CERES :: Browsing by Author "Nabavi, Seyed Ali"

Browsing by Author "Nabavi, Seyed Ali"

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Open Access
Advances, challenges, and perspectives of biogas cleaning, upgrading, and utilisation
(Elsevier, 2022-02-05) Golmakani, Ayub; Nabavi, Seyed Ali; Wadi, Basil; Manovic, Vasilije
Biogas as a renewable energy resource can be broadly recognised as a carbon–neutral fuel which reduces anthropogenic greenhouse gas emissions, mitigates global warming, and diversifies energy supply. However, the biogas share in the global renewable energy supply chain and technology deployment and maturity are not commensurate with the potential. The first half of this study critically reviews state of the art developments in biogas cleaning and upgrading technologies by considering their present status, current challenges, and barriers associated with their future development. The second part of this paper aims to address critical gaps in converting biogas to biomethane, proposing required pre-treatment steps for different technologies. The third part focuses on current policies concerning the strict regulations implemented for flaring consent applications. In this section, biogas upgrading technologies were compared by estimating the global warming potential (GWP) resulting from waste gases (WG). It was observed that due to high methane losses, WGs from membrane technologies have the highest GWP, but with flaring have the lowest GWP. In the last part of this review, the recent applications of biogas in cogeneration (CHP), tri-generation (CCHP), quad-generation systems, heat, and vehicles are discussed. The use of biogas by different technologies, and their resulting efficiencies were analysed in CHP applications, including microturbines, micro humid air turbine (mHAT), solid oxide fuel cells (SOFC) and hybrid systems of SOFC-microturbines.
Open Access
Assessment of optimal conditions for the performance of greenhouse gas removal methods
(Elsevier, 2021-06-18) Asibor, Jude Odianosen; Clough, Peter T.; Nabavi, Seyed Ali; Manovic, Vasilije
In this study, a comparative literature-based assessment of the impact of operational factors such as climatic condition, vegetation type, availability of land, water, energy and biomass, management practices, cost and soil characteristics was carried out on six greenhouse gas removal (GGR) methods. These methods which include forestation, enhanced weathering (EW), soil carbon sequestration (SCS), biochar, direct air capture with carbon storage (DACCS) and bioenergy with carbon capture and storage (BECCS) were accessed with the aim of identifying the conditions and requirements necessary for their optimum performance. The extent of influence of these factors on the performance of the various GGR methods was discussed and quantified on a scale of 0–5. The key conditions necessary for optimum performance were identified with forestation, EW, SCS and biochar found to be best deployed within the tropical and temperate climatic zones. The CCS technologies (BECCS and DACCS) which have been largely projected as major contributors to the attainment of the emission mitigation targets were found to have a larger locational flexibility. However, the need for cost optimal siting of the CCS plant is necessary and dependent on the presence of appropriate storage facilities, preferably geological. The need for global and regional cooperation as well as some current efforts at accelerating the development and deployment of these GGR methods were also highlighted.
Open Access
Beyond the triangle of renewable energy acceptance: The five dimensions of domestic hydrogen acceptance
(Elsevier, 2022-08-07) Gordon, Joel A.; Balta-Ozkan, Nazmiye; Nabavi, Seyed Ali
The ‘deep’ decarbonization of the residential sector is a priority for meeting national climate change targets, especially in countries such as the UK where natural gas has been the dominant fuel source for over half a century. Hydrogen blending and repurposing the national grid to supply low-carbon hydrogen gas may offer respective short- and long-term solutions to achieving emissions reduction across parts of the housing sector. Despite this imperative, the social acceptance of domestic hydrogen energy technologies remains underexplored by sustainability scholars, with limited insights regarding consumer perceptions and expectations of the transition. A knowledge deficit of this magnitude is likely to hinder effective policymaking and may result in sub-optimal rollout strategies that derail the trajectory of the net zero agenda. Addressing this knowledge gap, this study develops a conceptual framework for examining the consumer-facing side of the hydrogen transition. The paper affirms that the spatiotemporal patterns of renewable energy adoption are shaped by a range of interacting scales, dimensions, and factors. The UK’s emerging hydrogen landscape and its actor-network is characterized as a heterogenous system, composed of dynamic relationships and interdependencies. Future studies should engage with domestic hydrogen acceptance as a co-evolving, multi-scalar phenomenon rooted in the interplay of five distinct dimensions: attitudinal, sociopolitical, community, market, and behavioral acceptance. If arrived to, behavioral acceptance helps realize the domestication of hydrogen heating and cooking, established on grounds on cognitive, sociopolitical, and sociocultural legitimacy. The research community should internalize the complexity and richness of consumer attitudes and responses, through a more critical and reflexive approach to the study of social acceptance.
Open Access
Blue hydrogen production through partial oxidation: a techno‐economic and life cycle assessment
(Wiley, 2024) Khallaghi, Navid; Ghiami, Shamsoddin; Jeswani, Harish; Nabavi, Seyed Ali; Anthony, Edward J; Klyamkin, Semen
Partial oxidation (POx) as a hydrogen production method has not received comprehensive exploration as the resulting syngas has a relatively low H2/CO ratio compared to established techniques like steam methane reforming (SMR). As a result, this study aims to comprehensively investigate the feasibility of a low‐carbon hydrogen production process using POx from both technical‐economic and environmental standpoints. To achieve this, the Aspen Plus® software is employed to model a hydrogen production plant with carbon capture integration, referred to as POx‐CCS (carbon capture and storage). The research reveals that the overall energy efficiency of the POx‐CCS process is around 73%. Moreover, the economic evaluation indicates that the levelised cost of hydrogen (LCOH) is €1.8/ kgH2, given a fuel price of €5.7 per GJ. This cost competitiveness positions POx‐CCS in line with conventional hydrogen production methods. From an environmental perspective, the impact of climate change on hydrogen production through the POx‐CCS process is assessed to be 1.1 kg CO2 eq./kgH2. This impact is reduced by 69% compared to SMR with CCS.
Open Access
Carbon emissions and decarbonisation: the role and relevance of fermentation industry in chemical sector
(Elsevier, 2023-10-07) Agrawal, Deepti; Awani, Kelvin; Nabavi, Seyed Ali; Balan, Venkatesh; Jin, Mingjie; Aminabhavi, Tejraj M.; Dubey, Kashyap Kumar; Kumar, Vinod
Fermentation industry is emerging as sustainable technological alternative to cater the production of various chemical building blocks which are commercially manufactured by petrochemical route. The primary reason for this major transition is global commitment towards decarbonisation of chemical sector, as their conventional fossil-based routes pose serious environmental threat. For instance, in 2022, the direct carbon dioxide (CO2) emission during synthesis of primary chemicals accounted for ∼ 920 Mt. CO2 is one of the prominent greenhouse gases (GHG’s), contributing majorly towards global warming effect and drastic climate change. Fermentation industry largely thrives on exploiting fermentable and organic carbon derived from edible and/or non-edible biomass and transforming them to valorised products using microbial cell factories. Therefore, the production of bio-based chemicals via this route is often associated with low or zero-carbon footprint, resulting in either carbon neutral or carbon negative products. This review focuses on different types of fermentative processes and their impact on carbon release and decarbonisation. It further discusses the relevance and contribution of fermentation industry as well as biological processes to provide a sustainable solution towards decarbonisation of chemical sector. Further, it showcases the advantages of some commercial proven and/or pipeline bio-based products over their conventional competitor fossil-based products, especially from an environmental viewpoint. Finally, advantages of biogenic CO2 from fermentation industry over other sources and CO2 removal from fermentation as a platform for carbon offsetting are covered.
Open Access
Carbonation of lime-based materials under ambient conditions for direct air capture
(Elsevier, 2019-09-07) Erans, María; Nabavi, Seyed Ali; Manovic, Vasilije
Carbonation of lime-based materials at high temperatures has been extensively explored in the processes for decarbonisation of the power and industrial sectors. However, their capability to capture carbon dioxide from air at realistic ambient conditions in direct air capture technologies is less explored. In this work, lime and hydrated lime samples are exposed to ambient air for prolonged durations, as well as to calcination/ambient-carbonation cycles, to assess their carbonation performance. It is shown that the humidity plays a key role in carbonation of lime under ambient conditions. Furthermore, faster weathering and higher conversions are demonstrated by hydrated lime, showing a carbonation conversion of 70% after 300 h. Importantly, it was found that there was a negligible difference in the carbonation conversions during five calcination/ambient-carbonation cycles, which can be explained by simultaneous reactivation of cycled material by moist air. These findings indicated that lime-based materials are suitable for carbon dioxide capture from ambient air employing cyclic processes, in a practical time-scale, and that humidity of air plays a key role.
Open Access
CO2-brine-rock interactions: The effect of impurities on grain size distribution and reservoir permeability
(Elsevier, 2018-08-25) Aminu, Mohammed Dahiru; Nabavi, Seyed Ali; Manovic, Vasilije
The Bunter Sandstone formation in the UK’s southern North Sea has been identified as having the potential to store large volumes of CO2. Prior to injection, CO2 is captured with certain amounts of impurities, usually less than 5%vol. The dissolution of these impurities in formation water can cause chemical reactions between CO2, brine, and rock, which can affect the reservoir quality by altering properties such as permeability. In this study, we explored the effect of CO2 and impurities (NO2, SO2, H2S) on reservoir permeability by measuring changes in grain size distributions after a prolonged period of 9 months, simulating in situ experimental conditions. It was found that the effects of pure CO2 and CO2-H2S are relatively small, i.e., CO2 increased permeability by 5.5% and CO2-H2S decreased it by 5.5%. Also, CO2-SO2 slightly decreased permeability by 6.25%, while CO2-NO2 showed the most pronounced effect, reducing permeability by 41.6%. The decrease in permeability showed a correlation with decreasing pH of the formation water and this equally correlates with a decrease in geometric mean of the grain diameter. The findings from this study are aimed to be used in future modelling studies on reservoir performance during injection and storage, which also should account for the shifts in boundaries in the CO2 phase diagram, altering the reservoir properties and affecting the cost of storage.
Open Access
Comparative analysis of ammonia combustion for domestic applications
(Elsevier, 2022-12-02) Bazooyar, Bahamin; Coomson, George; Manovic, Vasilije; Nabavi, Seyed Ali
This article explores whether ammonia is a reliable fuel for heat and electricity generation in domestic applications. First, the ammonia combustion characteristics, including adiabatic flame temperature, ignition delay time, and laminar flame speed are analysed and compared with the conventional fuels such as natural gas, dimethyl ether, hydrogen, and syngas, under 12 kWe turbine and 45kWth boiler conditions. Furthermore, the combustion of ammonia at a conventional boiler and turbine combustor was numerically modelled, analysed, and compared with the available fuels. The finding demonstrates that ammonia provides inferior combustion characteristics in combustion heat releases, stability region, and ignition characteristics. The ammonia combustion characteristics including, laminar flame speed and ignition delay time, were comparable to those of methane. The flame temperature and exhaust gas composition of ammonia are rather different than those of methane which may vary the heat transfer during the operation of gas turbines and boilers. The combustion of ammonia in boilers may produce the required heat for heating purposes; however, it needs further modification to achieve better NOX control. In a gas turbine, on the other hand, combustion ammonia leads to remarkably higher temperatures if the same turbine inlet temperature is needed compared to other fuels, however, at the cost of significant NOX formation, which may go beyond 100 ppm with thermal NO formation on par of fuel NO.
Open Access
Comparative evaluation of PSA, PVSA, and twin PSA processes for biogas upgrading: the purity, recovery, and energy consumption dilemma
(MDPI, 2023-09-27) Golmakani, Ayub; Wadi, Basil; Manovic, Vasilije; Nabavi, Seyed Ali
The current challenges of commercial cyclic adsorption processes for biogas upgrading are associated with either high energy consumption or low recovery. To address these challenges, this work evaluates the performance of a range of configurations for biogas separations, including pressure swing adsorption (PSA), pressure vacuum swing adsorption (PVSA), and twin double-bed PSA, by dynamic modelling. Moreover, a sensitivity analysis was performed to explore the effect of various operating conditions, including adsorption time, purge-to-feed ratio, biogas feed temperature, and vacuum level, on recovery and energy consumption. It was found that the required energy for a twin double-bed PSA to produce biomethane with 87% purity is 903 kJ/kg CH4 with 90% recovery, compared to 961 kJ/kg CH4 and 76% recovery for a PVSA process. With respect to minimum purity requirements, increasing product purity from 95.35 to 99.96% resulted in a 32% increase in energy demand and a 23% drop in recovery, illustrating the degree of loss in process efficiency and the costly trade-off to produce ultra-high-purity biomethane. It was concluded that in processes with moderate vacuum requirements (>0.5 bar), a PVSA should be utilised when a high purity biomethane product is desirable. On the other hand, to minimise CH4 loss and enhance recovery, a twin double-bed PSA should be employed.
Open Access
Contributions of CH4-amine interactions by primary, secondary, and tertiary amines on CO2/CH4 separation efficiency
(Elsevier, 2023-03-17) Wadi, Basil; Li, Chenhao; Manovic, Vasilije; Moghadam, Peyman; Nabavi, Seyed Ali
In designing amine-incorporated adsorbents for CO2/CH4 separation, it is essential to understand the individual effects amine moieties have on the separation of CO2/CH4 mixtures. In this work, primary, secondary, and tertiary amines are moderately grafted on SBA-15 to examine factors affecting adsorption of CO2 and CH4. Materials were characterised by thermogravimetric and elemental analysis, and their performance was measured by volumetric and gravimetric gas adsorption. An amine density of 1.6–1.7 mmol/g in secondary and tertiary amines showed an equivalent CH4 uptake of <0.04 mmol/g at 25 °C, while primary amines adsorbed 0.05 mmol/g, indicating stronger interaction forces with CH4. In terms of selectivity, primary and secondary amines grafted at 1.3–1.4 mmol/g had similar values, unaffected by amine type. Adsorption results cross analysed with DFT simulations indicate similar binding energies for CH4 by both amine moieties, concluding the facilitated access of gas molecules to primary amine moieties is the primary factor dictating degree of adsorption. At an amine density of ∼ 1.7 mmol/g for both primary and secondary amines, an increase in temperature from 25 to 40 °C at a CO2 partial pressure of 40 kPa showed a decrease in CO2/CH4 selectivity of only primary amines. Secondary amines are thus more selective amine moieties at these conditions. Furthermore, in isothermal adsorption–desorption conditions, moderately grafted secondary amines have an equal working capacity to primary amines. Both these qualities support secondary amines at moderate densities as candidates for adsorbent development in CO2/CH4 separations.
Open Access
A country-level assessment of the deployment potential of greenhouse gas removal technologies
(Elsevier, 2022-09-13) Asibor, Jude Odianosen; Clough, Peter T.; Nabavi, Seyed Ali; Manovic, Vasilije
The deployment of greenhouse gas removal (GGR) technologies has been identified as an indispensable option in limiting global warming to 1.5 °C by the end of the century. Despite this, many countries are yet to include and promote this option in their long-term plans owing to factors such as uncertainty in technical potential, deployment feasibility and economic impact. This work presents a country-level assessment of the deployment potential of five GGR technologies, including forestation, enhanced weathering (EW), direct air carbon capture and storage (DACCS), bioenergy with carbon capture and storage (BECCS) and biochar. Using a multi criteria decision analysis (MCDA) approach consisting of bio-geophysical and techno-economic factors, priority regions for the deployment of these GGR technologies were identified. The extent of carbon dioxide removable by 2100 via these technologies was also estimated for each of the 182 countries considered. While the obtained results indicate the need for regional cooperation among countries, it also provides useful evidence on the need for countries to include and prioritise GGR technologies in their revised nationally determined contributions (NDCs).
Open Access
Coupling green hydrogen production to community benefits: a pathway to social acceptance?
(Elsevier, 2024-02-23) Gordon, Joel A.; Balta-Ozkan, Nazmiye; Haq, Anwar; Nabavi, Seyed Ali
Hydrogen energy technologies are forecasted to play a critical supporting role in global decarbonisation efforts, as reflected by the growth of national hydrogen energy strategies in recent years. Notably, the UK government published its Hydrogen Strategy in August 2021 to support decarbonisation targets and energy security ambitions. While establishing techno-economic feasibility for hydrogen energy systems is a prerequisite of the prospective transition, social acceptability is also needed to support visions for the ‘hydrogen economy’. However, to date, societal factors are yet to be embedded into policy prescriptions. Securing social acceptance is especially critical in the context of ‘hydrogen homes’, which entails replacing natural gas boilers and hobs with low-carbon hydrogen appliances. Reflecting the nascency of hydrogen heating and cooking technologies, the dynamics of social acceptance are yet to be explored in a comprehensive way. Similarly, public perceptions of the hydrogen economy and emerging national strategies remain poorly understood. Given the paucity of conceptual and empirical insights, this study develops an integrated acceptance framework and tests its predictive power using partial least squares structural equation modelling. Results highlight the importance of risk perceptions, trust dynamics, and emotions in shaping consumer perceptions. Foremost, prospects for deploying hydrogen homes at scale may rest with coupling renewable-based hydrogen production to local environmental and socio-economic benefits. Policy prescriptions should embed societal factors into the technological pursuit of large-scale, sustainable energy solutions to support socially acceptable transition pathways.
Open Access
Demonstration of a kW-scale solid oxide fuel cell-calciner for power generation and production of calcined materials
(Elsevier, 2019-08-27) Nabavi, Seyed Ali; Erans, María; Manovic, Vasilije
Carbonate looping (CaL) has been shown to be less energy-intensive when compared to mature carbon capture technologies. Further reduction in the efficiency penalties can be achieved by employing a more efficient source of heat for the calcination process, instead of oxy-fuel combustion. In this study, a kW-scale solid oxide fuel cell (SOFC)-integrated calciner was designed and developed to evaluate the technical feasibility of simultaneously generating power and driving the calcination process using the high-grade heat of the anode off-gas. Such a system can be integrated with CaL systems, or employed as a negative-emission technology, where the calcines are used to capture CO2 from the atmosphere. The demonstration unit consisted of a planar SOFC stack, operating at 750 °C, and a combined afterburner/calciner to combust hydrogen slip from the anode off-gas, and thermally decompose magnesite, dolomite, and limestone. The demonstrator generated up to 2 kWel,DC power, achieved a temperature in the range of 530–550 °C at the inlet of the afterburner, and up to 678 °C in the calciner, which was sufficient to demonstrate full calcination of magnesite, and partial calcination of dolomite. However, in order to achieve the temperature required for calcination of limestone, further scale-up and heat integration are needed. These results confirmed technical feasibility of the SOFC-calciner concept for production of calcined materials either for the market or for direct air capture (DAC).
Open Access
Design and performance testing of a monolithic nickel-based SiC catalyst for steam methane reforming
(Elsevier, 2023-12-13) Shen, Ziqi; Nabavi, Seyed Ali; Clough, Peter T.
Hydrogen is a highly promoted carbon-free energy carrier that has drawn significant attention recently due to its potential to decarbonise energy sector. More than three-quarters of hydrogen is currently produced via steam methane reforming (SMR), and nickel-based catalysts are used in most applications. Structured catalysts have been reported to be able to further improve catalyst performance as they can optimise heat and mass transfer, as well as prevent coke formation with its structural and textural proprieties. Silicon carbide (SiC) has excellent hardness, thermal conductivity, and chemical inertness, therefore is a promising material to develop structured nickel-based monolithic SiC catalysts for SMR. In this work, a structured monolithic catalyst support has been formed by a modified freeze-gelation method, initially starting from SiC powder, and nickel has been distributed to form a monolithic nickel-based catalyst by wet impregnation. The results showed that the catalysts can achieve thermodynamic equilibrium at 600 °C with a gas hourly space velocity (GHSV) of 10,000 h−1, while reaching a high methane conversion of 86% at 800 °C and GHSV value of 20,000 h−1 during the performance tests using low feeding concentration and low pressure. This is the first time SiC catalytic materials have had their performance demonstrated for SMR under realistic operating conditions.
Open Access
Development of bimetallic catalysts for (sorption-enhanced) steam methane reforming
(Cranfield University, 2023-12) Wang, Siqi; Clough, Peter T.; Nabavi, Seyed Ali
Hydrogen has gained increasing attention in recent years as one of the most promising solutions to decarbonize the energy sector, as it emits zero carbon when combusted. The demand for clean hydrogen continues to rise as government, industry, and academia endeavour to meet the net zero goal by the year 2050. Steam methane reforming is currently the predominant hydrogen production pathway and is predicted to remain so for the years to come. Many techniques exist for the optimization and decarbonization of the steam methane reforming process. Two of the most widely employed methods include using more efficient and stable catalysts and adding in an in-situ carbon capture step using solid CO₂ sorbents. The overall aim of this PhD study is to develop and evaluate the performance of novel bimetallic catalysts for the (sorption-enhanced) steam methane reforming process. Starting from a comprehensive literature review, recent advances in the field of bimetallic SMR catalysts were summarized and reviewed, based on their catalytic activity, stability, and physical-chemical properties. Based on the review, three bimetallic catalysts (Ni₃M ₁ /Al₂ O₃, M = Cu, Fe, and Ge) were synthesized, characterized using different techniques, and tested in a laboratory-scale fixed bed reactor under typical steam methane reforming conditions. CaO particles were then added to the system and the performance of the catalysts under sorption-enhanced steam methane reforming conditions was evaluated. A study on the influence of Cu loading on the bimetallic Ni-Cu catalysts was also carried out. The experimental studies were also accompanied by Density Functional Theory calculations of the carbon and oxygen adsorption energies on the bimetallic surfaces, and microkinetic modelling of the SMR reaction based on previous literature on its reaction mechanism. Finally, machine learning models were developed for the prediction of atomic adsorption energies using readily available elemental properties. Together with the previously developed microkinetic model, a fast high throughput screening of bimetallic alloys was carried out and catalysts with high sulphur resistance were successfully identified. Overall, the addition of Cu was found to be highly beneficial for promoting the catalytic activity of the conventional Ni catalysts, and the addition of Ge promotes the activity and can potentially improve the sulphur resistance of the catalysts. The wide application of these cost-effective and highly active bimetallic catalysts will contribute significantly to the decarbonisation of the energy sector by enabling the efficient production of hydrogen.
Open Access
Direct numerical simulation of packed and monolith syngas catalytic combustors for micro electrical mechanical systems
(Elsevier, 2023-08-19) Bazooyar, Bahamin; Zhu, Mingming; Manovic, Vasilije; Nabavi, Seyed Ali
In this work, a catalytic combustor for micro electrical mechanical system for syngas was designed and analysed using Direct Numerical Simulation (DNS) in conjunction with finite rate chemistry. The effect of catalyst (platinum (Pt), palladium (Pd), palladium oxide (PdO), and rhodium (Rh)), bed type (packed with twelve catalyst shapes and four catalyst monolith), shapes (packed: cylinder, hollow cylinder, four cylinder, single cylinder, single cylinder, cross-webb, grooved, pall-ring, hexagonal, berl-saddle, cube, intalox-saddle, and sphere, monolith: triangular, rectangular, hexagonal, and circular), and operating conditions (inlet temperature and velocity, fuel/air ratio, different concentrations CH4-H2-CO) on combustion efficiency and pressure drop were studied using different parameters (combustion efficiency (η), pressure drop, effectiveness factor (Ψ), and fuel conversions (H2 and CH4 conversions)). Analysis under different operating conditions reveals that the designed combustor can operate effectively with syngas of varying compositions with a high combustion efficiency of over 85%. Combustion mainly takes place on the surface of the catalyst without gas phase reaction with pressure drops between 18 Pa and 155 Pa. The intalox saddle shape catalysts resulted in the bed effectiveness factor 0.93.1 The Damköhler for hydroxyl radicals (OH) over the entire length of the reactor is uniformly distributed and well below 3, suggesting uniform combustion.
Open Access
Divergent consumer preferences and visions for cooking and heating technologies in the United Kingdom: make our homes clean, safe, warm and smart!
(Elsevier, 2023-08-12) Gordon, Joel A.; Balta-Ozkan, Nazmiye; Nabavi, Seyed Ali
Decarbonising the global housing stock is imperative for reaching climate change targets. In the United Kingdom, hydrogen is currently being tested as a replacement fuel for natural gas, which could be used to supply low-carbon energy to parts of the country. Transitioning the residential sector towards a net-zero future will call for an inclusive understanding of consumer preferences for emerging technologies. In response, this paper explores consumer attitudes towards domestic cooking and heating technologies, and energy appliances of the future, which could include a role for hydrogen hobs and boilers in UK homes. To access qualitative evidence on this topic, we conducted ten online focus groups (N = 58) with members of the UK public between February and April 2022. The study finds that existing gas users wish to preserve the best features of gas cooking, such as speed, responsiveness and controllability, but also desire the potential safety and aesthetic benefits of electric systems, principally induction hobs. Meanwhile, future heating systems should ensure thermal comfort, ease of use, energy efficiency and smart performance, while providing space savings and noise reduction, alongside demonstrable green benefits. Mixed-methods multigroup analysis suggests divergence between support levels for hydrogen homes, which implies a degree of consumer heterogeneity. Foremost, we find that domestic hydrogen acceptance is positively associated with interest and engagement with renewable energy and fuel poverty pressures. We conclude that internalising the perspectives of consumers is critical to enabling constructive socio-technical imaginaries for low-carbon domestic energy futures.
Open Access
Double emulsion production in glass capillary microfluidic device: parametric investigation of droplet generation behaviour
(Elsevier, 2015-03-20) Nabavi, Seyed Ali; Vladisavljević, G. T.; Gu, Sai; Ekanem, E. E.
A three-phase axisymmetric numerical model based on Volume of Fluid–Continuum Surface Force (VOF–CSF) model was developed to perform parametric analysis of compound droplet production in three-phase glass capillary devices that combine co-flow and countercurrent flow focusing. The model predicted successfully generation of core–shell and multi-cored double emulsion droplets in dripping and jetting (narrowing and widening) regime and was used to investigate the effects of phase flow rates, fluid properties, and geometry on the size, morphology, and production rate of droplets. As the outer fluid flow rate increased, the size of compound droplets was reduced until a dripping-to-jetting transition occurred. By increasing the middle fluid flow rate, the size of compound droplets increased, which led to a widening jetting regime. The jetting was supressed by increasing the orifice size in the collection capillary or increasing the interfacial tension at the outer interface up to 0.06 N/m. The experimental and simulation results can be used to encapsulate CO2 solvents within gas-permeable microcapsules.
Open Access
Dynamics of double emulsion break-up in three phase glass capillary microfluidic devices
(Elsevier, 2015-03-13) Nabavi, Seyed Ali; Gu, Sai; Vladisavljević, G. T.; Ekanem, E. E.
Pinch-off of a compound jet in 3D glass capillary microfluidic device, which combines co-flowing and countercurrent flow focusing geometries, was investigated using an incompressible three-phase axisymmetric Volume of Fluid–Continuum Surface Force (VOF–CSF) numerical model. The model showed good agreement with the experimental drop generation and was capable of predicting formation of core/shell droplets in dripping, narrowing jetting and widening jetting regimes. In dripping and widening jetting regimes, the presence of a vortex flow around the upstream end of the necking thread facilitates the jet break-up. No vortex flow was observed in narrowing jetting regime and pinch-off occurred due to higher velocity at the downstream end of the coaxial thread compared to that at the upstream end. In all regimes, the inner jet ruptured before the outer jet, preventing a leakage of the inner drop into the outer fluid. The necking region moves at the maximum speed in the narrowing jetting regime, due to the highest level of shear at the outer surface of the thread. However, in widening jetting regime, the neck travels the longest distance downstream before it breaks.
Open Access
Eco-friendly fabrication of highly selective amide-based polymer for CO2 capture
(American Chemical Society, 2019-09-05) Fayemiwo, Kehinde; Chiarasumran, Nutchapon; Nabavi, Seyed Ali; Loponov, Konstantin N.; Manovic, Vasilije; Benyahia, Brahim; Vladisavljevic, Goran T.
Porous polymeric adsorbents for CO2 capture (HCP-MAAMs) were fabricated by co-polymerisation of methacrylamide (MAAM) and ethylene glycol dimethacrylate (EGDMA) using acetonitrile and azobisisobutyronitrile as a porogen and initiator, respectively. The X-ray photoelectron and Fourier transform infrared spectra revealed a high density of amide groups in the polymer matrix of HCP-MAAMs, which enabled high selectivity to CO2. The polymers BET surface area and total pore volume was up to 277 m2 g-1 and 0.91 cm3 g-1, respectively. The highest CO2 uptake at 273 K and 1 bar CO2 pressure was 1.45 mmol g-1 and the heat of adsorption was 27-35 kJ mol-1. The polymer with the lowest crosslinking density exhibited unprecedented CO2/N2 selectivity of 394 at 273 K. Life cycle assessment revealed a lower environmental impact of HCP-MAAMs compared to molecularly imprinted polymers. HCP-MAAMs are eco-friendly CO2 adsorbents owing to their low regeneration energy, environmentally benign fabrication process, and high selectivity.