Search Results (211)

Hydrogen is being increasingly recognized as a promising clean, renewable energy carrier. Among the available production pathways, biological processes, particularly dark fermentation of residual biomasses and agricultural by-products, represent an appealing approach aligned with circular economy principles. These feedstocks are abundant and low cost; however, their relatively low energy density constrains process efficiency. To mitigate this limitation, research efforts have concentrated on optimizing substrate composition and implementing pre-treatment strategies to enhance hydrogen yields. Numerous studies have explored the potential of agricultural and livestock residue, yet reported outcomes are often heterogeneous in terms of units, systems, and experimental conditions, complicating direct comparison. This review consolidates current knowledge and identifies effective strategies to optimize biohydrogen generation. Among the investigated substrates, corn stover emerges as the most promising, with hydrogen yields up to 200 [mL H₂/gVS (Volatile Solids)]. Evidence further suggests that inoculum processing, including enrichment or pre-treatment, can substantially improve performance, often more effectively than substrate processing alone. When both inoculum and substrate are treated, hydrogen yields may increase up to fourfold relative to untreated systems. Overall, integrating suitable feedstocks with targeted processing strategies is crucial to advancing sustainable biohydrogen production. Full article

This study presents a comprehensive review of the viability of hydrogen as an energy carrier for offshore wind energy compared to existing electricity carrier systems. To enable a state-of-the-art system comparison, a review of wind-to-hydrogen energy conversion and transmission systems is conducted alongside wind-to-electricity systems. The review reveals that the wind-to-hydrogen energy conversion and transmission system becomes more cost-effective than the wind-to-electricity conversion and transmission system for offshore wind farms located far from the shore. Electrical transmission systems face increasing technical and economic challenges relative to the hydrogen transmission system when the systems move farther offshore. This study also explores the feasibility of using seawater for hydrogen production to conserve freshwater resources. It was found that while this approach conserves freshwater and can reduce transportation costs, it increases overall system costs due to challenges such as membrane fouling in desalination units. Findings indicated that for this approach to be sustainable, proper management of these challenges and responsible handling of saline waste are essential. For hydrogen energy transmission, this paper further explores the potential of repurposing existing oil and gas pipeline infrastructure instead of constructing new pipelines. Findings indicated that, with proper retrofitting, the existing natural gas pipelines could provide a cost-effective and environmentally sustainable solution for hydrogen transport in the near future. Full article

In the context of the growing adoption of alternative gas separation processes, combined with the interest in hydrogen as a fuel and energy carrier, the use of membrane technology in H₂/CH₄ purification is analyzed in this work, focusing on the techno-economic aspects. In particular, the separation and economic performance of three Pd–Ag/Si-CHA membrane plants are simulated, aiming to achieve high degrees of purity and recovery paired with cost-effective configurations. A single Pd–Ag membrane stage operating at 20 atm and 350 °C can theoretically guarantee a CH₄ concentration of 95%, while a completely pure H₂ stream leaves the plant as a permeate product. The choice of a less selective Si-CHA membrane allows a temperature reduction but implies the use of more stages to achieve the desired CH₄ target. In addition, H₂ purity does not exceed 98%. A two-stage hybrid process, in which the retentate gas leaving the Pd–Ag membrane is cooled and fed to the Si-CHA unit, is also a cost-effective solution, as feed pressure can be reduced to 10 atm with significant compression cost savings. All the configurations are able to provide positive values of economic potential (EP); however, the single Pd–Ag membrane plant is the best option since it guarantees the highest EP, net profit and net present value (NPV). Full article

The United Nations has set a global vision towards emissions reduction and green growth through the Sustainable Development Goals (SDGs). Towards the realisation of SDGS 7, 9, and 13, we focus on green hydrogen production as a potential pathway to achievement. Green hydrogen, produced via water electrolysis powered by renewable energy sources, represents a pivotal solution towards climate change mitigation. Energy access in West Africa remains a challenge, and dependency on fossil fuels persists. So, green hydrogen offers an opportunity to harness abundant solar resources, reduce carbon emissions, and foster economic development. This study evaluates the techno-economic feasibility of green hydrogen production in five West African countries: Ghana, Nigeria, Mali, Niger, and Senegal. The analyses cover the solar energy potential, hydrogen production capacities, and economic viability using the Levelised Cost of Hydrogen (LCOH) and Net Present Value (NPV). Results indicate substantial annual hydrogen production potential with LCOH values competitive with global benchmarks amidst the EU’s Carbon Border Adjustment Mechanism (CBAM). Despite this potential, several barriers exist, including high initial capital costs, policy and regulatory gaps, limited technical capacity, and water resource constraints. We recommend targeted strategies for strengthening policy frameworks, fostering international partnerships, enhancing regional infrastructure integration, and investing in capacity-building initiatives. By addressing these barriers, West Africa can be a key player in the global green hydrogen market. Full article

Blue hydrogen technology, generated from natural gas through carbon capture and storage (CCS) technology, is a promising solution to mitigate greenhouse gas emissions and meet the growing demand for clean energy. To improve the sustainability of blue hydrogen, it is crucial to explore alternative feedstocks, production methods, and improve the efficiency and economics of carbon capture, storage, and utilization strategies. Two established technologies for hydrogen synthesis are Steam Methane Reforming (SMR) and Autothermal Reforming (ATR). The choice between SMR and ATR depends on project specifics, including the infrastructure, energy availability, environmental goals, and economic considerations. ATR-based facilities typically generate hydrogen at a lower cost than SMR-based facilities, except in cases where electricity prices are elevated or the facility has reduced capacity. Both SMR and ATR are methods used for hydrogen production from methane, but ATR offers an advantage in minimizing CO₂ emissions per unit of hydrogen generated due to its enhanced energy efficiency and unique process characteristics. ATR provides enhanced utility and flexibility regarding energy sources due to its autothermal characteristics, potentially facilitating integration with renewable energy sources. However, SMR is easier to run but may lack flexibility compared to ATR, necessitating meticulous management. Capital expenditures for SMR and ATR hydrogen reactors are similar at the lower end of the capacity spectrum, but when plant capacity exceeds this threshold, the capital costs of SMR-based hydrogen production surpass those of ATR-based facilities. The less profitably scaled-up SMR relative to the ATR reactor contributes to the cost disparity. Additionally, individual train capacity constraints for SMR, CO₂ removal units, and PSA units increase the expenses of the SMR-based hydrogen facility significantly. Full article

The Allam power cycle is a groundbreaking elevated-pressure power generation unit that utilizes oxygen and fossil fuels to generate low-cost electricity while capturing carbon dioxide (CO₂) inherently. In this project, we utilize the CO₂ generated from the Allam cycle as feedstock for a newly envisioned industrial complex dedicated to producing renewable hydrocarbons. The industrial complex (FAAR) comprises four subsystems: (i) a Fischer–Tropsch synthesis plant (FTSP), (ii) an alkaline water electrolysis plant (AWEP), (iii) an Allam power cycle plant (APCP), and (iv) a reverse water-gas shift plant (RWGSP). Through effective material, heat, and power integration, the FAAR complex, utilizing 57.1% renewable energy for its electricity needs, can poly-generate sustainable hydrocarbons (C₁–C₃₀), pure hydrogen, and oxygen with near-zero emissions from natural gas and water. Economic analysis indicates strong financial performance of the development, with an internal rate of return (IRR) of 18%, a discounted payback period of 8.7 years, and a profitability index of 2.39. The complex has been validated through rigorous modeling and simulation using Aspen Plus version 14, including sensitivity analysis. Full article

This study presents the design and techno-economic optimization of a hybrid renewable energy system (HRES) for a coastal hotel in Manavgat, Türkiye. The system integrates photovoltaic (PV) panels, wind turbines (WT), pumped hydro storage (PHS), hydrogen storage (electrolyzer, tank, and fuel cell), batteries, a fuel cell-based combined heat and power (CHP) unit, and a boiler to meet both electrical and thermal demands. Within this broader optimization framework, six optimal configurations emerged, representing grid-connected and standalone operation modes. Optimization was performed in HOMER Pro to minimize net present cost (NPC) under strict reliability (0% unmet load) and renewable energy fraction (REF > 75%) constraints. The grid-connected PHS–PV–WT configuration achieved the lowest NPC ($1.33 million) and COE ($0.153/kWh), with a renewable fraction of ~96% and limited excess generation (~21%). Off-grid PHS-based and PHS–hydrogen configurations showed competitive performance with slightly higher costs. Hydrogen integration additionally provides complementary storage pathways, coordinated operation, waste heat utilization, and redundancy under component unavailability. Battery-only systems without PHS or hydrogen storage resulted in 37–39% higher capital costs and ~53% higher COE, confirming the economic advantage of long-duration PHS. Sensitivity analyses indicate that real discount rate variations notably affect NPC and COE, particularly for battery-only systems. Component cost sensitivity highlights PV and WT as dominant cost drivers, while PHS stabilizes system economics and the hydrogen subsystem contributes minimally due to its small scale. Overall, these results confirm the techno-economic and environmental benefits of combining seawater-based PHS with optional hydrogen and battery storage for sustainable hotel-scale applications. Full article

Decarbonizing the industrial sector is essential to achieving net-zero targets and ensuring a sustainable future. Carbon–Hydrogen–Oxygen Symbiosis Networks (CHOSYN) are a set of interconnected hydrocarbon-processing plants that optimize the synergistic use of mass and energy resources in pursuit of both environmental objectives and profitability enhancement. However, this interconnectedness also introduces fragility, arising from technical and administrative dependencies among the participating facilities. In this work, a systematic framework is introduced to incorporate resilience assessment and sustainability enhancement within CHOSYNs. A CHOSYN representation is developed for a proposed industrial cluster, where processes are linked through interceptor units, which facilitate the exchange and conversion of carbon-, hydrogen-, and oxygen-based streams to meet demands. A multi-objective optimization framework is formulated with four competing goals: minimizing cost, minimizing net CO₂ emissions, maximizing internal CO₂ utilization, and minimizing the number of interceptors’ processing steps. The augmented $\epsilon$-constraint method is used to generate a Pareto front that captures the trade-offs among these objectives. To complement the synthesis, a resilience assessment framework is applied to evaluate network performance under disruption by incorporating inter-plant dependencies and modeling disruption propagation. The results show that even under worst-case scenarios, integration through CHOSYN can achieve significant gains in CO₂ utilization and reductions in raw material procurement requirements. Resilience analysis adds an important dimension by quantifying the economic impacts of disruptions to both highly connected and sparsely connected yet critical nodes, revealing vulnerabilities not evident from topology alone. Full article

To effectively address the issues of curtailed wind and photovoltaic (PV) power caused by the high proportion of renewable energy integration and to promote the clean and low-carbon transformation of the energy system, this paper proposes a “chemical–mechanical” dual-pathway synergistic mechanism for the reversible solid oxide cell (RSOC) and flywheel energy storage system (FESS) electricity–hydrogen hybrid system. This mechanism aims to address both short-term and long-term energy storage fluctuations, thereby minimizing economic costs and curtailed wind and PV power. This synergistic mechanism is applied to regulate system operations under varying wind and PV power output and electricity–hydrogen load fluctuations across different seasons, thereby enhancing the power generation system’s ability to integrate wind and PV energy. An economic operation model is then established with the objective of minimizing the economic costs of the electricity–hydrogen hybrid system incorporating RSOC and FESS. Finally, taking a large-scale new energy industrial park in the northwest region as an example, case studies of different schemes were conducted on the MATLAB platform. Simulation results demonstrate that the reversible solid oxide cell (RSOC) system—integrated with a FESS and operating under the dual-path coordination mechanism—achieves a 14.32% reduction in wind and solar curtailment costs and a 1.16% decrease in total system costs. Furthermore, this hybrid system exhibits excellent adaptability to the dynamic fluctuations in electricity–hydrogen energy demand, which is accompanied by a 5.41% reduction in the output of gas turbine units. Notably, it also maintains strong adaptability under extreme weather conditions, with particular effectiveness in scenarios characterized by PV power shortage. Full article

Composite overwrapped pressure vessels (COPVs) have become the core unit for high-pressure hydrogen storage and transportation. However, excessive autofrettage pressure could induce unilateral buckling damage of the metal liner because of large rebound compressive stress induced by large plastic deformation in the depressurization stage. When the liner contains initial defects, its critical unilateral buckling pressure would be further reduced. In this paper, a critical buckling pressure calculation formula was established by finite element analysis and theoretical derivation. Firstly, the classical theoretical calculation models and research methods were analyzed and discussed. Then, by discussing the key influencing parameters, a semi-empirical calculation formula of nonlinear confined buckling pressure of a metal liner with ovality defects was established. Finally, the proposed semi-empirical formula was used to predict the critical internal pressure of a Type-III COPV, and the predicted value was compared with the experimental result. The predicted result was higher than the experimental result and the error range was −2.8%~−23%. The proposed semi-empirical formula of nonlinear confined buckling could provide theoretical support for designing the autofrettage pressure of Type-III COPVs and help to reduce the uncertainty and repeated test cost in the design process. Full article

Given the decline in fossil energy reserves and the need for less pollution, achieving carbon zero is challenging in major industrial sectors. However, the emergence of large-scale hydrogen production systems powered by renewable energy sources offers an achievable option for carbon neutrality in specific applications. When combined with energy storage systems, static power converters are crucial in these production systems. This paper offers a comprehensive review of various power converter topologies, focusing on AC– and DC–bus architectures that interface battery storage units, electrolyzers, and fuel cells. The evaluation of DC/AC, AC/DC, and DC/DC converter topologies, considering cost, energy efficiency, control complexity, power level suitability, and power quality, represents a significant advancement in the field. Furthermore, the subsequent exploration of battery aging behavioral modeling, characterization methods, and real-time parameter estimation of the battery’s equivalent electrical circuit model enhances our understanding of these systems. Large-scale hydrogen production systems most often use an AC–bus architecture. However, DC–bus configuration offers advantages over AC–bus architecture, including high efficiency, simpler energy management, and lower system costs. In addition, MVDC or HVDC DC/DC converters, including isolated and non-isolated designs based on multiple cascaded DABs and MMC-type topologies, have also been studied to adapt the DC–bus to loads. Finally, this work summarizes several battery energy storage projects in the European Union, specifically supporting the large-scale integration of renewable energy sources. It also provides recommendations, discussion results, and future research perspectives from this study. Full article

Since the hydrogen-production process is not yet fully efficient, this paper proposes a poly-generation system that is driven by a geothermal energy source and utilizes a combined Kalina/organic Rankine cycle coupled with an electrolyzer unit to produce, simultaneously, power and green hydrogen in an efficient way. A comprehensive thermodynamic analysis and an exergetic evaluation are carried out to assess the effect of key system parameters (geothermal temperature, high pressure, ammonia–water concentration ratio, and terminal thermal difference) on the performance of concurrent production of power and green hydrogen. Thereby, two configurations are investigated with/without the separation of turbines. The optimal ammonia mass fraction of the basic solution in KC is identified, which leads to an overall optimal system performance in terms of exergy efficiency and green hydrogen production rate. In both configurations, the optimal evaluation is made possible by conducting a genetic algorithm optimization. The simulation results without/with the separation of turbines demonstrate the potential of the suggested cycle combination and emphasize its effectiveness and efficiency. Exemplary, for the case without the separation of turbines, it turns out that the combination of ammonia–water and MD2M provides the best performance with net power of 1470 kW, energy efficiency of 0.1184, and exergy efficiency of 0.1258 while producing a significant green hydrogen amount of 620.17 kg/day. Finally, an economic study allows to determine the total investment and payback time of $3,342,000 and 5.37 years, respectively. The levelized cost of hydrogen (LCOH) for the proposed system is estimated at 3.007 USD/kg H₂, aligning well with values reported in the literature. Full article

A comprehensive literature review highlights how the nature of active metals, support materials, promoters, and synthesis methods influences catalytic performance, with particular attention to ruthenium-based catalysts as the current benchmark. Kinetic models are presented to describe the reaction pathway and predict catalyst behavior. Various reactor configurations, including fixed-bed, membrane, catalytic membrane, perovskite-based, and microreactors, are evaluated in terms of their suitability for ammonia decomposition. While ruthenium remains the benchmark catalyst, alternative transition metals such as iron, nickel, and cobalt have also been investigated, although they typically require higher operating temperatures (≥500 °C) to achieve comparable conversion levels. At the industrial scale, catalyst development must balance performance with cost. Inexpensive and scalable materials (e.g., MgO, Al₂O₃, CaO, K, Na) and simple preparation techniques (e.g., wet impregnation, incipient wetness) may offer lower performance than more advanced systems but are often favored for practical implementation. From a reactor engineering standpoint, membrane reactors emerge as the most promising technology for combining catalytic reaction and product separation in a single unit operation. This review provides a critical overview of current advances in ammonia decomposition for hydrogen production, offering insights into both catalytic materials and reactor design strategies for sustainable energy applications. Full article

Rapid socio-economic development has made energy application and environmental issues increasingly prominent. Hydrogen energy, clean, eco-friendly, and highly synergistic with renewable energy, has become a global research focus. This study, using the EnergyPLAN model that includes the electricity, transportation, and industrial sectors, takes Jinan City as the research object and explores how hydrogen penetration changes affect the decarbonization path of the urban integrated energy system under four scenarios. It evaluates the four hydrogen scenarios with the entropy weight method and technique, placing them in an order of preference according to their similarity to the ideal solution, considering comprehensive indicators like cost, carbon emissions, and sustainability. Results show the China Hydrogen Alliance potential scenario has better CO₂ emission reduction potential and unit emission reduction cost, reducing them by 7.98% and 29.39%, respectively. In a comprehensive evaluation, it ranks first with a score of 0.5961, meaning it is closest to the ideal scenario when cost, environmental, and sustainability indicators are comprehensively considered. The Climate Response Pioneer scenario follows with 0.4039, indicating that higher hydrogen penetration in terminal energy is not necessarily the most ideal solution. Instead, appropriate hydrogen penetration scenarios should be selected based on the actual situation of different energy systems. Full article

This paper investigates technological pathways for the conversion of coal-fired power plants toward sustainable energy sources, using an integrated multi-criteria decision-making approach that combines Proknow-C, AHP, and PROMETHEE. Eight alternatives were identified: full conversion to natural gas, full conversion to biomass, coal and natural gas hybridization, coal and biomass hybridization, electricity and hydrogen cogeneration, coal and solar energy hybridization, post-combustion carbon capture systems, and decommissioning with subsequent reuse. The analysis combined bibliographic data (26 scientific articles and 13 patents) with surveys from 14 energy experts, using Total Decision version 1.2.1041.0 and Visual PROMETHEE version 1.1.0.0 software tools. Based on six criteria (environmental, structural, technical, technological, economic, and social), the most viable option was full conversion to natural gas (ϕ = +0.0368), followed by coal and natural gas hybridization (ϕ = +0.0257), and coal and solar hybridization (ϕ = +0.0124). These alternatives emerged as the most balanced in terms of emissions reduction, infrastructure reuse, and cost efficiency. In contrast, decommissioning (ϕ = −0.0578) and carbon capture systems (ϕ = −0.0196) were less favorable. This study proposes a structured framework for strategic energy planning that supports a just energy transition and contributes to the United Nations Sustainable Development Goals (SDGs) 7 and 13, highlighting the need for public policies that enhance the competitiveness and scalability of sustainable alternatives. Full article