Economic feasibility of green hydrogen in providing flexibility to medium-voltage distribution grids in the presence of local-heat systems

The recent strong increase in the penetration of renewable energy sources (RESs) in medium-voltage distribution grids (MVDNs) has raised the need for congestion management in such grids, as they were not designed for this new condition. This paper examines to what extent producing green hydrogen through electrolyzers can profitably contribute to congestion alleviation in MVDNs in the presence of high amounts of RES, as well as flexible consumers of electricity and a local heat system. To address this issue, an incentive-based method for improving flexibility in MVDNs is used which is based on a single-leader–multiple-followers game formulated by bi-level mathematical programming. At the upper level, the distribution system operator, who is the leader of this game, determines dynamic prices as incentives at each node based on the levels of generation and load. Next, at the lower level, providers of flexibility, including producers using electrolyzers, price-responsive power consumers, heat consumers, as well as heat producers, respond to these incentives by reshaping their output and consumption patterns. The model is applied to a region in the North of The Netherlands. The obtained results demonstrate that converting power to hydrogen can be an economically efficient way to reduce congestion in MVDNs when there is a high amount of RES. However, the economic value of electrolyzers as providers of flexibility to MVDNs decreases when more other options for flexibility provision exist

Microhardness distribution and finite element method analysis of Al 5452 alloy processed by unconstrained high pressure torsion

High pressure torsion (HPT) is one of the successful and efficient methods of severe plastic deformation (SPD). In this research, disk-shaped specimens of aluminum alloy were exposed to high pressure and torsion, which are the key factors of HPT. Simultaneously applying high pressure and torsion causes shear strain and thus enhancement of mechanical properties such as microhardness. In order to understanding the behavior of local deformation on disks after HPT, the process has been simulated by using finite element analysis method in ABAQUS/Explicit software. Results of simulation showed that by increasing applied pressure and number of turns, more effective strain would be applied to the disks. By comparing results of experiment and simulation, it was concluded that there is a region in the middle of the disk that has higher microhardness value in comparison to other regions, which is caused by more strain that was applied to it. Also, dimensions and equivalent plastic strain (PEEQ) obtained in experiments and simulations are compared. It was observed that expected dimensions and PEEQ of simulations are in good agreement with experimental results. Keywords: High pressure torsion (HPT), Severe plastic deformation (SPD), Microhardness, Finite element analysis method, Equivalent plastic strain (PEEQ

Counter-hairpin vortices in the turbulent wake of a sharp trailing edge

Aerodynamics and Wind EnergyAerospace Engineerin

Effect of topology on strength and energy absorption of PA12 non-auxetic strut-based lattice structures

With the increasing development of additive manufacturing (AM) technology, lattice structure (LS) emerged and expanded as a subset of cellular materials. LSs' mechanical properties mainly depend on the relative density, the unit cell topology, the manufacturing processes, and the base material. In this research, PA12 lattice structures with non-auxetic strut-based topologies, including BCC, FCC, FCCz, FBCC, FBCCz, FBCCxyz, and OT, were manufactured by selective laser sintering (SLS) and were tested under quasi-static compression. Data from the compression test was analyzed and investigated to achieve mechanical properties such as strength, elastic modulus, and absorbed energy. OT has the highest yield strength (4.07 MPa), ultimate strength (4.53 MPa), specific ultimate strength (10.11 MPa), elastic modulus (0.099 GPa), specific elastic modulus (0.221 GPa), and plateau stress (9.98 MPa) among the investigated sturt-based topologies. BCC has the lowest properties. The absorbed energy (W) for OT and FBCCxyz is higher than in other topologies. FBCCz has the highest volumetric energy absorption (WV) (0.284 MJ/m3) up to the strain of the UTS point, and FCCz has the lowest (0.152 MJ/m3). The finite element method (FEM)-based ABAQUS software was used to simulate the behavior of LSs under compression test. Also, SEM micrographs of struts' fractured surfaces in the CP lattice block were investigated. In most strut-based LSs, the failure mechanism is the layer-by-layer failure of rows. According to finite element modeling results, stress concentration occurred in the nodes and adjacent areas, making cracks, and fractography exhibited ductile fracture in these regions