E. Zanetti
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1
Modelling and Optimisation of CO₂ Refrigeration Cycles with Advanced Subcooling Configurations
A technoeconomic investigation of waste heat integration
Transcritical CO2 refrigeration cycles offer meaningful environmental benefits as natural refrigerants, yet their efficiency degrades severely under elevated ambient temperatures—COP declining from 3.78 at 25°C to 1.83 at 40°C (51% reduction). This performance limitation necessitates advanced subcooling configurations to maintain competitiveness with conventional refrigeration technologies. While mechanical subcooling cycles (MSC) and ejector-based systems have been investigated separately, limited research has explored the integration of externally supplied low-grade waste heat to drive ejector refrigeration cycles for CO2 subcooling applications.
This thesis develops and optimizes thermodynamic models for waste-heat-driven ejector refrigeration cycles (EJRC) serving as mechanical subcooling units for transcritical CO2 vapor-compression systems. Three progressive configurations are analyzed: a baseline transcritical CO2 cycle establishing reference performance, an MSC system employing ammonia as auxiliary refrigerant, and an EJRC with both simplified Köhler efficiency models and detailed multi-ejector binary valve representations. The models are validated against established literature correlations and subjected to comprehensive parametric optimization across evaporating temperatures (−20°C to 20°C), ambient conditions (30°C to 40°C), and waste heat ratios (f = 0.8–20).
Results demonstrate that MSC achieves 56% COP improvement over baseline (COP = 2.91 vs. 1.83 at reference conditions: Tair = 40°C, Tevap = 0°C), while EJRC configurations deliver superior performance ranging from 45% to 75.7% improvement depending on waste heat availability. The optimal EJRC configuration—generator-off mode at waste heat temperature T9e = 90°C and ratio f = 10—achieves COP = 4.44, representing 73% improvement over MSC. The simplified model, calibrated with entrainment ratio ϕ = 0.4–0.7 and ejector efficiency ηej = 0.10, provides 200× computational speedup with deviations of 5.7–16.5% from multi-ejector simulations.
Techno-economic assessment reveals fundamental divergence between thermodynamic and economic optima. Generator-on configurations achieve superior COP (3.00–3.72) but exhibit negative net present value (NPV = −€117,220 to −€518,190) due to prohibitive capital expenditure and maintenance burdens. On the other hand, the generator-off configuration at f = 10 delivers marginal economic viability (NPV = €3,485, simple payback period = 12.24 years, LCOC = €0.165/kWh) compared to MSC (NPV = €206,400, LCOC = €0.1655/kWh). The analysis establishes that ejector technology becomes economically competitive only when high-grade waste heat (T9e ≥ 90°C) exists at sufficient ratios (f ≥ 10), generator operation is deactivated, and electricity pricing exceeds €0.30/kWh.
This research provides integrated thermodynamic-economic optimization framework for waste heat-driven refrigeration improvement, demonstrating that technology choice must be dictated by waste heat availability, quality, and economic boundary conditions rather than thermodynamic performance maximisation alone. ...
This thesis develops and optimizes thermodynamic models for waste-heat-driven ejector refrigeration cycles (EJRC) serving as mechanical subcooling units for transcritical CO2 vapor-compression systems. Three progressive configurations are analyzed: a baseline transcritical CO2 cycle establishing reference performance, an MSC system employing ammonia as auxiliary refrigerant, and an EJRC with both simplified Köhler efficiency models and detailed multi-ejector binary valve representations. The models are validated against established literature correlations and subjected to comprehensive parametric optimization across evaporating temperatures (−20°C to 20°C), ambient conditions (30°C to 40°C), and waste heat ratios (f = 0.8–20).
Results demonstrate that MSC achieves 56% COP improvement over baseline (COP = 2.91 vs. 1.83 at reference conditions: Tair = 40°C, Tevap = 0°C), while EJRC configurations deliver superior performance ranging from 45% to 75.7% improvement depending on waste heat availability. The optimal EJRC configuration—generator-off mode at waste heat temperature T9e = 90°C and ratio f = 10—achieves COP = 4.44, representing 73% improvement over MSC. The simplified model, calibrated with entrainment ratio ϕ = 0.4–0.7 and ejector efficiency ηej = 0.10, provides 200× computational speedup with deviations of 5.7–16.5% from multi-ejector simulations.
Techno-economic assessment reveals fundamental divergence between thermodynamic and economic optima. Generator-on configurations achieve superior COP (3.00–3.72) but exhibit negative net present value (NPV = −€117,220 to −€518,190) due to prohibitive capital expenditure and maintenance burdens. On the other hand, the generator-off configuration at f = 10 delivers marginal economic viability (NPV = €3,485, simple payback period = 12.24 years, LCOC = €0.165/kWh) compared to MSC (NPV = €206,400, LCOC = €0.1655/kWh). The analysis establishes that ejector technology becomes economically competitive only when high-grade waste heat (T9e ≥ 90°C) exists at sufficient ratios (f ≥ 10), generator operation is deactivated, and electricity pricing exceeds €0.30/kWh.
This research provides integrated thermodynamic-economic optimization framework for waste heat-driven refrigeration improvement, demonstrating that technology choice must be dictated by waste heat availability, quality, and economic boundary conditions rather than thermodynamic performance maximisation alone. ...
Transcritical CO2 refrigeration cycles offer meaningful environmental benefits as natural refrigerants, yet their efficiency degrades severely under elevated ambient temperatures—COP declining from 3.78 at 25°C to 1.83 at 40°C (51% reduction). This performance limitation necessitates advanced subcooling configurations to maintain competitiveness with conventional refrigeration technologies. While mechanical subcooling cycles (MSC) and ejector-based systems have been investigated separately, limited research has explored the integration of externally supplied low-grade waste heat to drive ejector refrigeration cycles for CO2 subcooling applications.
This thesis develops and optimizes thermodynamic models for waste-heat-driven ejector refrigeration cycles (EJRC) serving as mechanical subcooling units for transcritical CO2 vapor-compression systems. Three progressive configurations are analyzed: a baseline transcritical CO2 cycle establishing reference performance, an MSC system employing ammonia as auxiliary refrigerant, and an EJRC with both simplified Köhler efficiency models and detailed multi-ejector binary valve representations. The models are validated against established literature correlations and subjected to comprehensive parametric optimization across evaporating temperatures (−20°C to 20°C), ambient conditions (30°C to 40°C), and waste heat ratios (f = 0.8–20).
Results demonstrate that MSC achieves 56% COP improvement over baseline (COP = 2.91 vs. 1.83 at reference conditions: Tair = 40°C, Tevap = 0°C), while EJRC configurations deliver superior performance ranging from 45% to 75.7% improvement depending on waste heat availability. The optimal EJRC configuration—generator-off mode at waste heat temperature T9e = 90°C and ratio f = 10—achieves COP = 4.44, representing 73% improvement over MSC. The simplified model, calibrated with entrainment ratio ϕ = 0.4–0.7 and ejector efficiency ηej = 0.10, provides 200× computational speedup with deviations of 5.7–16.5% from multi-ejector simulations.
Techno-economic assessment reveals fundamental divergence between thermodynamic and economic optima. Generator-on configurations achieve superior COP (3.00–3.72) but exhibit negative net present value (NPV = −€117,220 to −€518,190) due to prohibitive capital expenditure and maintenance burdens. On the other hand, the generator-off configuration at f = 10 delivers marginal economic viability (NPV = €3,485, simple payback period = 12.24 years, LCOC = €0.165/kWh) compared to MSC (NPV = €206,400, LCOC = €0.1655/kWh). The analysis establishes that ejector technology becomes economically competitive only when high-grade waste heat (T9e ≥ 90°C) exists at sufficient ratios (f ≥ 10), generator operation is deactivated, and electricity pricing exceeds €0.30/kWh.
This research provides integrated thermodynamic-economic optimization framework for waste heat-driven refrigeration improvement, demonstrating that technology choice must be dictated by waste heat availability, quality, and economic boundary conditions rather than thermodynamic performance maximisation alone.
This thesis develops and optimizes thermodynamic models for waste-heat-driven ejector refrigeration cycles (EJRC) serving as mechanical subcooling units for transcritical CO2 vapor-compression systems. Three progressive configurations are analyzed: a baseline transcritical CO2 cycle establishing reference performance, an MSC system employing ammonia as auxiliary refrigerant, and an EJRC with both simplified Köhler efficiency models and detailed multi-ejector binary valve representations. The models are validated against established literature correlations and subjected to comprehensive parametric optimization across evaporating temperatures (−20°C to 20°C), ambient conditions (30°C to 40°C), and waste heat ratios (f = 0.8–20).
Results demonstrate that MSC achieves 56% COP improvement over baseline (COP = 2.91 vs. 1.83 at reference conditions: Tair = 40°C, Tevap = 0°C), while EJRC configurations deliver superior performance ranging from 45% to 75.7% improvement depending on waste heat availability. The optimal EJRC configuration—generator-off mode at waste heat temperature T9e = 90°C and ratio f = 10—achieves COP = 4.44, representing 73% improvement over MSC. The simplified model, calibrated with entrainment ratio ϕ = 0.4–0.7 and ejector efficiency ηej = 0.10, provides 200× computational speedup with deviations of 5.7–16.5% from multi-ejector simulations.
Techno-economic assessment reveals fundamental divergence between thermodynamic and economic optima. Generator-on configurations achieve superior COP (3.00–3.72) but exhibit negative net present value (NPV = −€117,220 to −€518,190) due to prohibitive capital expenditure and maintenance burdens. On the other hand, the generator-off configuration at f = 10 delivers marginal economic viability (NPV = €3,485, simple payback period = 12.24 years, LCOC = €0.165/kWh) compared to MSC (NPV = €206,400, LCOC = €0.1655/kWh). The analysis establishes that ejector technology becomes economically competitive only when high-grade waste heat (T9e ≥ 90°C) exists at sufficient ratios (f ≥ 10), generator operation is deactivated, and electricity pricing exceeds €0.30/kWh.
This research provides integrated thermodynamic-economic optimization framework for waste heat-driven refrigeration improvement, demonstrating that technology choice must be dictated by waste heat availability, quality, and economic boundary conditions rather than thermodynamic performance maximisation alone.
Dropwise Condensation in Refrigerants: Experimental Setup Design
Setup Designn and Verfication for Estimating the Heat Transfer Coefficient in Dropwise Condensation
Fluorinated refrigerants, widely used in refrigeration cycle applications, cause significant greenhouse gas emissions. In view of reducing environmental impact, natural refrigerants are applicable as an alternative. However, their imposed risks (flammability, toxicity & high pressure systems) raise safety concerns. These refrigeration cycle applications utilize a condensation process. By increasing the heat transfer coefficient, the damage potential can be reduced by decreasing the size of the condenser in its applications. Dropwise condensation has proven to significantly enhance the heat transfer coefficient relative to traditional filmwise condensation in steam applications. However, little research is conducted into the experimental heat transfer coefficient of dropwise condensation in refrigerants. Therefore, a setup is designed to estimate the heat transfer coefficient experimentally on different promoter layers. For derivative estimation, the total heat transfer rate, condensation wall temperature, and saturation temperature are needed. The optimal solution available to estimate these parameters is based on Fourier’s law of conduction in a designed test-section. Here, condensation takes place on one side and cooling on the other, causing heat transfer and a temperature gradient. By measuring the temperature at different points, the total heat transfer rate and wall temperature can be estimated. To supply saturated vapour, a pressurised loop is designed, including an evaporator, post-condenser, pump and coolant supply. While verifying the function of the test-section in a computational model, the resulting performance align with expectations. However, the one-dimensional model for estimation the heat transfer coefficient based on Fourier’s law of conduction, is not sufficient in accurately estimating the wall temperature. A temperature gradient occurs on the condensation surface, whereas the estimation model assumes a homogenous temperature. Therefore, the heat transfer coefficient of condensation will be severely underestimated at increased saturation and coolant temperatures.
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Fluorinated refrigerants, widely used in refrigeration cycle applications, cause significant greenhouse gas emissions. In view of reducing environmental impact, natural refrigerants are applicable as an alternative. However, their imposed risks (flammability, toxicity & high pressure systems) raise safety concerns. These refrigeration cycle applications utilize a condensation process. By increasing the heat transfer coefficient, the damage potential can be reduced by decreasing the size of the condenser in its applications. Dropwise condensation has proven to significantly enhance the heat transfer coefficient relative to traditional filmwise condensation in steam applications. However, little research is conducted into the experimental heat transfer coefficient of dropwise condensation in refrigerants. Therefore, a setup is designed to estimate the heat transfer coefficient experimentally on different promoter layers. For derivative estimation, the total heat transfer rate, condensation wall temperature, and saturation temperature are needed. The optimal solution available to estimate these parameters is based on Fourier’s law of conduction in a designed test-section. Here, condensation takes place on one side and cooling on the other, causing heat transfer and a temperature gradient. By measuring the temperature at different points, the total heat transfer rate and wall temperature can be estimated. To supply saturated vapour, a pressurised loop is designed, including an evaporator, post-condenser, pump and coolant supply. While verifying the function of the test-section in a computational model, the resulting performance align with expectations. However, the one-dimensional model for estimation the heat transfer coefficient based on Fourier’s law of conduction, is not sufficient in accurately estimating the wall temperature. A temperature gradient occurs on the condensation surface, whereas the estimation model assumes a homogenous temperature. Therefore, the heat transfer coefficient of condensation will be severely underestimated at increased saturation and coolant temperatures.
The increasing integration of intermittent renewable energy sources into the global energy grid necessitates the development of efficient and reliable long-duration energy storage systems. The Electron247, a thermal energy storage device developed by EnergyIntel Services, utilizes an alpha-type Stirling engine for heat-to-power conversion. However, the engine’s baseline performance is a significant bottleneck, operating at a simulated [REDACTED] with a thermal efficiency of [REDACTED] , which limits the overall round-trip efficiency of the system. This thesis presents a systematic approach to improve the power output and thermal efficiency of the Electron247 system through the parametric optimization of its Stirling engine components. A specialized third-order, quasi-steady thermodynamic model was developed to accurately simulate the engine’s performance, incorporating critical loss mechanisms such as imperfect heat transfer, pressure drops, regenerator ineffectiveness, and mechanical friction. The model’s predictive accuracy was validated using Helium as the working fluid, showing strong correlation (average error below 7%) with experimental data from two operational units in Masdar City, Abu Dhabi. Leveraging the validated model, a multi-objective optimization was performed using the Nondominated Sorting Genetic Algorithm II (NSGA-II). The optimization aimed to simultaneously maximize thermal efficiency and power output by varying ten key geometric parameters of the engine’s heater, cooler, and regenerator, subject to manufacturing and system-level constraints. The results produced a Pareto-optimal front of designs offering significant performance gains over the baseline configuration. Analysis of the optimal designs revealed that the regenerator’s geometry (specifically, its total volume and wire mesh characteristics) was the most critical factor in determining engine performance. Notably, the ”Maximum Efficiency” design achieved a thermal efficiency of [REDACTED] , while the balanced ”Closest to Ideal” design improved both power output to [REDACTED] and efficiency to [REDACTED] . Depending on the design choice, from a balanced-performance model to a maximum-efficiency configuration, these enhancements result in an additional 800 to 1,100 tons of CO2 emissions being spared per unit, demonstrating the critical impact of component-level optimization on the viability and environmental benefits of thermal energy storage technologies.
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The increasing integration of intermittent renewable energy sources into the global energy grid necessitates the development of efficient and reliable long-duration energy storage systems. The Electron247, a thermal energy storage device developed by EnergyIntel Services, utilizes an alpha-type Stirling engine for heat-to-power conversion. However, the engine’s baseline performance is a significant bottleneck, operating at a simulated [REDACTED] with a thermal efficiency of [REDACTED] , which limits the overall round-trip efficiency of the system. This thesis presents a systematic approach to improve the power output and thermal efficiency of the Electron247 system through the parametric optimization of its Stirling engine components. A specialized third-order, quasi-steady thermodynamic model was developed to accurately simulate the engine’s performance, incorporating critical loss mechanisms such as imperfect heat transfer, pressure drops, regenerator ineffectiveness, and mechanical friction. The model’s predictive accuracy was validated using Helium as the working fluid, showing strong correlation (average error below 7%) with experimental data from two operational units in Masdar City, Abu Dhabi. Leveraging the validated model, a multi-objective optimization was performed using the Nondominated Sorting Genetic Algorithm II (NSGA-II). The optimization aimed to simultaneously maximize thermal efficiency and power output by varying ten key geometric parameters of the engine’s heater, cooler, and regenerator, subject to manufacturing and system-level constraints. The results produced a Pareto-optimal front of designs offering significant performance gains over the baseline configuration. Analysis of the optimal designs revealed that the regenerator’s geometry (specifically, its total volume and wire mesh characteristics) was the most critical factor in determining engine performance. Notably, the ”Maximum Efficiency” design achieved a thermal efficiency of [REDACTED] , while the balanced ”Closest to Ideal” design improved both power output to [REDACTED] and efficiency to [REDACTED] . Depending on the design choice, from a balanced-performance model to a maximum-efficiency configuration, these enhancements result in an additional 800 to 1,100 tons of CO2 emissions being spared per unit, demonstrating the critical impact of component-level optimization on the viability and environmental benefits of thermal energy storage technologies.
Modeling and Optimizing Space Cooling with Solar Energy
Exploring the Potential of Ejector-Boosted and Mechanical Sub-Cooling Cycles
Heating and cooling systems contribute to approximately 50% of the world’s final energy consumption, highlighting their crucial role in the global energy transition. Ejector refrigeration cycles have the potential to convert heat into cooling, thereby improving refrigeration sustainability. This study aims to provide a thermodynamic performance analysis of solar ejector refrigeration cycles, specifically focusing on their applicability for residential air conditioning. To provide a framework for ejector refrigeration, all components of a solar ejector refrigeration system are analyzed, detailing their fundamental principles, working mechanisms and relevant nomenclature. The emphasis of this part of the study lies on the ejector itself, including an analysis of key factors determining ejector performance such as entrainment ratios, and the definition of ejector e!ciency along with typical values.
Next, conventional and ejector refrigeration cycles are explained, highlighting the function of the ejector inside a refrigeration cycle. An overview of refrigerants, emphasizing R744 (CO2) is also included. Following this, a short review on thermodynamic ejector modeling is presented, highlighting differences and similarities across existing models in literature. Based on this literature review, two thermodynamic ejector models are developed and presented. The first model can predict the outlet saturation temperature with a maximum error of 1.54°C for known entrainment ratios. The second thermodynamic ejector is able to predict entrainment ratios and outlet pressures with an average error of 5.86% and is used for the subsequent simulations.
Three ejector refrigeration cycles are presented in terms of configuration and COP calculation. One of the presented cycles uses ejector refrigeration for mechanical sub-cooling of a R744 vapor compression cycle. A thermodynamic model is developed for both the mechanical sub-cooling cycle and a hybrid ejector refrigeration cycle to evaluate their seasonal performance. The results of this evaluation are presented through a comparative study, comparing the performance of the proposed ejector refrigeration cycles to reference vapor compression refrigeration cycles. This comparison is carried out in four distinct Koppen climate types: tropical, arid, temperate and continental. The proposed hybrid ejector refrigeration system shows a seasonal coefficient of performance (SCOP) increase between 4.74% and 18.7% across the four climate types through the use of the refrigerant R290 (propane) and a solar thermal collector area of 25 m2. The mechanical sub-cooling cycle that combines R290 and R744 displays a SCOP increase between 11.3% and 25.1% through the use of a solar thermal area of 20 m2. A multi-ejector design is presented to enhance performance under varying refrigerant mass flow, as well as a short economic analysis of the proposed refrigeration cycles. This research aims to form a starting point for assessing the feasibility and potential of solar ejector refrigeration cycles in residential space cooling. ...
Heating and cooling systems contribute to approximately 50% of the world’s final energy consumption, highlighting their crucial role in the global energy transition. Ejector refrigeration cycles have the potential to convert heat into cooling, thereby improving refrigeration sustainability. This study aims to provide a thermodynamic performance analysis of solar ejector refrigeration cycles, specifically focusing on their applicability for residential air conditioning. To provide a framework for ejector refrigeration, all components of a solar ejector refrigeration system are analyzed, detailing their fundamental principles, working mechanisms and relevant nomenclature. The emphasis of this part of the study lies on the ejector itself, including an analysis of key factors determining ejector performance such as entrainment ratios, and the definition of ejector e!ciency along with typical values.
Next, conventional and ejector refrigeration cycles are explained, highlighting the function of the ejector inside a refrigeration cycle. An overview of refrigerants, emphasizing R744 (CO2) is also included. Following this, a short review on thermodynamic ejector modeling is presented, highlighting differences and similarities across existing models in literature. Based on this literature review, two thermodynamic ejector models are developed and presented. The first model can predict the outlet saturation temperature with a maximum error of 1.54°C for known entrainment ratios. The second thermodynamic ejector is able to predict entrainment ratios and outlet pressures with an average error of 5.86% and is used for the subsequent simulations.
Three ejector refrigeration cycles are presented in terms of configuration and COP calculation. One of the presented cycles uses ejector refrigeration for mechanical sub-cooling of a R744 vapor compression cycle. A thermodynamic model is developed for both the mechanical sub-cooling cycle and a hybrid ejector refrigeration cycle to evaluate their seasonal performance. The results of this evaluation are presented through a comparative study, comparing the performance of the proposed ejector refrigeration cycles to reference vapor compression refrigeration cycles. This comparison is carried out in four distinct Koppen climate types: tropical, arid, temperate and continental. The proposed hybrid ejector refrigeration system shows a seasonal coefficient of performance (SCOP) increase between 4.74% and 18.7% across the four climate types through the use of the refrigerant R290 (propane) and a solar thermal collector area of 25 m2. The mechanical sub-cooling cycle that combines R290 and R744 displays a SCOP increase between 11.3% and 25.1% through the use of a solar thermal area of 20 m2. A multi-ejector design is presented to enhance performance under varying refrigerant mass flow, as well as a short economic analysis of the proposed refrigeration cycles. This research aims to form a starting point for assessing the feasibility and potential of solar ejector refrigeration cycles in residential space cooling.
In this master thesis, an experimental study has been performed to explore if the temperature profile along a porous fin can be predicted by the existing analytical solution for solid cooling fins. The experiments performed during this thesis show that the temperature profile can indeed be represented by the existing solid-fin model. However, a correction for the existing model for the effective conductivity of a porous material is needed. The measurements were taken under a natural convection regime. The literature study revealed that very little experimental research has been done on porous cooling fins. The studies that were published, focus on the total heat removal of an entire heat sink, not just a single fin. These studies ignore the three-dimensional structure of the fin itself, which makes the results often case-specific and difficult to compare with each other. This method does not provide a way of predicting a fin's performance beforehand. The experiments indicate that the effective conductivity of a porous material will stay a material property, as is the case for solid material. The correction that is needed for existing model looks to be a strong function of porosity, but a very weak function of pore size and fin orientation. The porous samples outperformed the solid one in both heat removal and fin base temperature, which is in agreement with existing literature. The result from thesis can be used to design a setup in which the effective heat transfer coefficient and conductivity can be determined in a much simpler way. This enables for collecting more data and create empirical correlations for these two parameters, which predict fin performance.
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In this master thesis, an experimental study has been performed to explore if the temperature profile along a porous fin can be predicted by the existing analytical solution for solid cooling fins. The experiments performed during this thesis show that the temperature profile can indeed be represented by the existing solid-fin model. However, a correction for the existing model for the effective conductivity of a porous material is needed. The measurements were taken under a natural convection regime. The literature study revealed that very little experimental research has been done on porous cooling fins. The studies that were published, focus on the total heat removal of an entire heat sink, not just a single fin. These studies ignore the three-dimensional structure of the fin itself, which makes the results often case-specific and difficult to compare with each other. This method does not provide a way of predicting a fin's performance beforehand. The experiments indicate that the effective conductivity of a porous material will stay a material property, as is the case for solid material. The correction that is needed for existing model looks to be a strong function of porosity, but a very weak function of pore size and fin orientation. The porous samples outperformed the solid one in both heat removal and fin base temperature, which is in agreement with existing literature. The result from thesis can be used to design a setup in which the effective heat transfer coefficient and conductivity can be determined in a much simpler way. This enables for collecting more data and create empirical correlations for these two parameters, which predict fin performance.
Hydrogen in Motorsport
Liquid Hydrogen Storage System Study of a High Performance Vehicle
The transition to alternative propulsion technologies is driving the development of hydrogen powered vehicles in both road and motorsport applications. Liquid hydrogen offers significant advantages compared to other sustainable fuels due to its high energy density, making it a compelling solution for high performance racing. This thesis investigates the design and simulation of a liquid hydrogen storage system for a fuel cell electric vehicle developed in collaboration with Dallara Automobili S.p.A. and within the regulatory framework of the FIA.
A modular, system level 1D model of the complete LHSS was developed to evaluate the integration of a cryogenic tank, pump, and heat exchanger into the Dallara Stradale platform. The study addresses key research questions concerning the performance of liquid versus gaseous hydrogen storage, the optimization of tank and heat exchanger design and thermal behavior, and alternative system layouts.
Simulation results show that, despite packaging constraints and the Dallara Stradale's architecture, a liquid hydrogen configuration can achieve competitive dormancy and boil-off performance. The heat exchanger analysis highlights the potential for radiator downsizing when effectively integrated with the vehicle cooling system. Sensitivity analyses on insulation, ambient temperature, and MLI quality further underline the critical role of thermal management in achieving robust and predictable operation.
This work provides a validated modeling framework for the design of LHSS in motorsport applications and delivers key insights for future development. The results support the feasibility of liquid hydrogen as a high performance racing fuel while identifying key technological gaps such as pump reliability, insulation robustness, and system calibration that must be addressed to enable competitive hydrogen powered vehicles. ...
A modular, system level 1D model of the complete LHSS was developed to evaluate the integration of a cryogenic tank, pump, and heat exchanger into the Dallara Stradale platform. The study addresses key research questions concerning the performance of liquid versus gaseous hydrogen storage, the optimization of tank and heat exchanger design and thermal behavior, and alternative system layouts.
Simulation results show that, despite packaging constraints and the Dallara Stradale's architecture, a liquid hydrogen configuration can achieve competitive dormancy and boil-off performance. The heat exchanger analysis highlights the potential for radiator downsizing when effectively integrated with the vehicle cooling system. Sensitivity analyses on insulation, ambient temperature, and MLI quality further underline the critical role of thermal management in achieving robust and predictable operation.
This work provides a validated modeling framework for the design of LHSS in motorsport applications and delivers key insights for future development. The results support the feasibility of liquid hydrogen as a high performance racing fuel while identifying key technological gaps such as pump reliability, insulation robustness, and system calibration that must be addressed to enable competitive hydrogen powered vehicles. ...
The transition to alternative propulsion technologies is driving the development of hydrogen powered vehicles in both road and motorsport applications. Liquid hydrogen offers significant advantages compared to other sustainable fuels due to its high energy density, making it a compelling solution for high performance racing. This thesis investigates the design and simulation of a liquid hydrogen storage system for a fuel cell electric vehicle developed in collaboration with Dallara Automobili S.p.A. and within the regulatory framework of the FIA.
A modular, system level 1D model of the complete LHSS was developed to evaluate the integration of a cryogenic tank, pump, and heat exchanger into the Dallara Stradale platform. The study addresses key research questions concerning the performance of liquid versus gaseous hydrogen storage, the optimization of tank and heat exchanger design and thermal behavior, and alternative system layouts.
Simulation results show that, despite packaging constraints and the Dallara Stradale's architecture, a liquid hydrogen configuration can achieve competitive dormancy and boil-off performance. The heat exchanger analysis highlights the potential for radiator downsizing when effectively integrated with the vehicle cooling system. Sensitivity analyses on insulation, ambient temperature, and MLI quality further underline the critical role of thermal management in achieving robust and predictable operation.
This work provides a validated modeling framework for the design of LHSS in motorsport applications and delivers key insights for future development. The results support the feasibility of liquid hydrogen as a high performance racing fuel while identifying key technological gaps such as pump reliability, insulation robustness, and system calibration that must be addressed to enable competitive hydrogen powered vehicles.
A modular, system level 1D model of the complete LHSS was developed to evaluate the integration of a cryogenic tank, pump, and heat exchanger into the Dallara Stradale platform. The study addresses key research questions concerning the performance of liquid versus gaseous hydrogen storage, the optimization of tank and heat exchanger design and thermal behavior, and alternative system layouts.
Simulation results show that, despite packaging constraints and the Dallara Stradale's architecture, a liquid hydrogen configuration can achieve competitive dormancy and boil-off performance. The heat exchanger analysis highlights the potential for radiator downsizing when effectively integrated with the vehicle cooling system. Sensitivity analyses on insulation, ambient temperature, and MLI quality further underline the critical role of thermal management in achieving robust and predictable operation.
This work provides a validated modeling framework for the design of LHSS in motorsport applications and delivers key insights for future development. The results support the feasibility of liquid hydrogen as a high performance racing fuel while identifying key technological gaps such as pump reliability, insulation robustness, and system calibration that must be addressed to enable competitive hydrogen powered vehicles.
Design of fines separation system
Improving separation using 2D-simplified testing and coupled CFD-DEM simulation
The objective of this research is to reduce fines inside a novel comminution machine. Fines are detrimental to the energy efficiency of the comminution process and induce additional wear. An experimental setup was developed and built, the slice rig (SR), to obtain air flow measurements and mass rates which are used to determine the energy efficiency of the fines extraction.
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The objective of this research is to reduce fines inside a novel comminution machine. Fines are detrimental to the energy efficiency of the comminution process and induce additional wear. An experimental setup was developed and built, the slice rig (SR), to obtain air flow measurements and mass rates which are used to determine the energy efficiency of the fines extraction.
Evaluating thermal energy use in hydrogen production and import
A study on water electrolysis waste heat and ammonia cracking cold utilisation
In order to reach climate goals and limit global warming, an energy transition has to be made away from fossil fuels and towards renewables. Hydrogen has been recognized as having a crucial role as an energy carrier in this transition. The Port of Rotterdam in the Netherlands has set its goals on facilitating the transition by aiming to become the 'Hydrogen Hub' of Northwestern Europe. To reach this goal, the aim is set to transport 4.6 Mt of H2 by 2030 and 20 Mt by 2050. This will be accomplished both by hydrogen production and with import. It is expected that by 2030, 2 to 2.5 GW of (low temperature alkaline or PEM) electrolysis capacity will be installed and the rest of the hydrogen will be imported in the form of ammonia. Electrolysis produces significant amounts of waste heat and due to the storage conditions of ammonia, there is potential for cold utilisation (which is unexplored in the field of ammonia cracking). Instead of wasting this thermal energy, it would be more useful to recover and use it. Thereby potentially increasing total system efficiency and contributing to the energy transition.
The aim of this study is thus to quantify the identified thermal waste streams from water electrolysis and ammonia cracking, in order to determine how these should be reused in different applications. This will be done by using the Port of Rotterdam as a case study.
A dynamic electrolyser model was made to calculate the waste heat output as a result of fluctuating operation (due to intermittency of wind energy). A steady state thermal analysis was made of an ammonia cracking plant. Not only to determine the quality and quantity of potential cooling streams, but also to observe the effect of adding thermal energy on the ammonia cracking process (at different temperature levels). The results from these models were then used to evaluate multiple relevant and novel applications. Electrolysis waste heat modelling is applied in district heating and integration in the ammonia cracking process. Cold utilisation has been evaluated for CO2 and H2 compression, and for industrial cold storage.
From the different considered applications, the largest amount of electrolysis waste heat that can be reused in a single application is with integration in the ammonia cracking process. Not only can almost all the heat be directly integrated, it also creates a synergy within the hydrogen industry. This application has distinct advantages compared to other applications studied in this thesis, making it a preferred option. After that, it has been demonstrated that electrolysis waste heat can be used to provide reliable heating for a district heating network. This application is highly socially relevant, but might be a more complex option to integrate all of the waste heat. Ammonia cracking cold utilisation concluded that from a technical perspective multiple use cases are possible, however the practical feasibility must be further investigated.
This study has started to explore the potential of cold utilisation and i.e. the integration of low temperature waste heat in the ammonia cracking process. The surface of this topic has been scratched and shows results that indicate the potential it has and the need for more detailed research in this field.
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In order to reach climate goals and limit global warming, an energy transition has to be made away from fossil fuels and towards renewables. Hydrogen has been recognized as having a crucial role as an energy carrier in this transition. The Port of Rotterdam in the Netherlands has set its goals on facilitating the transition by aiming to become the 'Hydrogen Hub' of Northwestern Europe. To reach this goal, the aim is set to transport 4.6 Mt of H2 by 2030 and 20 Mt by 2050. This will be accomplished both by hydrogen production and with import. It is expected that by 2030, 2 to 2.5 GW of (low temperature alkaline or PEM) electrolysis capacity will be installed and the rest of the hydrogen will be imported in the form of ammonia. Electrolysis produces significant amounts of waste heat and due to the storage conditions of ammonia, there is potential for cold utilisation (which is unexplored in the field of ammonia cracking). Instead of wasting this thermal energy, it would be more useful to recover and use it. Thereby potentially increasing total system efficiency and contributing to the energy transition.
The aim of this study is thus to quantify the identified thermal waste streams from water electrolysis and ammonia cracking, in order to determine how these should be reused in different applications. This will be done by using the Port of Rotterdam as a case study.
A dynamic electrolyser model was made to calculate the waste heat output as a result of fluctuating operation (due to intermittency of wind energy). A steady state thermal analysis was made of an ammonia cracking plant. Not only to determine the quality and quantity of potential cooling streams, but also to observe the effect of adding thermal energy on the ammonia cracking process (at different temperature levels). The results from these models were then used to evaluate multiple relevant and novel applications. Electrolysis waste heat modelling is applied in district heating and integration in the ammonia cracking process. Cold utilisation has been evaluated for CO2 and H2 compression, and for industrial cold storage.
From the different considered applications, the largest amount of electrolysis waste heat that can be reused in a single application is with integration in the ammonia cracking process. Not only can almost all the heat be directly integrated, it also creates a synergy within the hydrogen industry. This application has distinct advantages compared to other applications studied in this thesis, making it a preferred option. After that, it has been demonstrated that electrolysis waste heat can be used to provide reliable heating for a district heating network. This application is highly socially relevant, but might be a more complex option to integrate all of the waste heat. Ammonia cracking cold utilisation concluded that from a technical perspective multiple use cases are possible, however the practical feasibility must be further investigated.
This study has started to explore the potential of cold utilisation and i.e. the integration of low temperature waste heat in the ammonia cracking process. The surface of this topic has been scratched and shows results that indicate the potential it has and the need for more detailed research in this field.
Latent heat storage using phase change materials (PCMs) is a promising technology for storing and recovering waste heat. PCMs offer high energy density and can be tailored for specific melting temperatures, making them suitable for various applications, including temperature stabilization in buildings and thermal management of electronics and batteries. However, a significant disadvantage of PCMs is their low thermal conductivity, which slows the process of charging and discharging thermal energy. This work explores a novel approach to enhance the melting rate of PCMs by incorporating thermally conductive objects (TCOs) within the PCM. The TCO density lies between the solid and liquid PCM densities and is designed to follow the solid-liquid interface. First, an analytical model based on the Stefan problem formulation and a numerical model developed using Ansys Fluent, with locally modified thermal conductivity at the solid-liquid interface, were created to simulate the thermal behavior of the PCM with the addition of TCOs. An experimental setup, consisting of a rectangular enclosure with an organic paraffin as the PCM and hollow aluminum cylinders as the TCOs, was employed to validate these models under purely conductive melting conditions, with heating from the top and cooling from the bottom. Experimental results indicate that the addition of cylinders increased the melting rate by 19% under purely conductive conditions compared to the scenario without cylinders. However, the cylinders enhanced heat flux only within the first 12 mm, beyond which the thermal resistance of the liquid PCM became dominant, preventing further heat flux improvements. During solidification, the cylinders did not move with the solid front and were engulfed at the bottom. In the second part of this work, the developed Fluent model is used to study hypothetical scenarios where a TCO is added to the PCM, but heating comes from the side walls and melting is driven by convection. In this scenario, the inclusion of a TCO at the solid-liquid interface acts as a moving fin, increasing the melting rate by 62% and enhancing thermal power dissipation from 26.5 W to 75.4 W. Future research should focus on experimentally validating this scenario under convective melting, exploring methods to mechanically return the TCO to its starting position for repeatability, and conducting an energy analysis to determine whether the benefits of an enhanced melting rate outweigh the energy required to move the object and the increased manufacturing costs of the latent heat storage system.
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Latent heat storage using phase change materials (PCMs) is a promising technology for storing and recovering waste heat. PCMs offer high energy density and can be tailored for specific melting temperatures, making them suitable for various applications, including temperature stabilization in buildings and thermal management of electronics and batteries. However, a significant disadvantage of PCMs is their low thermal conductivity, which slows the process of charging and discharging thermal energy. This work explores a novel approach to enhance the melting rate of PCMs by incorporating thermally conductive objects (TCOs) within the PCM. The TCO density lies between the solid and liquid PCM densities and is designed to follow the solid-liquid interface. First, an analytical model based on the Stefan problem formulation and a numerical model developed using Ansys Fluent, with locally modified thermal conductivity at the solid-liquid interface, were created to simulate the thermal behavior of the PCM with the addition of TCOs. An experimental setup, consisting of a rectangular enclosure with an organic paraffin as the PCM and hollow aluminum cylinders as the TCOs, was employed to validate these models under purely conductive melting conditions, with heating from the top and cooling from the bottom. Experimental results indicate that the addition of cylinders increased the melting rate by 19% under purely conductive conditions compared to the scenario without cylinders. However, the cylinders enhanced heat flux only within the first 12 mm, beyond which the thermal resistance of the liquid PCM became dominant, preventing further heat flux improvements. During solidification, the cylinders did not move with the solid front and were engulfed at the bottom. In the second part of this work, the developed Fluent model is used to study hypothetical scenarios where a TCO is added to the PCM, but heating comes from the side walls and melting is driven by convection. In this scenario, the inclusion of a TCO at the solid-liquid interface acts as a moving fin, increasing the melting rate by 62% and enhancing thermal power dissipation from 26.5 W to 75.4 W. Future research should focus on experimentally validating this scenario under convective melting, exploring methods to mechanically return the TCO to its starting position for repeatability, and conducting an energy analysis to determine whether the benefits of an enhanced melting rate outweigh the energy required to move the object and the increased manufacturing costs of the latent heat storage system.
The study delves into the critical necessity of long-duration energy storage to ensure the consistent reliability of electricity derived from renewable sources. Numerous technologies have emerged to address this need, enabling the storage of surplus energy generated by renewables in diverse materials, taking the forms of sensible or latent heat. The comprehensive analysis explores these various techniques in detail, providing a thorough examination of their respective advantages and disadvantages. High-temperature TES emerges as a pivotal component, particularly within CSP. This storage capability becomes imperative for maintaining a seamless and predictable power generation process, especially during periods of limited or intermittent sunshine, coinciding with high electricity demand and costs. Presently, CSP plants predominantly employ sensible energy storage in molten salt, which requires substantial salt volume, two large tanks, or a single tank system. A detailed study is conducted on a similar type of TES system using a PCM as an insulation to minimize the heat losses from the storage tank. The impact of the PCM layer in minimizing the heat loss is analyzed via an analytical model and CFD simulations. The cost incurred for the PCM is further compared with the cost of electrical heating.
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The study delves into the critical necessity of long-duration energy storage to ensure the consistent reliability of electricity derived from renewable sources. Numerous technologies have emerged to address this need, enabling the storage of surplus energy generated by renewables in diverse materials, taking the forms of sensible or latent heat. The comprehensive analysis explores these various techniques in detail, providing a thorough examination of their respective advantages and disadvantages. High-temperature TES emerges as a pivotal component, particularly within CSP. This storage capability becomes imperative for maintaining a seamless and predictable power generation process, especially during periods of limited or intermittent sunshine, coinciding with high electricity demand and costs. Presently, CSP plants predominantly employ sensible energy storage in molten salt, which requires substantial salt volume, two large tanks, or a single tank system. A detailed study is conducted on a similar type of TES system using a PCM as an insulation to minimize the heat losses from the storage tank. The impact of the PCM layer in minimizing the heat loss is analyzed via an analytical model and CFD simulations. The cost incurred for the PCM is further compared with the cost of electrical heating.