Experimental and Theoretical Investigations for the improvement of AGMD Energy Efficiency

Doctoral thesis (2022)

Water and power related resources (energy sources and required material) are both critical and crucial resources that have become even more and more strategic as a result of climate change and geopolitics ... [more ▼]

Water and power related resources (energy sources and required material) are both critical and crucial resources that have become even more and more strategic as a result of climate change and geopolitics. By making a large store of salty water available, desalination appears to be a viable solution to the water crisis already affecting 40% of the population today. However, because existing desalination procedures are power intensive and rely on non-renewable energy resources, their power use at large scale is unsustainable. Alternative techniques exist that are promising in terms of environmental impact, but not yet competitive in terms of fresh water outflow and energy efficiency. The focus of this work is on one of these alternatives, Air-Gap Membrane Distillation (AGMD), which was chosen because it relies on low-grade heat that is easy to collect from solar radiations or from industrial waste heat. This technique mimics the water cycle, thanks to the use of a membrane, allowing to bring the hot and cold water streams closer together. As a result, the temperature difference that drives evaporation is strengthened and the process accelerated. However, the development of a boundary layer at the membrane interface reduces this temperature difference and thus decreases the overall performance of the process. Thus this technique still requires some improvements to become industrially attractive, in terms of fresh water outflow per kWh and energy use. The goal of this thesis work is to contribute to AGMD energy efficiency and output flow enhancement by leveraging both experimental and theoretical considerations. A test facility characterizing the boundary layer based on a Schlieren method as well as an adapted AGMD module were designed and built. By interacting with the boundary layer, the laser allows the observation of the continuous temperature profile in the hot water channel of a at sheet AGMD module. The measurement can be performed in close proximity to the membrane and under a variety of operational conditions (inlet hot and cold temperatures, inlet velocities). In parallel, the fresh water outflow corresponding to these experimental conditions can be measured. Moreover, the experimental layout opens the way for further observations of the AGMD process from a different angle - such as concentration profiles or experimentation in the air-gap - with very little addition. The overall experimental set-up has eventually been used to produce a first set of data over a range of temperature (60-75◦C), which is then interpreted thanks to a custom algorithm deriving the temperature profiles and boundary layer thicknesses. A three dimensional heat and mass transfer model for AGMD (3DH&MT) - previously developed in the research team - has been used to numerically reproduce the experimental conditions and compare the results. The comparison showed promising results as the temperature gradients at the membrane interface and fresh water outflows present similar orders of magnitude and trends. The accuracy of the experiment can be further increased through several adaptations in the set-up. This 3DH&MT model could be used to simulate more complex AGMD module designs, such as spiral modules in order to optimize the operating conditions and the overall shape of the AGMD module to enhance its performances. Finally, in the aim of improving the energy efficiency and fresh water outflow of the AGMD process, spacers are usually added in the individual channels to boost mixing and thus reduce the boundary layer thickness, which improves evaporation flux. Two novel spacer geometries inspired by current industrial mixing state of the art and nature have been proposed and investigated, yielding interesting results for two distinct applications. One is particularly well-suited to maximizing mixing regardless of the energy used, hence improving the energy efficiency of the process. The second is optimal for minimizing energy consumption while maintaining a decent mixing result, thus enhancing the fresh water outflow of the process. A couple of indicators have also been proposed to assess the mixing performance of more complex 3D geometries. Overall this work broadens the current AGMD research by providing an experimental test-bench enabling the continuous temperature profile measurement, and the validation of a 3D heat and mass transfer model. Moreover, interesting tracks for improving the design of spacers are proposed in order to minimize the AGMD process's energy efficiency resistance. AGMD is an extremely promising water treatment technique since it is applicable to a broader range of waters than just seawater. The test equipment described in this work is sufficiently adaptable to investigate this potential as well as variants of AGMD processes that might boost its attractiveness. As it is based on readily available materials and technologies, it may be used anywhere and its reliance on a naturally available energy flow (solar radiation) makes it attractive in isolated regions. [less ▲]

An experimental approach to the dynamics of nuclear polarisation

in Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment (2004), 526

In the past 3 years a series of experiments have shed new light on the mechanism of dynamic nuclear polarisation (DNP). Time-resolved polarised small-angle neutron scattering and nuclear magnetic ... [more ▼]

In the past 3 years a series of experiments have shed new light on the mechanism of dynamic nuclear polarisation (DNP). Time-resolved polarised small-angle neutron scattering and nuclear magnetic resonance have been used simultaneously to study the nuclear polarisation build-up around paramagnetic centres during DNP. This approach, which aims at visualising the nuclear polarisation process on a microscopic scale, shall be exemplified and the experimental techniques used described in some detail. [less ▲]

Experimental characterization of the temperature gradient inside a membrane distillation module

in Energy Reports (2022)

An experimental comparison of security markets: call-auction vs. double-auction

Scientific Conference (2012)

Experimental design trade-offs for gene regulatory network inference: an in silico study of the yeast Saccharomyces cerevisiae cell cycle

in Proceedings of the 56th IEEE Conference on Decision and Control (2017, December)

Time-series of high throughput gene sequencing data intended for gene regulatory network (GRN) inference are often short due to the high costs of sampling cell systems. Moreover, experimentalists lack a ... [more ▼]

Time-series of high throughput gene sequencing data intended for gene regulatory network (GRN) inference are often short due to the high costs of sampling cell systems. Moreover, experimentalists lack a set of quantitative guidelines that prescribe the minimal number of samples required to infer a reliable GRN model. We study the temporal resolution of data vs.quality of GRN inference in order to ultimately overcome this deficit. The evolution of a Markovian jump process model for the Ras/cAMP/PKA pathway of proteins and metabolites in the G1 phase of the Saccharomyces cerevisiae cell cycle is sampled at a number of different rates. For each time-series we infer a linear regression model of the GRN using the LASSO method. The inferred network topology is evaluated in terms of the area under the precision-recall curve (AUPR). By plotting the AUPR against the number of samples, we show that the trade-off has a, roughly speaking, sigmoid shape. An optimal number of samples corresponds to values on the ridge of the sigmoid. [less ▲]

Experimental Evaluation of a Tool for Change Impact Prediction in Requirements Models: Design, Results, and Lessons Learned

in The Fourth International Model-Driven Requirements Engineering (MoDRE) workshop (2014)

There are commercial tools like IBM Rational RequisitePro and DOORS that support semi-automatic change impact analysis for requirements. These tools capture the requirements relations and allow tracing ... [more ▼]

There are commercial tools like IBM Rational RequisitePro and DOORS that support semi-automatic change impact analysis for requirements. These tools capture the requirements relations and allow tracing the paths they form. In most of these tools, relation types do not say anything about the meaning of the relations except the direction. When a change is introduced to a requirement, the requirements engineer analyzes the impact of the change in related requirements. In case semantic information is missing to determine precisely how requirements are related to each other, the requirements engineer generally has to assume the worst case dependencies based on the available syntactic information only. We developed a tool that uses formal semantics of requirements relations to support change impact analysis and prediction in requirements models. The tool TRIC (Tool for Requirements Inferencing and Consistency checking) works on models that explicitly represent requirements and the relations among them with their formal semantics. In this paper we report on the evaluation of how TRIC improves the quality of change impact predictions. A quasi-experiment is systematically designed and executed to empirically validate the impact of TRIC. We conduct the quasi-experiment with 21 master’s degree students predicting change impact for five change scenarios in a real software requirements specification. The participants are assigned with Microsoft Excel, IBM RequisitePro or TRIC to perform change impact prediction for the change scenarios. It is hypothesized that using TRIC would positively impact the quality of change impact predictions. Two formal hypotheses are developed. As a result of the experiment, we are not able to reject the null hypotheses, and thus we are not able to show experimentally the effectiveness of our tool. In the paper we discuss reasons for the failure to reject the null hypotheses in the experiment. [less ▲]

Experimental evaluation of RF waveform designs for Wireless Power Transfer using Software Defined Radio

in IEEE Access (2021), 9

The possibility to harvest energy from ambient radio-frequency (RF) sources has intrigued humankind for the past several decades. In this context, there has been a tremendously growing research interest ... [more ▼]

The possibility to harvest energy from ambient radio-frequency (RF) sources has intrigued humankind for the past several decades. In this context, there has been a tremendously growing research interest in the field of wireless power transfer (WPT) using the RF range of the electromagnetic (EM) spectrum. In this paper, we experimentally investigate the aspect of real-time energy harvesting (EH) via different types of waveform designs such as orthogonal frequency division multiplexing (OFDM), square, triangular, sinusoidal, and sawtooth. We make use of a Software Defined Radio (SDR) and a Powercast P21XXCSR-EVB EH module to carry out the experiments on a practical device to assess performance. Specifically, we are interested in obtaining some insights based on the comparison between the aforementioned waveform designs from the perspectives of the separation distance between the USRP and P21XXCSR-EVB EH module, and power emission via USRP. In this vein, we perform additional subsequent experiments after reporting the practical effectiveness of the OFDM waveform, which also follows our intuitive analysis. Correspondingly, we study the effect on WPT with variable USRP transmit power, the separation distance between the USRP and EH antennas, number of OFDM sub-carriers, and multipath setting. As an application of OFDM, the effectiveness of fifth generation-new radio (5G-NR) and long-term evolution (LTE) waveforms are also tested for the WPT mechanism. The demonstration of the EH is provided in terms of the above-mentioned investigation metrics while seeking the best waveform to support WPT. [less ▲]

The Experimental Governance of Smart Cities: an analysis of Amsterdam Smart City in relation to Amsterdam’s data center industry.

Presentation (2022)

Experimental identification of a lattice model for woven fabrics: Application to electronic textile

in Composites. Part A, Applied Science and Manufacturing (2013), 48

Lattice models employing trusses and beams are suitable to investigate the mechanical behavior of woven fabrics. The discrete features of the mesostructures of woven fabrics are naturally incorporated by ... [more ▼]

Lattice models employing trusses and beams are suitable to investigate the mechanical behavior of woven fabrics. The discrete features of the mesostructures of woven fabrics are naturally incorporated by the discrete elements of lattice models. In this paper, a lattice model for woven materials is adopted which consists of a network of trusses in warp and weft direction, which represent the response of the yarns. Additional diagonal trusses are included that provide a resistance against relative rotation of the yarns. The parameters of these families of discrete elements can be separately identified from tensile experiments in three in-plane directions which correspond with the orientations of the discrete elements. The lattice model and the identification approach are applied to electronic textile. This is a fabric in which conductive wires are incorporated to allow the embedment of electronic components such as light-emitting diodes. The model parameters are established based on tensile tests on samples of the electronic textile. A comparison between the experimental results of an out-of-plane punch test and the simulation results shows that the lattice model and its characterization procedure are accurate until extensive biaxial tensile deformation occurs. [less ▲]

Experimental Investigation of Soft-Landing of Quadrotors via Induced Wind Modeling Approach

in Experimental Investigation of Soft-Landing of Quadrotors via Induced Wind Modeling Approach (2021)