Large-scale import of green hydrogen is expected to become essential for the Netherlands to achieve its climate targets and secure its future energy supply, as domestic hydrogen production alone will not be sufficient to meet projected demand. However, hydrogen gas has a very low volumetric energy density, making direct long-distance transport economically challenging. To overcome this limitation, hydrogen can be compressed, liquefied, or converted into a chemical carrier. Although these transport pathways have been extensively studied, the conversion and reconversion stages are often treated as a black box, making a transparent comparison between different hydrogen carriers difficult. This study addresses this gap by developing detailed models of these stages under identical assumptions to determine which hydrogen carrier provides the most cost-effective import pathway to the Netherlands. Following a screening of multiple candidates, ammonia and a liquid organic hydrogen carrier (LOHC), in the form of methylcyclohexane (MCH), were selected for further evaluation.

A case study is considered in which hydrogen is imported from Brazil, where lower production costs are expected due to abundant renewable energy resources. The conversion and reconversion processes are modelled in Aspen Plus, including reaction kinetics, to quantify energy consumption and determine equipment requirements. Combined with shipping and storage costs, these results are used to calculate the total landed cost of hydrogen delivered to the Dutch hydrogen network.

At an assumed hydrogen production cost of 6 $/kg, both the ammonia and LOHC pathways result in a landed cost of approximately 11 $/kg, which is below the expected domestic production cost and therefore indicates a potential economic incentive for import. However, when a more conservative production cost of 8 $/kg is assumed, the landed cost exceeds the domestic production cost, removing this incentive. The two pathways show very similar overall costs, as the lower hydrogen efficiency of the ammonia route is largely offset by the lower energy density of MCH and its resulting transport requirements. Since neither carrier is clearly superior from an economic perspective, the final selection is likely to depend on additional factors such as technological maturity, safety considerations, and existing infrastructure.

It should be noted that these conclusions are specific to the Brazil-to-Netherlands case study. Due to the lower energy density of MCH, the LOHC pathway requires more shipping capacity and becomes increasingly sensitive to transport distance. For longer transport routes, the ammonia pathway is therefore expected to become the more economically favourable option. ... Read more

In 2023, the IMO introduced a new strategy to achieve net-zero greenhouse gas (GHG) emissions by or around 2050, establishing a clear target for ship owners and builders worldwide. In addition, measures are being taken to reduce harmful emissions such as NOx, SOx, and particulate matter. One promising sustainable fuel is ammonia, which offers a relatively high energy density, is easy to store, and emits only water and nitrogen during combustion. Although operating an internal combustion engine (ICE) on pure ammonia remains challenging, stable combustion can be achieved by adding a promoter fuel such as diesel or hydrogen.

A more novel propulsion concept is the use of Solid Oxide Fuel Cells (SOFCs), which electrochemically oxidize hydrogen to generate electricity with high efficiency and very low emissions. Hydrogen is produced by cracking ammonia at the high operating temperatures of the SOFC. However, SOFCs cannot utilize all supplied fuel without complex recirculation, resulting in an anode-off-gas (AOG) that still contains hydrogen.

Because ICEs provide higher power density, better transient response, and lower investment costs than SOFCs, combining both technologies is an attractive solution. In the AmmoniaDrive concept, ammonia is converted efficiently into electricity by the SOFC, while hydrogen in the SOFC anode-off-gas enhances ammonia combustion in the ICE. This hybrid configuration combines the efficiency of SOFCs with the operational flexibility of ICEs.

This study investigates the application of the AmmoniaDrive concept to a 14,000 TEU container vessel. The propulsion system consists of a low-speed two-stroke main engine directly driving the propeller, combined with an electric machine that enables power take-off (PTO), power take-in (PTI), and SOFC-only operation. The SOFC operates continuously, supplying electrical power during sailing, anchoring, and port stays. The system is evaluated for a voyage from Rotterdam to Shanghai via the Suez Canal, including four days in port or at anchor. Simulations consider high and low electrical power demand and three nominal power splits of 16.3%, 21.4%, and 30.4%.

The operational profile is simulated using a Matlab/Simulink model based on earlier work on the AmmoniaDrive concept. The original full-load model was extensively modified to simulate part-load operation of both the SOFC and the ICE. The SOFC model incorporates NTU-based heat exchangers, load-independent heat losses, a minimum cathode airflow, improved temperature control, and an optimized external ammonia cracking strategy using combustion of part of the anode-off-gas. The ICE model retains the five-point Seiliger cycle while incorporating load- and speed-dependent losses, auxiliary blowers for low-load operation, and electric machine models for hybrid power delivery.

The hybrid propulsion system is compared with a conventional reference system consisting of a main engine and generator sets. Fuel consumption is reduced by approximately 10%, 13%, and 16% for the low, medium, and high nominal power split configurations, respectively. Combined system efficiencies generally range from 55% to 70%, with higher power splits and lower propulsion loads resulting in better performance. System efficiency is primarily influenced by SOFC load, ICE load, operational power split, external cracking ratio, and fuel utilization.

Optimal SOFC load is generally between 85% and 100% at high sailing speeds, while the ICE supplies most transient power demand. At lower sailing speeds, SOFC load decreases only slightly, although electric machine limitations may restrict operation. Estimated NOx emissions decrease by 21–39%, depending mainly on the nominal power split. Although these estimates are based on published engine test-cycle data and do not account for hydrogen-ammonia combustion or part-load effects, a substantial reduction in NOx emissions is expected.

An alternative operating strategy, in which the SOFC continuously operates at full load while the ICE supplies all power variations, increases total fuel consumption by only 0.52% on average and slightly reduces NOx emissions. This strategy may improve load-following capability and reduce SOFC degradation. The study demonstrates that ammonia-fuelled SOFC-ICE hybrid systems can efficiently propel large container vessels under varying operating conditions, achieving fuel savings of 10–16% while providing a promising pathway towards cost-effective, CO₂-free shipping. ... Read more

Hydroisomerization of alkane isomers is an important step in the manufacture of current kerosene and sustainable aviation fuels. Zeolites are used as acid catalysts in the process. It is therefore important to have predictions of the maximum loading of hydrocarbons in zeolites. Here, a cascade model using machine learning models is used to predict the maximum loading of alkane isomers in zeolites. The cascade is composed of a gradient-boosted tree classifier stage that predicts whether adsorption occurs or not, and a regressor predicting the value of the maximum loading. The final dataset consists of 45 different molecules (both linear and branched alkanes up to C16) and 97 different zeolites structures, resulting in 4365 datapoints. Descriptors include information on the geometry and topology of zeolite channels, as well as shape and size of molecules. Extra composite descriptors are also present to provide the models a physical basis for predictions. Multiple regressors of different nature are considered: Support Vector Regressors, Gradient-Boosted Trees, extreme Gradient-Boosted Trees, and the TabPFN pretrained model. Out of all the models, TabPFN yields the highest generalization performance and lowest error. An interpretability analysis is conducted to assess whether the decisions abide by the governing physics of adposition. It is confirmed that the top descriptor choices abided by the necessary physical constraints, but also that secondary properties such as shape-based selectivity are also accounted for. It is shown that despite both classifier and regressor being insensitive to random splits in data, the regressor is prone to overfitting at low fractions of data withheld for testing. The cascade model is compared with an Artificial Neural Network for training and deployability. Despite training taking more resources for the neural network, the latter is lighter both in memory and storage when compared to the cascade. This work builds on previous research in predicting the Henry coefficient at zero loading. Using this previous model and the findings of this work, one can draw the full adsorption isotherm for any alkane, thus enabling the analysis of adsorption behaviour of alkane mixtures using IAST. ... Read more

Underground hydrogen storage (UHS) in porous reservoirs offers a promising solution for addressing the temporal and spatial variability of renewable energy sources. To safely and efficiently utilize these reservoirs for UHS at an affordable cost, it is essential to understand the diverse disciplines involved at various scales. This study combines large-scale techno-economic evaluations with micro- scale laboratory research to assess the commercial and technical viability of UHS in porous media. A techno-economic case study of commercial-scale UHS in a depleted gas field in the Dutch nearshore is investigated, defining the integrated scope of infrastructure and facilities and estimating associated costs. Additionally, the multiphase flow behavior and redistribution of hydrogen in sandstone rock are analyzed through experimental assessment of relative permeability, capillary trapping, dissolution, and Ostwald ripening using CT imagery. The case study compares various surface facility design concepts, revealing that the Levelized Cost of Hydrogen Storage (LCOHS)
ranges from [cannot be disclosed for confidentiality reasons] , depending on the required purification scope of the production stream. Cushion gas cost significantly impacts the LCOHS. The multiphase flow behavior was examined on a micro-scale by co-injecting hydrogen and brine at varying fractional flows into a vertically placed 17 cm Berea sandstone rock sample at 25°C and 50 bar, while observing under CT imaging during both drainage and imbibition. High- resolution CT imaging visualized Ostwald ripening at the pore scale after several periods without flow. The experimental results indicate a hydrogen end-point relative permeability of 0.043 and a linear trapping coefficient of 0.725. No preferential flow paths were observed, however, dissolution was shown to have an impact the saturation profiles. Pore-scale image analysis demonstrated that Ostwald ripening leads to the fragmentation of mid-sized hydrogen ganglia and the growth of larger ganglia over time. These findings provide valuable insights into optimizing UHS and provide input for large-scale reservoir simulations, emphasizing the importance of integrating techno-economic assessments with detailed laboratory research for the commercial success of UHS. ... Read more

This study investigates the technical feasibility and economic viability of utilizing depleted offshore gas reservoirs in the Dutch North Sea for underground hydrogen storage (UHS) to buffer intermittent hydrogen production from offshore wind farms in the Dutch North Sea. The research aims to address the existing knowledge gap in integrating an offshore hydrogen storage platform while considering the maximum re-useability of existing natural gas infrastructure. ... Read more

In the Dutch ”Warmte transitie,” district heating is set to play a predominant role, with the goal of achieving gas-free domestic heating by 2050. This necessitates upgrading traditional district heating networks to the fourth generation. To support this transition, the potential of decoupling heat production and demand through thermal storage is explored. A technoeconomic case study on the district heating network of Amsterdam-East/Almere evaluates the value of heat storage. The literature study concludes that, given the current supply temperatures and financial objectives, heat should be stored as sensible pressurized heat. The transition period between 2030 and 2040 is modeled, focusing on shifting from fossil based to power-to-heat-oriented district heating networks. A diverse asset configuration is implemented, providing affordable heat at low and medium electricity prices. The objective is to quantify the influence of thermal storage and its impact on asset dispatch dynamics. This study addresses a gap in the literature by providing a fundamental description of a diverse asset configuration transitioning towards a power-to-heat-based district heating network. A numerical model using linear programming, specifically a combination of dual simplex and barrier methods, is employed. The main input variables are based on long-term commodity price forecasts. A rolling optimization horizon is implemented to focus on mid/short interval storage optimization, acknowledging the unrealistic nature of perfect forecasts. Non-linearity in the Combined Heat and Power (CHP) systems is managed by pre-defining state points within the operational domain. Additional constraints such as start-up costs, subsidies, and carbon taxes are included. The correlation between increasing storage capacity and financial benefits appears logarithimic, primarily due to limited overcapacities in favorable power-to-heat assets. During the transition, the value of storage capacity diminishes due to rapidly decreasing operational costs, reducing the absolute value of Thermal Energy Storage (TES). Optimizing CHP dispatch generates significant value, attributed to its non-linear price formation. The transition shifts value generation from winter to summer months due to changes in overcapacity. The hybrid model, which optimizes both financial and environmental benefits, shows no significant decrease in carbon footprint but helps stabilize it while increasing financial gains, this is visualised with a Pareto front plot. The new generation district heating networks with limited overcapacity can benefit significantly from small-scale heat storage capacity. For this specific network, an optimal storage capacity of 1600 MWh has been identified. Additionally, it is concluded that incorporating storage capacity enhances dispatch flexibility and provides resilience against future uncertainties ... Read more

The utilization of waste heat from data centers in low-temperature district heating networks has emerged as a promising trend in the pursuit of enhanced energy efficiency, sustainability, and environmental stewardship. Data centers, known for their significant energy consumption and associated greenhouse gas emissions, have the opportunity to transform into energy providers rather than mere consumers by utilizing their waste heat. This innovative strategy has already gained traction in the Nordic regions, where the waste heat from data centers is harnessed to heat buildings and communities, thereby decreasing reliance on fossil fuels and cutting carbon emissions. Through leveraging waste heat, data centers can markedly reduce their environmental impact, thus aiding in the promotion of a more sustainable future. This transition towards waste heat utilization is essential for the data center sector to reach its net-zero energy targets, alleviate its environmental footprint, and support the global transition to a low-carbon economy. By optimizing energy efficiency, data centers can become a crucial component of sustainable urban development, fostering a healthier environment for future generations.
This report investigates the potential of utilizing residual heat that is continuously produced by the data centers by incorporating low-temperature district heating systems in the Amsterdam neighbourhood. The research highlights the possibility of data centers as a dependable source of waste heat and its integration into low-temperature district heating networks. This will thereby contribute to a more sustainable and energy-efficient future. The study scrutinizes the feasibility of waste heat utilization in a detailed manner, down to the component level. The results from the study presented here are discussed at a component as well as, a system-wide scale. Moreover, the paper elaborates on the potential of low-temperature district heating networks in Amsterdam neighborhoods undergoing upcoming refurbishments involving improving the housing insulation and a shift towards addressing energy poverty. The conclusions drawn from this research have the potential to encourage similar research endeavors aimed at large data centers across diverse regions. ... Read more

While CO₂ is one of the factors increasing the global temperature, it is also utilized in the agriculture to enhance crop yield. In the agriculture, a sustainable solution to CO₂ mitigation would potentially lie in the greenhouses. A moisture swing direct air capture system can adsorb CO₂ from the air through changes in humidity levels between the adsorption and the desorption stages. During adsorption dry air is required, while during desorption humid air is required. In a greenhouse, where humid air is typically required for the crops and CO₂ enhancement is often achieved through fossil-fuel combustion, a moisture swing system could be a sustainable innovation.

Insights into the feasibility and potential implementation of a moisture swing column designed to enhance CO₂ concentrations within a greenhouse are obtained through an investigation of the key parameters of the sorbent, the effect of global climate conditions on the sorbent, a parameter sensitivity analysis of the performance of the system, and a preliminary techno-economic viability assessment.

A one-dimensional numerical model was developed to solve the mass balance of a cylindrical adsorption column. Critical key parameters that affect the CO₂ saturation coverage of the sorbent are the gas phase CO₂ concentration, the relative humidity, and the temperature. Investigated is how these conditions vary globally, highlighting optimal arid climate regions with a high saturation coverage. It was found that seasonal and diurnal deviations are significantly higher in regions where a lower saturation coverage can be reached. From the sensitivity analysis of the parameters and conditions, it was that a 1.6-meter-long column achieved a system efficiency of 15.0 micromoles of CO₂ per kilogram sorbent per second, a water loss of 45.4 moles of water per mole of CO₂, and a system productivity of 9.05 moles of CO₂ per second. In the short term, the majority of costs are attributed to the capital expenditures, whereas in the long term, operational expenditures become the dominant expense. ... Read more

Steel manufacturing is a carbon intensive process, that is responsible for approximately 7% of the total global CO2 emissions. Therefore, TATA Steel IJmuiden aims to lower its carbon emissions. One way to bring down emissions, is to replace the existing blast furnace (BF) CO reduction process with the H2-based direct reduction of iron ore (DRI). The two most widely applied H2-DRI processes around the world are the low pressure MIDREX, abbreviated as MLP, and medium pressure HYL-Energiron, abbreviated as EMP. Since TATA Steel IJmuiden wants to study the switch from BF to H2-DRI steelmaking, it is relevant to gain insight into which gas phase reactions are dominant for both processes, into the direct reduction process itself and into the behaviour of the carburization reactions that improve the steel quality. In the gas phase reactions, it was seen that for the MLP process in situ reforming of natural gas can be a viable option before switching to a 100% H2 process. This may prove to be worthwhile in the early stages of H2-DRI steel production, when green H2 is still scarce and expensive. For EMP, internal reforming seems less of a possibility due to the high reaction rate for the reverse water gas-shift. When comparing both MLP and EMP, reaction rates are generally higher for EMP than for MLP and hence smaller reactor volumes are required for the EMP process to acquire the same amount of output. Direct reduction with H2 has a higher reaction rate than reduction with CO, while for the carburization reactions methane cracking was found to be the dominant reaction. Techno-economic scenarios for 100% H2-based DRI in which green H2 is imported are only feasible when H2-prices fall below €1.80/kg. Meanwhile, a scenario with an on-site electrolyzer powered by grey grid electricity only proves to be worthwhile for electricity prices lower than €20/MWh. The most promising techno-economic scenario, which includes an on-site electrolyzer and the construction of a wind farm just off the coast from the TATA Steel IJmuiden site, assumes an electricity price of €40/MWh. ... Read more

The increasing adoption of hydrogen in industrial applications is driven by its potential to decarbonize various industries. Among the various methods of hydrogen production, water electrolysis is considered one of the environmentally friendliest options. However, hydrogen produced from water electrolysis contains impurities such as oxygen and water vapour, and the required level of purity varies depending on the specific industrial application. To address this issue, catalytic recombination of hydrogen and oxygen into water is selected as a method for oxygen removal due to its high efficacy in completely converting oxygen. Subsequently, hydrogen drying is achieved using Pressure Swing Adsorption (PSA) following the catalytic recombination process. This thesis work primarily focuses on the modelling and sizing of adsorption columns within the PSA system. One-dimensional dynamic models describing the pressurization, adsorption, depressurization, and desorption steps of PSA are mathematically derived and developed in Python. The adsorption modelling approach is validated using experimental data from a scientific paper. Insightful information was obtained during the model validation process, shedding light on the consequences of the assumptions made to simplify the energy balance, as well as revealing the decrease in adsorption capacity during the pressurization process. The PSA system is designed to process 400 kg of hydrogen per day with the aim of reducing the water vapour content below 5 ppm. While pressure plays a central role in PSA control, it has been discovered that the primary design challenge relates to temperature control within the operating range. Therefore, adsorption column sizing is optimized, taking into account PSA performance and required energy input. A sensitivity analysis is conducted to identify the optimal adsorbent, considering zeolite 3A and silica gel. Based on the results, a column length of 2 meters and a diameter of 0.0914 meters are considered optimal for zeolite-packed adsorption columns, resulting in a productivity of 35.62 mol/hr/kg and requiring 50.21 kJ during the desorption step. The optimal size for silica gel-packed adsorption columns has not been determined due to a significant temperature drop during desorption, which could risk ice formation and subsequent flow blockage. Nevertheless, silica gel, with its higher adsorption capacity leading to a longer adsorption step, remains a viable option from an operational perspective and should not be disregarded as a potential choice. ... Read more

To comply with the Paris Agreement, the Dutch government has launched an energy transition process, with the goal of replacing coal and natural gas-based electricity with renewable sources. The intermittent nature of renewable electricity necessitates the installation of an energy storage system to balance supply and demand. Hydrogen is a potential energy storage and transport medium. However, its production is currently more expensive than natural gas, and storage and transport are energy-intensive due to its low density. Because the infrastructure necessary for the hydrogen supply chain necessitates significant capital investments, a techno-economic analysis of various techniques of hydrogen production, compression, storage, and transport is required.
The aim of this thesis was to evaluate the levelized costs of hydrogen at various phases of supply chain, from hydrogen production to utilization. In order to accomplish this task, a literature review was conducted to identify the most promising methods in hydrogen production, compression, storage and transport followed by developing mathematical models of various technologies. According to the literature review, water electrolysis using electrolyzers such as alkaline, polymer electrolyte membrane (PEM), and solid oxide was shown to be techno-economically feasible. The literature review also revealed that centrifugal and diaphragm compression, pipeline transmission, and salt cavern storage were all techno-economically feasible technologies. These technologies’ steady-state mathematical models were built for scaling and techno-economic analysis. In the end, learning curves were applied for electrolyzers to predict the cost reductions in future.
According to the results of mathematical modeling, hydrogen production contributes the most to total levelized costs of supply chain followed by overall compression costs. Moreover, capital costs of electrolyzer stack and electricity costs significantly influence the levelized costs of hydrogen production. For 1 MW electrolyzer capacity and average capital and operating costs of electrolyzer stack, alkaline electrolysis is currently the most cost-effective technique of producing hydrogen with levelized cost of hydrogen (LCOH) calculated to be 3.69 €/ kg, followed by solid oxide electrolysis (4.55 €/kg).However, the use of learning curves indicates that by 2050, solid oxide electrolysis may be the most cost-effective technique of producing hydrogen with projected levelized cost of 1.72 €/kg. The pipeline compression costs were found to be around 0.065 €/ kg whereas diaphragm compression costs were found to be in the range of 0.55 to 1.2 €/ kg depending on the outlet pressure. While hydrogen storage and transportation require substantial capital investment, their overall impact on levelized costs was found to be minimal compared to production and compression expenses, with storage costs averaging around 0.8 €/kg and transportation costs at approximately 0.0007 €/kg per kilometer. The same mathematical model was used to analyze two hydrogen utilization scenarios: fuel for fuel cell vehicles and feed for industry. Both pessimistic and optimistic cases were examined by varying cost-influencing parameters to predict the possible range of total levelized costs for the supply chain. The results showed that hydrogen as a fuel for fuel cell vehicles will stay more expensive than hydrogen as a feed for industry. ... Read more

Many of the high-performance portable electronics and electric vehicles (EVs) on the market depend on lithium-ion batteries (LIBs) as their primary energy source. If millions of EVs are to be manufactured each year, rigorous resource management for EV battery manufacturing, as well as a material- and energy efficient 3R system (reduce, re-use, recycle), will undoubtedly be required to assure the future sustainability of the automotive industry. Since lithium is only
found at a few locations around the world, there is an inherent danger from a geopolitical standpoint when it comes to accessibility. Political turmoil or instability in the nations controlling these lithium stockpiles may have a detrimental impact on world supply. Spent LIBs can be viewed as an alternative source of lithium. Considering that used LIBs contain toxic organic electrolytes and heavy metals, recycling them reduces resource waste and environmental contamination. Due to the difficulty of handling its complex composition and distribution, most recycling efforts and industrial processes focus solely on recycling the cathode and ignore the proper treatment of the aged electrolyte. Recovery of the electrolyte is crucial for achieving the legally mandated recycling efficiency set by the European Commission, as the electrolyte typically comprises of 10-15 wt% of a LIB cell. Therefore, this study explores the feasibility of
using crown ethers (12C4 and 15C5) to extract and recycle the lithium salt (LiPF6) from the electrolyte of spent LIBs. The extraction efficiency of these crown ethers is examined across various extraction conditions to identify the most favorable extraction condition. The results and findings obtained from the conducted experiments reveals that the extraction efficiency correlates with the mole ratio between crown ethers and lithium, up to a certain threshold (6:1 for 12C4 and 12:1 for 15C5) where further increase in mole ratio does not significantly enhance the extraction yield. The extraction yield displays an inverse relationship with temperature, indicating an exothermic extraction process that favors lower temperatures. Remarkably, varying the extraction time within the 5 to 30 min range exhibits negligible influence on extraction yield, suggesting rapid kinetics in the formation of the crown ether-lithium complex. Between the two crown ethers tested, 12C4 emerges as the more suitable option, achieving extraction yields of up to 60%. In contrast, the use of 15C5 necessitates larger quantities compared to 12C4 to achieve equivalent extraction yields. Consequently, using 15C5 not only increases the cost but also diminishes the overall process efficiency. Further research is proposed to conduct experiments for the extraction of the organic solvents in the electrolyte using CO2 and to develop methods for separating the extracted lithium from the crown ether without compromising the integrity of the crown ether, allowing for its reuse in subsequent extraction processes. ... Read more

In this work, the added value of machine learning (ML) molecular force fields (FF) for the community of molecular simulations is showcased by successfully calculating transport properties of aqueous potassium hydroxide (KOH (aq)). Classical FFs use relatively simple interatomic potentials to simulate the nano scale. These simulations can predict macroscopic properties, such as density, heat of evaporation, viscosity, and self-diffusivity of the modeled materials. However, these FFs struggle to model materials in which more complicated interactions are relevant for the macroscopic behavior. Examples of such interactions are three-body interactions and chemical reactions. Quantum scale simulation methods are able to compute properties of materials in which these challenging interactions occur, although these methods are limited in length and time scales that can be modeled with realistic computational costs. Transport properties, such as viscosity, self-diffusivity and electric conductivity need these larger length and time scales to be determined accurately. ML can be used for a multi scale approach, bridging the gap between the quantum and the nano scale by training coefficients of general interatomic potentials. This provides the possibility of reaching the time and length scales of traditional molecular simulations with the accuracy of quantum mechanic models. KOH (aq) is selected to highlight the prospects of these multi scale techniques, as the self-diffusion of OH- in this electrolyte is dominated by proton transfer reactions, which has not been modeled successfully with classical FFs.

Results of structure properties produced with ab initio molecular dynamics (AIMD, at quantum scale) simulations are compared with machine learning molecular dynamics (MLMD, at multi scale) simulations. There are no significant differences in the calculated shortest typical atomic distances and coordination numbers for both KOH (aq) and pure water systems. The determined transport properties are in the same order of magnitude as experimental results, although the calculated viscosity is overestimated and the self-diffusion of H2O and K+ are underestimated. This is because the system is simulated at a higher than experimental density and hydrogen bonding is overestimated with the selected quantum mechanics model. The proton transfer reactions are captured in the MLMD simulations, calculating the enhanced self-diffusion of OH- to be (6±2)e-9 m squared per second, which matches experimental results at infinite dilution. ... Read more

Current membrane fabrication processes are not sustainable as they are energy-intensive and require hazardous solvents. Additive manufacturing, due to its low waste production and the absence of harmful chemicals, can provide a more sustainable membrane manufacturing process. Up to this point, there was no way to 3D-print a membrane that meets the microfiltration pore sizes (1-10 μm) required in today’s industry. In this work, we showcase for the first time that membrane with pore size < 10 μm can be 3D-printed via a dual wavelength 3D printer. Polyethylene Glycol Diacrylate (PEGDA) hydrophilic membranes with cylindrical pores were designed and printed.

A dual-wavelength micro-stereolithography 3D printer has been employed to print the membranes. Photopolymerizable resins containing PEGDA monomers, were polymerized into membranes via a mixed projection of UV and blue light, creating unpolymerized pores and polymerized matrix respectively.

Using a pixel size of 1.4 μm, we could produce hydrophilic membranes with cylindrical pores and a diameter < 10 μm. These membranes were compared with benchmarking commercial PTFE membranes (JCWP14225, Merck, Germany) with the same pore size range. The resulting membranes exhibited good oil-repellent properties, indicated by the higher oil contact angle values under water. The permeability and filtration results also provide valuable insights into the material used for membrane printing. All in all, a successful microfiltration membrane has been produced via a fast, user-friendly and sustainable method.

We have introduced the next-generation 3D printing method for printing microfiltration membranes with precise pore size, shape, configuration, and arrangement. With further improvements, this technology will provide a new era in membrane manufacturing.
... Read more

At the moment, Tata Steel emits 12.6 Mt CO2 per year while producing 7.2 Mt steel per year. To reduce these emissions, Tata Steel has decided to replace the blast furnaces with direct reduced iron (DRI) plants in combination with reducing electrical furnaces. The DRI plants will first operate with a 100% natural gas feed. Whenever green hydrogen becomes available on the market, the natural gas will gradually be substituted with green hydrogen, reducing direct CO2 emissions. Producing steel using 100% green hydrogen as the reducing gas, called green steel, comes along with an awkward problem regarding the carbon content of the DRI. Green steel has a carbon content of 0%, while carbon is essential for multiple aspects of the production process. Furthermore, the metallization of the DRI is a critical parameter in the production process. Thus, the following research question is established: ”What is the influence of the ratio of hydrogen to natural gas inserted in the direct reduced iron plant on the performance of the reactor?”

To answer this research question, an extensive literature review is performed to gain knowledge of the reduction process, reduction technologies, and the existing mathematical models of the DRI plant. Furthermore, a multiscale mathematical model is made of the shaft furnace of the MIDREX plant. This model uses a grain-based pellet model, which incorporates the morphological structure of the pellets during the reduction process. The shaft furnace is modelled as a 1D model with multiple zones, in which the local energy, mass, and momentum equations are solved. However, due to the time restrictions of the thesis period, only the two reduction zones of the shaft furnace are incorporated. Hence, the shaft furnace model lacks the transition and cooling zones.

The shaft furnace model is compared to a real operating MIDREX plant named ”Gilmore”. The simulation results are validated against the simulation results from literature and the real plant data. The average relative error of the simulation results compared to the Gilmore plant is 14.4%. The most significant error can be attributed to the carbon weight fraction in the solid. This is the result of the missing transition and cooling zones, as most of the carburization occurs inside the transition zone. Neglecting the carbon weight fraction, the average relative error is 9.2%.

Increasing the ratio H2 / CH4 in the feed of the MIDREX plant results in an increasing H2 / CO ratio of the reducing gas entering the shaft furnace. Five cases with different H2 / CO ratios are simulated to answer the research question. The metallization of the DRI is affected by two different phenomena. First, increasing the H2 / CO ratio results in a larger gas input mole flow for the same input pressure, which is the effect of a smaller pressure drop over the shaft furnace. Subsequently, a larger gas input mole flow results in better metallization, which is the effect of more heat input and a lower gas oxidation degree in the shaft furnace. Second, as the hydrogen content increases, the temperature decreases as a result of more endothermic reduction. The thermodynamics and kinetics of reduction by hydrogen are favourable at higher temperatures, which results in a slow-down of the reduction. At lower temperatures, the thermodynamics of reduction by carbon monoxide is more favourable, realizing more reduction and increasing the temperature. This second phenomenon is predominant for equal input mole flow, resulting in worse metallization when increasing the H2 / CO ratio, as confirmed by literature. Consequently, to achieve equal metallization for a higher H2 / CO ratio, the process gas compressors of the MIDREX plant will consume more electrical energy. To conclude, substituting natural gas with hydrogen does have its disadvantages, but it is highly necessary to become CO2 neutral in the future.

For further research, the addition of transition and cooling zones to the shaft furnace model is recommended, allowing investigation of the carburization of the DRI. Furthermore, the shaft furnace model is extremely useful for implementation in a complete MIDREX plant model. Such a model could be used to investigate the total CO2, energy, and material balance of the plant for different H2 / CH4 ratios of the feed of the plant. ... Read more

Of the global energy demand, 20% can be allocated to residential energy demand. Most of this energy is produced by fossil fuels, which raises the importance of energy production in a more sustainable way. In order to do this on the level of residential heating applications, the Dutch government aims to make its residential neighborhoods natural gas-free. An often considered solution is making residential areas all-electric. However, when considering the heating of these households based on electricity, high peaks may occur in the electricity grid due to simultaneous heating at times of high demand. This could cause problems regarding the capacity of the electricity grid. Subsequently, the generation of electricity is nowadays associated with relatively high CO2 emissions, raising the awareness for alternative methods of heating. One of these methods is district heating coupled to (more) sustainable energy sources. A problem occurring with this combination is a possible discrepancy between the supply and demand of energy. Therefore, it could be beneficial to implement thermal energy storage in district heating. This research assesses the feasibility of different configurations of thermal energy storage integrated into district heating. For this research, a case study is conducted in which district heating for a residential area coupled with thermal energy storage is modeled. The model is based on the thermodynamic equilibrium of the network and is able to compute the required characteristics and key performance indicators of the district heating network. For the case study, multiple scenarios have been created which assess different distribution characteristics and heat sources. For reference, an all-electric scenario has been designed as well. The results of the case study show that the implementation of thermal energy storage in district heating is able to lower peak loads on the heat source by two-thirds. This implementation goes paired with an increase in levelized cost of energy of 10-16% and 8-73% higher CO2 emissions, compared to district heating without storage and depending on the characteristics of the district heating net and its heat source. However, for certain heat sources, the advantages of thermal energy storage outweigh the drawbacks or thermal energy storage might even be considered to be inevitable. This is especially the case for renewable heat sources, of which its share in the future energy market is considered to be substantial. Also, the results show that every scenario considering district heating performs better on levelized cost of energy and CO2 emissions than the all-electric scenario. When designing new DH projects, it is key that different available heat sources will be considered and that an accurate trade-off is made between the advantages and drawbacks of thermal energy storage. This research is based on the comparison of various scenarios for a case study. Therefore, it does not focus on finding the optimal parameters for either district heating or thermal energy storage. For finding these optimal parameters, future research must be conducted. ... Read more

The current industrial application of carbon capture utilization and storage (CCUS) is limited due to technological drawbacks such as high energy demand and environmental pollution. Ionic liquids (ILs) and deep eutectic solvents (DESs) are considered promising alternative solvents for the capture of carbon dioxide (CO2). DESs are often characterized by high viscosities, which hinders industrial application. This problem might be solved by mixing the DES with an organic solvent. This study aims to assess the DESs choline chloride-ethylene glycol (ethaline) and choline chloride-urea (reline) mixed with methanol and propylene carbonate (PC) for their suitability as a medium for the combined capture and electrochemical conversion of CO2. Molecular dynamics (MD) simulations are performed to obtain the densities, the viscosities, the self-diffusivities, the ionic conductivities and insight into the molecular interactions of these mixtures. Independent MD simulations are performed of these mixtures with low concentrations of the solutes CO2, oxalic acid and formic acid. Complementary studies within the Bio-cel project are conducted to characterize the solubility and electrochemical reaction of CO2 and the techno-economics.
The viscosities of the mixtures monotonically decrease for an increase of mole fraction of organic solvent, which is benign for the application of CCUS. The self-diffusivities of all constituents increase monotonically for an increase of mole fraction of organic solvent. The ionic conductivity is calculated based on the ion self-diffusivities. Ionic conductivity optima are found at a mole fraction of DES of approximately 0.6 for ethaline-PC and approximately 0.2 for ethaline-methanol and reline-methanol. For higher mole fractions of organic solvent, the ionic conductivity decreases due to a depletion of ions. Radial distribution functions (RDFs) are used to analyse the intermolecular interactions. RDF peaks between chloride-choline and chloride-ethylene glycol show an increase for an increasing mole fraction of organic solvent, which was unexpected. The numbers of hydrogen bonds decrease for addition of methanol to pure deep eutectic solvent. For addition of propylene carbonate, this decrease is less pronounced. The depletion of hydrogen bonds at low mole fractions of deep eutectic solvent is in correspondence with the decrease in viscosity and increase in self-diffusivities. The results indicate that, for the studied properties, deep eutectic solvents mixed with organic solvents are more favourable than pure deep eutectic solvents for the absorption and electrochemical conversion of CO2. ... Read more

Capturing CO2 directly from the atmosphere and subsequently using it to produce hydrocarbon fuels could help decrease mankind's reliance on fossil fuels and mitigate the risks of climate change. Zero Emission Fuels (ZEF) is developing a small-scale methanol plant, which utilizes atmospheric CO­2 and H2O vapor as feedstocks for renewable methanol synthesis. In this study, the vapor liquid equilibrium (VLE) of CO2 and aqueous solutions of tetraethylenepentamine (TEPA) was measured and correlated using thermodynamic models. The equilibrium pressure of aqueous solutions of 30, 70 and 80 wt% TEPA was measured from 313.15 to 393.15 K using a mechanically stirred and temperature controlled autoclave. The binary VLE data was correlated using Wilson's activity coefficient model. Using the same experimental set-up, the equilibrium solubility of CO2 in aqueous solutions of 30 and 70 wt% TEPA was measured at 313.15, 353.15 and 393.15 K. A simple chemical model, incorporating the extended Debye-Hückel law for activity coefficients of ionic species, was regressed to the ternary VLE data. Additionally, a theory was proposed that the polyamine can be modelled as a multiple of smaller amines, using the ratio of the amine groups as a scaling factor. Both models were applied in a simple process simulation of the absorption and stripping column of the direct air capture unit of ZEF to provide an estimation of the energy demand of the process under different conditions. The lowest regeneration energy demand was 533 kJ/mol CO2 absorbed, which is approximately 3 times higher than that of monoethanolamine, the current benchmark solvent for amine-based CO2 capture. However, through the addition of a rich-lean heat exchanger and process optimization to minimize the required reflux stream, this value could potentially be decreased. ... Read more

Steel plants are one of the largest sources of waste heat. Waste heat recovery throughout the steelmaking process is not a new phenomenon. One of the sources of waste heat is found in the coke plant. Cokes are an essential part of steel production. During the coking process hot cokes are cooled down. Most coke plants in the world traditionally use water, so called wet quenching. In this process, all the heat put into the cokes is dispersed to the environment as steam. This waste heat source has huge potential. The goal of this study is to find a method to utilise this waste heat and to evaluate this method’s technical and economic feasibilities.
The chief issue that must be tackled in a design is the fact that the steam generated during a quench is close to atmospheric pressure. Another issue to be solved is that of the solid particles suspended in the steam. Several potential designs were produced to use the steam from a quench to recover the waste heat. Based on several criteria, the design using the Synext engine was found to be the superior one and was developed further.
This design is divided into three sections, capture, cleaning and storage. A water wall and capture valve are used to capture the steam. An impaction and a cyclone separator are used to rid the steam of the solid particles to the extent that their detrimental effect to the Synext engine is minimised. The sepa-rators’ dimensions are derived based on the steam input and Synext engine requirements. The steam is then stored in a storage vessel.
A Simulink model of the design is composed to simulate the process and evaluate its efficiency and technical feasibility. The model’s findings show that the outputs for certain cases require unreasonable dimensions for the design. The economic analysis showed the designs costs make it an unlucrative investment. ... Read more

In some countries, drying processes use up to 20% of the total energy consumption. Within the agriculture sector, drying of food and flowering products is a necessary step in production. A lot of companies make use of hot air dryers where the heat is gained by burning natural gas. A novel method is to use a heat pump assisted drying systems instead. Heat pump assisted drying realises a better product quality due to the ability of humidity and climate control of the drying medium: air. Additionally, there are possibilities for energy savings up to 50%. This thesis project is mentioned as the first step for an initiative to introduce heat pump drying into the horticulture sector. The project started almost 1 year ago and is still far from finished. Main goal was to get a good understanding of the product drying behaviour, drying capacities and the system requirements and footprints. Conclusions should determine whether there is a possibil-ity for market implementation or not. The results in this report are promising. Heat pump drying is a trending research topic in science, where new developments on predicting the dynamic drying behaviour of agricultural products show up every month. This study involves a computational model, where the dynamic process of drying flower bulbs is simulated. This model is validated by measurements on existing drying in-stallations. Building this model resulted in a good understanding about the flower bulb characteris-tics and the necessary drying capacities. Additionally, Heat pump drying systems are evaluated and a dynamically modelled. When both models are the drying process of FB’s can be optimized. The first protype of the HP drying system that will be used in further research will be shortly discussed. Conclusion of this report is that heat pump drying is a promising technique for drying of FB’s. The combination of technical advantages with energy savings, could lead to better product quality and lower production costs. The business case is strengthened by future perspectives where energy efficiency and reduction of CO2 emissions will more and more important due to climate change. ... Read more