PhD, EngD and MSc by research theses (SWEE)

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Open Access
A whole systems view to driving decentralised renewable energy investments in Sub-Saharan Africa.
(Cranfield University, 2024-01) Abba, Yahajja Zara Ibrahim; Ozkan, Nazmiye; Drew, Gillian H.
The scaling-up of decentralised renewable energy (DRE), such as solar mini- grids, is vital to achieving climate goals and universal electricity access in sub- Saharan African (SSA) countries. However, high investor risk perception continues to impede DRE investment in SSA, highlighting the importance of understanding investors' risk perception and developing appropriate risk mitigation actions. Yet, the risk management (RM) literature offers a fragmented and singular approach, where the multidimensional nature of risk factors and their interactions are overlooked. In addition, current studies do not consider DRE site- specificity alongside investor heterogeneity in quantifying the implications of mitigation actions on the evolution of investment decisions. In this context, and to address these research gaps, this thesis aims to develop, validate, and implement a unified RM framework incorporating an investment decision model to assess the impacts of actions on investment and electricity access spatially, thus offering a more holistic outcome for decision-makers. This thesis focuses on solar mini-grids in Nigeria, which has one of the highest electricity deficits in SSA. The framework is implemented in two phases. In phase one, investment risks and potential mitigations were evaluated as perceived by four investor groups and various stakeholders through questionnaires, semi-structured interviews, focus groups, and an analytic hierarchy process methodology. In phase two, a novel DRE decision-support model was deployed to enhance existing methods by using a system dynamics-agent-based modelling (SD-ABM) approach. This approach incorporates complex interactions and feedback between heterogeneous investor and location attributes to establish investment outcomes for various case study mitigation scenarios. This thesis the following contributions. Phase one provides new empirical data comprising: identifying 13 additional risk factors compared to the literature, establishing importance of risk factors as perceived by diverse investor groups in Nigeria, and proposing mitigation strategies, some of which were tested in phase two as scenarios. The results indicated variations in risk importance among investors, with the most critical risk factors being revenue risks, limited access to low-cost capital, currency risks, insecurity, and inadequate policy implementation. Phase two contributes to the knowledge of how complex system modelling can be applied to evaluate the impact of mitigation actions on the spatial evolution of DRE investment in a liberalised market. The case study results revealed that the most impactful mitigation scenarios were increased funding availability and the implementation of renewable energy mandates for domestic finance institutions. Whilst our findings confirm the criticality of concessional investors as identified in the literature, we find that meeting electrification targets necessitates incentivising risk-averse non-concessional-type investors. The developed model can additionally enable policymakers to explore the potential implications of further policy actions and investors to identify potential projects that suit their investment profiles during the feasibility phase.
Open Access
Adaptation of two-stage vertical flow constructed wetlands for treating unscreened sewage in the UK.
(Cranfield University, 2019-03) Khomenko, Olha; Bajón Fernández, Yadira; Dotro, Gabriela
The UK water industry has made a priority of embracing low energy sewage treatment, making of two-stage vertical flow constructed wetlands (VFCWs) a plausible alternative to conventional systems. However, for successful implementation of the technology in the UK a further understanding of any required adaptations in its design and operation is required, in particular linked to the UK use of spot sampling regulation of treated effluents and differences in rain profile affecting hydraulic loads in combined sewers. There is also a paucity of information regarding required time for full maturation of the technology and of performance during early operation. In response, the first UK full-scale WWTP based on two-stage VFCWs was built in Derbyshire, UK, and closely monitored during the initial three years of operation, allowing investigation of the system performance and robustness. The efficacy of the system for removal of total suspended solids (TSS), BOD₅ and NH₄ +- N has been evaluated by composite and spot samples analysis. The technology was found to efficiently remove pollutants to the level of 6 ± 3 mg·L⁻ ¹ , 5 ± 2 mg·L⁻ ¹ and 5.8 ± 3.8 mg·L⁻ ¹ for TSS, BOD₅ and NH₄+- N, for 24 hour composite samples. After one year of operation the system was retrofitted with forced aeration on the second stage, which enabled a higher ammonia removal with concentrations in final effluent of 95th percentile concentration of 5.3 mg∙L⁻ ¹comparing to 9.6 mg∙L⁻ ¹achieved in the system with passive aeration. The first stage filters were observed to be hydraulically limited during the first year of operation, with a hydraulic conductivity (HC) of <5.7× 10⁻⁶ m∙s⁻ ¹ which caused prolonged ponding occurrence. This in turn led to poor re-oxygenation of the first stage filter beds and low mineralization of the sludge layer deposited on its surface, which was characterized by TS and VS content of 11.5% ± 1.9% and 64.5% ± 7.3% respectively. A more mineralised sludge layer was present after three operational years, with HC <4.9 × 10⁻⁴ m∙s⁻ ¹ and sludge properties of 20.4% ± 3.5% TS and 62.3% ± 3.5% VS. These values are comparable to data reported for two-stage VFCWs operated in France and ponding was minimal after three years, suggesting this as the required length for system maturation. Close monitoring of the system during the first three years of operation evidenced the need to adapt rotating period lengths according to system age and sludge layer properties. Resting periods of up to 14 days were required for the young system to encourage sufficient hydraulic conductivity of the sludge layer, while the conventional 3.5 days feed/ 7 days rest cycle is appropriate after three years of operation. The influence of sludge properties on permeability was assessed in laboratory experiments, as well as artificial modifications of the sludge surface that could sustain increased permeability and accelerate sludge layer mineralisation. A positive impact of increased VS on permeability was found, with an increase in VS from 60% to 75% improving permeability from 6.14 × 10⁻ ¹⁷ m∙s⁻ ¹ to 2.00 × 10⁻ ¹⁶ m∙s⁻ ¹ in samples with TS of 9% and from 2.06E × 10⁻ ¹⁷ m∙s⁻ ¹ to 1.25 × 10⁻ ¹⁶ m∙s⁻ ¹ in samples with TS 15%. A greater relative contribution to permeability of preferential flow pathways (PFPs) present in the sludge layer than of sludge properties (TS, VS) was observed. PFPs were scarce in the young full scale primary VFCWs, which was believed to be the reason for their poor hydraulic acceptance. A positive effect on PFP formation and sludge drying rate was observed when artificially modifying the sludge layer by application of secondary activated sludge or by making initial cuts on its surface. Artificial modifications of the sludge layer could be implemented in full-scale systems to improve hydraulic acceptance and re-oxygenation, to shorten maturation of primary filters and to maintain prolonged operational periods without desludging.
Open Access
Advanced data-driven methods for prognostics and life extension of assets using condition monitoring and sensor data.
(Cranfield University, 2021-12) Ochella, Sunday Moses; Sansom, Christopher L.; Shafiee, Mahmood
A considerable number of engineering assets are fast reaching and operating beyond their orignal design lives. This is the case across various industrial sectors, including oil and gas, wind energy, nuclear energy, etc. Another interesting evolution is the on-going advancement in cyber-physical systems (CPS), where assets within an industrial plant are now interconnected. Consequently, conventional ways of progressing engineering assets beyond their original design lives would need to change. This is the fundamental research gap that this PhD sets out to address. Due to the complexity of CPS assets, modelling their failure cannot be simplistically or analytically achieved as was the case with older assets. This research is a completely novel attempt at using advanced analytics techniques to address the core aspects of asset life extension (LE). The obvious challenge in a system with several pieces of disparate equipment under condition monitoring is how to identify those that need attention and prioritise them. To address this gap, a technique which combined machine learning algorithms and practices from reliability-centered maintenance was developed, along with the use of a novel health condition index called the potential failure interval factor (PFIF). The PFIF was shown to be a good indicator of asset health states, thus enabling the categorisation of equipment as “healthy”, “good ” or “soon-to-fail”. LE strategies were then devoted to the vulnerable group labelled “good – monitor” and “soon-to-fail”. Furthermore, a class of artificial intelligence (AI) algorithms known as Bayesian Neural Networks (BNNs) were used in predicting the remaining useful life (RUL) for the vulnerable assets. The novelty in this was the implicit modelling of the aleatoric and epistemic uncertainties in the RUL prediction, thus yielding interpretable predictions that were useful for LE decision-making. An advanced analytics approach to LE decision-making was then proposed, with the novelty of implementing LE as an on-going series of activities, similar to operation and maintenance (O&M). LE strategies would therefore be implemented at the system, sub-system or component level, meshing seamlessly with O&M, albeit with the clear goal of extending the useful life of the overall asset. The research findings buttress the need for a paradigm shift, from conventional ways of implementing LE in the form of a project at the end of design life, to a more systematic approach based on advanced analytics.
Open Access
Advanced quadrotor control strategies for health monitoring of overhead power lines.
(Cranfield University, 2021-07) Foudeh, Husam; Luk, Patrick Chi-Kwong; Whidborne, James F.
Research into autonomous control and behavior of mobile vehicles has become increasingly widespread. In particular, unmanned aerial vehicles (UAVs) have seen an upsurge of interest and of the many UAVs available, the multirotor has shown significant potential in monitoring and surveillance tasks. The objective of this research’s programme is to develop novel control that enable quadrotors to track and inspect on high voltage electricity networks. This is a research application that has elicited little attention. This thesis provides a succinct and comprehensive literature research in both state-of-art overhead power lines (OPL) inspection technologies, and quadrotor design and control. It proceeds to motivate, develop and evaluate a learning algorithms controller which exploit the repeated nature of the fault-finding task. Very few iterative learning control (ILC) algorithms have been implemented in this area, and no analysis or practical results exist to specifically investigate UAV performance to modelling uncertainty and exogenous disturbances. In particular, novel contributions are made in ILC algorithms are derived and validated by experimental results on an AscTec Hummingbird quadrotor. It has taken a robust comparisons among several ILC approaches (gradient-based, norm optimal and Newton method ICLs), and the comparisons are largely based on analytical calculated results. In the case of optimal ILC approaches, a new algorithm for nonlinear MIMO systems is developed to cope with exogenous disturbances and noise severely affect UAV as well as a novel tuning method for bnew variation is formulated and applied to the problem of reference tracking for a 6-degree-of-freedom UAV with a two-loop structure. The first loop addresses the system lag and another tackles the possibility of a disturbance commonly encountered when inspection of OPL. The new algorithm contributes to good trajectory tracking and very good convergence speed while minimizing disturbance effects. A linearisation design approach has been extended to enable new updates using quadcopters dynamics. Then constraints have embedded to meet the application demands. After overcoming this deficiency, the ILC controller is further extended based on point-to-point through a straight conductor to fulfil the full task and perform a 2-3 sequence of operations. Finally, the ILC development results are given follow-up using 3D analysis approach where these results are the first ever in this key area.
Open Access
Advanced reactor technology for wastewater treatment.
(Cranfield University, 2015-04) Hassard, Francis; Stephenson, Tom; Cartmell, Elise
Elevated stringency regarding discharges and an aging asset base represent challenges to modern wastewater treatment. This requires upgrade of existing wastewater assets for low energy nutrient removal for minimal cost. Advanced rotating biofilm reactors can be used as a pre-treatment, high organic loading rate (OLR), low hydraulic residence time (HRT) treatment facilitating upgrade of existing wastewater treatment plant (WWTP). The threshold for stable nitrification in rotating biological contactors (RBCs) was assumed to be 15 g.BOD₅.m⁻²d⁻¹ however media modifications have shown that this value can be elevated to ~35 g.sCOD.m⁻²d⁻¹ (73.5 g.BOD₅.m⁻²d⁻¹ ) in rotating biofilm reactors (RBR). Mesh media was compared to two different reticulated foam media, the mesh media had similar porosities but elevated performance compared to the foam media. Elevated OLR resulted in lower volumetric bacterial viability suggesting inhibition at >100 g.sCOD.m⁻²d⁻¹. Comparison of four different mesh media suggested that high porosity mesh media is best for performance and to prevent pore clogging. Bacterial specific activity increased with OLR, but performance at very high OLR decreased. Biofilm reactors can be operated in a ‘hybrid’ configuration where settled bacterial solids can be recycled into the biofilm reactor to improve performance by reducing the effective biofilm OLR. Studies at full scale revealed that extracellular enzyme activity was higher in biofilms compared to suspended growth bacteria. Hybrid upgrade of existing wastewater treatment works resulted in 52 and 40% increase in removal rate of COD and NH₄-N respectively. Comparing different solids type for hybrid reactors utilising activated sludge flocs had the greatest performance benefit compared to HS and FE respectively for sCOD and NH₄-N removal. Incorporating a solids feed in hybrid reactors improved nitrification and organics removal at lower loading. However the solids in the recycle feed reduced denitrification at very high OLR suggesting flocs inhibit denitrification. Hybrid RBRs have 4.8 fold increase in protein EEA compared to single pass reactors under similar conditions. Recycling bacterial solids reduces the effective OLR on the biofilm and confers significant performance benefits. Upfront RBRs provide suitable upgrade for existing WWTP.
Open Access
Advanced reliability analysis of complex offshore Energy systems subject to condition based maintenance.
(Cranfield University, 2021-04) Elusakin, Tobiloba; Simms, Nigel J.; Shafiee, Mahmood
As the demand for energy in our world today continues to increase and conventional reserves become less available, energy companies find themselves moving further offshore and into more remote locations for the promise of higher recoverable reserves. This has been accompanied by increased technical, safety and economic risks as the unpredictable and dynamic conditions provide a challenge for the reliable and safe operation of both oil and gas (O&G) and offshore wind energy assets. Condition-based maintenance (CBM) is growing in popularity and application in offshore energy production, and its integration into the reliability analysis process allows for more accurate representation of system performance. Advanced reliability analysis while taking condition-based maintenance (CBM) into account can be employed by researchers and practitioners to develop a better understanding of complex system behaviour in order to improve reliability allocation as well as operation and maintenance (O&M). The aim of this study is therefore to develop models for reliability analysis which take into account dynamic offshore conditions as well as condition-based maintenance (CBM) for improved reliability and O&M. To achieve this aim, models based on the stochastic petri net (SPN) and dynamic Bayesian network (DBN) techniques are developed to analyse the reliability and optimise the O&M of complex offshore energy assets. These models are built to take into account the non-binary nature, maintenance regime and repairability of most offshore energy systems. The models are then tested using benchmark case studies such as a subsea blowout preventer, a floating offshore wind turbine (FOWT), an offshore wind turbine (OWT) gearbox and an OWT monopile. Results from these analyses reveal that the incorporation of degradation and CBM can indeed be done and significantly influence the reliability analysis and O&M planning of offshore energy assets.
Open Access
Advancing biosensing techniques for detection of antimicrobial resistance genes and antibiotics in water
(Cranfield University, 2024-09) Li, Wenliang; Yang, Zhugen; Coulon, Frederic
Antimicrobial resistance (AMR) poses a significant global public health threat requiring urgent attention for surveillance of antibiotic resistance genes (ARGs) and antibiotics in the environment. In this PhD study, a real-time fluorescent detection assay of antimicrobial resistance genes (ARGs) was developed to specifically target two key ARGs, tet(M) and tet(x3) to detect tetracycline and tigecycline resistance respectively in water samples. Additionally, crassphage gene was investigated for anthropogenic activities since they also play a vital role in the AMR transmission. The advanced ARG detection assay was based on multiplexing recombinase polymerase amplification (RPA) and subsequent sequence-specific recognition by the trans-cleavage activity of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas12a. The assay achieved limits of detection (LODs) of 1 copy µL⁻¹ for all three gene targets with an accuracy of 100% in spiked tap and surface water samples. Expanding the assay by including two additional end-point detection modalities, lateral flow assay (LFA) and voltametric detection, further demonstrate its versatility. LODs of 1 copy µL⁻¹ for tet(x3) and crassphage, and 10 copies µL⁻¹ for tet(M) (LFA) and 10 copies µL⁻¹ for all three targets (electrochemical) were reached. Validation against gold standard quantitative polymerase chain reaction (qPCR) using real water samples, including wastewater and drinking water samples, revealed a remarkable 100% accuracy rate. Antibiotics detection assay was conceptualised based on the amplification of hybridisation chain reaction (HCR) followed by CRISPR/Cas mediated cleavage within a DNA hydrogel matrix. This approach aimed to release electroactive methylene blue (MB) particles, detectable and quantifiable by square wave voltammetry (SWV). While unforeseen circumstances impeded full assay development, the preliminary data illustrated the viability of the proposed method, suggesting avenues for further research to develop rapid and onsite antibiotics detection methods.
Open Access
Advancing the development and application of decision support systems for sustainable brownfield redevelopment.
(Cranfield University, 2023-12) Hammond, Ellis Bernard; Coulon, Frederic; Hallett, Stephen; Beriro, Darren
The redevelopment of brownfield sites is a vital part of ensuring sustainable urban development but has a range of challenges, including contamination and/or geotechnical hazards, leading to risk and cost implications. Brownfield redevelopment involves multiple stakeholders, from land use planners, land developers, and specialist consultants, to local community groups, and neighbouring residents. Understanding complex data and information can be difficult for decision-makers, which is exacerbated when communicating development scenarios and options with others. To support stakeholders, digital tools are often used, including specialised Decision Support Systems (DSSs). This PhD research investigates and contributes to the advancement of brownfield redevelopment DSSs. Existing and emerging challenges are evaluated, identifying improvement opportunities through a critical review of literature and large-scale sector- wide stakeholder consultation. A novel WebGIS-based DSS was developed in collaboration with land use planning stakeholders, applying the DSS to an area of post- industrial land within the Liverpool city region, UK. The DSS was evaluated through user testing, where improvements were identified and implemented, and verified, using a combination of empirical and user-testing methods. Overall, the approach and application of this PhD research demonstrates modern user led DSS development for brownfield applications, overcoming many of the limitations of existing work. The use of the DSS to support early-stage planning and redevelopment of brownfield land is aligned with and informs, multiple current policies for sustainable development and the use of applied digital technologies in planning and land development.
Open Access
Aerodynamic design optimization of large-scale offshore wind turbine blade using CFD
(Cranfield University, 2022-05) Koragappa, Pavana; Verdin, Patrick G.; Nabavi,Seyed Ali
Renewable energy is expected to be the main source of power by 2050, bringing an end to the use of fossil fuels; this is the only way to achieve Net Zero. Wind turbines which majorly contribute to this agenda, not only help to reduce CO₂ emission, they are also environmentally friendly and form a cost-effective solution. The aerodynamic study and design of a wind turbine blade is essential as it is directly linked to the performance of the wind turbine. The maximum power generating wind turbine currently operating is the Haliade-X (GE) turbine, which has set a trademark at producing 14 MW, 13 MW or 12 MW. However, a need for higher power generating wind turbines is present to be able to reach the Net Zero target. By upscaling the “DTU 10 MW Reference Wind Turbine” this research has achieved an aerodynamically stable 20 MW offshore wind turbine blade design. Variable rotation speed and variable pitch angle configurations have been considered to achieve an ideal power curve. The aerodynamic performance has been evaluated using CFD and quantified for a length optimized blade design. To ensure structural stability, chord and twist optimizations have also been performed. The chord and twist of the designed blade have been optimized through the momentum theory and the blade element theory. 2D numerical simulations on FFA- W3 aerofoils used in the design of the wind turbine blade have been carried out initially to determine the angle of attack at minimum C𝐷/C𝐿 ratios, which further helps to calculate the chord and twist of the blade. From the calculated value, a new design variant has been proposed and the aerodynamic performance has been evaluated using CFD.
Open Access
An agent-based model for improving museum design to enhance visitor experience.
(Cranfield University, 2022-11) Ji, Yijing; Tran, Trung Hieu; Simon, Jude; Williams, Leon
Museum experience is a multi-layered journey including ontological, sensory, intellectual, aesthetic, and social aspects. In recent years, the museum sector has faced a number of challenges in terms of the need to enhance the potential of the experience while maintaining authenticity and credibility. For public science communication in museums, exhibition is an important medium for connecting exhibits and visitors, and as such, the study of visitors' senses and behaviours under impact of various museum layout designs has become an important research direction. The purpose of this study is to explore the recall of visitors' memories in the exhibition space by integrating images, echoes and tactile senses, and then transform memories and interactions into their own experience and knowledge base. The impact of spatial design and other design elements on visitors' memories is also explored. We have conducted Agent-based simulation, by setting up virtual visitors, exhibition spaces and artefact based on real gallery spaces, as a time-saving and cost-saving method to improve exhibition interactivity and content coherence. Meanwhile, through the simulation of this novel way, visitors can observe and predict the interactive experience between visitors and the exhibition, so as to improve the curatorial team's research on tourist behaviour and spatial design scheme. Next, the simulated data on visitors' memory recall behaviour is compared with the actual observed data to explore the authenticity of visitors' behaviour in the simulated museum. The impact of this study is by integrating a variety of shared understandings between curators, exhibition management and participants, drawing on diverse information based on experience, practice and simulation. It seeks to provide future museum- oriented practitioners, particularly in small and medium-sized museum exhibition spaces, with a novel perspective and approach to observing or predicting the experience of visitors' sensory interactions within an exhibition. Furthermore, at the same time as enhancing the visitor’s exhibition experience, the content of exhibition story is fully transformed into its own knowledge accumulation.
Open Access
Agent-based modelling of crop management
(Cranfield University, 2024-07) El-Fartassi, Imane; Waine, Toby W.; Milne, Alice E.; El-Alami, Rafiq; Corstanje, Ronald; Metcalfe, Helen; Alonso-Chavez, Vasthi
This study aims to explore the benefits of integrating Agent-Based Models (ABMs) of farmer behaviour with biophysical models to describe and understand the complex agroecological systems that influence decision-making in arid and semi-arid regions. Through a mixed-methods approach combining surveys, interviews, and ABM, the research provides insights into the complex dynamics shaping farmer behaviour and evaluates the potential impacts of various management strategies on agricultural sustainability. Initial online surveys across diverse agro-climatic zones in Morocco revealed that farmer decisions are influenced by environmental pressures, crop characteristics, and water availability. Follow-up in-depth interviews in the Al Haouz Basin highlighted institutional barriers like land tenure insecurity and bureaucratic processes as key constraints to adopting sustainable practices. The study integrates empirical data with Structural Equation Modelling and the Theory of Planned Behaviour to parameterize an ABM. This coupled behavioural-biophysical simulation captures feedback loops between environmental conditions and human decisions. Model simulations revealed potential unintended consequences of policies aimed at increasing productivity, such as increased soil salinization and land abandonment resulting from expanded groundwater access. Key contributions include advancing the understanding of temporal adaptation dynamics in agricultural systems under climate change and developing a novel methodological framework integrating qualitative and quantitative approaches for studying complex socio- ecological systems. By bridging social and natural sciences, this research establishes a comprehensive framework for addressing agricultural sustainability challenges in water-scarce regions.
Open Access
Algae reactors for wastewater treatment
(Cranfield University, 2016-02) Whitton, Rachel Louise; Jefferson, Bruce; Villa, Raffaella
The onset of the Water Framework Directive (WFD) will challenge water utilities to further reduce their wastewater phosphorus discharges to < 0.5 mg.L- 1 . Whilst conventional treatments, such as chemical dosing, are able to meet these new discharge consents, the strategies are representative of a linear economy model where resources are unrecovered and disposed. An alternative solution which can contribute to the aspiration of a circular economy is microalgae. Microalgae are ubiquitous in wastewater environments and assimilate phosphorus during their growth, to residual concentrations complementary of the WFD. Furthermore, microalgal biomass can be anaerobically digested to produce biomethane offering the potential for an energy neutral approach. However, uptake of microalgal systems are lacking in the UK through limited knowledge of operation; and the belief that such solutions are synonymous to large, shallow open ponds with extensive treatment times. The development of alternative microalgal reactors are increasingly investigated to overcome these implementation challenges. Of these, immobilised microalgae has shown great potential; and whilst within its infancy demonstrates the greatest opportunity for development and optimisation. This thesis determines the critical operational parameters that influence the remediation efficacy of immobilised microalgae for tertiary nutrient removal; including species selection, biomass concentration, treatment period and lighting; with recommendations for optimal performance. These recommendations are then applied to the design and operation of an immobilised bioreactor (IBR) to understand the key design and operating components that influence the overall economic viability. In doing so, the potential for an IBR to be economically viable, within the next decade, in comparison to traditional approaches are discussed.
Open Access
Alternative cropping practices for sustainable soil management and yield optimisation in asparagus.
(Cranfield University, 2021-07) Maskova, Lucie; Simmons, Robert W.; Deeks, Lynda K.; De Baets, Sarah
Asparagus (Asparagus officinalis L.) is a high value perennial crop with long economic production period ranging between 10-20 years. Field operations associated with conventional UK asparagus production such as re-ridging and intensive foot and vehicular trafficking of the wheelings however run a danger of causing a range of negative environmental impacts and pose a risk to long-term asparagus productivity. Nonetheless, majority of British growers continues to cultivate asparagus in the conventional way due to a lack of alternatives to the conventional practice. The aim of this research is to critically evaluate the long-term efficacy of a set of potential best management practices (BMPs) targeted at preventing or remediating soil compaction in asparagus interrows, promoting root growth and increasing profitability of asparagus production. The research further aimed to quantify the impacts of annual re-ridging associated with the conventional production on soil compaction, root development, yields and on soil bio-chemical characteristics. The experimental field trial located in Herefordshire tested a range of potential BMPs inducing (i) companion cropping with either rye (Secale cereale L.) or mustard (Sinapis alba L.) which were re-ridged or non-ridged, (ii) interrow surface mulching with either straw mulch or compost which were re- ridged or non-ridged and (iii) a combination of tillage practices (ridging and shallow soil disturbance) applied to bare soil interrows. Treatments were applied annually from 2018-2020. This research showed that the field management practice currently adopted by the of British asparagus industry is unsustainable and poses high risks to both the soil environment and asparagus productivity. Key findings show that soil compaction, root growth, asparagus profitability and soil bio-chemistry in asparagus cropping systems can be effectively modified and managed by BMPs. Consequently, this research identified a set of BMPs to be considered for practical application.
Open Access
Ammonia recovery and utilisation for biogas upgrading in membrane contactors.
(Cranfield University, 2023-07) Luqmani, Benjamin A.; McAdam, Ewan; Pidou, Marc
This thesis has developed an innovative system for biogas upgrading using hollow fibre membrane contactors (HFMC) whilst recovering ammonia from wastewater as a reactive solvent to intensify CO₂ absorption. An expanded two- phase region for ammonia-water separation was identified and exploited to foster selective, low energy recovery of concentrated gas-phase ammonia from wastewater by vacuum thermal stripping. Selective stripping was translated to a gas-liquid contacting column which demonstrated mass transfer rates analogous to commercially established stripping processes. Investment in selective ammonia recovery from anaerobic digester centrate represents a cost saving over a 20-year economic lifetime relative to biological nitrogen removal. During physical CO₂ absorption in HFMC, solvent chilling and gas pressurisation were observed to increase flux and selectivity, thereby reducing membrane area and path length for biogas upgrading. Chilled conditions will promote wetting resilience to favour the application of microporous membranes, which are low- cost and technologically mature. Translation to recovered ammonia solvents will further intensify CO₂ absorption, but can result in gas-side reactions within the ternary CO₂-NH₃-H₂O system which reduce process stability. In a positive synergy, chilled, pressurised conditions could limit ammonia ‘slip’ and maintain the system below a critical threshold to prevent gas-side reactions and improve process resilience. Pressurised, reactive crystallisation in HFMC during CO₂ absorption by ammonia solvents was demonstrated for the first time, and observed to occur at a consistent supersaturation level. Consequently, ammonium bicarbonate crystals exhibited consistent characteristics independent of pressure which supports simplified online control and solids recovery for scale- up. The integrated system proposed in this thesis presents a cost effective, circular economy solution for ammonia recovery and biogas upgrading which is closely aligned to net zero ambitions within the water sector and wider society.
Open Access
An improved energy management system framework for solar energy integration.
(Cranfield University, 2024-05) Falope, Tolulope Olumuyiwa; Lao, Liyun; Huo, Da
Renewable energy sources like wind and solar play a crucial role in decarbonizing energy supply, but their variable and intermittent nature lead to reliability and stability issues. One way of sustainably integrating these energy sources into the grid is through an energy management system. The study reported in this thesis gives a comprehensive definition of an integrated energy management system and creates a novel framework that identifies energy forecasting, demand-side management, and supply-side management, as crucial components for grid balancing. In addition, this research looks particularly at solar integration, and how the integrated energy management system offers a unique combination of solar energy forecasting, time-of-use tariffs, direct load control demand response, and generator control, in increasing penetration levels of solar energy. The significance of this research is that the proposed system presents a viable, sustainable, and cheaper way of increasing PV usage and thereby grid penetration by prioritising efficient use of available PV supply before calling up additional supply. To validate the proposed integrated energy management system, this research looks to understand the functions of each individual component and how their interconnectedness creates a novel management system. Firstly, this research develops a three-step solar forecasting approach that uses low-level data fusion to combine weather variables from both an on-site and a local weather station to improve solar energy forecasting. The forecasting model response is historic PV generation, and the predictors are weather variables with moderate to strong positive correlations to solar radiation. Data obtained is preprocessed using Low-level Data Fusion, Pearson Correlation Coefficient analysis, Rescaling method, and List-wise Deletion method. This approach is then tested on a 1MW utility scale solar plant, resulting in a 6% and 13% prediction accuracy improvement when compared to solely using data from an on-site, and local weather stations respectively. This approach is also validated for three residential rooftop solar systems (8 kW, 10.5 kW and 15 kW), achieving root mean square error values of 0.0984, 0.1425, and 0.0885 respectively. The resulting low root mean square error values, a measure of the predicted PV to actual PV generation, proves that the model can be adopted for different PV plant sizes and is suitable for any customer across the distributed generation spectrum. To further improve the accuracy of the model, other preprocessing techniques are investigated and applied. The study shows that the combination of Low-level Data Fusion, Linear Interpolation, filling outliers, data smoothing, Rescaling method, moderate to strong PV correlation of weather parameters using Pearson Correlation Coefficient, day/time/month decomposition, seasonal decomposition, Principal Component Analysis, and holdout validation, increases the accuracy of the model by 75%. The ability of direct load control to manage energy consumption is validated in a case study by using Connected Power’s unique smart sockets and Lumen radio’s Mira Mesh Radio Frequency wireless network. Small plug-in loads were connected to ten smart sockets located in a robotics laboratory and a café, resulting in reduced energy consumption by 44% and 72% respectively when compared to the baseline without direct load control. Finally, the integrated energy management system framework is validated by testing its capacity to increase PV usage for an off-grid residential house with a PV/diesel generator power source. A decision-based algorithm is created that adjusts PV supply forecast errors, initiates direct load control responses to reduce excess load during periods of low PV supply, and/or increase power supply by calling up a diesel generator. In addition, this is combined with the proposed three-step solar energy forecasting approach and a programmable load schedule based on time-of-use criteria. The effects of customer behaviour are also analysed by using a 14% override rate, with 80% preconditioning and 20% rebounding. The hybrid PV/diesel generator power source with the proposed integrated energy management system is compared against two configurations: a baseline configuration that uses a solely diesel generator source, and a hybrid PV/diesel generator power source. Results show that the integrated energy management system reduced the lifetime expenditure costs and CO2 emissions by 44% and 46% respectively when compared to the baseline configuration, and by 8% and 9% in the hybrid photovoltaic/diesel generator, while also increasing the PV usage from this configuration by over 113%. This research also addresses opportunities and limitations of the proposed system and lays the foundation for future research using other intermittent renewable energy sources such as wind.
Open Access
An integrated knowledge transfer framework for enhancing international university-industry collaboration in novel sanitation technology development
(Cranfield University, 2023-12) Fox, Harvey; Encinas-Oropesa, Adriana; Lighterness, Paul
Approximately 3.5 billion people worldwide lack access to safe sanitation services, a challenge that demands innovative solutions. University-industry collaborations (UICs) are increasingly recognised as a means to develop and commercialise cutting-edge technologies addressing such global issues. However, these partnerships face complexities in transitioning lab-based inventions to market-ready products, especially during the critical stages of technology development and refinement. This thesis presents an integrated knowledge transfer framework for international UICs, focusing on the development and commercial handover of novel sanitation technology. Through a series of interconnected studies, the research explores the micro-level interactions and processes within the execution phase of international UICs. The framework synthesises insights from three key studies: field testing dynamics in cross-cultural settings, which reveals the effectiveness of diverse team structures in different geographical contexts; a novel iterative development process (ERDE: Experimenting, Reviewing, Distributing, Executing), which provides a structured approach to capturing and integrating multi-modal feedback from dispersed partners; and the role of physical and digital boundary objects in technology and knowledge synchronisation across dispersed partners, highlighting the challenges and successes of alignment between university and industry collaborators. Each study contributes unique insights: the field testing research informs practices for geographically dispersed collaborations; the ERDE framework addresses challenges in the technology ‘Valley of Death’ by facilitating decentralised development; and the boundary object study emphasises the need for adaptive communication strategies across cultural and institutional boundaries. By examining a range of critical activities in technology development, this research contributes to both theoretical understanding and practical management of knowledge transfer in international UICs. The integrated frameworks offers a comprehensive approach to navigating the complexities of geographically dispersed innovation processes and facilitating knowledge alignment within international collaborations, particularly for technologies intended for diverse global contexts. This work has implications for academics, practitioners, and policymakers involved in developing and transferring innovative technologies across institutional and international boundaries to achieve far-reaching societal impact
Embargo
An investigation of a novel monolithic nickel-based catalyst for clean hydrogen production
(Cranfield University, 2024-05) Shen, Ziqi; Clough, Peter T.; Nabavi, Seyed Ali; Wagland, Stuart T.
The decarbonisation of the energy sector can anticipate the future of net zero, and hydrogen is currently one of the most promising energy carriers to contribute to this goal. As for hydrogen production, steam methane reforming (SMR) occupies the predominant status and will remain in its position in the short term. The SMR process requires high-performance catalysts such as nickel-based catalysts, and carbon capture technology is of interest to decarbonise the SMR to produce clean hydrogen. The overall aim of the PhD project is to develop a novel monolithic nickel-based catalyst and evaluate its performance under SMR and sorbent-enhanced SMR (SE-SMR) conditions. The literature review looked back on the ceramic materials used in the SMR and SE-SMR processes, and also the method to prepare nickel-based catalysts. Silicon carbide was chosen as the support material due to its excellent thermal and mechanical properties. The monolithic nickel-based catalysts were designed, synthesised, characterised and tested in a fixed-bed reactor, in which the main reactor pipe and the steam generator were designed and constructed for this project. In addition, a pulse injection system was designed and installed on the reactor, and the SMR kinetics were studied using the monolithic catalysts. After the integration of the solid sorbents, a further study was conducted on the effect of structure within the SE-SMR process using the monolithic catalysts. The monolithic catalysts exhibited excellent activity at low SMR temperatures and pressures with a realistic gas space velocity. A kinetic model was established to describe the reaction rates using a novel and time-saving approach. The mass transfer limitations led to a low activation energy in kinetics and a reduction in activity when sorbents were applied. The monolithic catalysts will be a strong candidate for the decarbonisation of the energy sectors, with further improvement of its long-term stability and coordination with appropriate sorbents.
Open Access
Anaerobic Membrane Bioreactors for water reuse using municipal wastewater: the role of post-treatment
(Cranfield University, 2022-07) Huang, Yu; Pidou, Marc; Jeffrey, Paul
Anaerobic Membrane Bioreactors (AnMBRs) are seen as a promising alternative to Aerobic Membrane Bioreactor (AeMBR) based water reuse schemes as they better support a circular economy paradigm with the potential for recovery of energy and nutrients. However, evidence of their application for water reuse is very limited which significantly restricts their potential deployment. This research aimed to identify the current challenges of using AnMBRs for water reuse with respect to their ability to achieve the quality requirements in state of the art national and regional standards. The work investigates the performance and feasibility of technologies commonly applied as a post-treatment stage for AeMBRs and ultimately to provide references for possible treatment trains for future water reuse implementations. A critical review and controlled pilot scale AnMBR and AeMBR operations followed by lab-scale post-treatment trials were conducted to understand the performance of the investigated post-MBR processes and their potential role in AnMBR based water reuse applications. The distinctive matrices of AnMBR and AeMBR effluents, in particular the different nitrogen species as ammonia in the AnMBR effluent and nitrate in the AeMBR effluent, were found to influence different performance across the investigated post-MBR technologies. The presence of ammonia caused a higher membrane fouling and a potential failure to meet the standard for potable reuse during the RO filtration of the AnMBR effluent. When chlorinated, the AnMBR effluent provided a controllable residual ammonia and chlorine concentration while exhibiting lower disinfection by-products formation potential compared to the AeMBR effluent. UV/TiO₂ delivered a selective removal of organic and nutrient compounds as a function of varying the UV intensity and TiO₂ dose from the AnMBR effluent. These findings highlight the potential to combine these processes to achieve more sustainable treatment trains producing high quality effluents for various water reuse applications. In particular, the combination of AnMBR-Chlorination shows promise as a circular economy approach to municipal wastewater treatment for agriculture irrigation.
Embargo
Analysis of factors driving foreign direct investment in the liquefied natural gas sector: case study Nigeria
(Cranfield University, 2024-02) Ogunsanwo, Babafemi; Longhurst, Philip J.; Huo, Da
The empirical data revealed facts about factors driving foreign direct investment in the Nigerian LNG sector. This research uses the primary data gathered to contribute uniquely to empirical findings and knowledge. Some factors are deemed adequate when attracting foreign direct investment. The sufficient factors identified are political stability having a considerable impact on investor decisions, and long-term investment commitments in the LNG sector. The second significant factor identified is government efficiency, and the last factor is corruption with different components classified into two broad categories: attractors and deterrents. In this context, sufficiency is defined as the condition where FDI is likely to occur when a sufficient amount of the three factors listed are in place. Previous research has failed to understand and explain all three factors adequately. This is a new insight and contribution to knowledge. This study explains how factors driving foreign direct investment in Nigeria's liquefied natural gas sector have an impact. The research utilises the successful Bonny NLNG projects as an example to investigate the reasons behind the failure of the Olokola and Brass LNG projects, which were unable to reach a final investment decision. Distinct empirical analysis and research design show key factors driving foreign direct investment in the Nigerian LNG sector. Foreign direct investment is a type of cross-border investment that occurs when an investor from one country develops a long-term stake in and a considerable degree of control over an enterprise located in another country. Additionally, in green-field investment, foreign direct investment is in the form of a parent company establishing a subsidiary in another country and commencing operations from the ground up. The goal of foreign direct investment is the priority of gaining benefits from the investment, maximising return on investment, and seeking to control assets. It offers capital funding in exchange for an equity stake. LNG projects are capital- intensive, it requires sizable up-front financing. LNG project financing can be difficult due to their long-term nature, high costs, and associated risks. Securing funds from foreign lenders, equity investors, and project sponsors can be herculean, only the major exploration and production companies can achieve it. Thus, the research will focus on factors driving FDI in the LNG sector. Key stakeholders, policymakers, and investors will be interviewed. This thesis compiles feedback from stakeholders to identify the key factors driving foreign direct investment in Nigerian liquefied natural gas. The study presents evidence on the factors driving the inflow of foreign direct investment into the Nigerian LNG sector to policymakers, lawmakers, government executives, investors, community leaders, and financial institutions to test the effectiveness and efficiency of the research. The research design incorporates a mixed-method approach. Data collected through a questionnaire-based survey, semi-structured interviews, and focus group discussions, provide solid insight into the factors driving foreign direct investment in the Nigerian LNG sector. The questionnaire-based survey was used to gather data from 118 respondents. Data was gathered from 12 top gas stakeholders through semi-structured interviews, and an additional 4 executive participants participated in the focus group discussion. The study employs purposive sampling to identify the participants and interviewees. The fundamental value of the research comes from the real-world data it collects and the conclusions by looking at factors driving FDI in the LNG sector. Stakeholder theories were chosen as the theoretical framework for the research, emphasising the study's focus and applying the researcher's terminology to address the research questions. The literature review guided this decision. Nigeria's abundance of natural resources, particularly its substantial natural gas reserves, attracts foreign investors. The Nigerian gas sector presents opportunities for economic development, energy diversification, and environmental sustainability in the future. Nigeria has about nine hundred times more gas assets than the country's oil deposits, and its reputation as an oil producer overshadowed the gas sector's potential, even though the country's gas reserves are greater than oil. Gas asset is a necessary factor, but it is not sufficient enough to attract foreign direct investment.
Open Access
Annual performance of a novel configuration for an integrated solar combined cycle utilising municipal solid waste
(Cranfield University, 2022-08) Al Ramadhn, Ali; Patchigolla, Kumar; Sansom, Christopher L.
Climate change has been a major incentive for the global power generation industry to move towards the implementation of sustainable renewable energy technologies in order to reduce the emissions of greenhouse gases, especially carbon dioxide emissions. Concentrated solar power (CSP) has established itself as one of the common renewable energy technologies for large scale power generation. A further attractive feature of this solar technology is its hybrid operation in the form of integrated solar combined cycle (ISCC) which facilitates control and ensures that the power plant is available to meet demand whenever it occurs. ISCC commonly uses natural gas to operate the combined cycle but this CSP hybrid system also has the potential to limit its use of this fossil fuel with a more environmentally friendly fuel, namely the produced syngas from solid feedstock gasification which can be accomplished by further integration of the gasification reactor with ISCC. The organic fraction of municipal solid waste (MSW) was selected for this application, both to replace natural gas as well as for its value as a waste management method. In the present work, the thesis studies and contrasts four configurations of ISCC based on two factors, the type of fuel and the level of solar thermal contribution. One configuration represents the conventional form by using natural gas (ISCC 1) while another configuration uses municipal solid waste (ISCC 2) and in both cases, the solar field generates high -pressure saturated steam using parabolic trough with thermal oil. The last two configurations are related to the research proposal for ISCC which states that this hybrid system runs on municipal solid waste and utilises enhanced solar thermal contribution. This enhanced thermal power from the solar field is used to generate high-pressure superheated steam using parabolic trough with molten salt (ISCC 3) or solar power tower with molten salt (ISCC 4). In all cases, the fuel runs the combined cycle, and the solar field operates in parallel to provide extra steam for the hybrid system. However, the use of gasification in ISCC 2, ISCC 3 and ISCC 4 generates extra steam for the hybrid system through syngas cooling system which is attached to the low-pressure section of the steam turbine cycle. In this work, models are developed to investigate the differences between the various configurations in terms of technical and economic performances using Spain and Saudi Arabia as case studies. The results indicate that the use of a solar power tower in the proposed concept, ISCC 4, gave the highest electricity production at 646 GWh with a solar share of 12.80% under Spanish weather and 644 GWh with a solar share of 15.24% under the Saudi Arabian weather. Furthermore, ISCC 4 offered the lowest levelised cost of electricity at 28.45 $/MWh and 28.62 $/MWh for Saudi Arabia and Spain, respectively, when the novel concept (ISCC 3 and ISCC 4) is compared to the conventional concept (ISCC 1). The main thesis contribution was to reveal the impact of coupling the ISCC using enhanced solar thermal power with municipal solid waste gasification and its potential as Waste-to-Energy plant. Based on the study presented outcomes, The proposed concept of integrated solar combined cycle (ISCC 3 and ISCC 4) demonstrated its practicality against conventional concept (ISCC 1) due to achieving higher performance outcomes with lower costs. The outcomes of ISCC 2 in both countries presented slightly lower LCOE values than the novel concept indicating that the replacement of fuel alone did not show a significant impact against the novel concept in terms electricity production cost.

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