Achieving net-zero or carbon-negative energy systems requires technologies capable of generating power while capturing or utilising CO2 without significant efficiency losses. Molten carbonate fuel cells (MCFCs) offer such potential, yet their techno-economic competitiveness across different energy systems remains insufficiently quantified. Beyond conventional power-plant integration, this study explores a new application of MCFCs in biogas upgrading, where their electrochemical CO2-transfer capability is harnessed to purify raw biogas to near-pipeline-quality biomethane (BM) while simultaneously generating electricity. A process-simulation-informed, bottom-up techno-economic and environmental assessment was conducted to evaluate MCFC integration within natural gas combined cycle (NGCC), integrated gasification combined cycle (IGCC) and biogas-upgrading systems, each operated with air- or O2-fed cathodes. Results show that integrating MCFCs into different plant types significantly affects both plant efficiency and CO2 avoidance cost, with the air-fed NGCC-MCFC configuration demonstrating the most favourable techno-economic balance, while the O2-fed IGCC-MCFC system provides superior environmental performance in centralised applications. In decentralised settings, MCFC-assisted biogas upgrading can achieve cost-neutral or revenue-positive operation when stack costs fall below 1000 $& centerdot;kW-1, highlighting its potential as a self-sustaining CO2-removal route. These findings establish a unified cross-system performance map identifying where MCFCs are most competitive across centralised and decentralised energy systems, highlighting their potential as dual-function units for power decarbonisation and renewable-gas production.

This study investigates the impact of separator geometry on electrolyte stratification in lead-acid batteries through a comprehensive numerical modeling approach. The simulations include two-dimensional (2D) and three-dimensional (3D) models to accurately capture the spatial distribution of acid concentration during battery discharge. The 3D model, in particular, enables a more realistic analysis of vertical stratification by more accurately accounting for geometric constraints and flow behavior. It also allows the evaluation of various separator geometries, especially those with features along the cell depth, which cannot be adequately represented in a single 2D view. Based on these models, the performance of three separator configurations, simple, vertical rib, and horizontal rib, was evaluated. The 2D simulations showed that the ribbed separator exhibited greater stratification compared to the simple one, with concentration increases of 0.05 M, 0.05 M, and 0.02 M at 4000, 2000, and 1000 mA/cm2, respectively. In the 3D model, under 6000 mA/cm2 and 3200 s, the electrolyte concentration gradient along the cell height was 0.4 M for the vertical rib separator, 0.5 M for the simple separator, and 0.595 M for the horizontal rib separator, demonstrating the superior performance of the vertical rib design in mitigating stratification. The acid flow path over the separator and the geometry through which it moves can have a significant effect on electrolyte stratification. Additionally, increasing the porosity and electrolyte-interfacing surface area of the positive electrode was found to optimize battery performance. The findings suggest that vertical rib separators are more effective in reducing stratification, while horizontal ribs may hinder electrolyte flow and reduce efficiency. The proposed numerical models were validated through one-, two-, and three-dimensional simulations, providing reliable tools for the design and optimization of nextgeneration lead-acid.

This study develops and optimises a renewable-driven hybrid refrigeration system to enhance food preservation in off-grid rural areas. The system integrates solar photovoltaic, solar thermal collectors, wind energy, and battery storage to provide a sustainable, cost-effective cooling solution. A comprehensive techno-economic analysis was conducted using Ethiopia as a case study to evaluate system performance, cost-effectiveness, and market feasibility. The optimised system meets 22.42 kW of thermal power demand and 2.82 kW of electrical power demand, reducing daily operational costs from $100 to $86.2. Optimisation improved system efficiency by increasing photovoltaic panels to 15, reducing battery storage from 11 to 7 units, and optimising solar collector area to 322 m2. The length of underground thermal storage piping was reduced to 1366 m, enhancing thermal efficiency. The system achieved near off-grid operation, with grid dependency reduced from 9.3 W to 3.2 W and auxiliary heater reliance below 1 % of total demand. A business model incorporating subscription-based and lease-to-buy financing supports adoption by smallholder farmers and cooperatives, with a five-year payback period. Survey results indicate that 90 % of farmers lack cooling facilities, while 48 % of cooperatives favour government incentives. The system's environmental benefits include zero on-site (operational) CO2 emissions and eco-friendly refrigerants. This research demonstrates the feasibility of hybrid renewable energy integration in sustainable cold storage, reducing post-harvest losses and enhancing food supply chains in off-grid communities. Sensitivity analysis against inter-annual resource variability and +/- 20 % capital-cost dispersion confirms the robustness of the optimised configuration.

This study employs the finite line source (FLS) method, a fully analytical model, to evaluate thermal interactions, heat loss, and heat storage rates of borehole thermal energy storage (BTES) systems. The proposed model provides rapid and accurate simulations, in contrast with existing methodologies that rely on time-consuming numerical models. The model first assesses the temperature distribution within and around the boundaries of the BTES. Using the determined temperatures, Fourier's law is applied to calculate heat losses, and the principle of energy conservation is used to determine the thermal energy stored within the BTES. To account for variations in heat exchange rates among boreholes and over time, the FLS solution is superposed both spatially and temporally, and a specific load aggregation technique is employed to reduce computational cost. Further computational efficiency is achieved by approximating the error function required for the FLS solution with a Gaussian Q-function and by using hierarchical agglomerative clustering to categorize boreholes with similar temperatures and heat exchange rates. The proposed method is validated through several case scenarios of increasing complexity and compared against the publicly known duct ground storage (DST) model and simulations conducted using COMSOL software. The results demonstrate the effectiveness of the FLS method in assessing thermal interactions, heat loss, and heat storage rates of different BTES configurations with regular or irregular borehole arrangements, as well as various series-parallel connections. It is also observed that approximating the FLS solution and categorizing boreholes into groups can significantly reduce calculation time, depending on the size and complexity of the problem. An application of the proposed method is also presented, wherein the borehole spacing and length of a BTES are optimized to minimize heat losses and maximize heat storage over time. A grid independence analysis revealed that most inaccuracies of the proposed method occur during the early operational stages, particularly in the evaluation of heat storage rates. These inaccuracies can be mitigated by increasing the radial, axial, and angular segments around boreholes and refining time intervals. Alternatively, inaccuracies can be reduced by evaluating heat storage rates by subtracting heat loss rates from heat exchange rates, similar to the approach used in the DST model.

This study presents a comprehensive three-dimensional numerical simulation to assess the performance of a photovoltaic thermal (PVT) system utilizing nanofluids (NFs) and enhanced fin configurations. The system integrates a copper flat plate collector, where nanofluids circulate within heat absorber tubes, and rectangular fins are strategically arrayed to augment heat dissipation. The effects of fin dimensions, count, nanofluid concentration, flow rate, and solar intensity on the PVT's thermal and electrical performance are examined. Key findings illustrate that fin configuration, particularly the number of fins, significantly dictates the system's thermal management, with minimal impact from fin thickness. Optimal thermal behavior was observed with 0.5 wt% graphene nanoplatelet nanofluid at a mass flow rate of 0.1 kg/s, employing 400 fins. Analysis reveals that increasing the number of fins from 10 to 400 could enhance the thermal efficiency by approximately 18%, while reducing the overall system temperature by up to 7 degrees C under peak solar conditions. Furthermore, the study indicates that an increase in solar radiation intensity from 800 to 1000 W/m2 reduces the electrical efficiency by about 2%, even though the electrical power output increases by 5%.

This study explores the enhanced efficiency of solar-driven redox reactions using ceria foams coated with Ca-doped lanthanum manganite (LCM) perovskite, focusing on sustainable fuel production. The effects of substrate pore density (10, 30 ppi) and coating thickness (3 and 6 perovskite layers) were investigated. The LCM perovskite was synthesized and uniformly coated onto porous ceria substrates, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dual-scale porous structure of ceria enhanced the coating's effectiveness and reactivity, with coating thicknesses ranging from 75-140 mu m (three layers) to 100-400 mu m (six layers). Thermogravimetric analysis (TGA) showed superior reduction extents for LCM-coated ceria samples, with O2 production up to 131 mu mol/g, compared to 55 mu mol/g for pure ceria. This led to a 20-40 % increase in total fuel production, with CO yields up to 141 mu mol/g versus 98 mu mol/g for pure ceria. Performance stability for CO2 and H2O splitting was confirmed through fifteen consecutive cycles in a high-temperature solar reactor. Solar thermochemical cycling tests showed that LCM-coated ceria foams produced up to 244 mu mol/g CO, with a peak CO production rate of 6.22 mL & sdot;min-1 & sdot;g-1, during reduction at 1450 degrees C and oxidation under pure CO2 below 900 degrees C. However, pure ceria exhibited faster oxidation kinetics. This research underscores the importance of material design and optimization in improving solar thermochemical processes for large-scale solar fuel production.

To decrease carbon emissions in energy production systems, a new system has been introduced and investigated that utilizes solid oxide fuel cells (SOFC), a closed Bryton cycle (CBC), and a carbon dioxide capture unit (CCU). An extensive mathematical model has been created to evaluate the thermodynamic efficiency of this combined system. Findings show that the exergy efficiencies of the separate components, including SOFC and SOFC-CBC, are 39% and 79%, respectively, and the integrated system exhibits a total cost rate of 109.3 $/hr. The system is equipped with a CO2 capture unit, allowing it to efficiently separate the carbon dioxide produced during combustion and store it in a designated tank. The system is designed to effectively absorb 90% of carbon dioxide, successfully separating an impressive 221.94 kg/h. The exergy analysis of the system reveals that the afterburner has the greatest exergy destruction. Therefore, this component has the potential for system improvement from a thermodynamic perspective. Furthermore, a comprehensive study on the influence of the system's key parameters has been conducted to understand the system's performance. Maximum efficiency is realized when the SOFC functions at a temperature of 600 K with a fuel utilization ratio of 3.7.

Borehole thermal energy storage systems are emerging as a promising technology for storing intermittent renewable thermal energy sources. BTES systems utilize the underground as a thermal reservoir, where heat is stored during periods of excess energy production and retrieved when needed. This enables these systems to address the challenge of matching the supply of renewable energy with the demand for heating and cooling in buildings. This approach not only enhances the efficiency of renewable energy systems but also contributes to reducing greenhouse gas emissions and reliance on fossil fuels. This study introduces a novel approach to literature analysis in the BTES field by employing bibliometric and qualitative analysis tools, including SciMAT, VOSviewer, and NVivo, providing a systematic alternative to traditional manual review methods. The goal is to identify key publications, summarize their findings, and track the evolution of research directions over time, enhancing the understanding of the field. The paper is structured into six sections. The first section provides an overview of analytical and numerical models used to simulate the performance of BTES systems. The second section discusses the differences between traditional literature review methods and those employing bibliometric and qualitative analysis tools, highlighting their respective limitations and benefits. Additionally, it compares studies that have analyzed the BTES field using traditional review methods, explaining why a literature review with bibliometric and qualitative analysis tools is necessary and what advantages they offer. The third section outlines the research structure and employs bibliometric metrics to identify significant publications in the BTES field, while the fourth section uses SciMAT, VOSViewer, and NVivo to create scientific maps and networks of keywords, documents, publication sources, and active countries, revealing major research themes and influential publications. The fifth section organizes BTES publications into seven groups, reviewing selected studies within each to highlight recent developments, while the final section evaluates the dispersion of these studies to pinpoint well-researched areas as well as areas that require further exploration within the BTES field. The study highlights a growing interest in BTES research and identifies gaps in areas such as regulatory frameworks, market status, environmental impacts, and integration with smart energy systems. It also emphasizes the need to further investigate the thermal effects of groundwater, grout, ground thermal properties, and ground temperature imbalances on BTES system performance, underscoring the importance of continued research to address challenges and advance the development of BTES systems.

Rising ambient temperatures and tightening decarbonisation targets are compelling the cold-chain sector to adopt self-sustained cooling units. This study develops a high-fidelity digital twin of an electric refrigerated van that integrates roof-mounted photovoltaic (PV) modules, a 10 kWh lithium-ion battery, and a -21 degrees C organic phase-change material (PCM) thermal buffer. The system is modelled in Modelica and dynamically driven by typical meteorological year data for Birmingham (UK). Simulation outputs are used to train Random-Forest regressors that predict battery state-of-charge (SoC) and compressor speed in real time. Results for a 12-h delivery mission show that adding 4 kg of PCM halves compressor cycling frequency and improves final SoC by 11 %, while solar charging recovers up to 18 % of daily refrigeration energy. The Random-Forest model attains an R-2 of 0.9990 for SoC and 0.9683 for rotor-speed prediction, enabling proactive energy management. The proposed architecture therefore offers a practical pathway to extend BEV range and resilience in food logistics.

Hydrogen production using solar energy and blending in a natural gas pipeline is a cost-effective alternative to hydrogen storage and transmission that leads to lower CO2 emissions caused by the energy infrastructure. In this paper, energy, exergy, and Exergoeconomic analyses of a solar hydrogen production system and its blending with natural gas in a city gate station of Isfahan city are performed in three days with minimum, average, and maximum solar irradiations. The system includes photovoltaic arrays, anion exchange membrane electrolyzer cells (AEMECs), a hydrogen compressor, and a system blending. The AEMEC is used due to its less expensive catalysts, non-acidic electrolyte, and high efficiency at high pressures. A three-dimensional numerical model is developed to determine the AEMEC's polarization curve, accurately. The results show that with increasing solar irradiation and decreasing ambient temperature, the maximum power of the PV increases and the energy and exergy efficiency of the PV decreases. By increasing the injection of hydrogen into natural gas from 1% to 10% vol., the lower heating value of the fuel and the Wobbe Index decrease by 6% and 1.55%, respectively. By injection of 10% vol. hydrogen gas into natural gas compared to the case of using natural gas without hydrogen, the exergy cost of natural gas blended with hydrogen increases by 5.9%. Considering the environmental benefits of using hydrogen in combination with natural gas, including the reduction of greenhouse gases, and the fact that blending hydrogen up to 10% vol. with natural gas does not require any change in urban gas supply facilities, this process is feasible. In the case of using high-pressure AEMEC and removing the compressor to produce hydrogen at high pressure, the exergy cost of high-pressure hydrogen reduces by 29.3%.

This study presents a new method for sustainable cooling systems using a hybrid refrigeration system powered by hybrid renewable energy sources. The system comprises a modular unit of vertical wind turbines integrated with bio-photovoltaic films to provide sustainable energy. The hybrid refrigeration system combines evaporative and solar thermal-driven adsorption cooling systems. In addition, a finite volume of soil is proposed for thermal energy storage. Experimental data inform the development of a digital twin for an integrated system, soil thermophysical characteristics, wind turbine performance, and technical specifications for other system components. This sustainable cooling package is cost-effective and space-efficient, particularly in remote or off-grid locations. Notably, the evaporative cooler and chilled water coil contribute to a cooling effect of 20.4 kW, and solar power generation reaches 12.38 kW at an intensity of 1053 W/m2. The annual electrical output averages 1.7 kW at a wind speed of 3.5 m/s. Under best conditions, wind power can surge to 7.99 kW at 9.88 m/s. The ratio of power generated by wind to solar energy ranges from 1.1 to 1.3. The system effectively meets a peak thermal energy demand of approximately 74 GJ/month, facilitated by solar collectors, underground thermal storage, and a renewable energy-fed auxiliary heater. This study paves the way for future techno-economic optimisation and advancements in sustainable energy solutions for remote cold storage facilities.

The increasing carbon footprint associated with conventional cooling methods underscores the urgent need for sustainable alternatives. This study investigates the economic and environmental advantages of various solar-thermal cooling systems, with a focus on optimizing their performance across different climate conditions. Employing a multi-objective approach, the research emphasizes exergy-economic indices to optimize selected cycles. The analysis covers multiple refrigeration technologies, including liquid absorption, solid adsorption, and solid desiccant cycles. Results indicate that the liquid absorption cycle performs optimally in hot, arid climates, reducing the payback period to approximately 8 years when optimized. In hot and humid regions, the solid desiccant cycle proves most effective due to its superior humidity control, yielding a payback period of 5.3 years. For cold and mountainous areas, the solid adsorption cycle is preferred, with a payback period of 13.5 years, while moderate and humid climates benefit from the solid desiccant cycle for both cooling and humidity regulation. The exergy-economic factors for the solar refrigeration systems across semi-arid, hot and arid, hot and humid, cold and mountainous, and moderate and humid climates are 0.758, 0.602, 0.698, 0.74, and 0.575, respectively.

Due to the widespread use of multi-generation systems utilizing renewable energy sources and the growing global demand for such systems from both economic and environmental considerations, numerous researchers have focused on the design and evaluation of their performance. To this end, this research presents a biomass-based multi-generation system with an innovative and practical design that can generate electricity, heat, and hydrogen. This system includes a modified gas turbine cycle, a supercritical CO2 (SCO2) cycle, a transcritical CO2 (TCO2) cycle, a proton exchange membrane (PEM) electrolyzer, and a PEM fuel cell unit. This study aims to evaluate the impact of various biomass sources (paper, wood, paddy husk, and municipal solid waste) on the system performance. The proposed system has been analyzed using the first and second laws of thermodynamics. This system uses the maximum capacity to produce power, heat and hydrogen. A fuel cell unit has been used to consume hydrogen and generate more electricity. In the basic mode, the system has energy and exergy efficiencies of 47.89% and 32.26%, respectively, and can produce 2.74 kg/h of hydrogen. The biomass fuel consumption rate within the system is 0.055 kg/s. The overall exergy destruction of the system amounts to 1240 kW, with the biomass boiler and the condenser being the components that experience the greatest exergy destruction, registering values of 535.5 kW and 432.3 kW, respectively. Notably, employing municipal waste as biomass increases the system's exergy efficiency to 33.16%.

In this paper, a three-dimensional numerical model is developed for an anion exchange membrane electrolyser cell (AEMEC) with a double serpentine flow field pattern. The focus on the AEMEC is due to its benefits, including the solid membrane, inexpensive catalysts and membrane, and high stability. The effect of important operating parameters, i.e. cell temperature and cathode pressure, on the performance of the electrolyser is numerically modeled by considering different causes of performance degradation. The polarization curve, uniformity index, and the distribution of the hydrogen concentration, current density, temperature, and pressure in different operating conditions are presented. By increasing the operating temperature and decreasing the cathode pressure, the voltage of the elctrolyser decreases. Due to the higher concentration of water at the inlet of the cathode channel, more hydrogen is produced, and the current density is higher. The maximum current density and hydrogen concentrations are 7868 m2A and 0:898 mol tively, when the operating condition is set to the temperature of 343 K, the pressure of 1 bar, and the cell voltage of 1.85 V. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Steel production is a highly energy-intensive industry, responsible for significant greenhouse gas emissions. Electrification of this sector is challenging, making green hydrogen technology a promising alternative. This research performs a thermodynamic analysis of green hydrogen production for steel manufacturing using the direct reduction method. Four solid oxide electrolyzer (SOE) modules replace the traditional reformer to produce 2.88 kg/s of hydrogen gas, serving as a reducing agent for iron pellets to yield 30 kg/s of molten steel. These modules are powered by 37,801 photovoltaic units. Additionally, a thermal storage system utilizing 1,342 tons of steel slag stores waste heat from Electric Arc Furnace (EAF) exhaust gases. This stored energy preheats iron scraps charged into the EAF, reducing energy consumption by 5%. A life cycle assessment, conducted using open LCA software, reveals that the global warming potential (GWP) for the entire process, with a capacity of 30 kg/s, equates to 93 kg of CO2. The study also assesses other environmental impacts such as acidification potential, ozone formation, fine particle formation, and human toxicity. Results indicate that the EAF significantly contributes to global warming and fine particle formation, while the direct reduction process notably impacts ozone formation and acidification potential.

In this study, four different cooling techniques with a variety type of coolant for a commercial photovoltaic- thermal collector have been simulated optically and thermally by using the discrete ordinate radiation model (DO) and compared in a hot climate. These methods include a cooling channel with lateral inlet and outlet (case II), a cooling channel with uniquely designed fins (case III), a channel with circular inlet and many elliptical outlets patterns (case IV), and a specific pattern of copper tubes containing water beneath the solar module (case V), in comparison with a standard PV module (case I). The cooling fluids utilized in this research consist of dry air, moist air with relative humidity of 20 %, 40 %, and 60 %, and water in an active cooling method. The results indicate that using fins and copper pipes reduces the temperature, respectively, by 12 degrees C and 23 degrees C, leading to 4.10% and 7.92% improvement in electrical efficiency, which corresponds to a power improvement of 4.12% and 7.98% in cases III and V. In comparison, in cases II and IV, temperature reductions were only 6.5 degrees C and 9 degrees C, respectively, leading to a smaller improvement in efficiency of 2.20% and 4.10% in both scenarios where no fins are present. Consequently, the shape of the inlet and outlet, along with the distribution of air inside the channel, influences the cooling performance of the solar module significantly. It is observed that in cases II, III, and IV, by increasing the relative humidity of the incoming air to 60 % with an inlet velocity of 1 m/s, the electrical efficiency improves approximately 4.21 %, 5.5%, and 4.91 %, respectively, compared to Case I.

In general, for installing multilayer insulation (MLI) blankets on curved spacecraft equipment, creating a pattern that has multiple sectors is necessary because of the impossibility of establishing a single piece of MLI. The sector area of the MLI contains numerous seams and sewing. Therefore, prediction of overall performance or effective emittance is not simply possible, and they need to be tested in some experimental ways. The aim of the current research is to present a methodology for determining the conductivity between layers in both nonsewing and sewing regions of MLI to correctly estimate the effective emittance coefficient and the thermal behavior of MLI. Firstly, by conducting two experimental tests, both sewn and nonsewn square MLIs' effective emittance coefficients are computed. In the second step, the conductive thermal coupling coefficients of nonsewing and sewing regions are determined as 1.615 and 1.95 W/(m2 & sdot;K) respectively, utilizing experimental data. In the third step, a spherical geometry fuel tank is selected as a case study, and these coefficients are utilized in the simulation process of an MLI tank. Finally, the overall effective emittance coefficient of that tank is determined. The results indicate that the effective emittance is reduced by about 8%.

AbstractDecarbonizing heat-intensive industries by reusing the waste heat for power or combined heat and power systems is becoming increasingly important to address global warming. The Organic Rankine Cycle has shown a high level of feasibility and performed efficiently for utilizing medium-to-low-grade heat from renewable resources and heat-intensive industries for direct power generation. This study contributes to the field by conducting a techno-economic investigation of various Organic Rankine Cycle configurations to enhance energy conversion when real-life transient waste heat sources are available. These configurations were optimized to maximize energy output along with economic benefits. The non-linear programming by quadratic Lagrangian, a computational unintensive yet accurate optimization algorithm, was utilized for the multi-objective optimization. The optimized cycle configurations showed a 12.57% enhancement of turbine efficiency. Combining regeneration and recuperation enhanced the superheating by 32%, and the optimized air preheater cycle improved the overall objective by 64.2% compared to the pre-optimized conventional cycle, leading to a feasible 1.72-year payback period.