with efficiency increased by 6.04 % under the over-load operation condition. Moreover, the bionic tubercles structure at the blade's leading edge can improves the impeller's local flow characteristics and effectively reduces the amplitude of dominant frequency in the main domains of PATs. The maximum reduction amplitude of pressure pulsations in the impeller with the bionic tubercle leading-edge under 0.7Qb, Qb, and 1.3Qb operating conditions is 29.8 %, 23.3 % and 61.1 %, respectively. This research provides a reference for the use of bionic blades to improve the energy recovery efficiency and operation stability of PATs.

CO2 enhanced continuous microwave pyrolysis of low-density polyethylene to produce high-quality products: Energy recovery balance and intrinsic mechanism exploration

The utilization of microwave pyrolysis technology and CO2 dry reforming to recover high-quality products from waste plastics has become a research hotspot. In this work, light fuels were recovered by CO2-enhanced continuous microwave pyrolysis (CMP) of low-density polyethylene (LDPE). The balanced relationship between CO2 utilization and energy recovery was investigated, and the intrinsic pyrolysis mechanism was analyzed. Increasing the pyrolysis temperatures and CO2 concentrations helped to increase the pyrolysis gas yield and the syngas content, which were 96.44 wt% and 65.61 vol%, respectively. CO2 enhanced the CMP degree of LDPE and reacted with intermediates to form oxygen-containing intermediates to produce high-quality products and release CO, thereby regulating the syngas content and H2/CO ratio (0.62–3.99). Although an increase in CO2 concentration enhanced CO2 utilization efficiency, it reduced energy recovery efficiency by increasing energy consumption. The efficiencies of CO2 utilization and energy recovery could reach 81.69% and 75.29% at pyrolysis conditions of 650 °C-75 vol% CO2 and 650 °C-25 vol% CO2, respectively. Appropriate CO2 concentration (25 vol%) was the key to synergistically improving product quality, resource utilization, and energy recovery. This work evaluated the potential of CO2-enhanced CMP to produce high-quality products and provided novel insights for improving the resource utilization efficiency of waste plastics and CO2.

A Logic Threshold Control Strategy to Improve the Regenerative Braking Energy Recovery of Electric Vehicles

With increasing global attention to climate change and environmental sustainability, the sustainable development of the automotive industry has become an important issue. This study focuses on the regenerative braking issues in pure electric vehicles. Specifically, it intends to elucidate the influence of the braking force distribution of the front and rear axles on access to energy recovery efficiency. Combining the I curve of a pure electric vehicle and the boundary line of the Economic Commission of Europe (ECE) regulations, the braking force distribution relationship between the front and rear axles is formulated to satisfy braking stability. The maximum regenerative braking force of the motor is determined based on the motor torque characteristics and battery charging power, and the regenerative braking torque is optimized by combining the constraints of the braking strength, battery state of charge (SOC), and vehicle speed. Six road working conditions are built, including the New European Driving Cycle (NEDC), the World Light-Duty Vehicle Test Cycle (WLTC), Federal Test Procedure 72 (FTP-72), Federal Test Procedure 75 (FTP-75), the China Light-Duty Vehicle Test Cycle—Passenger (CLTC-P), and the New York City Cycle (NYCC). The efficiency of the regenerative braking strategy is validated by using the Simulink/MATLAB simulation. The simulation results show that the proposed dynamic logic threshold control strategy can significantly improve the energy recovery effect of electric vehicles, and the energy recovery efficiency can be improved by at least 25% compared to the situation without regenerative braking. Specifically, under the aforementioned road working conditions, the braking energy recovery efficiency levels are 27.69%, 42.18%, 49.54%, 47.60%, 49.28%, and 51.06%, respectively. Moreover, the energy recovery efficiency obtained by the current dynamic logic threshold is also compared with other published results. The regenerative braking control method proposed in this article makes the braking control of electric vehicles more precise, effectively reducing energy consumption and improving the driving range of electric vehicles.

Anti-lock braking control using an interval type-2 fuzzy neural network scheme for electric vehicles

Control precision and robustness can be regarded as essential challenges of slip ratio control because of the external uncertainties of road conditions and the internal delay response of braking actuators. In addition, it is difficult to obtain a trade-off between braking energy recovery efficiency and braking safety under some extreme braking conditions. To synchronously improve both slip ratio control and braking energy recovery efficiency for different road conditions, an anti-lock braking system (ABS) using a novel interval type-2 fuzzy neural network (IT2FNN) control scheme is proposed for electrohydraulic braking systems. The novel IT2FNN control scheme with five layers is designed to calculate the commanded braking torque. The membership function layer utilizes type-2 fuzzy sets to describe the slip ratio error degree, which enhances the scheme’s anti-interference ability, and the enhanced Karnik-Mendel (EKM) algorithm is used in the type-reduction layer to accelerate computation. Additionally, the network adjusts the parameters of the membership function and rules by decreasing the performance function value corresponding to the braking torque error to improve slip ratio control and enhance the self-adaptation capacity. Simulations showed that IT2FNN control can not only improve slip ratio control performance and decrease the braking torque error but also enhance the energy recovery efficiency of regenerative braking on different road surfaces.

Characteristics of cavitating flows in cryogenic pump units in a combined cycle power system based on liquefied natural gas and solar energy

The cavitation of cryogenic pump units is an important cause for the low cold energy recovery efficiency and low utilization efficiency of solar energy in combined cycle power systems based on liquefied natural gas (LNG) and solar energy. Through numerical simulation of cavitation in cryogenic pump units, the research established the correlation mechanism between cavitation evolution and energy characteristics. By using the transport-based cavitation model considering the thermomechanical effect of cryogenic media, a novel numerical simulation model for two-phase flows during cryogenic cavitation was developed. In addition, the numerical model of cavitation was verified to be reliable. The cavitation performance of the two-stage LNG submerged pump in cryogenic pump units was studied under multiple conditions. In addition, the evolution of cavitating flow regimes under conditions of different flow rates and its influences on flow patterns of various flow passage components were investigated by combining analysis on temperature changes and flow fields. The entropy production diagnostic model (EPDM) was also adopted to discuss the distribution of the irreversible entropy production rate (EPR) in the evolution process of cavitation. Results show that the interfacial EPR that characterizes the phase-transition intensity after inception of cavitation exerts significant influences. Analysis of influencing mechanisms of changes in temperature, changes in flow fields, and distribution characteristics of energy consumption can provide a theoretical basis for further optimization.

Changes in environmental and engineered conditions alter the plasma membrane lipidome of fractured shale bacteria.

Microorganisms inadvertently introduced into the shale reservoir during fracturing face multiple stressors including brine-level salinities and starvation. However, some anaerobic halotolerant bacteria adapt and persist for long periods of time. They produce hydrogen sulfide, which sours the reservoir and corrodes engineering infrastructure. In addition, they form biofilms on rock matrices, which decrease shale permeability and clog fracture networks. These reduce well productivity and increase extraction costs. Under stress, microbes remodel their plasma membrane to optimize its roles in protection and mediating cellular processes such as signaling, transport, and energy metabolism. Hence, by observing changes in the membrane lipidome of model shale bacteria, Halanaerobium congolense WG10, and mixed consortia enriched from produced fluids under varying subsurface conditions and growth modes, we provide insight that advances our knowledge of the fractured shale biosystem. We also offer data-driven recommendations for improving biocontrol efficacy and the efficiency of energy recovery from unconventional formations.

Green and Efficient Recovery and Optimization of Waste Heat and LNG Cold Energy in LNG-Powered Ship Engines

This study focuses on the Wartsila 9L34DF engine and proposes an integrated system for low-temperature carbon capture using the coupling of cold and hot energy recovery with membrane separation in LNG-powered ships. By utilizing a series dual-pressure organic Rankine cycle (SDPORC) system to recover waste heat from the engine exhaust gases and generate electricity, the system provides power support for the low-temperature carbon capture compression process without consuming additional ship power. To validate the accuracy and reliability of the mathematical model, the simulation results are compared with the literature’s data. Once the model’s accuracy is ensured, the operational parameters of the integrated system are analyzed. Subsequently, working fluid optimization and genetic algorithm sensitive parameter optimization are conducted. Finally, under the optimal operating conditions, the thermodynamic performance and economic evaluation of the integrated system are assessed. The results demonstrate that the net power output of the integrated system is 100.95 kW, with an exergy efficiency of 45.19%. The unit carbon capture cost (UCC) is 14.24 $/ton, and for each unit of consumed LNG, 1.97 kg of liquid CO2 with a concentration of 99.5% can be captured. This integrated system significantly improves the energy utilization efficiency of ships and reduces CO2 emissions.

The role of ionic blockades in controlling the efficiency of energy recovery in forward bias bipolar membranes

The role of ionic blockades in controlling the efficiency of energy recovery in forward bias bipolar membranes

Advancing Energy Recovery from Sugarcane Leaf via Two-Stage Anaerobic Digestion for Hydrogen and Methane Production: Impacts on Greenhouse Gas Mitigation and Sustainable Energy Production

This study aims to enhance energy recovery from sugarcane leaf (SCL) through two-stage anaerobic digestion (TSAD) for hydrogen and methane production. The influence of hydraulic retention time (HRT) on this process was investigated. Optimal conditions established through batch experiments (5% total solids (TS) (w/v) and rice straw compost inoculum) were applied in semi-continuous stirred tank reactors (CSTR-H2 and CSTR-CH4). Remarkably, the highest production rates were achieved with HRTs of 5 days for CSTR-H2 (60.1 mL-H2/L·d) and 25 days for CSTR-CH4 (238.6 mL-CH4/L·d). Microbiological analysis by 16s rRNA sequencing identified Bacillus as predominant in CSTR-H2 followed by Lactobacillus and Clostridium. Utilizing SCL for TSAD could reduce greenhouse gas (GHG) emissions by 2.88 Mt-CO2 eq/year, compared to open-field burning, and mitigate emissions from fossil-fuel-based power plants by 228 kt-CO2 eq/year. This research underscores the potential of TSAD for efficient energy recovery and significant GHG emission reductions.

Energy yield from wastewater by supercritical water oxidation process: Experimental validation and simulation from the viewpoint of energy system

The degradation of high concentration organic wastewater and the recovery of energy using supercritical water oxidation (SCWO) technology have the potential to become viable in the future. High concentration organic wastewater contains a significant amount of energy. This paper focuses on utilizing high concentrated wastewater as a renewable energy source, from an energy system perspective, an experimental rig was designed to determine the optimal working conditions. The experiments were conducted with an oxidation coefficient of 1.1, a flow rate of high concentration organic wastewater of 9 ml/min, a heating temperature of 400 °C, and a reaction pressure of 25 MPa. Under these conditions, the COD and TOC removal rates of the high concentration organic wastewater were found to be 99.383 % and 99.876 % respectively. Additionally, the phenomenon of “Abnormalities in pressure sensitivity” observed during high concentration organic wastewater the experiment was further explained through additional experiments. Finally, by comparing the experimental energy recovery with the simulation results, an energy recovery efficiency of 78.95 % was achieved. The feasibility of the simulated energy recovery in practice was verified, confirming the potential to convert the previous energy-consuming wastewater treatment process into a productive one. This study provides a theoretical and experimental foundation for further related research.

Role of sulfate in regulating performance and metabolic mechanisms of bioelectrochemical up-flow anaerobic sludge blanket fed with methanolic wastewater

To investigate the impact of sulfate (SO42−) on the performance of bioelectrochemical up-flow anaerobic sludge blanket (BE-UASB), the COD/SO42− ratio of sulfate-containing methanolic wastewater was gradually decreased from 20 to 3. The results showed that BE-UASB maintained higher COD and SO42− removal (i.e., 91% and 70%, respectively) with methane production rate of 278.7 mL/Lreactor/d at COD/SO42− ratio from 10 to 5, ensuring efficient energy recovery. Sulfidogenesis enabled the sludge re-granulation while bioelectrocatalysis further contributed to the growth/proliferation of biomass with interwoven filaments, rods, and spherical microorganisms. 16 S rRNA gene analysis demonstrated that bioelectrocatalysis promoted the diversity of methane-producing archaea (MPA), including Methanomethylovorans, Methanosaeta, Candidatus_Methanofastidiosum, and Methanobacterium. Sulfate-reducing bacteria (SRB), mainly comprising G_norank_f_Syntrophobacteraceae, Desulfomonile, and Syntrophobacter, tended to be enriched on bioelectrodes, which not only eased the competition with MPA but also achieved simultaneous removal of COD and SO42− in synergy with MPA.

A Novel Cascade Utilization System of Liquid Hydrogen Cold Energy: Energy, Exergy, and Economic Analysis

In order to effectively improve the cold energy recovery efficiency and thermodynamic performance of liquid hydrogen regasification process, a novel type of liquid hydrogen cold energy cascade utilization (RC-HT-AS-DI-CS-AC) system is proposed, which includes Rankine cycle power generation (RC), hydrogen turbine power generation (HT), air separation (AS), production of dry ice (DI), cold storage (CS) and air conditioning (AC). A comprehensive energy, exergy and economic analysis is carried out to compare the proposed system with a comparison system scheme (CSS). For RC-HT-AS-DI-CS-AC system, the energy efficiency of overall system is 79.74%. The cold energy provided by the hydrogen stream achieve 182.31 kW, which is 61.18% increase compared with the CSS. The acquired exergy and exergy efficiency of the RC-HT-AS-DI-CS-AC system increase by 119.6% and 115.9% compared with the CSS. It reveals the importance of liquid hydrogen pressurization to improve exergy efficiency for overall system. However, in the economic analysis, the total annual cost (TAC) of the system of RC-HT-AS-DI-CS-AC system is 278,400 US $, which is significantly higher than TAC of CSS. As a result, the IRR of CSS and RC-HT-AS-DI-CS-AC systems are 87.39% and 15.10% respectively. Therefore, from a commercial point of view, CSS is more worthy of industrialization.

Pilot-scale biogas and in-situ struvite production from pig slurry: A novel integrated approach

Excess ammonia produced during the decomposition of nitrogen-rich substrates inhibits the anaerobic digestion (AD) process while it increases the concentration of ammonium nitrogen (NH4+) in the digestate. Digestate is commonly applied to farmland, causing nitrogen loss via runoff and volatilization. Therefore, developing an integrated strategy to promote the overall efficiency of AD systems susceptible to ammonia toxicity events, is worthy of consideration. Herein, a step-feeding approach to combat ammonia toxicity in AD process in which, intermittent rather than continuous substrate feeding was tested. A pilot-scale, mesophilic (37 ± 1 °C), fed-batch AD reactor (working volume ∼ 6.67 m3), was operated as the biomethanation step in a novel biorefinery concept, to recover bioenergy and nutrients (struvite) from pig slurry. The results showed that methane production yield achieved was 89.7 % of the theoretical at high ammonia levels (4.44 g NH4+-N L−1), indicating an efficient AD process under strong ammonia stress. The production rate of precipitate was 4.0 kg t−1 feedstock, while X-Ray Diffraction analysis revealed that purity of struvite crystal was 98 % w/w. Orthorhombic crystals and homogeneous distribution of significant elements (O, P, N, and Mg) in the precipitate were observed through scanning electron microscopy coupled with energy dispersive X-ray analysis. Recoveries of nitrogen and phosphorus were 48.5 % and 68.5 % from the digestate, respectively. Furthermore, the chemical and sanitary (i.e., Escherichia coli, Enterobacteriaceae and Salmonella) indicators of the precipitate were in line with the EU Fertilizer Regulation. Overall, the obtained results indicate that it is possible to establish an integrated efficient nutrient and energy recovery process for the simultaneous production of high-yield biogas and high-purity struvite fertilizer from pig slurry, which could yield a gross profit of 5.79 € t−1 feedstock.

Unlocking the potential: A paradigm-shifting approach for valorizing lignocellulosic waste biomass of constructed wetland enabling environmental and societal sustainability

Constructed wetlands (CWs) are widely recognized as nature-based solutions for wastewater treatment, offering various socio-economic and ecological benefits. However, the sustainable management and disposal of waste biomass generated from CWs have received limited attention. Owing to the rich lignocellulosic proportions, the harvested vegetation can potentially serve as a feedstock for various value-added products, including natural fiber-reinforced polymeric composites (NFRPCs). In this context, for the first time, we present a comprehensive review exploring different valorization routes employed to gainfully utilize waste biomass from CWs. The study discusses various value-added products developed so far from the waste biomass of CW. Biogas generation and bioethanol production are the most commonly explored valorization pathways. However, the commercial implementation of these value-added products is stalled by factors such as growth conditions, pretreatment, moisture content, process conditions, and limited energy recovery efficiency. Furthermore, this article introduces a novel class of sustainable materials, namely NFRPCs, developed for the first time by utilizing waste biomass from CWs as a reinforcement element in the polymeric matrix. A detailed analysis of the physical, mechanical, structural, and crystallographic characteristics of Canna indica (CI)-reinforced polypropylene (PP) composites is also discussed to evaluate their pertinence for structural applications. Additionally, we provide an in-depth review of natural-fiber-reinforced polypropylene composites, comprising single-fiber composites, hybrid fiber composites, and composites reinforced with organic/inorganic fillers. This comprehensive review emphasizes the potential of utilizing waste biomass from CWs as a sustainable feedstock for developing NFRPCs. It also highlights the promising prospects of NFRPCs as a sustainable substitute to synthetic fiber-reinforced composites, contributing to a circular economy and a greener future.