Search Results (232)

Torrefaction, a mild thermochemical pretreatment process, is widely acknowledged as an effective strategy for enhancing the energy potential of lignocellulosic biomass. This review systematically evaluates the technological, environmental, and economic dimensions of lignocellulosic biomass torrefaction with the objective of clarifying its critical role in sustainable energy production and circular economy frameworks. Drawing from recent literature, the review covers process fundamentals, feedstock characteristics and operational parameters—typically 200–300 °C, heating rates below 50 °C per minute, ~1 h residence time, and oxygen-deficient conditions. The impacts of torrefaction on fuel properties, such as increased energy density, improved grindability and pelletability, enhanced storage stability, and reduced microbial degradation are critically assessed along with its contribution to waste valorization and renewable energy conversion. Particular emphasis is placed on the application of torrefied biomass (biochar) in sustainable agriculture, where it can enhance nutrient retention, improve soil quality and promote long-term carbon sequestration. This review identifies an unresolved research gap in aligning large-scale techno-economic feasibility with environmental impacts, specifically concerning the high process energy requirements, emission mitigation and regulatory integration. Process optimization, reactor design and supportive policy frameworks are identified as key strategies that could significantly improve the economic viability and sustainability outcomes. Overall, torrefaction demonstrates substantial potential as a scalable pathway for converting waste agricultural and forest residues into carbon-neutral biofuels. By effectively linking biomass waste valorization with renewable energy production and sustainable agricultural practices, this review offers a practical route to reducing environmental impacts while supporting the broader objectives of the global circular economy. Full article

The global energy transition and increasingly rigorous legal regulations aimed at climate protection are driving the search for alternative energy sources, including renewable energy sources (RESs) and waste heat. However, the mismatch between supply and demand presents a significant challenge. Thermal energy storage (TES) technologies, particularly mobile thermal energy storage (M-TES), offer a potential solution to address this gap. M-TES can not only balance supply and demand but also facilitate the transportation of heat from the source to the recipient. This paper reviews the current state of M-TES technologies, focusing on their technology readiness level, key operating parameters, and advantages and disadvantages. It is found that M-TES can be based on sensible heat, latent heat, or thermochemical reactions, with the majority of research and projects centered around latent heat storage. Regarding the type of research, significant progress has been made at the laboratory and simulation levels, while real-world implementation remains limited, with few pilot projects and commercially available systems. Despite the limited number of real-world M-TES implementations, currently existing M-TES systems can store up to 5.4 MWh in temperatures ranging from 58 °C to as high as 1300 °C. These findings highlight the potential of the M-TES and offer data for technology selection, simultaneously indicating the research gaps and future research directions. Full article

Although concentrated solar power (CSP) coupled with calcium looping (CaL) offers a promising avenue for efficient thermal chemical energy storage, calcium-based sorbents suffer from accelerated structural degradation and decreased CO₂ capture capacity during multiple cycles. This study used Density Functional Theory (DFT) calculations to investigate the mechanism by which Mg and Ni doping improves the adsorption/desorption performance of CaO. The DFT results indicate that Mg and Ni doping can effectively reduce the formation energy of oxygen vacancies on the CaO surface. Mg–Ni co-doping exhibits a significant synergistic effect, with the formation energy of oxygen vacancies reduced to 5.072 eV. Meanwhile, the O²⁻ diffusion energy barrier in the co-doped system was reduced to 2.692 eV, significantly improving the ion transport efficiency. In terms of CO₂ adsorption, Mg and Ni co-doping enhances the interaction between surface O atoms and CO₂, increasing the adsorption energy to −1.703 eV and forming a more stable CO₃²⁻ structure. For the desorption process, Mg and Ni co-doping restructured the CaCO₃ surface structure, reducing the CO₂ desorption energy barrier to 3.922 eV and significantly promoting carbonate decomposition. This work reveals, at the molecular level, how Mg and Ni doping optimizes adsorption–desorption in calcium-based materials, providing theoretical guidance for designing high-performance sorbents. Full article

In this study, sugarcane bagasse (SCB), an abundant agricultural byproduct, was transformed into activated carbon via a controlled thermochemical pyrolysis route for high-performance energy storage applications. Herein, we utilized the activated carbon derived from pure sugarcane bagasse (SCB-AC) and further activated using KOH (SCB-KOH-AC) as an electrode material in aqueous symmetric supercapacitor configurations. The synthesized activated carbon was subjected to analysis using a range of characteristics including FT-Raman spectroscopy, which was employed to confirm the functional groups present in the carbon materials. The XPS analysis provided insights into the elemental composition and ionic states. The SEM analysis revealed that both activated carbon and KOH/activated carbon materials exhibited a layered or stacked, albeit slightly random, orientation. Electrochemical studies demonstrated that the synthesized carbon electrodes exhibited impressive specific capacitance values of (SCB) activated carbon (132.20 F/g) and KOH-activated, pure SCB AC (SCB-A) 253.41 F/g at 0.5 A/g. Furthermore, the SCB KOH-activated carbon (AC) electrode revealed a higher specific capacitance value and A//SCB-A symmetric devices delivered energy density reaching 17.91 Wh/kg and power density up to 2990 W/kg. The KOH-activated carbon electrode demonstrated remarkable cycling stability retaining 93.89%, even after 10,000 cycles. These results suggest that the sugarcane bagasse-derived activated carbon is a sustainable and low-cost candidate for next-generation supercapacitor electrodes. The results demonstrate enhanced capacitance, stability, and pore structure tailored for energy storage applications. The KOH-activated carbon SCB carbon symmetric device with symmetric electrodes exhibited a suitable bio-mass carbon for future energy storage applications. Full article

Using the combination of Concentrated solar power (CSP) and calcium looping (CaL) technology is an effective way to solve the problems of intermittent solar energy, but calcium-based materials are prone to sintering due to the densification of the surface structure during high-temperature cycling. In this study, the enhancement mechanism of Co and Cr doping in terms of the adsorption properties of CaO was investigated by Density Functional Theory (DFT) calculations. The results indicate that Co and Cr doping shortens the bond length between metal and oxygen atoms, enhances covalent bonding interactions, and reduces the oxygen vacancy formation energy. Meanwhile, the O²⁻ diffusion energy barrier decreased from 4.606 eV for CaO to 3.648 eV for Co-CaO and 2.854 eV for Cr-CaO, which promoted CO₂ adsorption kinetics. The CO₂ adsorption energy was significantly increased in terms of the absolute value, and a partial density of states (PDOS) analysis indicated that doping enhanced the C-O orbital hybridization strength. In addition, Ca₄O₄ cluster adsorption calculations indicated that the formation of stronger metal–oxygen bonds on the doped surface effectively inhibited particle migration and sintering. This work reveals the mechanisms of transition metal doping in optimizing the electronic structure of CaO and enhancing CO₂ adsorption performance and sintering resistance, which provides a theoretical basis for the design of efficient calcium-based sorbents. Full article

Thermal Energy Storage (TES) technologies improve solar power dispatchability by addressing the important challenge of energy intermittency. Sensible heat energy storage technology using materials based on Ordinary Portland Cement (OPC) is the simplest and most economical. However, the operation of these materials is limited to temperatures below 400 °C due to the structural degradation of OPC at this temperature. This paper investigates the design and development of inorganic polymers based on Construction and Demolition Waste (CDW) as a sustainable, low-cost, and environmentally friendly alternative to OPC-based materials for high-temperature sensible TES applications. Based on the ternary systems Na₂O-SiO₂-Al₂O₃ and K₂O-SiO₂-Al₂O₃, representative compositions of CDW-based inorganic polymers were theoretically designed and evaluated using the thermochemical software FactSage 7.0. The experimental verification of the theoretically designed inorganic polymers confirmed that they can withstand temperatures higher than 500 and up to 700 °C. The optimized materials developed compressive strength around 20 MPa, which was improved with temperatures up to 500 °C and then decreased. Moreover, they presented thermal capacities from 600 to 1090 J kg⁻¹ °C ⁻¹, thermal diffusivity in the range of 4.7–5.6 × 10⁻⁷ m² s⁻¹, and thermal conductivity from 0.6 to 1 W m⁻¹ °C⁻¹. These properties render the developed inorganic polymers significant candidates for TES applications. Full article

Fuel cell electric vehicles (FCEVs) offer a promising solution for energy saving and emission reduction in transportation. However, several challenges must be addressed for their application. This study conducts a full life cycle assessment (LCA) of FCEVs, dividing it into the fuel cycle and vehicle cycle to separately assess energy consumption (EC) and emissions. The fuel cycle examined 18 hydrogen production–storage–transport pathways, while the vehicle cycle evaluates energy use and emissions associated with vehicle component production, assembly, disposal, battery production, and fluid consumption. Based on the GREET database, total energy consumption and emissions over a lifetime were calculated. Five environmental impact indicators were used for evaluation, and a comprehensive environmental assessment (CEA) indicator was established for different scenarios. Results indicate that nuclear thermochemical water splitting is the best hydrogen production method, and pipeline transportation is the most efficient for hydrogen transport. Additionally, water electrolysis for hydrogen production is only practical when paired with renewable energy. The study also identified that the Hydrogen production method, “Body”, “Proton Exchange Membrane Fuel Cells (PEMFCs) System”, “Chassis”, “Hydrogen Storage System” and lifetime significantly impact energy consumption and emissions. These stages or products represent high-impact leverage points for enhancing the lifecycle sustainability evaluation of FCEVs. Full article

Hydrogen is critical for achieving carbon neutrality as a clean energy source. However, its low ambient energy density poses challenges for storage, making efficient and safe hydrogen storage a bottleneck. Metal hydride-based solid-state hydrogen storage has emerged as a promising solution due to its high energy density, low operating pressure, and safety. In this work, the thermodynamic and kinetic characteristics of the hydrogenation and dehydrogenation processes are investigated and analyzed in detail, and the effects of initial conditions on the thermochemical hydrogen storage reactor are discussed. Multiphysics field modeling of the magnesium-based hydrogen storage tank was conducted to analyze the reaction processes. Distributions of temperature and reaction rate in the reactor and temperature and pressure during the hydrogen loading process were discussed. Radially, wall-adjacent regions rapidly dissipate heat with short reaction times, while the central area warms into a thermal plateau. Inward cooling propagation shortens the plateau, homogenizing temperatures—reflecting inward-to-outward thermal diffusion and exothermic attenuation, alongside a reaction rate peak migrating from edge to center. Axially, initial uniformity transitions to bottom-up thermal expansion after 60 min, with sustained high top temperatures showing nonlinear decay under $∆$t = 20 min intervals, where cooling rates monotonically accelerate. The greater the hydrogen pressure, the shorter the period of the temperature rise and the steeper the curve, while lower initial temperatures preserve local maxima but shorten plateaus and cooling time via enhanced thermal gradients. Full article

Nuclear energy cogeneration, which integrates electricity generation with thermal energy utilization, presents a transformative pathway for enhancing energy efficiency and decarbonizing industrial and urban sectors. This comprehensive review synthesizes advancements in technological stratification, economic modeling, and sectoral practices to evaluate the viability of nuclear cogeneration as a cornerstone of low-carbon energy transitions. By categorizing applications based on temperature requirements (low: <250 °C, medium: 250–550 °C, high: >550 °C), the study highlights the adaptability of reactor technologies, including light water reactors (LWRs), high-temperature gas-cooled reactors (HTGRs), and molten salt reactors (MSRs), to sector-specific demands. Key findings reveal that nuclear cogeneration systems achieve thermal efficiencies exceeding 80% in low-temperature applications and reduce CO₂ emissions by 1.5–2.5 million tons annually per reactor by displacing fossil fuel-based heat sources. Economic analyses emphasize the critical role of cost allocation methodologies, with exergy-based approaches reducing levelized costs by 18% in high-temperature applications. Policy instruments, such as carbon pricing, value-added tax (VAT) exemptions, and subsidized loans, enhance project viability, elevating net present values by 25–40% for district heating systems. Case studies from Finland, China, and Canada demonstrate operational successes, including 30% emission reductions in oil sands processing and hydrogen production costs as low as USD 3–5/kg via thermochemical cycles. Hybrid nuclear–renewable systems further stabilize energy supply, reducing the levelized cost of heat by 18%. The review underscores the necessity of integrating Generation IV reactors, thermal storage, and policy alignment to unlock nuclear cogeneration’s full potential in achieving global decarbonization and energy security goals. Full article

Thermal energy storage technologies are essential for balancing energy demand and supply. There are three main types: sensible heat, latent heat, and thermochemical energy storage. Among them, thermochemical energy storage offers the highest energy density (1–3 GJ/m³) and long-term storage capability. Salt hydrates have attracted attention as energy storage materials due to their low cost, wide availability, and operating temperatures being well-suited for residential and low-temperature applications. This review focuses on the use of salt hydrates in sorption-based thermochemical energy storage systems. It summarizes the current state of knowledge, including screening studies of various salt hydrates, their thermodynamic and operational limitations, advantages, and performance in composite materials. This review also covers recent projects and common reactor designs used in TCES applications. Based on the literature analysis, the most promising salt hydrates for sorption-based TCES systems include SrCl₂, SrBr₂, K₂CO₃, MgSO₄, MgCl₂, and CaCl₂. Despite the high theoretical energy density of many salt hydrates, future work should focus on experimental studies in large-scale reactor systems to better evaluate the practical discharge behavior of the energy storage system beyond theoretical hydration enthalpies or small-scale thermal analyses. Full article

This review paper presents an overview of fuel cell electrochemical systems that can be used for clean large-scale power generation and energy storage as global energy concerns regarding emissions and greenhouse gases escalate. The fundamental thermochemical and operational principles of fuel cell power generation and electrolyzer technologies are discussed with a focus on high-temperature solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) that are best suited for grid scale energy generation. SOFCs and SOECs share similar promising characteristics and have the potential to revolutionize energy conversion and storage due to improved energy efficiency and reduced carbon emissions. Electrochemical and thermodynamic foundations are presented while exploring energy conversion mechanisms, electric parameters, and efficiency in comparison with conventional power generation systems. Methods of converting hydrocarbon fuels to chemicals that can serve as fuel cell fuels are also presented. Key fuel cell challenges are also discussed, including degradation, thermal cycling, and long-term stability. The latest advancements, including in materials selection research, design, and manufacturing methods, are also presented, as they are essential for unlocking the full potential of these technologies and achieving a sustainable, near zero-emission energy future. Full article

Superdeep diamonds and their syngenetic inclusions are crucial for understanding Earth’s deep carbon cycle and slab–mantle redox dynamics. The origins of these diamonds, especially their links to iron (Fe) carbides and ferropericlase with varying Mg# [=Mg/(Mg+Fe)_at], however, remain elusive. In this study, we performed high pressure–temperature (P-T) experiments (10–16 GPa and 1200–1700 K) across cold-to-warm subduction zones using a multi-anvil press. The results reveal a stepwise Fe-mediated carbonate reduction process for the formation of superdeep diamonds: MgCO₃ → Fe-carbides (Fe₃C/Fe₇C₃) → graphite/diamond. This mechanism explains two phenomena regarding superdeep diamonds: (1) anomalous ¹³C depletion results from kinetic isotope fractionation during ¹²C enrichment into the intermediate Fe-carbides; (2) nitrogen scarcity is due to Fe-carbides acting as nitrogen sinks. Ferropericlase [(Mg,Fe)O] formed during the reactions in our experiments shows Mg# variations (0.2–0.9), similar to those found in natural samples. High Mg# (>0.7) variants from lower temperature experiments indicate diamond crystallization from carbonatitic melts in the shallow lower mantle, while the broad Mg# range (0.2–0.9) from experiments at higher temperatures suggests multi-depth formation processes as found in Brazilian diamonds. These findings suggest that slab–mantle interactions produce superdeep diamonds with distinctive Fe-carbides and ferropericlase assemblages as inclusions, coupled with their ¹³C- and nitrogen-depleted signatures, which underscore thermochemical carbon cycling as a key factor in deep carbon storage and mantle mineralogy. Full article

Solar power generation systems, recognized for their high energy quality and environmental benefits, require efficient energy storage to ensure stable grid integration and reduce reliance on fossil fuels. Thermochemical energy storage (TCS) using metal oxides, such as the Mn₂O₃/Mn₃O₄ redox system, offers advantages like high energy density, wide temperature range, and stability, making it ideal for solar power applications. This study investigates Mn₃O₄ and Mn₂O₃ as initial reactants, analyzing reaction temperature range, rate, conversion efficiency, and cyclic performance via synchronous thermal analysis. Microstructural characterization was performed using XRD, SEM, BET, XPS, nanoparticle size, and zeta potential measurements. The results show that Mn₃O₄ reversibly converts to Mn₂O₃ with over 100% conversion efficiency over five cycles with 3.3% weight loss, indicating stable performance. Mn₃O₄ oxidation follows Arrhenius’ Law below 700 °C but deviates at higher temperatures. The oxidation mechanism function is G(α) = α and f(α) = 1, with an activation energy of 20.47 kJ/mol and a pre-exponential factor of 0.268/s. Mn₂O₃ synthesized via ammonia precipitation exhibits reversible redox behavior with 3.3% weight loss but samples from low-concentration precursors show poor cyclic performance. The reduction reaction of Mn₂O₃ has an activation energy of 249.87 kJ/mol. By investigating the Mn₂O₃/Mn₃O₄ redox system for TCS, this study advances its practical integration into solar thermal power systems and offers critical guidance for developing scalable, low-carbon energy storage technologies. These findings can support Sustainable Development Goals (SDGs) by advancing renewable energy storage technologies, reducing carbon emissions, and promoting the integration of solar power into sustainable energy grids. Full article

This work demonstrates the feasibility of using biochars derived from a variety of waste feedstocks, such as food organics and garden organics (FOGOs), garden organics (GOs), and biosolids (BSs), provided by Barwon Water (BW) and South East Water (SEW), as active electrode material for supercapacitor application. Four different biochars were produced by the co-pyrolysis of pre-treated mixed waste feedstocks, which were fabricated into a two-electrode symmetric supercapacitor set-up to evaluate their energy storage potential. Two different approaches, (i) carbon nanoparticle coating/modification and (ii) thermochemical activation, were employed to improve the electrochemical properties of the biochars. Potassium hydroxide-activated biochar derived from BW’s triple waste feedstock mixture (comprising 70% GOs, 20% FOGOs, and 10% BSs) demonstrated the highest specific capacitance (30.33 F/g at 0.1 A/g), energy density (4.21 Wh/kg), and power density (2.15 kW/kg) among the tested samples. Such waste-derived biochar offers several benefits for energy storage, including cost-efficiency and sustainable alternatives to traditional electrode materials. The biochar’s electrochemical performance can be further improved by improving the feedstock quality by different pre-treatments. Full article

This study elucidates the mechanism of fluidization instability during limestone carbonation under a 100% CO₂ atmosphere and determines the influence of Al₂O₃ fluidization aids (dosage and particle size) on exothermic performance. The experiments demonstrate that rapid CO₂ absorption in the emulsion phase, coupled with insufficient gas replenishment from the bubble phase, disrupts the balance between drag force and buoyancy, leading to localized defluidization. This instability impedes gas exchange between the bubble and emulsion phases, resulting in bubble coalescence and channeling across the bed. The fluidization instability reduces the maximum exothermic temperature and causes significant temperature heterogeneity in the bed. With repeated thermal cycles (20 cycles), the CO₂ absorption capacity of limestone diminishes (the effective conversion rate drops to 0.25), and the instability disappears. The addition of 5wt.% Al₂O₃ (particle size: 0.05–0.075 mm) stabilizes the fluidization state during carbonation, significantly homogenizing the bed temperature distribution, with maximum and average temperature differentials reduced by 63% and 89%, respectively, compared to pure limestone systems. Full article