About the journal The journal Energy Conversions is an international, peer-reviewed open-access journal that aims to advance the science, engineering, and policy aspects of sustainable energy systems. The journal focuses on the transformation, integration, utilization, and management of energy in its various forms to improve efficiency, reduce environmental impact, and accelerate the transition toward decarbonized systems. View full aims & scope Article publishing options Open Access Article Publishing Charge (APC): USD 200 (excluding taxes). The amount you pay may be reduced during submission if applicable. Subscription No publication fee charged to authors, and published articles are immediately available to subscribers. <table class="MsoNormalTable" style="border-collapse: collapse; border: none; mso-border-left-alt: solid windowtext .5pt; mso-border-right-alt: solid windowtext .5pt; mso-yfti-tbllook: 1184; mso-padding-alt: 0in 5.4pt 0in 5.4pt; mso-border-insideh: 1.5pt solid #76923C; mso-border-insideh-themecolor: accent3; mso-border-insideh-themeshade: 191; mso-border-insidev: 1.5pt solid #76923C; mso-border-insidev-themecolor: accent3; mso-border-insidev-themeshade: 191;" border="1" cellspacing="0" cellpadding="0"> 1 day Time to first decision 6 days Review Time 7 days Submission to acceptance 1 day Acceptance to publication View all insights Editor-in-chief l View Full editorial board Dr. Malcolm D. Hartwell Professor of Thermal Systems Engineering Midwestern Institute of Energy Innovation, USA Articles Research article lOpen access Evaluating Solar Tracking System Efficiency in Dusty and Humid Environments Anwar H. Al-Assaf 23 July 2025 Research article lOpen access Desalination in the Anthropocene: Technologies, Energy, Brine Management, and Pathways to Ultra-Low-Carbon Water Laila M. Alhumaydi 23 July 2025 Research article lOpen access Cooling Efficiency in Thermal Systems: Metrics, Drivers, and Pathways to Ultra-Low Energy Cooling Jazmynn K. Haffez 23 July 2025 Research article lOpen access Built Environment 2050: Integrating Efficiency, Health, and Carbon Neutrality Across Buildings Jaalaa M. El-Shamyy 23 July 2025 Research article lOpen access A Comprehensive Review of Air Quality Science, Measurement, Health Impacts, and Policy Pathways for Clean Air Narriam A. El Dayd 23 July 2025 Research article lOpen access Advances and Challenges in Solar Energy Conversion: Technologies, Integration Pathways, and Future Prospect Shen Zei 15 Aug 2025 Research article lOpen access Geothermal Energy: Pathways, Technologies, and Prospects for Sustainable Power Generation Hmeed Karm 23 July 2025 Research article lOpen access Hydrogen Energy: Pathways, Technologies, and Global Prospects for a Decarbonized Future Markcus Vogar 23 July 2025 Read latest issue
Desalination at Scale:Technology Choices, Energy Pathways, and Circular Brine Management for Low-Carbon Water
Growing water stress, stricter discharge regulations, and the need to decarbonize utilities are pushing desalination from a niche option to a core component of resilient water portfolios. This review synthesizes the fundamentals and current best practice of thermal desalination (MSF, MED), membrane routes (SWRO/BWRO, electrodialysis), and emerging systems (membrane distillation and electro‑sorption) through a unified lens of thermodynamic limits, practical losses, and plant-level integration. We compare specific energy consumption (SEC), recovery ratio, and permeate quality using harmonized assumptions representative of contemporary operation, emphasizing the roles of high‑efficiency pumps, isobaric energy‑recovery devices, pretreatment robustness, and flexible dispatch under renewable-rich grids. Because concentrate handling is now a dominant sustainability constraint, we map brine pathways spanning engineered marine outfalls, inland MLD/ZLD trains, and targeted valorization (salts, magnesium products, and acid/base generation), highlighting when circular options are credible versus when they add avoidable complexity. New scenario visualizations are provided to summarize (i) sector capacity growth, (ii) technology SEC ranges, (iii) energy-supply shares, (iv) the salinity–recovery trade space, (v) permeate TDS variability, and (vi) the fleet distribution of SWRO energy use. We conclude with design guidelines that connect technology selection, controls, and brine strategy to cost, reliability, and ultra‑low‑carbon targets for site-specific constraints.
Desalination; Reverse osmosis; Thermal desalination; Energy efficiency; Brine valorization; Hybrid systems; Zero-liquid-discharge; Membrane materials; Renewable desalination; Life-cycle assessment
Toward Net-Zero Flight: Scaling Sustainable Aviation Fuel Pathways and Policy
Aviation contributes a meaningful share of global climate forcing and its fuel demand is expected to grow substantially toward mid-century. Sustainable Aviation Fuel (SAF) is widely viewed as the most practical near-term decarbonization lever for long-haul fleets because it can be blended with Jet A-1 and used within existing aircraft and airport infrastructure. This review synthesizes the state of SAF feedstocks and conversion routes, spanning lipid-based hydroprocessing (HEFA), gasification and Fischer-Tropsch synthesis (FT), Alcohol-to-Jet (ATJ), and emerging Power-to-Liquid (PtL) e-fuels produced from CO₂ and renewable hydrogen. We compare indicative yields, lifecycle greenhouse-gas performance, and cost drivers, and we summarize policy and certification enablers including CORSIA and the EU Fit for 55 package. The analysis highlights a central deployment tension: near-term volume growth is constrained by sustainable feedstock availability, while the deepest long-term abatement hinges on scaling low-carbon electricity and green hydrogen. We conclude with priority research and market-structuring actions to accelerate credible, scalable SAF deployment.
Sustainable Aviation Fuel (SAF), Conversion pathways (HEFA, FT, ATJ, PtL), Policy and certification (CORSIA, EU Fit for 55)
Solar Energy Conversion at Scale: Performance Progress, Integration Strategies, and the Next Technology Frontiers
Solar energy is increasingly central to decarbonization because it can be deployed at multiple scales—from rooftops to utility-scale plants—and coupled to storage and sector-coupling pathways. This review synthesizes progress across photovoltaics (PV), concentrated solar power (CSP), photothermal conversion, and solar-driven fuel production, with an emphasis on integration options that improve reliability and system value. We compare technology pathways using conversion performance, levelized cost of electricity (LCOE), storage compatibility, and life-cycle indicators, complemented by case-study evidence from diverse climates and grid contexts. Reported trends show large cost declines for PV since 2010, dispatchability advantages for CSP when paired with molten-salt thermal storage, and fast-rising laboratory efficiencies for emerging absorbers such as perovskites and tandem architectures. We also discuss intermittency management through batteries, thermal storage, and hydrogen as a long-duration option, alongside sustainability challenges including land-use trade-offs, water constraints for steam-cycle CSP, and end-of-life recycling and critical-material recovery for PV modules. The analysis highlights that the next phase of solar deployment depends less on proving technical feasibility and more on scaling integrated, circular, and equitable energy-system designs.
Solar photovoltaics, Concentrated solar power, Energy storage, Photothermal conversion, Hybrid systems, Solar fuels, Sustainability, Smart grids, Solar integration, Renewable energy
Bioelectrochemical and Anaerobic Pathways for Microbial Energy Recovery: Progress, Performance Metrics, and Deployment Challenges
Microbial energy technologies convert organic matter and carbon dioxide into useful energy carriers by exploiting microbial metabolism and electron-transfer networks. This review compares four representative platforms—anaerobic digestion (AD), microbial fuel cells (MFCs), microbial electrolysis cells (MECs), and microbial electrosynthesis (MES)—using a unified lens of biochemical pathways, reactor/electrode design, microbial ecology, and scalability. We highlight how extracellular electron transfer (EET), biofilm structure, and electrode surface chemistry govern bioelectrochemical performance, while syntrophic consortia and retention time control AD conversion. Recent advances in omics-enabled community management, non-precious cathode catalysts, and structured/3D electrodes have improved efficiency and robustness, yet major barriers remain: internal resistance, membrane fouling, product selectivity, and scale-up losses. We close by outlining practical integration routes with wastewater treatment and carbon-management infrastructure, clarifying where each technology is best positioned—from mature centralized biogas to decentralized treatment-power co-benefits, renewable hydrogen coupling, and carbon-to-chemicals conversion.
Microbial fuel cells (MFCs), Anaerobic digestion, Wastewater-to-energy integration
From Blend Limits to Net-Zero Flight: Comparing SAF Pathways, Costs, and the Scale-Up to 2050
Aviation’s reliance on energy-dense liquid fuels makes deep decarbonization challenging, and Sustainable Aviation Fuel (SAF) remains the most immediately deployable lever because it can be used within existing aircraft and fueling infrastructure. This paper reviews SAF as a portfolio of routes rather than a single solution, synthesizing the techno-performance, lifecycle impacts, certification status, and deployment constraints of today’s leading pathways. We compare lipid-based HEFA, waste/residue-enabled Fischer–Tropsch (FT), Alcohol-to-Jet (ATJ), and Power-to-Liquid (PtL) e-kerosene, highlighting how yield/efficiency, upstream energy inputs, and feedstock availability jointly determine climate benefit and cost. Reported performance spans high HEFA yields (80–90%) versus lower FT yields (35–45%) and PtL electricity-to-liquid efficiencies (35–45%), while lifecycle GHG reductions vary from ~40–70% (ATJ) to ~90–100% for PtL under fully renewable electricity and atmospheric CO2 sourcing. Economic barriers persist: SAF costs commonly exceed fossil jet fuel, with pathway-dependent ranges that can reach multiple dollars per liter, especially for PtL dominated by hydrogen cost. Finally, we frame deployment as a scale problem: moving from today’s sub-billion-liter production to hundreds of billions of liters by 2050 requires sustained, policy-backed capacity growth and rapid infrastructure learning curves.
Sustainable Aviation Fuel (SAF), Conversion pathways (HEFA, FT, ATJ, PtL), Lifecycle greenhouse gas (GHG) emissions
From Molecules to Megatons: Materials, Process Intensification, and Infrastructure Integration for Scalable CO₂ Capture
Carbon capture is moving from single-unit demonstrations toward integrated, multi-sector deployment—yet scale-up remains constrained by the coupled limits of materials performance, regeneration energy, and infrastructure readiness. This review synthesizes advances across post-combustion, pre-combustion, oxy-fuel, and direct air capture routes, with a comparative focus on adsorption, absorption, membrane separation, and cryogenic methods under realistic operating conditions. Emphasis is placed on how humidity, trace impurities, and low CO₂ partial pressure reshape sorbent/solvent selection and dictate practical process windows. We consolidate reported benchmarks for capacity, kinetics, cyclic stability, heat duties, and cost ranges, and connect these metrics to process intensification strategies such as structured contactors, hybrid solvent–sorbent concepts, and low-grade heat utilization. In parallel, we assess integration pathways—industrial clusters, renewable coupling, and CO₂ transport/storage networks—highlighting how shared infrastructure and heat/power integration can reduce energy penalties and improve technoeconomic feasibility. Finally, we outline research and deployment priorities for the next decade, including standardized testing protocols, durability-focused material design, and system-level optimization that links capture performance to downstream utilization or permanent storage.
Carbon Capture, CCS, CCUS, Direct Air Capture, Adsorption, Absorption, Membranes, Climate Change Mitigation, Energy Systems, Decarbonization
Combustion-to-Work Conversion: A Cross-Platform Review of Thermo‑Chemical Pathways, Cycles, and Emerging Low‑Carbon Directions
Combustion-to-work systems convert fuel chemical energy into mechanical power through coupled thermo‑chemical processes and heat‑engine cycles. This review synthesizes the pathway across reciprocating internal combustion engines, gas turbines, and combined cycles, emphasizing how irreversibilities accumulate from mixing and finite‑rate chemistry to component aerodynamics, heat transfer, friction, and auxiliary loads. A loss‑based framework is used to compare platforms on a consistent lower-heating-value basis and, where informative, through exergy destruction localization. The synthesis highlights that efficiency gains increasingly require coordinated improvements—heat‑release shaping, effective expansion, minimized pressure drops, and recovery of high‑quality exhaust exergy—rather than isolated component upgrades. Emissions are treated as intrinsic constraints that reshape the achievable optimum, with NOx, soot/PM, CO, and unburned hydrocarbons responding differently to temperature–mixture distributions, dilution, and residence time. Emerging directions are reviewed, including lean and staged combustors, low-temperature compression‑ignition modes, hybridized operation, supercritical CO₂ bottoming cycles, and pressure‑gain combustion. Finally, the review discusses fuel transitions (hydrogen, ammonia, sustainable and synthetic fuels) and the implications for stability, materials, and net climate benefit.
combustion, heat engines, Otto cycle, Diesel cycle, Brayton cycle, combined cycle, exergy analysis, emissions, low‑carbon fuels, pressure‑gain combustion
Thermal Energy Storage for Flexible, Low-Carbon Energy Systems: Materials, Architectures, Design Metrics, and Deployment Pathways
Thermal energy storage (TES) is a cornerstone technology for decarbonizing heating and cooling, increasing renewable penetration, and improving grid flexibility by shifting thermal demand in time. This review consolidates TES fundamentals and deployment practice across sensible, latent, and thermochemical pathways, emphasizing how material properties and system architectures translate into practical metrics such as energy density, power density, round-trip efficiency, cycling durability, and levelized cost. Sensible TES remains the most mature and widely deployed, ranging from chilled-water tanks and ice storage in buildings to packed-bed rock, concrete, and molten-salt systems for industrial heat and concentrating solar power. Latent TES (phase change materials, PCMs) enables quasi-isothermal operation and compactness but is constrained by low thermal conductivity, phase segregation, subcooling, and packaging complexity. Thermochemical TES offers the highest theoretical energy density and the possibility of long-duration storage with limited standing losses, yet faces challenges in reactor/contactor design, kinetics, cycling stability, and integration. The review proposes a consistent framework for material screening, component sizing, and system-level evaluation, and summarizes emerging enhancement strategies including encapsulation, finned heat exchangers, metal foams, graphite additives, and cascading temperature stages. Six illustrative figures and three design-oriented tables are provided to connect key concepts: technology classification, energy-density ranges, temperature signatures, PCM property trade-space, suitability scoring, and multi-criteria comparison.
Thermal energy storage; sensible heat; phase change materials; thermochemical storage; district cooling; concentrating solar power; underground thermal energy storage; heat exchangers; energy flexibility; techno-economic metrics
Hybrid Cooling–Desalination Systems for Water–Energy Co-Production: Architectures, Integration Strategies, Performance Metrics, and Research Needs
Cooling and desalination increasingly co-locate in arid coastal regions, creating an opportunity for hybrid systems that co-produce chilled water (or conditioned air) and freshwater while improving total resource utilization. This review surveys hybrid cooling–desalination architectures including absorption cooling integrated with thermal desalination or membrane distillation, adsorption desalination cycles that inherently co-generate cooling and freshwater, seawater air conditioning coupled with reverse osmosis, and solar-assisted multigeneration configurations. The synthesis emphasizes integration mechanisms such as heat cascading from chillers to desalination modules, shared heat rejection, coupling through seawater intake and brine management, and operational coordination under variable ambient conditions. Performance metrics are harmonized across studies using specific electricity consumption, gain-output ratio, cooling COP, exergy efficiency, and water–energy productivity indicators, with attention to constraints like scaling/fouling, intake temperature, and environmental discharge. Recent reviews on synergistic desalination/cooling and on hybrid membrane–thermal desalination underscore both near-term integration benefits and the need for robust, validated designs that can be deployed at scale.
Hybrid desalination, absorption cooling, adsorption desalination, membrane distillation, reverse osmosis, trigeneration, seawater air conditioning, waste heat utilization, solar-driven systems
Organic Rankine Cycle for Low-to-Medium Temperature Heat Recovery: Working Fluids, Architectures, Expanders, Control, and Deployment Pathways
Organic Rankine cycles (ORCs) have matured into a leading technology for converting low-to-medium temperature heat into electricity in applications spanning industrial waste heat, geothermal, biomass, and solar thermal systems. Their competitiveness stems from the ability to match diverse heat-source temperature profiles using organic fluids, flexible architectures (subcritical, recuperated, regenerative, transcritical, and supercritical variants), and compact turbomachinery or volumetric expanders. This review consolidates the state of the art across (i) working-fluid selection under simultaneous thermodynamic, environmental, safety, and cost constraints; (ii) plant architectures and heat-exchanger design that govern pinch losses and off-design behavior; (iii) expander choices from radial turbines to scroll, screw, and piston machines; and (iv) modeling, control, and techno-economic assessment frameworks for robust deployment. The paper synthesizes performance trends drawn from experimental surveys and system demonstrations, highlighting that heat exchangers dominate irreversibilities and dynamic response, while expander efficiency and stable condensation strongly shape net output in small-to-mid scale systems. Recent advances in off-design optimization, moving-boundary dynamics, and supervisory control improve annual energy production and operational reliability. Remaining bottlenecks include fluid regulation transitions, high-temperature stability of “dry” fluids, cost-effective scaling below ~100 kWe, and integration constraints (cooling availability, fouling, and transient heat-source behavior).
Organic Rankine cycle; waste heat recovery; working fluid selection; expander technology; recuperated ORC; supercritical ORC; thermo-economic optimization; dynamic control; exergy analysis
A Comprehensive Review of Air Quality Science, Measurement, Health Impacts, and Policy Pathways for Clean Air
Air pollution remains the leading environmental risk factor for premature mortality worldwide, driven primarily by fine particulate matter (PM₂.₅) and ozone exposure. This review synthesizes advances in atmospheric science, exposure assessment, health evidence, and policy design to inform effective clean‑air strategies. We summarize the physical and chemical formation pathways of key pollutants, evaluate the expanding measurement toolkit from regulatory reference monitors to satellite remote sensing and dense low‑cost sensor networks, and compare modeling architectures that convert emissions and meteorology into concentration fields and population exposure. We assess the strength of the epidemiological evidence linking air pollution to cardiovascular, respiratory, and metabolic outcomes, emphasizing developments in causal inference, non‑linear concentration–response relationships, and the global transferability of risk functions. The review highlights source apportionment insights that prioritize action on residential solid fuel use, traffic, industry, power generation, agriculture, and natural sources. We discuss policy architectures—ambient standards, emission controls, market instruments, and integrated climate‑air frameworks—and quantify health, climate, and economic co‑benefits of mitigation. Six original illustrative figures and three methodological tables are provided to aid teaching and practice. We conclude with a research and policy agenda centered on equity, transparency, sensor fusion, accountability, and sustained implementation
ambient air quality; PM₂.₅; NO₂; ozone; health burden; source apportionment; exposure assessment; low cost sensors; policy; co benefits ambient air quality; PM₂.₅; NO₂; ozone; health burden; source apportionment; exposure assessment; low cost sensors; policy; co benefits
Built Environment 2050: Integrating Efficiency, Health, and Carbon Neutrality Across Buildings and Cities
The built environment accounts for a substantial share of global energy demand, greenhouse gas emissions, and time spent indoors, positioning buildings and urban form at the center of climate mitigation and human well-being. This review synthesizes advances across building physics, systems engineering, and urban design to identify coordinated strategies that lower operational energy, reduce embodied carbon, improve indoor air quality and thermal comfort, and enhance resilience. We map evidence from laboratory studies, field monitoring, and city-scale modeling to show that demand reduction through envelopes, efficient and electrified HVAC, lighting, and controls remains the least-cost pathway in most contexts, particularly when sequenced with grid-interactive demand flexibility and onsite renewables. We highlight the convergence of materials science (low-carbon materials, phase change media), mechatronics (heat pumps, active façades), and data science (digital twins, AI-based controls), and we discuss trade-offs between air quality, ventilation energy, and filtration. Finally, we frame a research agenda around climate-appropriate design, performance verification, and equity-centered retrofits that deliver persistent emissions reductions and healthier indoor environments. Six original figures and three tables summarize trends, correlations, performance distributions, and adoption barriers for decision-makers and researchers.
built environment; building energy; retrofits; HVAC; indoor air quality; thermal comfort; embodied carbon; digital twins; urban morphology; resilience
Cooling Efficiency in Thermal Systems: Metrics, Drivers, and Pathways to Ultra-Low Energy Cooling
Cooling services—space conditioning, industrial refrigeration, and process thermal management—are expanding rapidly with urbanization, rising ambient temperatures, and escalating internal heat densities. This review synthesizes definitions and metrics of cooling efficiency, classifies technological families, analyzes part-load behavior, and maps the roles of climate, humidity, controls, refrigerants, and heat rejection on seasonal performance. We unify performance assessment across rating schemes (COP, EER, SEER, SCOP, IPLV) and discuss end-use context, including comfort, dehumidification, and ventilation penalties. We highlight pathways to high performance—variable-speed compression, advanced heat exchangers, low-GWP refrigerants, hybrid evaporative cycles, sorption and thermally driven systems, free cooling, and system-level optimization—alongside emerging digital enablers such as model-predictive control and fault detection. Original figures illustrate COP degradation with temperature, part-load gains, climate sensitivity, and building energy distributions. The review culminates with a roadmap emphasizing integrated design, verified seasonal metrics, and grid-interactive operation to minimize life-cycle energy and emissions.
Cooling efficiency; COP; EER/SEER; IPLV; evaporative cooling; heat pumps; variable speed; part-load performance; urban heat; waste-heat driven cooling
Desalination in the Anthropocene: Technologies, Energy, Brine Management, and Pathways to Ultra-Low-Carbon Water
Escalating water stress and coastal urbanization are accelerating the deployment of desalination, with global installed capacity exceeding tens of millions of cubic meters per day and growing rapidly in arid and semi-arid regions. This review consolidates technological fundamentals and state-of-practice across thermal processes—multistage flash and multiple-effect distillation—membrane technologies such as reverse osmosis, electrodialysis, and emerging approaches including membrane distillation and capacitive deionization. We critically examine specific energy consumption, thermodynamic limits, and practical strategies that have driven step-changes in energy efficiency, including high-pressure pump advances, energy recovery devices, staging, hybridization, and flexible operation with renewables. Brine management emerges as a central multi-objective challenge linking environment, regulation, and circular-economy opportunities; we survey dilution outfalls, crystallization, mineral recovery, and zero-liquid-discharge architectures. Using harmonized assumptions, we develop comparative performance maps and scenario figures (supplied) to visualize capacity growth, energy mix, recovery vs. feed salinity, permeate quality distributions, and technology-specific energy ranges. We conclude with design guidelines that align plant-level choices with decarbonization targets and resource constraints, highlighting research avenues in low-defect membranes, fouling-resilient pretreatment, high-salinity RO, brine valorization, and system-level controls. The review provides a transparent basis for techno-economic and environmental decision-making in the transition toward ultra-low-carbon desalination.
Evaluating Solar Tracking System Efficiency in Dusty and Humid Environments
This paper will conduct an analysis and comparison of the efficiency of the fixed, single axis and dual axis solar tracking systems based on climate conditions in Jordan. An Altera Field-Programmable Gate Array (FPGA) kit was used to apply the solar tracking and showed a great increase in energy generation. The single-axis tracking system created 51.4 more Wh per day, which resulted in a total of 702.02 Wh generated, as opposed to 582.95 Wh generated by the fixed system. The fixed system showed a peak power output of 70 W, the single-axis tracker was 75 W and the dual-axis tracker at 80 W. The findings also emphasize the environmental factors which significantly affected the daily energy production with dust lowering it by about 40 % and humidity lowering it by up to 12 %. Although the dual-axis system was the most robust in operation, its sensitivity to the environment requires it to be cleaned and maintained on a regular basis. In general, the results show that solar tracking systems result in a substantial improvement of the photovoltaic performance, especially when the device is used in conjunction with proper management of the environment.
Solar tracking, single-axis, dual-axis, fixed PV, dust impact, humidity, photovoltaic performance
Advances and Perspectives in Carbon Capture: Materials, Processes, and System Integration for a Low-Carbon Future
Carbon capture technologies have emerged as critical pillars in the global strategy to mitigate anthropogenic greenhouse gas emissions and achieve net-zero targets. This review synthesizes the current state of the art across capture pathways, including post-combustion, pre-combustion, oxy-fuel, and emerging direct air capture (DAC) approaches. The article provides a comparative evaluation of adsorption, absorption, cryogenic, and membrane-based systems, emphasizing their thermodynamic limits, process intensification strategies, and integration within industrial sectors. Special attention is given to sorbent design, from amine-functionalized materials to next-generation physisorbents such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), highlighting performance under humid and low-partial-pressure conditions. The methodology section outlines a systematic review framework combining bibliometric mapping, technology readiness assessment, and critical benchmarking of energy consumption and cost metrics. Results discuss breakthroughs in structured contactors, hybrid solvent–sorbent systems, and advanced regeneration schemes, supported by figures and tables that visualize trends in capture cost reduction, material performance, and large-scale deployment scenarios. A comprehensive discussion explores scalability, environmental impacts, and integration of capture systems with renewable energy, carbon utilization, and storage infrastructures. The conclusion underscores the role of carbon capture as both a bridging and transformative technology, stressing the urgent need for policy support, public acceptance, and cross-disciplinary innovation. By providing a consolidated overview of materials, processes, and systemic implications, this review aims to guide researchers, engineers, and policymakers toward accelerating the deployment of sustainable carbon capture solutions worldwide.
Biomass Energy: Pathways, Potentials, and Challenges for a Sustainable Energy Future
Biomass energy represents one of the most versatile renewable energy sources, offering a pathway to reduce reliance on fossil fuels while simultaneously addressing waste management challenges. Derived from organic matter such as agricultural residues, forestry by-products, energy crops, and municipal solid waste, biomass can be transformed into solid, liquid, and gaseous fuels through a variety of thermochemical and biochemical processes. This review critically examines the current state of biomass energy, with emphasis on global resource availability, conversion technologies, sustainability implications, and techno-economic perspectives. The paper explores biochemical routes including anaerobic digestion and fermentation, as well as thermochemical processes such as combustion, pyrolysis, and gasification. Special focus is given to the role of biomass in achieving net-zero emissions and its integration within the circular economy. Benchmarking against fossil-based systems is presented to evaluate efficiency, cost, and life-cycle carbon footprints. Results indicate that biomass energy can contribute up to 20% of global primary energy demand by 2050 under favorable policies, yet challenges such as feedstock logistics, land-use competition, and technological optimization remain. The review concludes that the future of biomass lies in hybrid systems, waste valorization, and integration with carbon capture technologies to ensure both environmental and economic viability.
Biomass energy; biofuels; biogas; waste-to-energy; sustainability; carbon neutrality; renewable energy; circular economy; climate change mitigation
Hydrogen Energy: Pathways, Technologies, and Global Prospects for a Decarbonized Future
Hydrogen has emerged as a central pillar in global strategies for achieving net-zero emissions, owing to its versatility, scalability, and compatibility with diverse energy systems. As a clean energy carrier, hydrogen can decouple renewable generation from demand, serve as a fuel in hard-to-abate sectors such as heavy industry and aviation, and act as a long-term energy storage medium. This review comprehensively evaluates the state of hydrogen energy, spanning production technologies, storage and transport systems, end-use applications, and techno-economic considerations. Emphasis is placed on green hydrogen from renewable electrolysis, blue hydrogen with carbon capture, and emerging technologies such as turquoise hydrogen via methane pyrolysis. A methodological framework is developed to compare hydrogen pathways based on efficiency, cost, emissions, and scalability. Results highlight the critical role of policy incentives, international hydrogen trade routes, and infrastructure development in driving hydrogen deployment. Discussion underscores challenges of energy losses, water footprint, and material requirements, while the conclusion outlines future research directions and policy priorities for establishing a sustainable hydrogen economy.
Hydrogen energy; fuel cells; electrolysis; storage; transport; decarbonization; renewable integration; energy systems; global hydrogen economy
Geothermal Energy: Pathways, Technologies, and Prospects for Sustainable Power Generation
Geothermal energy represents a promising and underexploited source of renewable energy that provides baseload electricity and direct heat applications with minimal environmental impact. Unlike solar and wind energy, which suffer intermittency, geothermal systems offer a continuous and stable supply, enabling integration into national grids and industrial operations. This review critically examines the current state of geothermal energy technologies, including dry steam, flash, binary, and emerging enhanced geothermal systems (EGS). A systematic analysis of resource potential, geological considerations, drilling innovations, and power conversion technologies is provided. Moreover, environmental aspects, lifecycle emissions, economic feasibility, and global deployment trends are evaluated. The methodology emphasizes a comprehensive literature survey, comparative assessment, and integration of real-world data to contextualize geothermal energy’s role in decarbonization pathways. The results highlight geothermal’s strong potential to provide up to 8.5% of global electricity demand by 2050, while addressing limitations such as high upfront capital costs and site-specific constraints. Figures and tables illustrate geothermal resource distribution, plant designs, efficiency comparisons, and environmental benefits. The discussion underscores geothermal energy’s advantages in energy security and climate mitigation while identifying research priorities in subsurface imaging, drilling cost reduction, and hybrid system integration. This review concludes that geothermal energy can be a cornerstone of a diversified renewable portfolio, provided technological, financial, and policy challenges are strategically addressed.
Geothermal energy; renewable energy; enhanced geothermal systems; geothermal power plants; sustainability; low-carbon energy; binary cycle; direct use; geothermal heat pumps; reservoir engineering
Advances and Challenges in Solar Energy Conversion: Technologies, Integration Pathways, and Future Prospect
Solar energy stands as the cornerstone of the global transition towards sustainable energy systems. Its abundance, scalability, and technological diversity make it the most promising renewable resource to address the twin challenges of climate change mitigation and energy security. This review paper provides a comprehensive analysis of recent advances in solar energy harvesting technologies, spanning photovoltaic (PV) devices, concentrated solar power (CSP), photothermal systems, solar-driven hydrogen production, and hybrid solar-energy storage integration. The paper examines material innovations, including perovskites, tandem solar cells, and nanostructured absorbers, alongside system-level strategies such as grid integration, demand-response coupling, and smart solar architectures. A comparative methodology is employed to evaluate efficiency improvements, cost reductions, lifecycle sustainability, and techno-economic viability across solar pathways. Results highlight that PV costs have fallen by over 85% since 2010, CSP systems achieve dispatchability through molten-salt storage, and emerging solar-to-hydrogen routes exhibit efficiencies above 15% at lab scale. Figures and tables present data trends, deployment scales, efficiency records, and integration challenges. Discussion emphasizes the barriers to large-scale solar deployment, including intermittency, land-use trade-offs, recycling of solar modules, and socio-economic considerations in different global regions. The review concludes that while no single solar pathway provides a universal solution, a diversified portfolio combining PV, CSP, storage, and solar fuels offers the most resilient route towards achieving net-zero energy systems. Future research must prioritize durability, circular economy principles, and policy frameworks that accelerate solar integration worldwide.
Concentrated solar power, Energy storage, Photothermal conversion, Hybrid systems, Solar fuels, Sustainability, Smart grids, Solar integration, Renewable energy
Catalytic Innovation for Green Fuel Production: Progress and Prospects
Catalysis lies at the heart of modern fuel production, enabling the transformation of feedstocks ranging from fossil resources to biomass and CO₂ into valuable fuels. Over recent decades, tremendous advancements have been achieved in catalyst design, characterization, and deployment in both conventional and sustainable fuel production processes. This review examines the pivotal roles of heterogeneous and homogeneous catalysts across various thermochemical and electrochemical pathways such as hydrocracking, Fischer-Tropsch synthesis, steam reforming, and CO₂ hydrogenation. We discuss active materials, promoters, supports, and deactivation mechanisms, as well as emerging nanocatalysts, bifunctional systems, and single-atom catalysts. Through a comparative analysis of catalytic performances in different systems, the review identifies bottlenecks in catalyst efficiency, selectivity, and stability. Future trends in rational catalyst design, in situ characterization, and AI-guided catalyst discovery are also explored to guide next-generation fuel technologies toward net-zero emissions.
Catalysis, Fuel Production, Fischer-Tropsch Synthesis, Hydrogenation, Zeolites, Reforming, Biofuels, Syngas Conversion, Selectivity, Deactivation
From Simulation to Application: Advancements in Numerical Modeling of Energy Systems
Numerical modeling has emerged as a cornerstone in the design, optimization, and control of modern energy systems. This review explores the evolution and application of numerical techniques, including computational fluid dynamics (CFD), finite element methods (FEM), and transient energy simulation tools, across various domains such as solar thermal collectors, fuel cells, wind turbines, and heat exchangers. The paper discusses governing equations, solution strategies, and model validation techniques. Recent advancements in coupling numerical models with artificial intelligence and optimization algorithms are highlighted. Results from selected case studies are analyzed to illustrate the impact of modeling assumptions, boundary conditions, and grid refinement on prediction accuracy. Finally, challenges such as numerical instability, computational cost, and data integration are discussed, along with future directions emphasizing real-time simulations and digital twins for energy systems.
Numerical modeling, CFD, energy systems, renewable energy, thermal modeling
Electrolytic Hydrogen for a Decarbonized Future
Green hydrogen has emerged as a pivotal energy vector in the global pursuit of decarbonization, energy security, and climate resilience. Produced through electrolysis powered by renewable sources such as wind, solar, or hydro, green hydrogen offers a clean, scalable alternative to fossil fuels for sectors that are hard to abate—including heavy industry, shipping, aviation, and grid storage. This review presents a comprehensive analysis of global efforts in green hydrogen production, deployment strategies, policy support, and technological innovation. The paper evaluates country-specific roadmaps, electrolyzer technologies, cost trajectories, infrastructure challenges, and integration with renewable power systems. A comparative analysis of leading regions—such as the European Union, Gulf countries, Australia, China, and North America—illustrates different strategic pathways and progress levels. The study also highlights critical bottlenecks including water availability, electrolyzer efficiency, hydrogen transport and storage, and the lack of harmonized standards. Based on a synthesis of over 70 high-impact publications and project databases, this review outlines the techno-economic potential of green hydrogen and its role in future energy systems. Key findings indicate that while the levelized cost of hydrogen (LCOH) remains above $4/kg in most regions, rapid deployment and innovation are expected to reduce this to below $2/kg by 2030. The paper concludes by recommending pathways for international collaboration, investment frameworks, and research priorities to accelerate the green hydrogen transition.
Green hydrogen, Renewable-powered electrolysis, Hydrogen cost trajectories (LCOH)
Efficient Journeys: The Future of Aviation Routing
The aviation sector contributes approximately 2–3% of global carbon dioxide emissions, with fuel consumption representing a major operational cost for airlines. As the demand for air travel continues to rise, optimizing flight routes presents a critical opportunity to reduce fuel usage, cut emissions, and improve overall efficiency. This review presents a comprehensive analysis of current strategies and emerging technologies in aviation route optimization, including wind-aware trajectory planning, machine learning algorithms, network-level airspace decongestion, and integration with sustainable aviation fuels (SAF). A wide range of studies demonstrate that wind-optimal routing can yield 1–4% fuel savings on long-haul flights, while artificial intelligence (AI)-based planning methods report reductions up to 14%. Meanwhile, SAF adoption shows strong compatibility with existing propulsion systems and contributes to lifecycle emission reductions. This review also examines hybrid-electric aircraft models and predictive energy management systems as complementary developments in energy optimization. Key findings indicate that combining route optimization with fuel innovation can substantially lower the environmental impact of aviation without requiring major infrastructure changes. The paper concludes with recommendations for integrated optimization approaches and identifies future research opportunities, including real-time decision support systems, SAF scaling, and regulatory incentives. This work provides valuable insights for researchers, engineers, policymakers, and airline operators working to enhance the energy efficiency and sustainability of aviation.
Aviation route optimization, Wind-aware trajectory planning, AI/ML flight planning
Pathways to Net-Zero: Sustainable Aviation Fuel in Action
The aviation sector accounts for over 2% of global CO₂ emissions and is projected to triple by 2050 without intervention. Sustainable Aviation Fuel (SAF) represents a pivotal decarbonization solution, offering net lifecycle greenhouse gas (GHG) reductions of up to 80% compared to conventional jet fuel. This review presents a holistic analysis of SAF development, covering biomass-based and non-biomass feedstocks, conversion pathways (including HEFA, Fischer-Tropsch, ATJ, and Power-to-Liquid), techno-economic performance, and environmental impacts. Key enabling policies such as CORSIA and the EU Fit for 55 framework are examined, alongside challenges like scalability, feedstock availability, and certification bottlenecks. The review concludes by outlining promising research and industrial pathways for accelerating SAF deployment at scale.
This paper reviews the theoretical methodologies used to quantify engine power, focusing on models rooted in thermodynamics, fluid mechanics, and combustion kinetics. With the increasing demand for high-efficiency engines and strict emission regulations, theoretical tools play a vital role in estimating power output without extensive empirical testing. The paper critically examines classical approaches like the air-standard cycle analysis, mean effective pressure calculations, and zero-dimensional thermodynamic models, alongside modern computational techniques including quasi-dimensional modeling and heat-release analysis using pressure data. Furthermore, the paper explores how fuel properties, compression ratio, and engine geometry influence the predictive accuracy of theoretical models. A comparison of different modeling strategies highlights the trade-offs between complexity, computational cost, and precision. Six figures illustrate the diversity of modeling outcomes, covering P–V diagrams, temperature profiles, performance maps, bar plots, pie charts of loss distributions, and 3D contour plots of cylinder temperature. The discussion provides insight into the validity range of each method, proposes guidelines for appropriate model selection, and suggests future directions for model enhancement through hybridization and machine learning.
A Comprehensive Review of Alternative Fuels for Power Generation
The accelerating urgency to mitigate climate change and reduce dependence on fossil fuels has positioned alternative fuels as a critical element in transitioning to a sustainable energy system. This review comprehensively investigates the landscape of alternative fuels, including biofuels, synthetic fuels, hydrogen, ammonia, and alcohol-based fuels, examining their production pathways, environmental benefits, technical challenges, and policy considerations. Emphasis is placed on recent advancements in conversion technologies, lifecycle emissions analysis, and the integration of alternative fuels in existing energy infrastructure. The review also discusses comparative performance and technoeconomic viability across sectors such as transportation, aviation, and power generation. By synthesizing current knowledge and identifying key research gaps, this paper contributes to a deeper understanding of the potential and limitations of alternative fuels in achieving global decarbonization goals.
Alternative fuels, Production pathways and conversion technologies, Lifecycle emissions and technoeconomic analysis
Solid biomass energy has emerged as a crucial pillar in the global transition towards renewable and low-carbon energy systems. Derived from diverse sources including agricultural residues, forestry waste, energy crops, and municipal organic waste, solid biomass offers a sustainable and carbon-neutral alternative to fossil fuels. This review comprehensively explores the current state of solid biomass energy, addressing feedstock availability, conversion technologies such as combustion, pyrolysis, and gasification, and their integration into power generation and heating applications. It critically evaluates environmental impacts, energy yields, and techno-economic viability. Furthermore, the paper discusses barriers related to feedstock logistics, policy uncertainty, and technological limitations, while outlining strategies to enhance efficiency, carbon reduction potential, and rural development. Future prospects are examined through the lens of advanced conversion technologies, integrated bio-refinery models, and circular economy frameworks. The findings suggest that while solid biomass cannot entirely replace fossil fuels, it can significantly contribute to localized, sustainable energy systems and decarbonization goals when appropriately managed and supported through robust policies.
Solid biomass energy, Biomass conversion technologies (combustion/pyrolysis/gasification), Techno-economic and environmental assessment
Waste Food to Energy: Sustainable Bioenergy Conversion
Food waste represents a significant fraction of global municipal solid waste and constitutes a critical environmental and economic challenge. With rising urbanization and food consumption patterns, the need for sustainable and circular solutions is paramount. This review comprehensively evaluates the potential of converting waste food into energy via various biochemical and thermochemical technologies, focusing on anaerobic digestion, gasification, pyrolysis, and direct combustion. Emphasis is placed on technological feasibility, energy efficiency, environmental impacts, and integration into existing energy frameworks. The paper also explores the barriers to commercialization, such as feedstock heterogeneity, pretreatment complexity, policy limitations, and public perception. A comparative analysis is presented to assess the scalability and techno-economic viability of different conversion methods. Ultimately, the review proposes an integrated system combining pre-sorting, microbial enhancement, and hybrid thermochemical-biochemical routes to maximize yield and minimize emissions. This work highlights the underutilized potential of food waste as a renewable energy source and outlines future research directions for optimizing waste-to-energy (WTE) solutions in alignment with global sustainability goals.
Food waste-to-energy (WTE), Anaerobic digestion, Thermochemical conversion (gasification/pyrolysis
Microbiological energy harnesses the metabolic activities of microorganisms to convert organic and inorganic substrates into usable energy forms, primarily electricity, hydrogen, and methane. It offers a sustainable, low-emission alternative to fossil fuels while providing simultaneous benefits such as waste reduction and nutrient recovery. This review explores the major pathways and technologies in microbiological energy, including microbial fuel cells (MFCs), microbial electrolysis cells (MECs), anaerobic digestion, and microbial electrosynthesis. We discuss microbial community dynamics, biofilm formation, and electron transfer mechanisms central to energy generation. Recent advancements in metabolic engineering, materials science, and bioreactor design have significantly improved conversion efficiencies and system scalability. Additionally, we assess techno-economic feasibility, integration with wastewater treatment, and potential roles in decentralized energy systems. Challenges such as electron transfer limitations, low power densities, and upscaling are addressed alongside future directions. Microbiological energy stands as a transformative pillar in the global shift toward sustainable, circular bioeconomies.