Previous studies demonstrated the feasibility of vertical axis wind turbine (VAWT)-driven reverse osmosis (RO) units integrated with compressed air energy storage (CAES) to manage renewable energy intermittency. However, an integrated multi-objective strategy for optimal configuration was missing. This study addresses this gap by developing and applying a novel integrated framework coupling multi-objective optimisation with life cycle assessment (LCA) to evaluate technical, economic, and environmental performance. The system was modelled using six design variables, exploring 118,800 configurations to balance annual water production, levelised cost of water (LCOW), and global warming potential (GWP). Machine learning techniques were used to develop surrogate models to identify Pareto-optimal solutions, while a TOPSIS analysis selected four scenarios representing diverse stakeholder priorities. Results revealed that the sizing and number of VAWTs are the dominant factors influencing both LCOW and GWP. The optimisation yielded an LCOW-prioritised scenario that achieved a cost of 1.39 US$/m³, while the GWP-prioritised scenario reached a footprint of 0.70 kg CO₂eq/m³. This work provides a novel methodology for the simultaneous techno-economic and environmental design of off-grid water infrastructure, establishing optimal strategies for renewable desalination to address global water scarcity.

Hydrogen has been increasingly recognized as a promising clean energy carrier to support global climate change mitigation efforts. Among various production routes, the utilization of municipal solid waste (MSW), particularly plastic and food waste, offers a dual benefit: reducing the environmental burden of high-volume waste streams and producing a low-carbon energy carrier. Despite growing interest in waste-to-hydrogen technologies, few studies have explored an integrated pathway that simultaneously utilizes both plastic and food waste while incorporating carbon mitigation strategies. This study proposes and assesses, for the first time, a novel MSW-to-hydrogen and combined cooling, heating and power (CCHP) pathway fitted with carbon capture and storage (CCS). Two CCS configurations were examined: a pre-combustion CCS scheme (Scenario 1) and a post-combustion CCS scheme (Scenario 2). Three process cases were designed and evaluated using techno-economic analysis (TEA) and life cycle assessment (LCA) under conditions representative of Indonesia. In Case 1, plastic and food waste are separately processed via plasma gasification and anaerobic digestion, with syngas and biogas subsequently reformed into hydrogen. Case 2 co-processes the waste streams through plasma gasification. Case 3 builds on Case 1 by adding steam methane reforming (SMR) of biogas prior to mixing. For a feedstock of 13.97 kg/s of food waste and 5.0 kg/s of plastic waste, the systems deliver 0.27-0.70 kg/s of hydrogen across all cases and scenarios, with energy and exergy efficiencies of 19-42% and 13-34%, respectively. The levelized cost of hydrogen (LCOH) is estimated at 3.52-13.37 USD/kg, while LCA reveals global warming potentials (GWP) ranging from - 0.159 to 0.048 kgCO2-eq/kg of waste treated. These results demonstrate the technical feasibility and environmental promise of integrating plasma gasification, anaerobic digestion, and CCS for hydrogen production. By valorizing municipal waste while achieving carbon mitigation, this novel multi-integration of plasma gasification, anaerobic digestion, PSA, CCS, CCGT, and ARC represents a compelling and scalable solution for sustainable hydrogen deployment in developing economies.

Previous studies demonstrated the feasibility of vertical axis wind turbine (VAWT)-driven reverse osmosis (RO) units integrated with compressed air energy storage (CAES) to manage renewable energy intermittency. However, an integrated multi-objective strategy for optimal configuration was missing. This study addresses this gap by developing and applying a novel integrated framework coupling multi-objective optimisation with life cycle assessment (LCA) to evaluate technical, economic, and environmental performance. The system was modelled using six design variables, exploring 118,800 configurations to balance annual water production, levelised cost of water (LCOW), and global warming potential (GWP). Machine learning techniques were used to develop surrogate models to identify Pareto-optimal solutions, while a TOPSIS analysis selected four scenarios representing diverse stakeholder priorities. Results revealed that the sizing and number of VAWTs are the dominant factors influencing both LCOW and GWP. The optimisation yielded an LCOW-prioritised scenario that achieved a cost of 1.39 US$/m3, while the GWP-prioritised scenario reached a footprint of 0.70 kg CO2eq/m3. This work provides a novel methodology for the simultaneous techno-economic and environmental design of off-grid water infrastructure, establishing optimal strategies for renewable desalination to address global water scarcity.

An amine-based CO2 capture plant could mitigate CO2 emissions from a combined-cycle gas turbine (CCGT) plant, but it would require substantial energy. This investigation tackles this issue by assessing the merits of absorber intercooling (AIC) for a CO2 capture plant under the exhaust gas recirculation (50%EGR) and selective exhaust gas recirculation (70%SEGR) flue gas conditions for a CCGT plant, which, to the best of the authors' knowledge, has not been addressed in previous studies. The findings revealed that the greatest benefits of AIC were observed when the bulge temperature peaked at the center of the absorber under the critical lean loading. At the critical lean loading (mol CO2/mol MEA) of 0.35, 0.34, and 0.28 for baseline, EGR, and SEGR, respectively, installing three intercoolers in the absorber can reduce the bulge temperature by approximately 5-9 degrees C. This results in a 22-29% reduction in specific reboiler duty (SRD) across all configurations. In comparison, at the optimal lean loading of 0.20 across all configurations, the advantages of three intercoolers were limited to approximately 1-2 degrees C reductions in bulge temperature and around 7-9% reductions in SRD.

The coal gasification and flash ironmaking (CG-FI) process can simultaneously produce iron and syngas, with a substantial amount of iron ore co-injected into the gasifier for reduction. However, the slag tapping process, as affected by different iron species, is not yet well understood. This work aims to explore the mechanisms of iron precipitation and slag formation using FactSage thermodynamic simulations and experimental methods. The different gasification types and operating conditions, including the iron ore-to-coal (O/C) and CaO addition mass ratios, are systematically discussed. The results indicate that water-coal slurry gasification (WCSG) is better suited to flash ironmaking than dry pulverized coal gasification (DPCG). Metallic iron can precipitate successfully over a wide range of O/C mass ratios, from 0.4 to 1, with 1 representing the upper practical limit for extracting iron from 1350 degrees C to 1400 degrees C. The highest iron recovery is obtained at a ratio of 0.4. With a 10 % CaO addition, liquid iron can be efficiently reclaimed from the molten slag while maintaining a stable crystallization temperature window. Experiments demonstrate that the presence of CaO alters the dissolution morphology of iron crystals and mitigates adhesion, thereby reducing the risk of slag blockage. Accordingly, proper adjustments of feedstock and the slag port are indispensable. This work illustrates that continuous precipitation of metallic iron and sooth slag tapping can be realized in CG-FI.

The global transition toward renewable energy has been accelerating in response to climate change. South Korea has increasingly expanded the adoption of renewable energy, especially solar power. Smart farms are one example of renewable energy applications but require both electricity and heat demand. Previous studies have shown that the target smart farm does not achieve 100% energy self-sufficiency rate under current conditions. Therefore, renewable energy-based autonomous energy systems and their operational strategy are required to reduce grid dependency with full energy autonomy. This study proposes a scenario-based energy autonomy framework that integrates life-cycle assessment and techno-economic analysis for smart farms with coupled electricity and heat demands using measured operational data. Analysis results indicated that the proposed energy autonomous scenario could reduce CO2 emissions by up to approximately 92% compared to a centralized grid-based system. It also improved economic viability, lowering the LCOE from $0.435 to $0.287/kWh compared with the existing operating model. Sensitivity analysis identified electricity and wood pellet prices as the most influential economic factors. Consequently, a 60% solar-40% biomass configuration provides the optimal balance between environmental performance and economic efficiency. These findings demonstrate the practical feasibility of applying renewable and low-carbon technologies to smart farms within agricultural systems.

A novel layout of a biogas-based poly-generation system is proposed, designed and techno-economically analysed to satisfy the energy requirements for cooking and other household electric loads, as well as for drying and cooling agricultural produce in rural areas. The integrated system comprises anaerobic digester (AD), internal combustion engine (ICE), absorption chiller, in-bin dryer and CO2 capture unit. The ICEs operate with a high level of flexibility by adjusting their power output according to the power demand variability. The energy demand is modelled based on appliances' power ratings and usage time windows using an advanced stochastic estimation technique. Under the simulated conditions of a rural unelectrified community in Northern Nigeria, the system can meet approximately 94.6% of the combined cooking and domestic energy requirements. The remaining unmet load is primarily attributed to peak demand periods associated with electric cooking. A supplementary gas burner is integrated to stabilize fluctuations in the ICE energy supply, ensuring a consistent energy supply for both the absorption cooling and the grain drying processes via dedicated heat exchangers. The proposed system provides sufficient thermal energy to achieve a cooling capacity of 160 kW at 7 degrees C using the absorption chiller whereas the in-bin dryer can dry approximately 1,900 kg/h of maize, decreasing their moisture content from 25% to 13%. Excess biogas stored in the tank is upgraded by removing CO2 via amine scrubbing and liquefied through Linde-Hampsons cycle to produce liquefied biomethane (LBM), to be used for transporting feedstocks to the AD plant over a 90 km distance. The levelized cost of electricity (LCOE) for the proposed system is estimated at $0.055/kWh, with an associated payback period of 8 years. Finally, a Cradle-to-Gate life cycle assessment (LCA) estimated the global warming potential (GWP) of 51.01 gCO2eq/kWh for the proposed poly-generation system.

Coal pyrolysis is one of the key technologies for clean and efficient coal utilization in China, given its energy structure characterized by abundant coal but scarce oil and gas resources. However, conventional circulating fluidized bed (CFB) power plants are increasingly constrained by bottlenecks in energy efficiency, emissions, and economic performance, while existing coal pyrolysis technologies still face challenges in energy matching and insufficient synergetic optimization of low-carbon performance and value creation. To address these issues, this study proposes a coal-to-hydrogen, chemicals, and power (CtHCP) polygeneration system and compares it with a conventional CFB power generation system. First, system modeling and simulation were performed. Then, technical evaluation was carried out by establishing carbon and exergy balances to quantify carbon utilization and CO2 emission characteristics, enabling a comprehensive benchmarking analysis of energy efficiency, carbon utilization, and carbon emissions. Finally, the economic performance of the systems was evaluated based on product and feedstock market prices. The results show that the exergy efficiency of the CtHCP polygeneration system reaches 53.12%, which is significantly higher than that of the conventional CFB power generation system. The carbon utilization rate of the CtHCP system is 13.91%, and its CO2 emissions are reduced by 29.8%. Although the total investment cost of the CtHCP system is higher than that of the conventional CFB power generation system, its payback period is substantially shorter. Meanwhile, the CtHCP system demonstrates favorable economic feasibility and strong resilience to market fluctuations. This study provides a pathway for the synergistic optimization of energy efficiency, low-carbon performance, and economic benefits in conventional CFB power plants, and offers guidance for the development of coal-based polygeneration systems integrating chemicals, power, and hydrogen production.

Ash-related issues such as slagging and ash deposition in the heat transfer region of the grate boiler have been considered serious problems for safe and efficient operation. These issues must be addressed to avoid any unplanned shutdown due to failure in controlling the agglomeration and slagging during combustion. Various methods have been proposed, such as the injection of chemical additives into the grate boiler to reduce the alkali species in the bottom ash and depositions in the heat transfer region during combustion. However, the impacts of the boiler condition especially the bed conditions of the grate boiler have not been understood well in the past when adding the kaolin. Therefore, the aim of this work is to investigate, both experimentally and theoretically, the effects of blending biomass fuels with kaolin on ash-related issues in a 250 kW field-scale grate boiler. It was found that the kaolin powder performed quite effectively as an absorbent for potassium under firing conditions. The deposition propensity of fly ash was found to reduce by at least 50 % after the addition of the kaolin to the fuel mixtures. However, an increase in the degree of agglomeration was observed in the combustion chamber of the grate boiler when the kaolin was added to the fuel mixtures. High sintering was observed for the virgin wood and the recycled wood fuel blended with the kaolin at any dosages in the grate boiler. According to the elemental analysis by ICP-MS, the most dominant element found in the bottom ash, slag, and coarse fly ash was silica which captured potassium-related species and promoted the formation of slags. This also can be confirmed by the X-ray diffraction (XRD) analysis which shows that a high concentration of silica in crystalline structures were observed in both fuel mixtures. Moreover, according to the XRD analysis and thermodynamic equilibrium model prediction, adding kaolin to the feedstocks significantly influences the crystalline structure formation in the bottom ash such as the formation of Kalsilite, Leucite, Sanidine and many more.

A novel layout of a biogas-based poly-generation system is proposed, designed and techno-economically analysed to satisfy the energy requirements for cooking and other household uses, including lighting, as well as for drying and cooling agricultural produce in rural areas. The integrated system comprises anaerobic digester (AD), internal combustion engine (ICE), absorption chiller, in-bin dryer and CO2 capture unit. The ICEs operate with a high level of flexibility by adjusting their power output according to the power demand variability. The energy demand is modelled based on appliances’ power ratings and usage time windows using an advanced stochastic estimation technique. Under the simulated conditions of a rural unelectrified community in Northern Nigeria, the system can meet approximately 94.6% of the combined cooking and domestic energy requirements. The remaining unmet load is primarily attributed to peak demand periods associated with electric cooking. A supplementary gas burner is integrated to stabilize fluctuations in the ICE energy supply, ensuring a consistent energy supply for both the absorption cooling and the grain drying processes via dedicated heat exchangers. The proposed system provides sufficient thermal energy to achieve a cooling capacity of 160 kW at 7 °C using the absorption chiller whereas the in-bin dryer can dry approximately 1,900 kg/h of maize, decreasing their moisture content from 25% to 13%. Excess biogas stored in the tank is upgraded by removing CO2 via amine scrubbing and liquefied through Linde-Hampsons cycle to produce liquefied biomethane (LBM), to be used for transporting feedstocks to the AD plant over a 90 km distance. The levelized cost of electricity (LCOE) for the proposed system is estimated at $0.055/kWh, with an associated payback period of 8 years.

The aerodynamic behavior of vertical-axis wind turbines (VAWTs), particularly the H-type Darrieus configuration, remains central to renewable energy research due to persistent challenges in self-starting and efficiency at low tip speed ratios (TSRs). This study presents a numerical investigation of a modified NACA0018 aerofoil with chordwise surface openings, termed a J-shaped aerofoil, operating under Darrieus motion. Two-dimensional CFD simulations in ANSYS Fluent evaluated opening ratios of 30%, 60%, and 90% of chord length, focusing on lift, drag, and chordwise force coefficients during dynamic stall. A validated oscillating aerofoil model with user-defined pitching replicated Darrieus kinematics, with systematic variation of TSR and pitch angle. Results show that larger openings enhance lift and delay stall onset in the positive angle of attack phase, improving self-starting potential. However, these gains are offset by increased drag and reduced performance during the negative phase, particularly downstream. The J-shaped aerofoil with 90% opening achieved similar to 30% higher peak lift than the conventional profile, with improved flow reattachment and vortex dynamics observed. Despite elevated downstream losses, the enhanced upstream torque indicates a net advantage for turbine start-up capability. These findings provide insight for optimizing blade design in low-Reynolds-number VAWTs, balancing self-starting improvement against efficiency at higher TSRs.

While the rotating packed bed (RPB) shows good potential for CO2 absorption, it is still not used in large commercial scales largely due to the uncertainty about its real advantages over conventional packed column beds (CPB). In this paper, a large pilot-scale RPB model with an outer packing diameter of 1.2 m has been designed and effectively simulated using the Eulerian porous medium approach for the first time. Various sub-models have been extensively utilized to investigate the CO2 capture processes, including the hydrodynamics, thermodynamics, and mass transfer, within the RPB, comparing it critically with an equivalent CPB. The RPB, which has a much smaller size and footprint, could save 30 % in the liquid flow rate compared to the CPB to achieve the same capture rate using a 50 % MEA solution, coupled with an 80 % reduction in the packed bed volume. The results also show that at higher rotational speeds, increasing the liquid flow sometimes may not consistently improve the capture performance.

The primary challenge in integrating post-combustion CO2 capture (PCC) with natural gas combined cycle (NGCC) is the significant energy consumption and capital costs. The novelty of this paper lies in proposing for the first time an advanced novel configuration that combines lean vapor compression (LVC) for the PCC plant with the NGCC plant incorporating exhaust gas recirculation (EGR) and selective exhaust gas recirculation (SEGR). The simulation results illustrated that implementing 33 % EGR can increase the CO2 level in exhaust gas from a baseline of 4.2 to 6.3 mol%. In comparison, 53 % SEGR increased the CO2 concentration in the flue gas to 8.8 mol %. Among the different configurations examined, SEGR + LVC achieved the highest energy saving for reboiler duty, which was 14 % compared to the baseline. In contrast, the EGR + LVC recorded the highest enhancement in thermal efficiency by 0.7 % points compared to the reference case. The LVC alone resulted in approximately 0.4 % points improvement in thermal efficiency for all configurations evaluated when the gas turbine loads were reduced from 100 to 60 %. This indicates that LVC is effective under partial loads. Finally, SEGR + LVC results in the greatest cost reduction for the PCC plant equipment, lowering the cost by 26 % compared to the baseline. However, the SEGR has the highest total plant cost and total overnight cost due to additional costs for the CO2 membrane separation system.

Accurately modelling the self-starting of vertical-axis wind turbines (VAWTs) requires careful selection and tests of various computational model parameters which is a tedious task. This study applies the Taguchi Design of Experiments (TDE) to evaluate the influence of key numerical parameters such as freestream turbulence intensity, blade boundary layer mesh, time step size, average computational cell size, inner iterations within each time step, etc. The Taguchi study indicated that the time step size and mesh refinement within the rotating domain, particularly in the blade's boundary layer regions, were the most critical factors in the prediction of the self-starting process. Based on the Taguchi analysis, followed by a more detailed sensitivity analysis of these most critical factors on the accuracy of the CFD simulations, a robust CFD approach was successfully developed in order to correctly simulate the dynamic passive self-starting process of a VAWT. The simulation results of the robust model were found to compare well with the experimental measurements. The influence of the computational model settings on the predicted aerodynamics that are critical to the self-starting of the turbine were discussed. Finally, some practical guidelines were provided for building a robust CFD model for self-starting simulations of the VAWT applications.

The growing global population is leading to a surge in waste generation, with plastic waste posing a major pollution challenge due to its resistance to decomposition. Simultaneously, the energy sector is one of the largest contributors to air pollution, which highlights the urgent need for cleaner fuels to mitigate emissions. Innovative solutions, such as converting non-recyclable plastic waste into valuable energy carriers like hydrogen, are crucial to address both issues. This research aims to evaluate the thermodynamic and economic performance of hydrogen production from plastic waste via plasma gasification integrated with a carbon capture and storage plant. To the best of our knowledge, such information is currently unavailable in the literature, and this study represents the first attempt to bridge this gap. The system is modelled using ASPEN Plus software, with mass and energy balances from the simulation used to evaluate performance. Results show that processing 5 kg/s of plastic waste produces 1.20 kg/s of hydrogen, achieving overall energy and exergy efficiencies of 57.40% and 54.12%, respectively. The levelized cost of hydrogen ( LCOH) for economic viability is estimated at 3.3 USD/kgH(2). Monte Carlo simulations indicate a 95% confidence interval for the LCOH, which spans from 2.98 to 4.25 USD/kgH(2).

Waste generation and energy demand are increasing and both require innovative energy symbiosis strategies to meet climate targets. Traditional waste-to-energy processes rely on incineration, but more efficient and sustainable solutions are needed. The aim of the study is to investigate for the first time the feasibility of generating cooling, heating, power (CCHP), and liquid biomethane from plastics and food waste integrated with carbon capture and storage (CCS). The system, modelled in Aspen Plus, consists of a plasma gasifier (PG), anaerobic digester (AD), combined cycle gas turbine (CCGT), absorption refrigeration cooler (ARC), and biomethane liquefier. Two scenarios were analyzed: (1) a standalone CCHP system and (2) its integration with liquid biomethane production. Each scenario includes a baseline (without CCS), pre-combustion CCS, and post-combustion CCS, both with a 95% CO₂ capture fraction. Utilising 5 kg/s of plastic and 13.97 kg/s of food waste, the system generates net power (29.76–85.67 MW), cooling (2.72–4.04 MW), heating (13.99–27.87 MW), and 43.26 MW of liquid biomethane. The highest energy and exergy efficiencies achieved are 49.44% and 41.20%, with carbon emissions ranging from 0.008 to 0.247 kgCO₂/kg waste. The findings of this novel study highlight the potential of integrating several energy systems for an effective waste management strategy that can contribute to the provision of several energy vectors while the inclusion of CCS ensures that significant emission reduction can be attained.

Achieving climate goals demands novel system designs that enable the conversion of municipal waste, such as plastic and food waste into energy and fuels with minimal environmental impact. This study proposes an innovative multi-energy generation system that integrates plasma gasification for plastic waste and anaerobic digestion for food waste, coupled with carbon capture and storage (CCS) technologies. This novel conceptual design aims to maximize energy recovery while reducing lifecycle emissions compared to conventional waste-to-energy (WtE) pathways. Two novel system configurations were assessed: (1) a combined cooling, heating, and power (CCHP) system, and (2) a CCHP system integrated with liquid biomethane production. Each configuration was evaluated under three CCS strategies: no CCS, pre-combustion CCS, and post-combustion CCS. The economic analysis and life cycle assessment (LCA) highlight the economic and environmental trade-offs of each design. Specifically, in Scenario 1, the levelized cost of electricity (LCOE) increases from 0.171 USD/kWh (no CCS) to 0.311 and 0.354 USD/kWh while in Scenario 2, the levelized cost of biomethane (LCObM) rises from 0.176 USD/kWh to 0.314 and 0.374 USD/kWh for pre- and post-combustion CCS, respectively. While CCS raises production costs, they also represent a tangible commitment to reducing emissions and underscore that transitioning to cleaner energy systems often entails higher near-term expenditures. Across both scenarios, the levelized cost of waste treatment (LCOWT) spans 0.081–0.236 USD/kg of waste. Global warming potential (GWP) ranges from −0.191 to 0.662 kgCO2-eq/kg of feedstock for Scenario 1, and 0.123 to 0.746 kgCO2-eq/kg for Scenario 2. This work provides the first integrated assessment of such a hybrid WtE system, offering new insights for sustainable waste valorisation. The proposed novel designs support future detailed engineering studies and inform policymaking for low-carbon waste management.

Due to their outstanding structural, transport and electrical characteristics, nickel foams serve as excellent candidate materials for gas diffusion layers (GDLs) in polymer electrolyte fuel cells (PEFCs). In this work, a new three-dimensional PEFC model was developed to explore the local and global fuel cell performance with nickel foam-based GDLs. The fuel cell operating with nickel foam GDLs was shown to have, due to its superior mass and charge transport properties, higher oxygen and water concentration and current density compared to that operating with the conventional carbon fibre-based GDLs. The results show that the pumping power should be taken into account when optimising the dimensions of the flow channels and as such the net power density must be the criterion for optimisation. The optimal dimensions of the flow channels for the fuel cell operating with nickel foam based GDLs were found to be 0.25 mm for the channel height and 1 mm for the channel width; the maximum net power density with these dimensions was around 0.95 W/cm2 which is two times higher than that operating with carbon fibre based GDLs. All the results have been presented and critically discussed.

An improved predictive numerical index has been developed to predict the tendency of bed agglomeration in fluidized bed boilers. The index was developed based on the melt fraction resulting from the thermodynamic equilibrium model of fuel ash compositions together with SiO2 as the bed material at temperatures ranging from 700 to 900 degrees C. The partial least squares regression (PLSR) coupled with the cross-validation technique is utilized to establish the correlation for the bed agglomeration index, Ia. The improved index, Ia has been validated by experimental observations found in various literature sources. The results obtained using the improved index, Ia demonstrated a significantly higher success rate in predicting the bed agglomeration tendency of biomass fuel ash compared to the other four conventional bed agglomeration indices. In addition, K2O is the main element that accelerates the formation of bed agglomeration in the biomass firing while CaO was found to reduce the tendency of bed agglomeration in the fluidized bed combustion system.