• Energy Research
• 2021-2025close
• FR close
• VBN close

This paper presents a novel online technique, which simultaneously exploits the global search ability of differential evolution (DE) and rapid convergence of Newton Raphson (NR) methods (named as DE-NR) to solve intricate simultaneous transcendental trigonometric set of harmonic elimination pulse width modulation equations for modular multilevel cascade converters based power systems. Major contribution of this paper is a harmonically efficient online algorithm with rapid convergence. Switching angles for an extensive range of modulation index (M,0.86⩽M≤9.97) are computed online to demonstrate the harmonically efficient working of proposed method. Total harmonic distortion values of the filtered line-to-line output voltages during online operation are restricted to 0.35% of the fundamental component, which depict successful removal of unwanted harmonics and are significantly better than the values allowed by IEEE standard 519-2014. Comparison between DE-NR, differential evolution and Newton Raphson methods demonstrates the rapid convergence behavior of DE-NR as it requires only (on average) 4 iterations compared to 490 and 182 iterations respectively. It has also shown superior harmonic control than the recently devised online Middle-Level Selective Harmonic Elimination Pulse-Amplitude Modulation method. Successful simulation and experimental validations of DE-NR method have been done by developing three-phase modular multilevel cascade converter in MATLAB-Simulink and single-phase eleven-level modular multilevel cascade converter hardware prototype.

The wave energy control competition established a benchmark problem which was offered as an open challenge to the wave energy system control community. The competition had two stages: In the first stage, competitors used a standard wave energy simulation platform (WEC-Sim) to evaluate their controllers while, in the second stage, competitors were invited to test their controllers in a real-time implementation on a prototype system in a wave tank. The performance function used was based on converted energy across a range of standard sea states, but also included aspects related to economic performance, such as peak/average power, peak force, etc. This paper compares simulated and experimental results and, in particular, examines if the results obtained in a linear system simulation are borne out in reality. Overall, within the scope of the device tested, the range of sea states employed, and the performance metric used, the conclusion is that high-performance WEC controllers work well in practice, with good carry-over from simulation to experimentation. However, the availability of a good WEC mathematical model is deemed to be crucial.

In this work, we propose a framework for energy-efficient trajectory design of an unmanned aerial vehicle (UAV)-based portable access point (PAP) deployed to serve a set of ground nodes (GNs). In addition to the PAP and GNs, the system consists of a set of intelligent reflecting surfaces (IRSs) mounted on man-made structures to increase the number of bits transmitted per Joule of energy consumed measured as the global energy efficiency (GEE). The GEE trajectory for the PAP is designed by considering the UAV propulsion energy consumption and the Peukert effect of the PAP battery, which represents an accurate battery discharge profile as a non-linear function of the UAV power consumption profile. The GEE trajectory design problem is solved in two phases: in the first, a path for the PAP and feasible positions for the IRS modules are found using a multi-tier circle packing method, and the required IRS phase shift values are calculated using an alternate optimization method that considers the interdependence between the amplitude and phase responses of an IRS element; in the second phase, the PAP flying velocity and user scheduling are calculated using a novel multilap trajectory design algorithm. Numerical evaluations show that: neglecting the Peukert effect overestimates the available flight time of the PAP; after a certain threshold, increasing the battery size reduces the available flight time of the PAP; the presence of IRS modules improves the GEE of the system compared to other baseline scenarios; the multi-lap trajectory saves more energy compared to a single-lap trajectory developed using a combination of sequential convex programming and Dinkelbach algorithm. 12 pages, 11 Figures, accepted as a Paper in IEEE Transactions on Vehicular Technology

Against the backdrop of a climate crisis, HCI researchers and designers are reflecting upon, reconsidering, and re-imagining the work that we do through the lens of sustainability. In this Studio, we propose to adopt this critical perspective to Sustainable HCI through an examination and reflection on the environmental impact of research conferences. Our Studio builds upon our prior work that explored sustainable methods and toolkits for facilitating data physicalization workshops. We apply the tools and strategies developed through this prior work within a Studio in which participants are facilitated to engage with, reflect upon, and create with data relating to the sustainability of HCI conferences such as Tangible, Embedded and Embodied Interaction (TEI). Through the creation of data artefacts that can be displayed, worn, or shared throughout the conference beyond the Studio, we aim to spark wider conversations about the environmental sustainability of TEI2024, as well as HCI conferences more generally.

Cities across the globe recognise their role in climate mitigation and are acting to reduce carbon emissions. Knowing whether cities set ambitious climate and energy targets is critical for determining their contribution towards the global 1.5 °C target, partly because it helps to identify areas where further action is necessary. This paper presents a comparative analysis of the mitigation targets of 327 European cities, as declared in their local climate plans. The sample encompasses over 25% of the EU population and includes cities of all sizes across all Member States, plus the UK. The study analyses whether the type of plan, city size, membership of climate networks, and its regional location are associated with different levels of mitigation ambition. Results reveal that 78% of the cities have a GHG emissions reduction target. However, with an average target of 47%, European cities are not on track to reach the Paris Agreement: they need to roughly double their ambitions and efforts. Some cities are ambitious, e.g. 25% of our sample (81) aim to reach carbon neutrality, with the earliest target date being 2020.90% of these cities are members of the Climate Alliance and 75% of the Covenant of Mayors. City size is the strongest predictor for carbon neutrality, whilst climate network(s) membership, combining adaptation and mitigation into a single strategy, and local motivation also play a role. The methods, data, results and analysis of this study can serve as a reference and baseline for tracking climate mitigation ambitions across European and global cities.

This work concerns the adaptation of the Herschel–Quincke filters (HQ) known in the case of plane acoustic waves in tubes to the case of bending waves in beams. The objective is to develop new techniques to design vibration filters in thin structures. In acoustics, an HQ filter consists of the insertion of a bifurcation in a primary tube, so as to create two tubes in parallel and of different length. The phase difference creates destructive interference at certain frequencies which gives rise to zero transmission. In the case of the bending waves considered here, the HQ interference is obtained by locally splitting a thin beam into two segments of the same length but of different thickness. The difference in travel time is then created by the difference in bending stiffness between the two segments. A semi-analytical wave decomposition model using Timoshenko's theory is developed to perform parametric studies of behaviour of such a device. Finite element simulations and experimental demonstrations confirm the predictions of a semi-analytical model. The results highlight the link between the geometric parameters of the device and its filtering properties. Therefore, this paper establishes a novel strategy of design of vibration filters, which utilizes the HQ effect for bending waves in beams.

The penetration of renewable energy sources (RES) has caused some challenges for grid operation, including frequency variation, low power quality, and reliability issues. These challenges can be mitigated with the help of battery energy storage systems (BESS) which are characterized by long lifetime and high-power capability. Among the different types of high-power storage devices, lithium titanate oxide (LTO) batteries and lithium-ion capacitor (LIC) cells attract more attention. The performance behavior, the total cost of the battery system, and the system’s size are some other criteria for cell selection. This research compares the performance behavior of an LTO battery type for this application with two LIC type storage system at positive and negative temperatures and also considers the system size, cost, and lifetime of the BESS. The result proves that LICs are better candidates for low and high temperature applications in terms of energy efficiency and capacity drop. However, in terms of cost and size, the high energy LTO cells are a better selection.

This paper investigates the problem of controlling a single phase shunt active power filter (SAPF) connected to two photovoltaic arrays through a half bridge inverter involving two DC link capacitors. The control aims are threefold: ensuring a satisfactory power factor correction (PFC) at the grid-power filter connection point by compensating the harmonic and reactive currents produced by the nonlinear loads; extracting a maximum active power in the output photovoltaic arrays by applying the maximum power point tracking (MPPT) block and balancing the power exchange between the photovoltaic source and the AC power grid by regulating the DC link capacitors voltages. The problem is dealt with using a cascade nonlinear adaptive controller. The inner loop is designed using sliding mode and Lyapunov stability techniques so that to ensure a unity power factor. It also includes an adaptive observer that performs online estimation of the grid state variables which are not accessible to measurements. The outer loop is mainly constituted of filtered proportional-integral (PI) regulator, that ensures a tight regulation of the photovoltaic voltage, and the incremental conductance (IC) algorithm to meet MPPT. The resulting controller performances are formally analyzed making use of averaging theory. The theoritical analysis results are confirmed by numerical simulation within MATLAB/SimPowerSystems environment.