Browsing by Author "Nabavi, Ali"

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    Advancements in sorption-enhanced steam reforming for clean hydrogen production: a comprehensive review
    (Elsevier, 2025-03-01) Farooqi, Ahmad Salam; Allam, Abdelwahab N.; Shahid, Muhammad Zubair; Aqil, Anas; Fajri, Kevin; Park, Sunhwa; Abdelaziz, Omar Y.; Abdelnaby, Mahmoud M.; Hossain, Mohammad Mozahar; Habib, Mohamed A.; Hasnain, Syed Muhammad Wajahat ul; Nabavi, Ali; Zhu, Mingming; Manovic, Vasilije; Nemitallah, Medhat A.
    The sorption-enhanced steam methane reforming (SE-SMR) process, which integrates methane steam reforming with in situ CO2 capture, represents a breakthrough technology for clean hydrogen production. This comprehensive review thoroughly explores the SE-SMR process, highlighting its ability to efficiently combine carbon capture with hydrogen generation. The review evaluates the mechanisms of SE-SMR and evaluates a range of innovative sorbent materials, such as CaO-based, alkali-ceramic, hydrotalcite, and waste-derived sorbents. The role of catalysts in enhancing hydrogen production within SE-SMR processes is also discussed, with a focus on bi-functional materials. In addition to examining reaction kinetics and advanced process configurations, this review touches on the techno-economic aspects of SE-SMR. While the analysis does not provide an in-depth economic evaluation, key factors such as potential capital costs (CAPEX), operational expenses (OPEX), and scalability are considered. The review outlines the potential of SE-SMR to offer more efficient hydrogen production, with the added benefit of in situ carbon capture simplifying the process design. Although a detailed economic comparison with other hydrogen production technologies was not the focus, this review emphasizes SE-SMR's promise as a scalable and flexible solution for clean energy. With its integrated design, SE-SMR offers pathways to industrial-scale hydrogen production. This review serves as a valuable resource for researchers, policymakers, and industry experts committed to advancing sustainable and efficient hydrogen production technologies.
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    Co₂ separations and the role of surface functionality
    (Cranfield University, 2021) Wadi, Basil; Nabavi, Ali; Manovic, Vasilije
    To curb irreversible environmental effects of climate change, urgent measures must be taken to limit anthropogenic emissions and achieve net-zero carbon goals by 2050. Carbon capture technology to meet these goals is wide ranging, with novel methods directed at biogas upgrading or direct air capture. Biogas is produced from the anaerobic digestion of biological waste and considered a valuable renewable energy source; to produce biomethane for use interchangeably with natural gas. However, widespread use of established separation processes is limited, primarily due to low CO₂ selectivity or high energy demands of cyclic operation. One method to tackle these issues is the development of novel sorbents for use in pressure swing adsorption, targeting maximum CO₂ capacity and selectivity, while minimising regeneration energy penalties. Adsorbents incorporated with amines can meet one of these criteria, selectively adsorbing CO₂, but require high regeneration energies. Herein, the adsorption performance of a diverse range of amines grafted on mesoporous silica at varying densities is studied, to understand developing adsorption mechanisms, and identify the ideal degree of functionalisation for gas separations. It was found that although high amine densities led to the highest enhancement in CO₂ capacity and selectivity, moderate levels have comparable selectivity and capacity in isothermal adsorption-desorption conditions, standing out are di- and secondary amines. Diamine loadings achieved an adsorption capacity of 1.12 mmol/g, a heat of adsorption of 35-50 kJ/mol, and an IAST selectivity of 374 at CO₂ partial pressures of 40 kPa. Secondary amines had a low capacity of 0.67 mmol/g, but a higher heat of adsorption comparatively. The optimal binder formulation for pellet preparation of amine grafted silicas was also studied, a necessary step in conducting laboratory scale fixed-bed adsorption studies. When applying amines for ambient air adsorption, very high amine loadings result in slow adsorption kinetics, rendering the advantage of their high capacity debatable. Moderate loadings of primary and triamine under humid conditions have higher adsorption rates >250 µg/g/min, making them more suited for fast cycle processes.
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    The effect of hydrogen fuel on the performance and emissions of 3 kWe natural gas fuelled microturbine
    (Elsevier, 2024-11-15) Jomekian, Abolfazl; Alhasnawi, Bilal Naji; Bazooyar, Bahamin; Nabavi, Ali; Varasteh, Hirbod
    Hydrogen is an alternative fuel to power microturbines. In this work, the application of H2 in a 3 kWe microturbine combustor is investigated. First, the combustor is tested with different molar concentrations of hydrogen in methane fuel (XH2= 5%, 10% and 20%). Afterward, the operation of the microturbine is verified using thermodynamic analysis of the microturbine cycle. The combustion of the fuels is investigated using CFD analysis. The level of gaseous emissions including (CO2, CO, and NOX) and the microturbine overall operability in terms of turbomachine mechanical and thermal efficiencies are compared in each case to find out the influence of hydrogen addition on the natural gas combustion in the microturbine (MT). Findings show that the application of hydrogen in the MT combustor decreases the level of CO2 and CO emissions while increasing NOX emissions. Despite the improvement in combustion, hydrogen could deteriorate the MT effectiveness and overall efficiency. The findings demonstrate that if the hydrogen mole percent in the fuel rises from 0 to 10, the cycle efficiency decreases from 4.73% to 4.7% and if it increases to 20 percent, the efficiency of the cycle increases from 4.7% to 4.92%.
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    Towards a unified theory of domestic hydrogen acceptance: a mixed-methods multigroup analysis.
    (Cranfield University, 2023-10) Gordon, Joel Adam; Ozkan, Nazmiye; Nabavi, Ali
    The historical record reflects the need to understand the dynamics of social acceptance in advance of technology deployment to minimise the risk of non-adoption or slow diffusion. In the emerging context of hydrogen energy technologies, research on social acceptance has ebbed and flowed, reflecting various hype cycles associated with the hydrogen economy. Following primary interest in public perceptions of hydrogen for transport applications, a social science research agenda on hydrogen energy technologies for domestic space and hot water heating, and cooking has recently emerged. Research uptake follows growing policy interest in converting the national gas grid to hydrogen in countries such as the United Kingdom. The question remains, how do existing gas users in the United Kingdom perceive the prospect of switching to a hydrogen home? In response, this thesis advances a unified theory and establishes a comprehensive typology of domestic hydrogen acceptance, which embed multiple dimensions such as knowledge and awareness, environmental attitude, and financial perceptions. Partial least squares structural equation modelling is employed to determine the antecedents of domestic hydrogen acceptance and adoption intention, which include perceived community benefits, perceptions of hydrogen production pathways, public trust, and positive emotions. Subsequently, partial least squares multigroup analysis is applied to explore the potential for divergent consumer perceptions and preferences. Notably, the statistical findings suggest technology perceptions is the main determinant of adoption potential among consumers who are non-engaged in technology and the environment. By contrast, production perceptions and safety perceptions hold the strongest influence among consumers who are at least moderately engaged in technology and the environment. This thesis enriches conceptual and empirical understanding on the dynamics of domestic hydrogen acceptance and adoption in support of securing a socially acceptable transition pathway for residential decarbonisation. Foremost, segment- specific strategies should be embedded into national and regional policy making on the domestic hydrogen transition to steer progress towards realising a net-zero society.