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Magnetic Field Data in Signal Matching Models
Feasibility Study of Using Magnetic Field Measurements to Estimate Soil resistance Properties Using Multiple Predictive Models
Master thesis
(2026)
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J.B. van der Hoorn, P.C. Meijers, E. Kementzetzidis, E. Sulollari, Robert Hasselaar
Reliable soil resistance estimates are essential for the safe and efficient design and installation of offshore monopile foundations. These are currently obtained by feeding Pile Driving Analyser (PDA) data into a signal matching model, but installing a PDA offshore requires sensors to be bolted onto the pile and later removed, a slow and costly process. This thesis investigates a non-contact alternative: using the change in magnetic flux around a steel monopile during driving as a substitute for the PDA's force signal. CAPWAP was selected as the basis for the model, since it produces a full soil resistance distribution rather than a single capacity value. Several CAPWAP driving configurations were tested with magnetic flux, including the standard wave separation formulation and a "Pulse" approach, in which the flux signal drives the model only during the initial hammer impact, after which the model matches purely on velocity. The Pulse approach proved substantially more tolerant of the flux signal's deviation from true force than wave separation, which produced unreliable estimates when driven by flux. Using Pulse, both the radial and axial flux signals produced shaft resistance and soil resistance distribution estimates in close agreement with the force-driven Pulse model and the wave separation approach. The main remaining discrepancy is in toe resistance, attributed to the Pulse model's reliance on velocity alone, which is more sensitive to the errors present in the available velocity signal. Repeating each model's optimisation from many independent starting points further showed that the shaft and toe resistance, and most other parameters under the Pulse formulation, converge consistently to well defined, unique solutions. These results show that magnetic field data can be used to estimate soil resistance parameters to a meaningful extent, closely comparable to a conventional PDA-based model. The flux signal must still be scaled to a measured force peak, so the approach is not yet fully non-contact; removing this dependency, along with closing the toe resistance gap, depends primarily on obtaining more accurate velocity measurements. A preliminary comparison against Laser Doppler Vibrometer data showed a promising alignment between the measured and impedance-based velocity peak, though the velocity signal could not yet be fully validated beyond this initial peak. A genuinely non-contact alternative to conventional PDA-based pile driving analysis therefore appears within reach.
...
Reliable soil resistance estimates are essential for the safe and efficient design and installation of offshore monopile foundations. These are currently obtained by feeding Pile Driving Analyser (PDA) data into a signal matching model, but installing a PDA offshore requires sensors to be bolted onto the pile and later removed, a slow and costly process. This thesis investigates a non-contact alternative: using the change in magnetic flux around a steel monopile during driving as a substitute for the PDA's force signal. CAPWAP was selected as the basis for the model, since it produces a full soil resistance distribution rather than a single capacity value. Several CAPWAP driving configurations were tested with magnetic flux, including the standard wave separation formulation and a "Pulse" approach, in which the flux signal drives the model only during the initial hammer impact, after which the model matches purely on velocity. The Pulse approach proved substantially more tolerant of the flux signal's deviation from true force than wave separation, which produced unreliable estimates when driven by flux. Using Pulse, both the radial and axial flux signals produced shaft resistance and soil resistance distribution estimates in close agreement with the force-driven Pulse model and the wave separation approach. The main remaining discrepancy is in toe resistance, attributed to the Pulse model's reliance on velocity alone, which is more sensitive to the errors present in the available velocity signal. Repeating each model's optimisation from many independent starting points further showed that the shaft and toe resistance, and most other parameters under the Pulse formulation, converge consistently to well defined, unique solutions. These results show that magnetic field data can be used to estimate soil resistance parameters to a meaningful extent, closely comparable to a conventional PDA-based model. The flux signal must still be scaled to a measured force peak, so the approach is not yet fully non-contact; removing this dependency, along with closing the toe resistance gap, depends primarily on obtaining more accurate velocity measurements. A preliminary comparison against Laser Doppler Vibrometer data showed a promising alignment between the measured and impedance-based velocity peak, though the velocity signal could not yet be fully validated beyond this initial peak. A genuinely non-contact alternative to conventional PDA-based pile driving analysis therefore appears within reach.
Air-pollution is one of the most critical ecological and public health challenges of the 21st century. Its pre-emptive, passive, and reactive control is a fundamental aspect of environmental management, that is aimed at minimising the release of harmful substances and their impact on human health and natural systems. An effective pollution control strategy involves the scientific modelling of the pollution dispersion so as to either prevent pollutants from being emitted or mitigate the effects after their release in specified areas of interest. One mathematical framework suitable for this purpose, includes the solution of partial differential equations in order to accurately simulate the physical phenomenon in question. By coupling this model with an optimisation scheme, it is possible to design targeted interventions, such as the real-time adjustment of emission rates, the optimal placement of industrial facilities, and other related countermeasures. These actions can guarantee that the concentration of a pollutant will be within specified safe margins inside the regions of interest. The main objectives of this thesis are to propose an accurate mathematical model that describes the dispersion of air-pollutants in a wide range of scenarios, and implement it successfully within an appropriate parallel optimisation scheme, while evaluating its convergence under specific assumptions. The formulation of an optimisation methodology under those requirements, will result in a large-scale numerical problems with different properties depending on the application parameters, and with various limitations regarding their numerical solution. In an attempt to overcome them, this thesis examines the use of PDE-constrained optimisation methods in combination with parallel techniques so as to achieve the minimisation of the air-pollutants’ effects along with the distribution of the computational burden. More specifically, it will provide insight on the implementation of the augmented Lagrangian technique with the use of a Newton method in the formulation of a robust and accurate optimisation framework. In addition, emphasis will be given in the utilisation of parallel algorithms based on domain decomposition methodologies (DDM) in order to produce faster results, improve scalability, and allow the time-sensitive regulation of the pollutants’ emission rate.
...
Air-pollution is one of the most critical ecological and public health challenges of the 21st century. Its pre-emptive, passive, and reactive control is a fundamental aspect of environmental management, that is aimed at minimising the release of harmful substances and their impact on human health and natural systems. An effective pollution control strategy involves the scientific modelling of the pollution dispersion so as to either prevent pollutants from being emitted or mitigate the effects after their release in specified areas of interest. One mathematical framework suitable for this purpose, includes the solution of partial differential equations in order to accurately simulate the physical phenomenon in question. By coupling this model with an optimisation scheme, it is possible to design targeted interventions, such as the real-time adjustment of emission rates, the optimal placement of industrial facilities, and other related countermeasures. These actions can guarantee that the concentration of a pollutant will be within specified safe margins inside the regions of interest. The main objectives of this thesis are to propose an accurate mathematical model that describes the dispersion of air-pollutants in a wide range of scenarios, and implement it successfully within an appropriate parallel optimisation scheme, while evaluating its convergence under specific assumptions. The formulation of an optimisation methodology under those requirements, will result in a large-scale numerical problems with different properties depending on the application parameters, and with various limitations regarding their numerical solution. In an attempt to overcome them, this thesis examines the use of PDE-constrained optimisation methods in combination with parallel techniques so as to achieve the minimisation of the air-pollutants’ effects along with the distribution of the computational burden. More specifically, it will provide insight on the implementation of the augmented Lagrangian technique with the use of a Newton method in the formulation of a robust and accurate optimisation framework. In addition, emphasis will be given in the utilisation of parallel algorithms based on domain decomposition methodologies (DDM) in order to produce faster results, improve scalability, and allow the time-sensitive regulation of the pollutants’ emission rate.
Dynamic Methanol Reforming in Fixed Bed Reactors
2D unsteady modelling of shipboard hydrogen production
This study concerns the dynamic operation of methanol steam reforming in fixed bed reactors for shipboard hydrogen production. The work is motivated by the need to reduce greenhouse gas emissions and harmful exhaust pollutants from the maritime sector, while also addressing the practical difficulty of storing hydrogen directly on board ships. Methanol is considered a promising alternative fuel and hydrogen carrier because it is liquid under ambient conditions, has relatively high energy density, is already handled at industrial scale, and can be used both in combustion-based transition technologies and in future fuel cell systems. In this context, methanol reforming offers a route to produce hydrogen on demand, avoiding some of the storage challenges associated with compressed or cryogenic hydrogen.
The dissertation focuses specifically on methanol steam reforming for polymer electrolyte membrane fuel cell systems. This reforming route is attractive because it provides a high hydrogen yield and comparatively low carbon monoxide selectivity. This is important because PEM fuel cells require pure hydrogen feed. The selected reactor type is a fixed randomly packed catalytic bed. This a configuration is widely used and commercially relevant for reforming applications.
The shipboard operation introduces requirements that are not prioritized in conventional land-based chemical plants. A ship power system must respond to changing loads, and therefore the reformer must be understood in transient operation, in addition to steady state operation. The central question of this dissertation is how fixed-bed methanol reformers behave dynamically, what limits their response time, and what modelling or experimental tools are needed for their reliable analysis.
The second chapter examines the broader problem of dynamic operation in fixed bed reactors. It shows that dynamic behaviour can arise from several motivations, including process flexibility, periodic operation, and on-demand production. These different cases require different performance metrics, modelling approaches, and measurement strategies. The dissertation points how dynamic reactor analysis cannot simply reuse steady state design priorities. Moreover, the objective of the transient analysis must first be clearly defined in each case. This chapter also reviews available numerical modelling approaches and analytical techniques for measuring changing gas compositions. A key point is that models of higher fidelity than 1D are often necessary for dynamic analysis, but not always readily available or computationally convenient. Likewise, transient experiments require instruments with suitable sampling rates, and often a combination of analytical techniques is more likely than using a single method.
To demonstrate the importance of model fidelity, this study develops and applies a dynamic 2D fixed bed reactor model for methanol steam reforming. A comparison with a 1D plug flow model shows that models may agree reasonably well at steady state but differ during transients, especially when predicting local temperature fields and species selectivity. This is important because transient CO formation and hydrogen production are directly relevant to operation and control in fuel cell systems. The 2D model therefore becomes the central tool for the later chapters, which focus on origins of reformer response time.
The second major part of the dissertation, starting with chapter 3, investigates the internal heat transfer dynamics of the fixed bed reactor. Methanol steam reforming is endothermic, so reactor performance depends strongly on heat transport from the reactor wall into the catalyst bed. For this work, the model only deals with the internal packed bed behaviour by imposing changes directly in wall temperature and reactant throughput. Thus the limitations of the external heating system influence is excluded. This allows for an estimation of a theoretical lower limit for the reactor transient time. The results show that, for typical tube diameters of 2-3 cm, internal heat and mass transfer lead to transient times of up to about one minute. This suggests that internal radial heat transfer alone is unlikely to explain the much slower response times often associated with practical methanol reformer systems. The packed bed may only amplify slow external heat supply changes, but it is probably not the dominant source of long load-change durations.
Chapter 4 combines experiments and modelling to study external heat transfer effects and validate the dynamic reactor model. A laboratory fixed bed methanol steam reformer is used for gathering steady state and transient data, mainly consisting of internal bed temperatures and reformate carbon monoxide content. The model is adapted to include all detected experimental non-uniformities and heat transfer imperfections. This enables a complete comparison between simulated and measured reactor behaviour. The results show that the model can capture the main dynamic trends, but they also reveal a strong influence of practical heating details during transient operation. Important external factors include the heat capacity of the reactor and supporting structure, axial heat loss profiles, non-uniform axial heat supply, and instability in inlet reactant temperature. Among these, the heat capacity of the reactor assembly is especially influential because it stores and releases heat during load changes, thereby prolonging the transient response even in a relatively small and well-insulated laboratory reactor.
Overall, the conclusions of this study is that dynamic shipboard methanol reformer design requires a broader approach than conventional steady state reactor sizing. A comprehensive analysis includes definition of the cause and purpose of dynamic operation, selection of a model with sufficient spatial and temporal fidelity, and finally the use analytical instruments fast enough to validate transient predictions. From this study it is also concluded that the intrinsic internal dynamics of typical fixed bed reformer tubes are relatively fast compared with the load change times reported for practical systems. Therefore, future improvements in transient performance should focus strongly on the external heating arrangement, reactor thermal mass, heat integration strategy, and system level control. These findings are relevant not only for methanol reforming but also for other shipboard chemical reactors that may become part of future low emission maritime energy systems. ...
The dissertation focuses specifically on methanol steam reforming for polymer electrolyte membrane fuel cell systems. This reforming route is attractive because it provides a high hydrogen yield and comparatively low carbon monoxide selectivity. This is important because PEM fuel cells require pure hydrogen feed. The selected reactor type is a fixed randomly packed catalytic bed. This a configuration is widely used and commercially relevant for reforming applications.
The shipboard operation introduces requirements that are not prioritized in conventional land-based chemical plants. A ship power system must respond to changing loads, and therefore the reformer must be understood in transient operation, in addition to steady state operation. The central question of this dissertation is how fixed-bed methanol reformers behave dynamically, what limits their response time, and what modelling or experimental tools are needed for their reliable analysis.
The second chapter examines the broader problem of dynamic operation in fixed bed reactors. It shows that dynamic behaviour can arise from several motivations, including process flexibility, periodic operation, and on-demand production. These different cases require different performance metrics, modelling approaches, and measurement strategies. The dissertation points how dynamic reactor analysis cannot simply reuse steady state design priorities. Moreover, the objective of the transient analysis must first be clearly defined in each case. This chapter also reviews available numerical modelling approaches and analytical techniques for measuring changing gas compositions. A key point is that models of higher fidelity than 1D are often necessary for dynamic analysis, but not always readily available or computationally convenient. Likewise, transient experiments require instruments with suitable sampling rates, and often a combination of analytical techniques is more likely than using a single method.
To demonstrate the importance of model fidelity, this study develops and applies a dynamic 2D fixed bed reactor model for methanol steam reforming. A comparison with a 1D plug flow model shows that models may agree reasonably well at steady state but differ during transients, especially when predicting local temperature fields and species selectivity. This is important because transient CO formation and hydrogen production are directly relevant to operation and control in fuel cell systems. The 2D model therefore becomes the central tool for the later chapters, which focus on origins of reformer response time.
The second major part of the dissertation, starting with chapter 3, investigates the internal heat transfer dynamics of the fixed bed reactor. Methanol steam reforming is endothermic, so reactor performance depends strongly on heat transport from the reactor wall into the catalyst bed. For this work, the model only deals with the internal packed bed behaviour by imposing changes directly in wall temperature and reactant throughput. Thus the limitations of the external heating system influence is excluded. This allows for an estimation of a theoretical lower limit for the reactor transient time. The results show that, for typical tube diameters of 2-3 cm, internal heat and mass transfer lead to transient times of up to about one minute. This suggests that internal radial heat transfer alone is unlikely to explain the much slower response times often associated with practical methanol reformer systems. The packed bed may only amplify slow external heat supply changes, but it is probably not the dominant source of long load-change durations.
Chapter 4 combines experiments and modelling to study external heat transfer effects and validate the dynamic reactor model. A laboratory fixed bed methanol steam reformer is used for gathering steady state and transient data, mainly consisting of internal bed temperatures and reformate carbon monoxide content. The model is adapted to include all detected experimental non-uniformities and heat transfer imperfections. This enables a complete comparison between simulated and measured reactor behaviour. The results show that the model can capture the main dynamic trends, but they also reveal a strong influence of practical heating details during transient operation. Important external factors include the heat capacity of the reactor and supporting structure, axial heat loss profiles, non-uniform axial heat supply, and instability in inlet reactant temperature. Among these, the heat capacity of the reactor assembly is especially influential because it stores and releases heat during load changes, thereby prolonging the transient response even in a relatively small and well-insulated laboratory reactor.
Overall, the conclusions of this study is that dynamic shipboard methanol reformer design requires a broader approach than conventional steady state reactor sizing. A comprehensive analysis includes definition of the cause and purpose of dynamic operation, selection of a model with sufficient spatial and temporal fidelity, and finally the use analytical instruments fast enough to validate transient predictions. From this study it is also concluded that the intrinsic internal dynamics of typical fixed bed reformer tubes are relatively fast compared with the load change times reported for practical systems. Therefore, future improvements in transient performance should focus strongly on the external heating arrangement, reactor thermal mass, heat integration strategy, and system level control. These findings are relevant not only for methanol reforming but also for other shipboard chemical reactors that may become part of future low emission maritime energy systems. ...
This study concerns the dynamic operation of methanol steam reforming in fixed bed reactors for shipboard hydrogen production. The work is motivated by the need to reduce greenhouse gas emissions and harmful exhaust pollutants from the maritime sector, while also addressing the practical difficulty of storing hydrogen directly on board ships. Methanol is considered a promising alternative fuel and hydrogen carrier because it is liquid under ambient conditions, has relatively high energy density, is already handled at industrial scale, and can be used both in combustion-based transition technologies and in future fuel cell systems. In this context, methanol reforming offers a route to produce hydrogen on demand, avoiding some of the storage challenges associated with compressed or cryogenic hydrogen.
The dissertation focuses specifically on methanol steam reforming for polymer electrolyte membrane fuel cell systems. This reforming route is attractive because it provides a high hydrogen yield and comparatively low carbon monoxide selectivity. This is important because PEM fuel cells require pure hydrogen feed. The selected reactor type is a fixed randomly packed catalytic bed. This a configuration is widely used and commercially relevant for reforming applications.
The shipboard operation introduces requirements that are not prioritized in conventional land-based chemical plants. A ship power system must respond to changing loads, and therefore the reformer must be understood in transient operation, in addition to steady state operation. The central question of this dissertation is how fixed-bed methanol reformers behave dynamically, what limits their response time, and what modelling or experimental tools are needed for their reliable analysis.
The second chapter examines the broader problem of dynamic operation in fixed bed reactors. It shows that dynamic behaviour can arise from several motivations, including process flexibility, periodic operation, and on-demand production. These different cases require different performance metrics, modelling approaches, and measurement strategies. The dissertation points how dynamic reactor analysis cannot simply reuse steady state design priorities. Moreover, the objective of the transient analysis must first be clearly defined in each case. This chapter also reviews available numerical modelling approaches and analytical techniques for measuring changing gas compositions. A key point is that models of higher fidelity than 1D are often necessary for dynamic analysis, but not always readily available or computationally convenient. Likewise, transient experiments require instruments with suitable sampling rates, and often a combination of analytical techniques is more likely than using a single method.
To demonstrate the importance of model fidelity, this study develops and applies a dynamic 2D fixed bed reactor model for methanol steam reforming. A comparison with a 1D plug flow model shows that models may agree reasonably well at steady state but differ during transients, especially when predicting local temperature fields and species selectivity. This is important because transient CO formation and hydrogen production are directly relevant to operation and control in fuel cell systems. The 2D model therefore becomes the central tool for the later chapters, which focus on origins of reformer response time.
The second major part of the dissertation, starting with chapter 3, investigates the internal heat transfer dynamics of the fixed bed reactor. Methanol steam reforming is endothermic, so reactor performance depends strongly on heat transport from the reactor wall into the catalyst bed. For this work, the model only deals with the internal packed bed behaviour by imposing changes directly in wall temperature and reactant throughput. Thus the limitations of the external heating system influence is excluded. This allows for an estimation of a theoretical lower limit for the reactor transient time. The results show that, for typical tube diameters of 2-3 cm, internal heat and mass transfer lead to transient times of up to about one minute. This suggests that internal radial heat transfer alone is unlikely to explain the much slower response times often associated with practical methanol reformer systems. The packed bed may only amplify slow external heat supply changes, but it is probably not the dominant source of long load-change durations.
Chapter 4 combines experiments and modelling to study external heat transfer effects and validate the dynamic reactor model. A laboratory fixed bed methanol steam reformer is used for gathering steady state and transient data, mainly consisting of internal bed temperatures and reformate carbon monoxide content. The model is adapted to include all detected experimental non-uniformities and heat transfer imperfections. This enables a complete comparison between simulated and measured reactor behaviour. The results show that the model can capture the main dynamic trends, but they also reveal a strong influence of practical heating details during transient operation. Important external factors include the heat capacity of the reactor and supporting structure, axial heat loss profiles, non-uniform axial heat supply, and instability in inlet reactant temperature. Among these, the heat capacity of the reactor assembly is especially influential because it stores and releases heat during load changes, thereby prolonging the transient response even in a relatively small and well-insulated laboratory reactor.
Overall, the conclusions of this study is that dynamic shipboard methanol reformer design requires a broader approach than conventional steady state reactor sizing. A comprehensive analysis includes definition of the cause and purpose of dynamic operation, selection of a model with sufficient spatial and temporal fidelity, and finally the use analytical instruments fast enough to validate transient predictions. From this study it is also concluded that the intrinsic internal dynamics of typical fixed bed reformer tubes are relatively fast compared with the load change times reported for practical systems. Therefore, future improvements in transient performance should focus strongly on the external heating arrangement, reactor thermal mass, heat integration strategy, and system level control. These findings are relevant not only for methanol reforming but also for other shipboard chemical reactors that may become part of future low emission maritime energy systems.
The dissertation focuses specifically on methanol steam reforming for polymer electrolyte membrane fuel cell systems. This reforming route is attractive because it provides a high hydrogen yield and comparatively low carbon monoxide selectivity. This is important because PEM fuel cells require pure hydrogen feed. The selected reactor type is a fixed randomly packed catalytic bed. This a configuration is widely used and commercially relevant for reforming applications.
The shipboard operation introduces requirements that are not prioritized in conventional land-based chemical plants. A ship power system must respond to changing loads, and therefore the reformer must be understood in transient operation, in addition to steady state operation. The central question of this dissertation is how fixed-bed methanol reformers behave dynamically, what limits their response time, and what modelling or experimental tools are needed for their reliable analysis.
The second chapter examines the broader problem of dynamic operation in fixed bed reactors. It shows that dynamic behaviour can arise from several motivations, including process flexibility, periodic operation, and on-demand production. These different cases require different performance metrics, modelling approaches, and measurement strategies. The dissertation points how dynamic reactor analysis cannot simply reuse steady state design priorities. Moreover, the objective of the transient analysis must first be clearly defined in each case. This chapter also reviews available numerical modelling approaches and analytical techniques for measuring changing gas compositions. A key point is that models of higher fidelity than 1D are often necessary for dynamic analysis, but not always readily available or computationally convenient. Likewise, transient experiments require instruments with suitable sampling rates, and often a combination of analytical techniques is more likely than using a single method.
To demonstrate the importance of model fidelity, this study develops and applies a dynamic 2D fixed bed reactor model for methanol steam reforming. A comparison with a 1D plug flow model shows that models may agree reasonably well at steady state but differ during transients, especially when predicting local temperature fields and species selectivity. This is important because transient CO formation and hydrogen production are directly relevant to operation and control in fuel cell systems. The 2D model therefore becomes the central tool for the later chapters, which focus on origins of reformer response time.
The second major part of the dissertation, starting with chapter 3, investigates the internal heat transfer dynamics of the fixed bed reactor. Methanol steam reforming is endothermic, so reactor performance depends strongly on heat transport from the reactor wall into the catalyst bed. For this work, the model only deals with the internal packed bed behaviour by imposing changes directly in wall temperature and reactant throughput. Thus the limitations of the external heating system influence is excluded. This allows for an estimation of a theoretical lower limit for the reactor transient time. The results show that, for typical tube diameters of 2-3 cm, internal heat and mass transfer lead to transient times of up to about one minute. This suggests that internal radial heat transfer alone is unlikely to explain the much slower response times often associated with practical methanol reformer systems. The packed bed may only amplify slow external heat supply changes, but it is probably not the dominant source of long load-change durations.
Chapter 4 combines experiments and modelling to study external heat transfer effects and validate the dynamic reactor model. A laboratory fixed bed methanol steam reformer is used for gathering steady state and transient data, mainly consisting of internal bed temperatures and reformate carbon monoxide content. The model is adapted to include all detected experimental non-uniformities and heat transfer imperfections. This enables a complete comparison between simulated and measured reactor behaviour. The results show that the model can capture the main dynamic trends, but they also reveal a strong influence of practical heating details during transient operation. Important external factors include the heat capacity of the reactor and supporting structure, axial heat loss profiles, non-uniform axial heat supply, and instability in inlet reactant temperature. Among these, the heat capacity of the reactor assembly is especially influential because it stores and releases heat during load changes, thereby prolonging the transient response even in a relatively small and well-insulated laboratory reactor.
Overall, the conclusions of this study is that dynamic shipboard methanol reformer design requires a broader approach than conventional steady state reactor sizing. A comprehensive analysis includes definition of the cause and purpose of dynamic operation, selection of a model with sufficient spatial and temporal fidelity, and finally the use analytical instruments fast enough to validate transient predictions. From this study it is also concluded that the intrinsic internal dynamics of typical fixed bed reformer tubes are relatively fast compared with the load change times reported for practical systems. Therefore, future improvements in transient performance should focus strongly on the external heating arrangement, reactor thermal mass, heat integration strategy, and system level control. These findings are relevant not only for methanol reforming but also for other shipboard chemical reactors that may become part of future low emission maritime energy systems.
The increasing scale of offshore energy infrastructure has created a demand for foundation concepts that remain technically and economically viable for larger topsides and greater water depths. While monopile foundations dominate shallow-water applications due to their simplicity and cost-effectiveness, their applicability becomes increasingly constrained by manufacturing, transportation, installation, and structural limitations. Larger offshore topsides are therefore commonly supported by jacket foundations, which provide efficient load transfer and high structural robustness. However, jackets require more complex design, fabrication, and installation processes, resulting in longer project schedules and increased costs. This research investigates the technical feasibility of an alternative support concept consisting of four large-diameter piles, referred to as a four-megapile foundation, for offshore topside structures.
A simplified numerical modelling framework was developed in Python to evaluate the global behaviour of offshore structures supported by large-diameter piles. Based on the three-dimensional matrix method, the model incorporates soil-structure interaction, hydrodynamic loading, structural dynamics, and limit state assessment procedures. Soil behaviour was represented using linearized stiffness formulations derived from the PISA framework. The model was verified against commercial software and benchmark calculations before being applied to a representative North Sea case study.
The verified model was used to assess the structural performance of a four-megapile-supported topside under Ultimate, Fatigue, and Serviceability Limit State conditions. Sensitivity analyses were performed to evaluate the influence of uncertainties in soil properties, environmental loading, and modelling assumptions. In addition, a parametric study compared monopile and four-megapile concepts across a range of water depths and topside dimensions.
The results demonstrate that the four-megapile concept is technically feasible within the investigated range of conditions. ULS, FLS, and SLS requirements can be satisfied through an appropriate combination of pile diameter, penetration depth, wall thickness, and pile spacing. Soil properties, water depth, damping ratio, topside mass, and the rotational stiffness of the topside-pile connection were identified as the most influential parameters governing structural performance. Compared to monopiles, the four-megapile concept exhibits more favourable scaling with increasing water depth and topside size, maintaining practical pile dimensions while avoiding several manufacturing limitations associated with very large monopiles.
To conclude, the study demonstrates that four-megapile foundations represent a promising alternative to conventional monopile foundations, particularly for large offshore topsides and deeper-water applications. The findings provide insight into the governing design parameters and establish a basis for future investigations into advanced soil modelling, installation methodologies, and economic feasibility.
...
The increasing scale of offshore energy infrastructure has created a demand for foundation concepts that remain technically and economically viable for larger topsides and greater water depths. While monopile foundations dominate shallow-water applications due to their simplicity and cost-effectiveness, their applicability becomes increasingly constrained by manufacturing, transportation, installation, and structural limitations. Larger offshore topsides are therefore commonly supported by jacket foundations, which provide efficient load transfer and high structural robustness. However, jackets require more complex design, fabrication, and installation processes, resulting in longer project schedules and increased costs. This research investigates the technical feasibility of an alternative support concept consisting of four large-diameter piles, referred to as a four-megapile foundation, for offshore topside structures.
A simplified numerical modelling framework was developed in Python to evaluate the global behaviour of offshore structures supported by large-diameter piles. Based on the three-dimensional matrix method, the model incorporates soil-structure interaction, hydrodynamic loading, structural dynamics, and limit state assessment procedures. Soil behaviour was represented using linearized stiffness formulations derived from the PISA framework. The model was verified against commercial software and benchmark calculations before being applied to a representative North Sea case study.
The verified model was used to assess the structural performance of a four-megapile-supported topside under Ultimate, Fatigue, and Serviceability Limit State conditions. Sensitivity analyses were performed to evaluate the influence of uncertainties in soil properties, environmental loading, and modelling assumptions. In addition, a parametric study compared monopile and four-megapile concepts across a range of water depths and topside dimensions.
The results demonstrate that the four-megapile concept is technically feasible within the investigated range of conditions. ULS, FLS, and SLS requirements can be satisfied through an appropriate combination of pile diameter, penetration depth, wall thickness, and pile spacing. Soil properties, water depth, damping ratio, topside mass, and the rotational stiffness of the topside-pile connection were identified as the most influential parameters governing structural performance. Compared to monopiles, the four-megapile concept exhibits more favourable scaling with increasing water depth and topside size, maintaining practical pile dimensions while avoiding several manufacturing limitations associated with very large monopiles.
To conclude, the study demonstrates that four-megapile foundations represent a promising alternative to conventional monopile foundations, particularly for large offshore topsides and deeper-water applications. The findings provide insight into the governing design parameters and establish a basis for future investigations into advanced soil modelling, installation methodologies, and economic feasibility.
In order to accelerate the energy transition, policies have proven successful to reduce emissions, but more policy innovations are needed to reach carbon neutrality. Despite some understanding of the process of such innovations, the role of knowledge is not addressed in a systematic way. In particular, the role of energy models has not been investigated thoroughly. In this article, we examined the types of knowledge utilization and the ways in which they influence the development of policy innovation. We focused on energy modelling and conducted a case study of the European Union's (EU) 55% climate target for 2030, and analytically distinguish three uses of model outputs (rational, legitimizing and enlightening), for which we nuance who uses what knowledge to what effect. Based on a qualitative content analysis of 33 text documents and 12 semi-structured interviews with EU policy modelers and policymakers, the results indicate that energy models enable and constrain policy innovations. Model outputs were mainly utilized to legitimize the previously formulated 55% target, but also in rational and enlightening ways for the development of a policy mix to achieve this target. However, the absence of assessments of higher targets might have inhibited the adoption of a more ambitious policy. Based on these results we identify enabling and inhibiting factors for the use of energy models in policymaking. Beyond energy modelling, the study develops our understanding of how different uses of knowledge affect policy innovation and lays the foundation for future studies on the uses of different kinds of knowledge.
...
In order to accelerate the energy transition, policies have proven successful to reduce emissions, but more policy innovations are needed to reach carbon neutrality. Despite some understanding of the process of such innovations, the role of knowledge is not addressed in a systematic way. In particular, the role of energy models has not been investigated thoroughly. In this article, we examined the types of knowledge utilization and the ways in which they influence the development of policy innovation. We focused on energy modelling and conducted a case study of the European Union's (EU) 55% climate target for 2030, and analytically distinguish three uses of model outputs (rational, legitimizing and enlightening), for which we nuance who uses what knowledge to what effect. Based on a qualitative content analysis of 33 text documents and 12 semi-structured interviews with EU policy modelers and policymakers, the results indicate that energy models enable and constrain policy innovations. Model outputs were mainly utilized to legitimize the previously formulated 55% target, but also in rational and enlightening ways for the development of a policy mix to achieve this target. However, the absence of assessments of higher targets might have inhibited the adoption of a more ambitious policy. Based on these results we identify enabling and inhibiting factors for the use of energy models in policymaking. Beyond energy modelling, the study develops our understanding of how different uses of knowledge affect policy innovation and lays the foundation for future studies on the uses of different kinds of knowledge.