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Developing and implementing toolbox integrations for storing excess heat generated by a PVT system
No full textThis thesis addresses a critical challenge in the field of renewable energy, focusing on the efficient utilization of Photovoltaic-thermal (PVT) systems. Despite their promising role in sustainable energy production, PVT systems often grapple with excess heat generation, impacting their efficiency and longevity. The primary objective of this research is to explore the synergy between PVT modules and heat storage systems. It aims to develop and implement solutions for effectively storing this surplus heat. This work involves the formulation of new models for heat storage solutions and their assimilation into the PVMD Toolbox, housed within the Photovoltaic Materials and Devices research group at TU Delft. By enhancing the capability of PVT systems to manage excess heat, this thesis contributes to optimizing these systems for broader applications in sustainable energy generation.Electrical Engineering | Sustainable Energy Technolog
Ocean Bottom Seismometer Clock Correction using Ambient Seismic Noise
No full textOcean-bottom seismometers (OBSs) are equipped with seismic sensors that record acoustic and seismic events at the seafloor, which makes them suitable for investigating tectonic structures capable of generating earthquakes offshore. One critical parameter to obtain accurate earthquake locations is the absolute time of the incoming seismic signals recorded by the OBSs. It is, however, not possible to synchronize the internal clocks of the OBSs with a known reference time, given that GNSS signals are unable to reach the instrument at the sea bottom. To address this issue, here we introduce a new method to synchronize the clocks of large-scale OBS deployments. Our approach relies on the theoretical time-symmetry of time-lapse (averaged) crosscorrelations of ambient seismic noise. Deviations from symmetry are attributed to clock errors. This implies that the recovered clock errors will be obscured by lapse crosscorrelations' deviations from symmetry that are not due to clock errors. Non-uniform surface wave illumination patterns are arguably the most notable source which breaks the time symmetry. Using field data, we demonstrate that the adverse effects of non-uniform illumination patterns on the recovered clock errors can be mitigated by means of a weighted least-squares inversion that is based on station-station distances. In addition, our methodology permits the recovery of timing errors at the time of deployment of the OBSs. This error can be attributed to either: i) a wrong initial time synchronization of the OBS or ii) a timing error induced by changing temperature and pressure conditions while the OBS is sunk to the ocean floor. The methodology is implemented in an open-source Python package named OCloC, and we applied it to the OBS recordings acquired in the context of the IMAGE project in and around Reykjanes, Iceland. As expected, most OBSs suffered from clock drift. Surprisingly, we found incurred timing errors at the time of deployment for most of the OBSs.Applied Geophysics and Petrophysic
Marine Pumped Hydro Energy Storage: Shape design of the reservoir
No full textThe offshore renewable energy market is rapidly growing, particularly in wind and solar sectors. The intermittent nature of these energy sources underscores the necessity for offshore energy storage solutions. Among the techniques being explored, Marine Pumped Hydro-Energy Storage (MPHES) emerges as a promising option. This innovative concept operates similarly to artificial lakes, where water is stored and released to generate electricity. In the MPHES system, a seabed-based reservoir is established, in which water flows, driving turbines to generate electricity. During periods of energy surplus, the system is charged by pumping water out of the reservoir...Civil Engineering | Structural Engineering | Concrete Structure
Design of Integrated Hybrid Configuration of Modular Multilevel Converter and Marx Generator to Generate Complex Waveforms for Dielectric Testing of Grid Assets
No full textThis article proposes a new configuration of a modular multilevel converter (MMC) and a Marx generator to generate fast-rising impulse waveforms. This new configuration improves the capabilities of the MMC-based high voltage arbitrary wave shape generator to generate fast-rising impulse since the MMC topology faces many inherent limitations. Similar to the conventional superimposed circuit of the ac transformer or dc rectifier circuit with the Marx generator, three hybrid circuits of MMC and the Marx generator are introduced, where the most optimal choice is made considering the practical aspects of testing, such as the size, cost, and preparation time. Then, a detailed analytical study is performed on the Marx generator circuit and the MMC circuit, and both circuits are coupled together to deliver a complete guideline on choosing various system parameters when the impulse wave shape and the load capacitor are given. The concept of this new hybrid configuration is demonstrated with a scaled-down prototype where the impulse with a rise time of 1 μs is superimposed on different arbitrary wave shapes. Similarly, the MATLAB-Simulink simulation model validates the proposed configuration for a 200, k V dc link voltage and 67 submodules with the desired impulse performance.High Voltage Technology GroupDC systems, Energy conversion & Storag
Green ammonia supply chain and associated market structure
No full textGreen ammonia is poised to be a key part in the hydrogen economy. This paper discusses green ammonia supply chains with a focus on market structures. The architecture of upstream and downstream supply chains is explored. Market structure prototypes in different stages are explored based on transaction cost economics and lessons from the energy industry. In the infancy, a highly vertically integrated structure is proposed to reduce risks and ensure capital recovery. A restructuring towards a disintegrated structure is necessary in the next stage to improve the efficiency. In the late stage, a competitive structure characterized by a separation between asset ownership and production activities and further development of short-term and spot markets are proposed towards a market-driven industry. Mixed structures combining multiple structure features are also discussed due to the dependency on actual conditions. Further, a multi-linear regression model is developed to evaluate the designed structures using a case in the gas industry, due to the commonality in vertical integration and data availability. Results indicate that high asset specificity and uncertainty and low frequency lead to a more disintegrated market structure, and vice versa, thus supporting the structures designed. In addition, evidence from the latest trends in the clean ammonia market also verifies the designed early structure. Besides, potential ways to accelerate market emergence are also discussed. We assume the findings and results contribute to developing green ammonia supply chains and the hydrogen economy.Energie and Industri
Ride experience in automated minibuses: measuring users' transport mode preferences before and after a test ride
No full textIn the present study, we explored the influence of ride experience in automated minibuses (AmBs) on transport mode choice that includes the automated shuttles as well as conventional transport options (car, bus and bicycle) on the first-/ last-mile stage of rail trips. We used the case study of the connection between Brandevoort train station and the newly developing working and living area in Helmond (the Netherlands) where an AmB was tested in the February-March period of 2021. We conducted a two-wave stated preference experiment wherein data was gathered both before and after the participants had a test ride in the AmB. The results of the joint hybrid mixed logit model indicate a clear preference towards flexible-service AmBs, particularly in relation to travel time and costs. While preferences for less favoured regular-service AmBs experienced a noteworthy shift in travel time and costs, waiting and walking time parameters influenced by participants' ride experience in this pilot and by prior ride experience from other pilots. This reinforces the idea that the ride experience in AmBs even in a short pilot trial like the one conducted in Helmond has a significant impact on preferences for AmBs in comparison with car, bus and bicycle alternatives. Hence, panel studies can provide a more comprehensive understanding of how attitudes and preferences of potential users evolve over time.Transport and Plannin
Fatigue behaviour of toe and root stiffener cracks in stiffener-to-deck plate weld of orthotropic bridge decks
No full textFatigue cracks in the stiffener-to-deck plate connections of orthotropic bridge decks, initiating from the weld toe or root and propagating into the stiffener or weld throat, are experimentally and numerically studied. A statistical analysis of the structural stress is carried out using the experimental data. Automatic welded specimens show a significantly higher fatigue resistance than manual welded ones for both details of the study. Including results in the literature, the characteristic fatigue resistances appear larger than the values in current standards and range between 100 and 160 MPa. A proposal for the fatigue resistance values is given for design purposes. The effective notch stress, averaged strain energy density factor, and fracture mechanics methods are employed to study the sensitivity of the weld toe and root cracks for different (geometrical) variations, such as the lack of weld penetration. Among them, the fracture mechanics method agrees best with the experimental data. With the increase of weld penetration ratios from 75% to 100%, the fracture mechanics predicted fatigue resistances remain approximately equal for the weld toe cracks and increase for the weld root cracks.Steel & Composite Structure
On Non-Stationarity in Reinforced Deep Markov Models with Applications in Portfolio Optimization
No full textIn this thesis, we aim to improve the application of deep reinforcement learning in portfo- lio optimization. Reinforcement learning has in recent years been applied to a wide range of problems, from games to control systems in the physical world and also to finance. While reinforcement learning has shown success in simulated environments (e.g. matching or exceeding human performance in games), its adoption in practical applications (non- simulated environments) has lagged. Dulac-Arnold et al. [2019] suggest this is caused by a discrepancy in the experimental set-up in research and the conditions in practice. Specifically, they present a list of challenges that make the application of reinforcement learning in real-world settings more difficult. One of these challenges is non-stationary environments, which is common in financial environments. It is a challenge since, given an observed state, the optimal action may not always be the same as it may change over time due to non-stationarity. Therefore, more specifically, the goal of this thesis is to overcome the challenge of non-stationarity in the application of reinforcement learning to portfolio optimization. In this thesis, we use reinforced deep Markov models (RDMM) introduced by Ferreira [2020] (applied to an optimal execution problem and later used by Cartea et al. [2021] for statistical arbitrage on simulated price movements of an FX triplet) for its data efficiency and ability to handle complex environments. RDMM involve a partially observ- able Markov decision process (POMDP) which is also the setting used by Xie et al. [2021] to model non-stationarity in reinforcement learning. We extend RDMM to incorporate non-stationarity, using the framework suggested by Xie et al. [2021], and apply it to port- folio optimization. Our implementation is sample efficient which allows for quick learning, by doing this we attempt to improve on another challenge of reinforcement learning — i.e. sample-inefficiency [Dulac-Arnold et al., 2019]. Moreover, our implementation can handle continuous state and action spaces.We compare the performance of our algorithms to classical portfolio optimization tech- niques such as Mean-Variance (MV) and Equal Risk Contribution (ERC), and to popular reinforcement learning techniques such as Deep Deterministic Policy Gradient (DDPG) and Soft Actor-Critic (SAC). We observe our implementation has higher sample-efficiency compared DDPG and SAC, and higher cumulative returns on the test set compared to MV, ERC, DDPG, and SAC.Applied Mathematics | Stochastic
Fabrication of Living Entangled Network Composites Enabled by Mycelium
No full textOrganic polymer-based composite materials with favorable mechanical performance and functionalities are keystones to various modern industries; however, the environmental pollution stemming from their processing poses a great challenge. In this study, by finding an autonomous phase separating ability of fungal mycelium, a new material fabrication approach is introduced that leverages such biological metabolism-driven, mycelial growth-induced phase separation to bypass high-energy cost and labor-intensive synthetic methods. The resulting self-regenerative composites, featuring an entangled network structure of mycelium and assembled organic polymers, exhibit remarkable self-healing properties, being capable of reversing complete separation and restoring ≈90% of the original strength. These composites further show exceptional mechanical strength, with a high specific strength of 8.15 MPa g.cm−3, and low water absorption properties (≈33% after 15 days of immersion). This approach spearheads the development of state-of-the-art living composites, which directly utilize bioactive materials to “self-grow” into materials endowed with exceptional mechanical and functional properties.Aerospace Manufacturing TechnologiesGroup MasaniaGeo-engineerin
Exploring cross-cultural design through a concept on value exchange: How redefining public space can create socio-economic space
No full textThis graduation project takes place in Kampala, Uganda, in collaboration with Design without Borders Africa (Dwb).The aim of the project is threefold:Create social impact in the domain of value exchange in the public space of Kampala,Apply the Vision in Product design (ViP) method for the first time in the designer’s career andEvaluate the responsibility of the designer in relation to a cross-cultural design project.After establishing the ViP domain as ‘value exchange in the public space’ and performing two deconstructions (one by the designer and one by Dwb) extensive research is performed.It focuses on a time 10 years ahead (2034) and collects 215 factors (statements about the domain): 161 from literature, and 54 from interviews with 35 vendors in Kampala. The factors are clustered into 16 driving forces of the future context.With the driving forces a framework is constructed of 12 cells, the directions the future context can move into. The axes of the framework reveal the root of the problems around street vending.(1*) the organization of public space: Kampala’s public space receives meaning from many, misaligned origins. Government planning is not consistent with the use of space.(*2) socio-economic uncertainty: the sheer numbers of people combined with a lack of jobs creates uncertainty to which people react in different ways. These reactions create their motive to participate in value exchange.3 cells are chosen to formulate a vision statement. We want to decrease discrimination, provide stability for hustlers and steer investments to where they are needed. Three goals which correspond to the main stakeholders: vendors, clients and the local authority (KCCA). The lost in translation between them must be addressed to enable any social transformation. Integration of vendors must become the goal rather than expulsion. To achieve this we want to reveal the value of value exchange: showing vendors’ contribution in terms of convenience, urban life and economic potential.With individual and group ideation the concept is developed. It consists of a stall and street design assigning space to vendors in pedestrian zones. Vendors are given fixed categories, streets are replanned and vendors are made the guardians and cleaners of the street. Placement of spots is used to regulate traffic flow and decongest the city. The concept couples this reorganization of public space to the other axis of socio-economic insecurity, by turning street vending from a last resort into a first step up the formal ladder. Vendors can only rent a stall for six months during which they are educated, build a network and are helped in saving money – after the 6 months they are ready to start a full business. The financial and organizational aspects of the concept are also thought out.Elaborate testing is performed with vendors and authorities. Most of the feedback is worked into the concept. Recommendations for further development include directions for stall design and a road map for taking the concept to a pilot level.The reflection results in 6 design principles guiding western designers doing projects in radically different contexts.Integrated Product Desig