Electric vehicles have become the focal point to reduce GHG in the quest for cleaner and more efficient means of transportation. At the core of this transition lies the key component of energy storage, the battery pack. The battery pack has electrodes manufactured with the binder PVDF. Using fluorine-rich compounds makes processing and recycling a more difficult process and it is also harmful for the environment. Therefore, alternative binders should be explored to adhere to the principles of sustainability. In this thesis, a comparative study is presented between electrodes fabricated with fluorine free polymeric binders and PVDF. Moreover, a battery cell solely constituted of fluorine free components is fabricated and tested. By using the analysis techniques electrochemical performance testing, electrochemical impedance spectroscopy and scanning electron microscopy the effect of the binders and electrolytes on the electrode performance is explored. The findings reveal that during rate performance cycling, graphite half cells based on the binder PAA demonstrated the highest discharge capacities at C-rates up to 4C with a capacity retention of 39%. NMC811 half cells based on a composite binder CMC/SBR achieved the highest capacity retention after 100 cycles, being 24%. All the fabricated full cells suffered from a 30-40% initial capacity depletion after the first charge, presumably originating from oxidative degradation of the electrolyte. Consequently, the highest capacity retention after 150 cycles was 14% for a PVDF based full cell. Fluorine free cells using a PAA anode and CMC/SBR cathode exhibited expected capacities with a higher overpotential.

Carbon sequestration involves the conversion of carbon dioxide gas into carbonates through reactions with magnesium or calcium bearing minerals, presenting a potential method to mitigate CO2 emissions and reduce their release into the atmosphere. This process can be classified into two categories: in-situ (subsurface) and ex-situ (surface). CO2 mineralization has demonstrated the ability to permanently store substantial quantities of CO2 without the need for extensive post-monitoring efforts, while also offering potential business model benefits for the generated end products. However, the field of mineralization still faces substantial technical and economic challenges, including high cost projections and slow carbonation kinetics, impeding further technological advancements in the field. Additionally, logistical challenges related to plant design and associated emissions contribute to the complexity of finding solutions to these problems. In this particular study, the investigation focused on ex-situ carbon dioxide sequestration primarily through direct aqueous mineral carbonation, incorporating a direct air capture element. This approach was chosen due to the flexibility provided by direct air capture in terms of CO2 supply and the desirable characteristics of direct aqueous carbonation. Various models were developed using Aspen Plus software and compared, leading to the selection of the direct aqueous carbonation system as the optimal choice for CO2 carbonation. Further enhancements were implemented in the system, including recycled streams and heat integration, to reduce overall energy consumption. Optimization steps were also undertaken to determine the appropriate sizing of key equipment that make up the majority of the system's overall costs and to improve system efficiency. An economic analysis was then performed, revealing that plant scales of 50 ktons/year yielded a positive Net Present Value (NPV), indicating profitability. Conversely, smaller-scale plants of 0.5 ktons/year and 5 ktons/year did not generate positive revenue, even with a high carbon credit price. This was followed by a sensitivity analysis that showcased the relevant parameters that holds significant effects on the economic performance of the system. Moreover, business model cases were also explored, and it was concluded that utilizing the end products in building materials and road construction could potentially generate additional revenue for the mineralization system beyond storage options. Overall, this investigation highlights the potential of ex-situ carbon sequestration through direct aqueous mineral carbonation, considering direct air capture, and emphasizes the importance of economic viability and revenue diversification in the successful implementation of mineralization systems to mitigate the effects of global warming.

As the variable renewable energy share keep on increasing throughout the energy transition, power systems require more and different flexibility measures. Battery energy storage can provide these essential services that enable the energy system to carbonise and transform on short time scales. Energy arbitrage, the trading of electricity on the electricity markets, can create economic value for batteries. This research assesses the energy arbitrage opportunities for utility-scale battery energy storage in the Netherlands. It compares five different battery technologies and defines the optimal size and power capacity with a linear mixed-integer Matlab optimization model. Furthermore, the operation of for the most optimal technology is simulated for one year with a Model Predictive Control algorithm to be able to compare the effects of forecasting accuracy of the electricity prices on the estimated profits. The results show that according to optimized planning and dispatch in the operation of a battery system can lead to financial opportunities in the Netherlands regarding energy arbitrage for flow batteries. If not today, then in the future. It has been shown that towards 2030 the business case for battery energy storage will significantly increase due to decreasing capital costs and increasing price volatility with the rise of the VRES and phase-out of fossil energy sources. With this research, a contribution is delivered towards the realisation of commercially operating an independent utility-scale battery energy storage facility. Insights are provided on what battery configuration is best suited for energy arbitrage purposes and the effectiveness of simulating the optimized operation of a battery facility with a model predictive control method has been shown. This has lead to clearer insights into the profitability of operating a BESF in the Netherlands.

This report aims to evaluate the feasibility of a small pilot plant placed near Broome, Australia to produce 3 tons of hydrogen per day using photovoltaic (PV) energy. Using PVsyst, a PV modelling software, the maximum power operating points were determined for a test layout. This was then transformed to other layouts which allowed the optimum layout to be found for a system connected to electrolyzers using maximum power point tracking technology. A second scenario using a battery was also modelled and optimized. Finally, the third scenario used direct coupling, meaning that the PV panels were not operated at their maximum power point but rather at where the electrolyzer and PV current and voltage lines crossed. This resulted in a lower power yield but also lower costs. To find the current and voltage curve for the PV field, the data from PVsyst analyzed to find the short circuit current and the open circuit voltage. This allowed the full current and voltage curve to be determined, which allowed the intersection point with the (experimental) electrolyzer current and voltage curve to be determined. In all simulations piping storage was used to remove the intermittency of the hydrogen production by having a capacity of 3 tons of gaseous H2. This ensures a constant stream of hydrogen to the liquefaction system. Using preliminary results an electrolyzer degradation simulation was carried out, to find how the electrolyzer would behave after 20 years of use. Although the influence of intermittency could not be found in literature, it was shown that the electrolyzer produces, on average during its 20 year lifetime, approximately 5.7% less hydrogen than it would without any degradation. This has been included in all financial analyses carried out in this report, along with a 7% weighted average cost of capital. The financial framework has been based off of a number of different sources and forecasts. Due to the limitations of publicly available data some forecasts were replaced with constant prices which do not evolve throughout the years. Using the hydrogen production models and financial frameworks it is possible to compare the different scenarios. From this a price of 4.16$/kg was found for a MPP coupled system, 4.39$/kg for a MPP coupled system including a battery, and 4.02$/kg for a direct coupled system. The third scenario was furthermore looked at in terms of physical layout; it was found that the decentralized layout consisting of smaller subplots was slightly more expensive than the standard centralized layout (4.09$/kg). For this pilot plant it is advised to use a decentralized topology, combined with a decentralized layout consisting of multiple smaller plots. Although the centralized layout is slightly cheaper, it contains more system critical components which could cause a large portion of the system to be inactive if they are broken.

In the study described in this thesis, it is demonstrated that combined short-term and long-term energy storage in one device, the battolyzer, is possible. The battolyzer is a device that works as a rechargeable battery, and that is capable of performing highly efficient electrolysis with any excess electricity. The battolyzer was based on the Nickel-Iron-Battery, which was developed by Thomas Edison and Waldemar Jungner, and on alkaline electrolysis. Both are well-established technologies that were developed more than a century ago. The main research question in this thesis is: "Is an energy storage system based on Nickel and Iron suitable to operate as an integrated battery and electrolyzer, and what would be the overall energy efficiency of such a device?". Firstly, a test-series that was designed to simulate various real-life situations, including partial and full charging and discharging, rapid switching, continuous overcharging, and the around-the-clock cycling. Neither the battery, nor the electrolysis have noticeably deteriorated after the many cycles. The remarkable finding is that the reversible discharge capacity of the battery is not adversely affected by such harsh test conditions. Secondly, the gas quality was analyzed, qualitatively and quantitatively. The outcome of these tests was that overcharging leads to gas production with a Coulombic (or Faradaic) conversion efficiency of equal to 100%, within the experimental accuracy. In a final step, optimal operating conditions for the battolyzer have been identified. Tests show that the overall energy efficiency of the battolyzer could surpass 90%. However, the most remarkable finding of the whole project is the stability of the energetic efficiency at 80-90% over many different types of cycles, including all cycles to simulate real-life situations. We anticipate these results to be a starting point for a robust grid-scale energy storage solution in a low-cost, abundant-element based, intrinsically flexible device that has close to full-time operability: as electrical power storage, switchable electricity supply, and as a hydrogen producer.

Ammonia is essential for global food production as a component of fertiliser, and a potential energy carrier in the energy transition. Electrochemical ammonia synthesis faces numerous challenges as an alternative to the carbon intensive Haber-Bosch process, including competition from hydrogen evolution, and mass transport limitations. An unconventional cell design with a hydrogen permeable electrode could help to address these problems. The reaction mechanism and performance of ammonia synthesis using hydrogen permeable electrodes was investigated at elevated temperatures and pressures of up to 120 °C and 8 bar. Furthermore, a facile method for enhancing the electrochemical surface area of the electrode was developed and tested. Operation at elevated pressure resulted in a moderate increase in cell performance. However, replenishment of the nitrogen vacancies in the nickel nitride catalyst through dinitrogen adsorption is identified as the elementary step that limits activity and stability. The amount of pre-deposited N is found to significantly influence the ammonia production rate and its stability. Dynamics of ammonia desorption could also play a role in nitride regeneration. In future studies, the presence of a decomposition reaction of the nitride should be investigated. Usage of more stable nitride species or a combination of host nitride and dopants is recommended to improve stability and simultaneously promote dinitrogen activation and hydrogenation to ammonia. These findings expand the understanding of the mechanisms underlying the nitrogen reduction reaction, paving the way for the development of a more efficient green ammonia synthesis process.

We have to overcome the intermittent nature of renewables to master the energy transition. Harvesting renewable electricity is only part of the solution. Energy storage is another part and the main challenge of our time. Only with efficient storage solutions can big industries switch to renewables. Electricity storage is most efficient with batteries while industrial sites and synthetic fuel production require a sustained hydrogen input to drive the processes. The aim of this thesis was the research and development of storage solutions mainly based on earth-abundant iron to bridge intermittency. The following scientific questions were at the basis of the conducted research: 1. Combined battery and electrolyser: is it possible and reasonable to develop a device that serves two purposes? Do the materials endure and support this double functionality? 2. Multiple electrodes: nickel is required for electricity and oxygen storage; iron is required for electricity and hydrogen storage. Is it possible to store electricity, oxygen and hydrogen in one electrochemical cell? Is it possible to decouple the electricity input from the oxygen and hydrogen output? Can a single electrode be used for two purposes simultaneously? Are configurations with multiple electrodes scalable to larger arrays? 3. Fundamentals of iron electrodes: Which phases occur for the first and second iron discharge plateau? And why are iron electrodes less responsive to higher discharge rates? 4. Sustained hydrogen from intermittent sources: Decoupling of the electricity input and the hydrogen output is possible with an electrochemical cell consisting of at least three electrodes. Is more sustained hydrogen from intermittent sources also feasible with a standard electrochemical cell with two electrodes? 5. Doped iron electrodes: Iron electrodes can have a limited rechargeability and can show gas accumulation inside the electrode. Does the addition of dopants enhance the ability of the iron electrode to recharge? Do these dopants enhance performance and the material utilisation? Battolyser NiFe batteries are known to be practically indestructible. However, these NiFe batteries have the disadvantages of hydrogen and oxygen production and selfdischarge which makes them inefficient as a battery. In the battolyser we promote this “hydrogen-side-effect”, and obtain an energy-efficient device that produces hydrogen with excess energy with the potential to reduce undesirable renewable electricity curtailments. Such a device can be operational around the clock: either the surplus of electricity is used to charge the battery and to produce hydrogen or electricity is provided to consumers. The battolyser will supply hydrogen when overcharged, following an intermittent pattern of renewables availability. Therefore, downstream infrastructure needs the capability to handle an intermittent hydrogen input or requires a hydrogen storage infrastructure. Under these conditions the battolyser has the potential to become an essential single-combined tool for the energy transition since renewable electricity can be stored and excess electricity can be converted efficiently into hydrogen. Multi-Controlled (MC-)electrodes Then we demonstrated that we could supply a sustained hydrogen output from an intermittent energy input and that time shifting the hydrogen output comes at low energy costs. We accomplished that by creating electrochemical systems consisting of more than two electrodes within a single electrochemical cell. Here the storage electrodes can be charged/discharged while gas production, hydrogen and oxygen, can occur simultaneously and at independent rates. We also demonstrated that storage electrodes can serve two different processes at the same time. The proposed concept of MC-electrodes allows for controlling and scaling up multi-electrode configurations to larger arrays. Most importantly we used it for decoupling the electricity input from the hydrogen output by the combination of an iron storage electrode with two gas evolution electrodes, one for hydrogen evolution and one for oxygen evolution with two independent circuits. The position of the electrode phases in the Pourbaix diagram indicates that charging the iron electrode together with oxygen production requires most of the energy while little energy is required to generate hydrogen from previously charged iron electrodes. Independent operation of both circuits enables decoupling of the electricity input and the hydrogen output, and the iron storage electrode serves as an electrochemical storage reservoir. Time-shifting 50% of the hydrogen production requires only 5% of the energy while 95% of the required energy can be fed through a main controller when electricity is cheap and abundant. Moreover, hydrogen can later be provided from reduced iron electrodes with a substantial reduction of backup power. Compared to electrolysers, the electricity storage requirement is reduced by 85% to provide the same amount of hydrogen, using the previously reduced iron oxidation. In other words, seven times more hydrogen can now be provided from existing backup power, which can serve as a booster for delayed hydrogen generation. Half-cell used as Hydrogen Storage and Production cell (HSP-cell) We reduced the complexity of the system by combining the iron storage electrode with a bifunctional electrode for oxygen and hydrogen production which led to the concept of the HSP-cell. The HSP-cell is a simple half-cell, consisting of two electrodes which makes it easily scalable to larger bi-polar configurations. The HSP-cell can utilize the entire capacity of the iron electrode, comparable to the iron-air battery or battolyser, but delivers hydrogen instead of electricity. Both configurations can operate as a low-cost sink to store energy in reduced iron and both systems can use excess electricity for direct hydrogen generation to reduce undesirable curtailment of renewable power. The replacement of the nickel hydroxide battery electrode by a thin bifunctional nickel metal electrode provides space and allows to increase the storage density. Considering only the iron electrode (and omitting counter electrode, electrolyte, casing, valves or other parts), a storage density of 0.78 Ah/cm3 is currently feasible, equivalent to 29 kgH2/m3 or to a compressed hydrogen storage density of 500 bar. The stored hydrogen can be released easily and controlled by applying a current. This reduces the safety risk associated with the storage of compressed hydrogen gas. During electrochemical hydrogen release, only hydrogen is generated inside the cell, which offers an oxygen-free hydrogen gas output even at low discharge rates. The HSP-cells can be configured in a self-sustaining manner and in a way to provide a sustained hydrogen output from an intermittent input by simultaneous and phase-shifted operation of several units. The concept can provide sustained hydrogen to industrial processes or synthetic fuel production with an overall efficiency including storage and production which exceeds 80% when operated at 40 ◦C. Therefore, the HSP-cell has the potential to become an essential device to boost the energy transition. Doped Iron electrodes The iron electrode is the common part of all previously discussed configurations. Having an optimal iron electrode is essential since the iron electrode determines the rate capabilities and the efficiencies. In the battolyser thin iron electrodes suffice because the nickel electrode is capacity limiting. Thicker iron electrodes can be used in the iron-air battery/battolyser, in the MC-cell and in the HSPcell. We developed a strategy to produce sintered iron electrodes to study the phase behaviour of the electrode in operando by means of neutron diffraction. The study revealed that substantial amounts of iron hydroxide were inside the bulk of the sample which could not be reduced back to metallic iron upon charging. We concluded that the electrochemical circuit within the electrode must be interrupted, and it is our hypothesis that gas accumulation within the cell negatively affected the ionic conductivity. We assume that gas accumulation within the electrode replaces electrolyte which increases the ionic resistance for phase transition. As a consequence, the inserted charge shifts from battery charging with phase transition to hydrogen evolution. We wanted to improve the material utilization of the sintered iron electrodes and therefore needed to improve the ability of these electrodes to recharge. For this purpose, we added either zirconia oxide or alumina oxide to the electrodes. By adding metal-oxides to the electrode-composition we enhance the processability of the materials and the electrode performance. With the new synthesis strategy, we produced thick sintered iron electrodes which show a volumetric storage density of up to 0.8 Ah/cm3 and reach areal storage densities of up to 160mAh/cm2. These values are among the best reported values in literature for sintered iron electrodes. In the process we may create a sulphur free system which potentially reduces corrosion issues, and which potentially reduce the deterioration of air electrodes. Bridging intermittency with iron electrodes Summing up, the creation of an energy system based on renewables confronts us with the intermittent nature of renewable power generation. To bridge the intermittency we need storage solutions for electricity and hydrogen. With a sustained hydrogen output synthetic fuels based on renewables could be produced on a large scale. With the nickel-iron battolyser and the iron-air battolyser we can store electricity and we can convert excess electricity into hydrogen to overcome the curtailment-problem. With the concept of MC-electrodes and of the HSP-cell we can efficiently control, store, and postpone the hydrogen output, to provide a more sustained hydrogen output. The iron electrode is present in all configurations and recharging was the main challenge. We addressed the issue of rechargeability with a modified synthesis strategy for sintered iron electrodes doped with Zr and Al instead of sulphur. Electrodes produced with this strategy may have the potential to perform as effective sintered iron electrodes. With these new simple concepts and cost-efficient iron electrodes we offer new tools to support and accelerate the storage and conversion of renewable power, which is necessary for the energy transition and to overcome intermittency. We have to speed up the energy transition to limit the impact of climate change.@en

Modern life is moving towards a mobile and sustainable energy economy, in which rechargeable batteries play an essential role as a power supply. The current battery of choice is Li ion battery that is dominating the market but faces great challenges for future use mainly due to the demand for higher capacities and target for cost reduction. Next-generation rechargeable batteries such as Li-O2, Li-S and Na ion batteries, which offers higher capacities and cost-effectiveness, are being intensively researched as potential solutions to meet the future energy storage demand.  This thesis focuses on the search of high-performance anode materials for both Li and Na ion batteries, including metallic Li and Na, Si, MgH2, and black P and Sn4P3 based composites. Various methods are involved to synthesize the active materials and electrodes in a cost-effective manner; and comprehensive characterization on the physico-chemical and electrochemical properties has been performed to provide fundamental understanding and insights into the electrochemical processes. This work has achieved long-lifespan and safe Li and Na metal anodes by suppressing the hazardous dendrite growth. The Si, P and MgH2 anodes presented in this work also exhibit high and stable electrochemical performance for Li and Na ion storage. Notably, the Na ion uptake in Si and MgH2 has been, for the first time, realized in experiments. This research shows great promise towards the commercial introduction of these anodes in next-generation high energy density Li and Na ion batteries.@en

Electrochemical cells and systems have been around for a few centuries. Lately, these technologies have been attracting attention. Although the technology to generate electricity from renewable sources is well developed and widely available -such as photovoltaic and wind energy- this is not always available. Because of this, it is necessary to store produced surplus electricity to be able to use it at moments when the sun is not shining or the wind is not blowing. Many different electrochemical technologies can be used to store electricity or transform it to a useful energy carrier- such as hydrogen. However, the energy transition will also need to address the optimal usage of critical materials. Integrating functionalities and optimizing energy storage can help bridge the gap between electricity production and consumption using only a limited amount of critical materials. New innovative technologies that use less critical materials will be key to sustainably transition to a fossil-fuel free future. It will be necessary to move forward and upscale technologies at a quick pace. A combined modeling and experimental approach can help move through the TRL development stages quickly, optimizing the use of resources and experimental work required. The battolyser is a new integrated battery and electrolyser system that provides flexibility in energy storage. During periods of high availability of renewable energy it can be charged indefinitely, filling up the battery capacity first and producing hydrogen from there on out. A battolyser system can be used to guarantee access to cheap electricity and green hydrogen, all in one device and using the materials required for one device. Modeling the electrochemical reactions of the battolyser and optimizing the cell design parameters when moving towards an upscaled system is a tool that can be used for the continuous development of a better prototype and scaling up. Chapter 3 describes the modeling studies performed on the battolyser system, including the relevant experimental validation. Here, a 1D COMSOL model was developed to study the cell parameters and understand the effect of electrode and gap thickness, electrode porosity, and electrolyte conductivity. Testing experimentally at larger scales is challenging and often not done. Highly alkaline KOH electrolytes are usually not tested in lab conditions, and therefore the effect of higher concentrations than 5M KOH is unknown on new electrode material developments. To optimize an integrated device, the effect on both the electrolysis function and the battery function need to be reconciled and designed for the specific application. In Chapter 4, extensive lab scale experiments on the electrolyte concentration are described, including different alkali metal cation concentrations. To optimize for different functionalities of the battolyser, different cations can be used at specific concentrations. A flow cell was designed and built, and different flow configurations were tested. 3D printing technology allows for quick iterations and modifications of the design, however the proprietary resins are usually not tested at highly alkaline conditions which could potentially cause degradation of the cell components. Working with higher than 5MKOH concentrations results in practical difficulties that will only scale with plant capacity. In Chapter 5, the preliminary results of a flow cell configuration are included. The results of this work can be applied directly to predict the optimal design and operating parameters of an up-scaled battolyser cell. This will allow for quicker iterations of up-scaled designs to further develop the prototype technology. For this, it is important to verify simulation results with experimental data. Using a combined approach including simulations and experimental work allows testing various setups and optimizing the energetic efficiency of the device. 3D printing manufacturing technology can also help speed up this iterative process to generate design modifications and quickly manufacture experimental setups to validate the simulation data. @en

The Paris Agreement aims to limit global warming to 2 degrees Celsius by reducing carbon dioxide emissions. Data centers are essential to the digital world and contribute approximately 1% to global electricity consumption. Major tech companies like Amazon, Microsoft, Google, and Meta are large contributors to this consumption. In countries like the Netherlands, this contribution is higher due to the Netherlands being a digital hub, accounting for 3% of the total national electricity consumption. Considering their significant energy usage, it is interesting to research how data centers can transition to using only renewable energy sources on an hourly basis so they can decrease their footprint. This thesis aims to identify a feasible and cost-effective configuration for a 100 MW data center that operates 100% on renewable energy on an hourly basis. The research will assess the environmental impacts, focusing on CO2 emissions (CO2e) and land usage, with the main goal of achieving the lowest Levelized Cost of Electricity (LCOE). First, an overview of potential energy storage technologies is provided to find suitable solutions. Based on different criteria, Lithium-ion (Li-ion), lead-acid, vanadium redox flow batteries (VRFB), zinc-bromide flow batteries (ZBFB), alkaline and PEM (proton exchange membrane) electrolyzers, storage tanks, and PEM fuel cells are chosen. With these technologies, eight different configurations are composed, combining various battery types and electrolyzer types with the storage tank and PEM fuel cell: Li-ion with alkaline (1), lead-acid with alkaline (2), Li-ion with PEM (3), lead-acid with PEM (4), VRFB with alkaline (5), ZBFB with alkaline (6), VRFB with PEM (7), and ZBFB with PEM (8). An energy model is developed to identify the most feasible and cost-effective solution, using solar, wind, and load profiles as input. The assets are modeled based on their technical parameters and limitations. A 10-year simulation of the hourly energy flows is executed. In this simulation, the constraints, degradation, and replacement of the assets are taken into account. The costs are determined based on Capital Expenditures (CAPEX), Operating Expenses (OPEX), replacement costs, and residual costs of the asset after 10-year. The connection costs are also considered. The configuration dimensions are optimized based on the LCOE using the particle swarm optimization method. The two configurations with the lowest LCOE are evaluated for environmental impacts, including CO2e and land usage. The study shows that combining a Li-ion battery or VRFB with an alkaline electrolyzer is the most cost-effective and feasible configuration for a data center. The LCOE is 0.243 and 0.241 €/kWh, respectively. Additionally, this reduces kg CO2e/kWh by 7-8 times compared to the current grid emissions in the Netherlands, which are approximately 0.037 and 0.032 kg CO2e/kWh. However, the required land usage is approximately 20 km², and the LCOE of the configuration is about 2.5 times higher than the current power purchase agreement (PPA) price for a data center, which is 0.10 €/kWh. Therefore, it is recommended to initially start with an 80% renewable scenario using only a Li-ion battery and renewable energy sources. This approach reduces the LCOE to 0.12 €/kWh, which is approximately the same as the current PPA price if an additional 0.01 €/kWh for the connection to the grid is included. Furthermore, kg CO2e/kWh is three times lower compared to the current situation, which is 0.08 kg CO2e/kWh. This strategy also mitigates the potential risks associated with the infancy of VRFB and the combination of intermittent renewable sources and an electrolyzer, as these are excluded in this scenario.

The Paris Agreement aims to limit global warming to 2 degrees Celsius by reducing carbon dioxide emissions. Data centers are essential to the digital world and contribute approximately 1% to global electricity consumption. Major tech companies like Amazon, Microsoft, Google, and Meta are large contributors to this consumption. In countries like the Netherlands, this contribution is higher due to the Netherlands being a digital hub, accounting for 3% of the total national electricity consumption. Considering their significant energy usage, it is interesting to research how data centers can transition to using only renewable energy sources on an hourly basis so they can decrease their footprint. This thesis aims to identify a feasible and cost-effective configuration for a 100 MW data center that operates 100% on renewable energy on an hourly basis. The research will assess the environmental impacts, focusing on CO2 emissions (CO2e) and land usage, with the main goal of achieving the lowest Levelized Cost of Electricity (LCOE). First, an overview of potential energy storage technologies is provided to find suitable solutions. Based on different criteria, Lithium-ion (Li-ion), lead-acid, vanadium redox flow batteries (VRFB), zinc-bromide flow batteries (ZBFB), alkaline and PEM (proton exchange membrane) electrolyzers, storage tanks, and PEM fuel cells are chosen. With these technologies, eight different configurations are composed, combining various battery types and electrolyzer types with the storage tank and PEM fuel cell: Li-ion with alkaline (1), lead-acid with alkaline (2), Li-ion with PEM (3), lead-acid with PEM (4), VRFB with alkaline (5), ZBFB with alkaline (6), VRFB with PEM (7), and ZBFB with PEM (8). An energy model is developed to identify the most feasible and cost-effective solution, using solar, wind, and load profiles as input. The assets are modeled based on their technical parameters and limitations. A 10-year simulation of the hourly energy flows is executed. In this simulation, the constraints, degradation, and replacement of the assets are taken into account. The costs are determined based on Capital Expenditures (CAPEX), Operating Expenses (OPEX), replacement costs, and residual costs of the asset after 10-year. The connection costs are also considered. The configuration dimensions are optimized based on the LCOE using the particle swarm optimization method. The two configurations with the lowest LCOE are evaluated for environmental impacts, including CO2e and land usage. The study shows that combining a Li-ion battery or VRFB with an alkaline electrolyzer is the most cost-effective and feasible configuration for a data center. The LCOE is 0.243 and 0.241 €/kWh, respectively. Additionally, this reduces kg CO2e/kWh by 7-8 times compared to the current grid emissions in the Netherlands, which are approximately 0.037 and 0.032 kg CO2e/kWh. However, the required land usage is approximately 20 km², and the LCOE of the configuration is about 2.5 times higher than the current power purchase agreement (PPA) price for a data center, which is 0.10 €/kWh. Therefore, it is recommended to initially start with an 80% renewable scenario using only a Li-ion battery and renewable energy sources. This approach reduces the LCOE to 0.12 €/kWh, which is approximately the same as the current PPA price if an additional 0.01 €/kWh for the connection to the grid is included. Furthermore, kg CO2e/kWh is three times lower compared to the current situation, which is 0.08 kg CO2e/kWh. This strategy also mitigates the potential risks associated with the infancy of VRFB and the combination of intermittent renewable sources and an electrolyzer, as these are excluded in this scenario.

The Paris Agreement aims to limit global warming to 2 degrees Celsius by reducing carbon dioxide emissions. Data centers are essential to the digital world and contribute approximately 1% to global electricity consumption. Major tech companies like Amazon, Microsoft, Google, and Meta are large contributors to this consumption. In countries like the Netherlands, this contribution is higher due to the Netherlands being a digital hub, accounting for 3% of the total national electricity consumption. Considering their significant energy usage, it is interesting to research how data centers can transition to using only renewable energy sources on an hourly basis so they can decrease their footprint. This thesis aims to identify a feasible and cost-effective configuration for a 100 MW data center that operates 100% on renewable energy on an hourly basis. The research will assess the environmental impacts, focusing on CO2 emissions (CO2e) and land usage, with the main goal of achieving the lowest Levelized Cost of Electricity (LCOE). First, an overview of potential energy storage technologies is provided to find suitable solutions. Based on different criteria, Lithium-ion (Li-ion), lead-acid, vanadium redox flow batteries (VRFB), zinc-bromide flow batteries (ZBFB), alkaline and PEM (proton exchange membrane) electrolyzers, storage tanks, and PEM fuel cells are chosen. With these technologies, eight different configurations are composed, combining various battery types and electrolyzer types with the storage tank and PEM fuel cell: Li-ion with alkaline (1), lead-acid with alkaline (2), Li-ion with PEM (3), lead-acid with PEM (4), VRFB with alkaline (5), ZBFB with alkaline (6), VRFB with PEM (7), and ZBFB with PEM (8). An energy model is developed to identify the most feasible and cost-effective solution, using solar, wind, and load profiles as input. The assets are modeled based on their technical parameters and limitations. A 10-year simulation of the hourly energy flows is executed. In this simulation, the constraints, degradation, and replacement of the assets are taken into account. The costs are determined based on Capital Expenditures (CAPEX), Operating Expenses (OPEX), replacement costs, and residual costs of the asset after 10-year. The connection costs are also considered. The configuration dimensions are optimized based on the LCOE using the particle swarm optimization method. The two configurations with the lowest LCOE are evaluated for environmental impacts, including CO2e and land usage. The study shows that combining a Li-ion battery or VRFB with an alkaline electrolyzer is the most cost-effective and feasible configuration for a data center. The LCOE is 0.243 and 0.241 €/kWh, respectively. Additionally, this reduces kg CO2e/kWh by 7-8 times compared to the current grid emissions in the Netherlands, which are approximately 0.037 and 0.032 kg CO2e/kWh. However, the required land usage is approximately 20 km², and the LCOE of the configuration is about 2.5 times higher than the current power purchase agreement (PPA) price for a data center, which is 0.10 €/kWh. Therefore, it is recommended to initially start with an 80% renewable scenario using only a Li-ion battery and renewable energy sources. This approach reduces the LCOE to 0.12 €/kWh, which is approximately the same as the current PPA price if an additional 0.01 €/kWh for the connection to the grid is included. Furthermore, kg CO2e/kWh is three times lower compared to the current situation, which is 0.08 kg CO2e/kWh. This strategy also mitigates the potential risks associated with the infancy of VRFB and the combination of intermittent renewable sources and an electrolyzer, as these are excluded in this scenario.

Up until now, ammonia has primarily served the fertilizer and chemical industry with limited regards to carbon emissions. The hydrogen within the ammonia molecule is commonly produced using fossil fuels; this process accounts for 1,2 % of the global CO2 emissions. Rather than using fossils fuels, electrolysis with renewable energy could be used to produce “green” carbon-free hydrogen and ammonia. The transition could decarbonize the ammonia industry and reduce carbon emissions drastically. Considering future emission restrictions and emerging new technologies, the techno-economic cost of green ammonia is expected to decrease. Accordingly, the the research question to be answered was: What are the effects of techno-economic induced cost reductions on the potential for green ammonia in the current and future global ammonia market? This report investigates the production and import costs over several global-oriented supply chains using a supply chain model. Rather than predicting the future, the aim is to gain an insight into the future of the global ammonia market. The scope of this thesis considers world scale ammonia production facilities with a capacity of 2200 ton NH3 per day. Due to their potential to become a producer or consumer of green and grey ammonia, the following countries are examined in more detail: Australia, Brazil, Chile, China, India, Japan, Morocco, Mexico, the Netherlands, Norway, Oman, South Korea, Trinidad & Tobago, United Kingdom, United States. The supply chain model distinguishes between the “grey” (with hydrogen from natural gas through SMR) and “green” (with hydrogen from electrolysis on renewable energy) production process. The supply chain model that is used to gain insight into the future global ammonia market models a green ammonia production process. The following components are included in the model: a 1,5 GW electrolyser (78 % efficient, 2020), 100 MW Haber-Bosch reactor, 57 MW air separation unit, and a 94 MW fuel cell (60 % efficient) for a location that has 5000 FLH. The modelled production plant is sized according to the full load hours in a given country and implemented electrolyser efficiency according following a learning curve (75 % in 2020 to more than 82 % from 2030. In future research, it would be more exact to optimize the production plant’s exact sizing using the available resources at one specific location. Results show that up until 2030 importing grey ammonia is cheaper than domestically producing green ammonia. In addition, due to the sensitivity of the ammonia industry to carbon leakage, a strong CO2 policy is essential to the transition. The main cost drivers for green ammonia are the hydrogen buffer and firm up power of the Haber-Bosch reactor and air separation unit; both are directly related to the cost of the renewable energy, which in turn is strongly dependent on the weather conditions. Currently, Morocco, Chile and China are considering the domestic production of green energy as it is expected to become cost-competitive with domestic grey production of ammonia by 2020. The analyses show that in addition to these countries, Australia, the United States of America and Oman show optimal conditions for domestic production of green ammonia as well.

Ammonia is a precursor in fertilizer production and a potential carbon-free energy carrier, which is essential for the energy transition to more renewable energy sources. To that end, the current fossil fuel based method of industrial ammonia production through the Haber-Bosch process should be replaced by electrochemical ammonia synthesis. However, research into this topic faces several challenges, including a strong dinitrogen bond, competition from the hydrogen evolution reaction and low solubility of nitrogen in aqueous electrolytes, limiting the availability of nitrogen at the reaction sites on the electrode surface. In this study, in order to better understand these limitations to electrochemical nitrogen reduction to ammonia, a porous iron electrode is used in a cell design allowing both aqueous electrolyte and nitrogen gas access to the surface, which is successfully reduced electrochemically to serve as a nitrogen dissociation catalyst. Careful control of the applied potential limits the competition from the hydrogen evolution reaction. Nuclear magnetic resonance spectroscopy and ion chromatography measurements of the electrolyte were performed to check for possible contamination by nitrogen containing species. Small amounts of ammonia were measured using gas chromatography-mass spectroscopy on the gas output, but only with a high residence time of the nitrogen gas inside the cell. Since reduced iron surfaces are known to be good nitrogen dissociation catalysts, even at ambient temperature and pressure, the cause of the low ammonia production rate reported here is the abundant presence of water, which blocks nitrogen from the surface adsorption sites even when the catalytic surface is not submerged in the electrolyte. These results show that creating a surface with sufficient catalytic activity to break the dinitrogen bond is very well possible, but the main challenge is keeping the surface clean to prevent blocking of the reaction sites. This gives additional insight for future efforts in developing electrochemical ammonia synthesis methods.

Ammonia is an important chemical used in the production of fertilizers and has the potential to become a green energy carrier. It is synthesized through the Haber-Bosch (HB) process, which involves nitrogen and hydrogen reacting at high temperature and pressure and consumes approximately 2% of the global energy supply. An alternative to this energy intensive process is the electrocatalytic nitrogen reduction reaction (NRR). The main challenge of this approach is the competing hydrogen evolution reaction (HER) that consumes most of the applied electricity, making the ammonia production inefficient. Based on the Sabatier principle, an ideal catalyst for the NRR would bind nitrogen and ammonia optimally, while hydrogen would be bound too strongly or too weakly, suppressing the HER. So far, no such catalyst has been found. A strategy that could lead to the discovery of a suitable catalyst is alloying, since materials with new adsorption properties can be created this way. The main goal of this project is to design an electrochemical cell that can be used for the screening of large numbers of bimetallic catalysts, increasing the chance of finding a suitable NRR catalyst. For this so-called high-throughput approach an electrochemical cell was designed that allows the screening of up to 16 catalysts in parallel. Furthermore, methods for sample preparation, characterisation and detection were developed that are compatible with a high-throughput technique

The battolyser concept is based on an old fashioned nickel iron battery, consisting of a positive nickel(oxy) hydroxide electrode and negative iron (hydroxide) electrode. Research has been performed on the structural changes of the nickel and iron electrode upon charge and discharge. A lot of research can be found for the nickel electrode, but crystal structure studies are few. Much less research is performed on the iron electrode. Therefore the structural changes of the nickel(oxy) hydroxide and iron (hydroxide) electrodes during operation are further researched. Ni(OH)2 exists in the form of an α- or β-modification and NiOOH in a β- or γ-modification. The structure of the nickel(oxy)hydroxide phases has layers of edge-sharing NiO2 octahedra, where in between guest atoms can situate. Conventional nickel electrodes operate mainly between β-Ni(OH)2 and β-NiOOH, so most research focussed on this area. Upon overcharge the γ-NiOOH is formed and when discharging a direct reduction of β-NiOOH and γ-NiOOH into β-Ni(OH)2 occurs. The research on the nickel electrode published in this thesis is compared with a previous discharge study performed by Morishita et al. In their Rietveld refinement of the β-phases an ideal and fault phase model are assumed and the weight fraction of all phases present in the samples at 0, 50, 100 and 150% of state of charge (SOC) are determined. For the iron electrode four phases can be distinguished. The pure Fe in the electrode upon discharge becomes Fe(OH)2, under deep discharge this transforms even further towards FeOOH. For the deactivation process the reaction moves towards magnetite (Fe3O4). First the battery electrodes from the shelf are analysed by SEM-edx , X-ray diffraction and neutron diffraction. Then neutron powder and X-ray diffraction analysis have been performed to study the structural changes of the electrodes during charge and discharge. The nickel electrodes are measured at various states of charge from 0 to 100% and iron electrodes 0 to 90%. Preliminary experiments for the in-situ neutron diffraction test setup are performed. Different thicknesses of quartz glass, several sizes of nickel foam current collectors are tested for the amount of their background noise. In the nickel electrode are next to the carbon, 3 phases present. In the comparison with Morishita et al. significant differences are found. The transition towards β-NiOOH and subsequently γ-NiOOH occurs faster. Already at 50% of SOC the weight fraction of β-NiOOH is 58 wt% and at 100% of SOC the γ-NiOOH is 57 wt%. The c-parameter of γ-NiOOH is in agreement with Morishita et al. with a lattice distance of 20.8 Å. Morishita et al. did not specify how they determined the state of charge, so maybe they calculated the SOC in a different way. In the iron electrode three phases are identified, namely iron (Fe), goethite (FeOOH) and magnetite (Fe3O4). This is a strange result, because where Fe(OH)2 is expected, FeOOH is found. Probably discharged too far, moving the reaction into the second discharge plateau. The weight fraction of Fe increases and FeOOH decreases with increasing state of charge. The hydrogen content is decreasing with increasing SOC proportional to the background function for both the nickel and iron electrode.

Zero Emission Fuels B.V. (ZEF) is developing an integrated micro-plant to produce methanol from captured CO2 and green Hydrogen produced via alkaline water electrolysis. The electrolysis unit represents one of the largest financial and energetic costs in the system and is required to operate at 166 mA/cm2 under 2 V. In order to decrease the costs, ZEF is looking to synthesize highly efficient nickel-based electrodes to avoid using expensive noble-metal ones. The objective of this work was the synthesis of efficient and stable nickel-based electrodes. Two electrodes were synthesized through electrodeposition (Raney nickel and NiFe) and one was synthesized through hydrothermal treatment (NiFe-LDH) and were compared to a RuO2-containing (Permascand) electrode and to a smooth nickel electrode. On/off cycles for 2.5 hours were carried out to measure the stability of the electrodes. Additionally, performance tests in a pressure range of 1-5 bar were carried out to measure the effect of increasing pressure. The experiments were carried out in an in-house designed and built zero-gap alkaline electrolysis cell. Raney nickel, with a measured roughness factor of 150 was the best performing of the synthesized electrodes. After the stability tests, it was able to produce 166 mA/cm2 at 1.9 V (1.73 and 2.12 V for Permascand and smooth nickel, respectively). Raney nickel as anode material presented significant degradation. Raney nickel is the most promising material for HER, none of the synthesized materials presented significant stability for OER. From the nickel-iron electrodes, NiFe with a roughness factor of 19.5 presented the best performance of the synthesized materials with 2.04 V for the mentioned current density. NiFe presented significant degradation, especially as anode material. NiFe presented a relative high performance considering its low electrochemical active surface area attributed to the presence of highly efficient active sites. NiFe-LDH was quickly degraded during the tests as cathode and anode material. The pressure tests showed an inverse relationship between voltage and pressure. This hints that a decrease in bubble size with pressure is the cause behind the decrease in voltage. A simple model, based on experimental data and thermodynamic considerations, estimated that operating the cell at 50 bar reduces the voltage by 0.25 V compared to operation at 1 bar. The estimated reduction in voltage at a pressure of 50 bar would allow to operate the electrolysis cell under 2 V even with smooth nickel mesh as electrode.