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Distributed Resources Shift Paradigms on Power System Design, Planning, and Operation: An Application of the GAP Model
Power systems have evolved following a century-old paradigm of planning and operating a grid based on large central generation plants connected to load centers through a transmission grid and distribution lines with radial flows. This paradigm is being challenged by the development and diffusion of modular generation and storage technologies. We use a novel approach to assess the sequencing and pacing of centralized, distributed, and off-grid electrification strategies by developing and employing the grid and access planning (GAP) model. GAP is a capacity expansion model to jointly assess operation and investment in utility-scale generation, transmission, distribution, and demand-side resources. This paper conceptually studies the investment and operation decisions for a power system with and without distributed resources. Contrary to the current practice, we find hybrid systems that pair grid connections with distributed energy resources (DERs) are the preferred mode of electricity supply for greenfield expansion under conservative reductions in photovoltaic panel (PV) and energy storage prices. We also find that when distributed PV and storage are employed in power system expansion, there are savings of 15%-20% mostly in capital deferment and reduced diesel use. Results show that enhanced financing mechanisms for DER PV and storage could enable 50%-60% of additional deployment and save 15 /MWh in system costs. These results have important implications to reform current utility business models in developed power systems and to guide the development of electrification strategies in underdeveloped grids
Towards Multi-Scale Modeling of Carbon Nanotube Transistors
Multiscale simulation approaches are needed in order to address scientific
and technological questions in the rapidly developing field of carbon nanotube
electronics. In this paper, we describe an effort underway to develop a
comprehensive capability for multiscale simulation of carbon nanotube
electronics. We focus in this paper on one element of that hierarchy, the
simulation of ballistic CNTFETs by self-consistently solving the Poisson and
Schrodinger equations using the non-equilibrium Greens function (NEGF)
formalism. The NEGF transport equation is solved at two levels: i) a
semi-empirical atomistic level using the pz orbitals of carbon atoms as the
basis, and ii) an atomistic mode space approach, which only treats a few
subbands in the tube-circumferential direction while retaining an atomistic
grid along the carrier transport direction. Simulation examples show that these
approaches describe quantum transport effects in nanotube transistors. The
paper concludes with a brief discussion of how these semi-empirical device
level simulations can be connected to ab initio, continuum, and circuit level
simulations in the multi-scale hierarchy
Comparison of Staggered Grid Finite Difference Schemes for Ultrasound Simulation in Curving Composites
The optimization of ultrasonic nondestructive evaluation (NDE) simulation tools for composites has the potential to reduce both individual part inspection time and overall certification time for composite parts and structures. Inspection guidance based on simulation provides increased confidence in the veracity of inspection results in addition to time reductions. This paper outlines ongoing work targeted to advance this objective through the use of finite difference (FD) simulation techniques formulated for composite structures with realistic geometries. Two staggered grid explicit FD schemes which show promise for this purpose are assessed: the Lebedev FD scheme and the rotated staggered grid (RSG) FD scheme. Algorithmic points which provide challenges for complex geometries are addressed, in particular handling of traction free surfaces and bi-material interfaces present at lamina boundaries. Code execution time estimates are performed as well to guide feasible domain sizes relative to algorithm choice and available hardware. Three test cases are simulated: a delaminated plate, a cylinder, and a triclinic lamina. These tests demonstrate that the Lebedev FD scheme needs additional work to handle inter-laminar interfaces and traction free boundaries in the presence of stair-stepping approximations. In contrast, the simple structure of the RSG unit cell makes it more straightforward to construct a 3D simulation technique for curved composite laminates
Simulation of an Axial Vircator
An algorithm of particle-in-cell simulations is described and tested to aid
further the actual design of simple vircators working on axially symmetric
modes. The methods of correction of the numerical solution, have been chosen
and jointly tested, allow the stable simulation of the fast nonlinear multiflow
dynamics of virtual cathode formation and evolution, as well as the fields
generated by the virtual cathode. The selected combination of the correction
methods can be straightforwardly generalized to the case of axially
nonsymmetric modes, while the parameters of these correction methods can be
widely used to improve an agreement between the simulation predictions and the
experimental data.Comment: 9 pages, 3 figure
Eras of electric vehicles: electric mobility on the Verge. Focus Attention Scale
Daily or casual passenger vehicles in cities have negative burden on our finite world. Transport sector has been one of the main contributors to air pollution and energy depletion.
Providing alternative means of transport is a promising strategy perceived by motor manufacturers and researchers. The paper presents the battery electric vehicles-BEVs bibliography that starts with the early eras of invention up till 2015 outlook. It gives a broad overview of BEV market and its technology in a chronological classification while sheds light on the stakeholders’ focus attentions in each stage, the so called, Focus-Attention-Scale-FAS. The attention given in each era is projected and parsed in a scale graph, which varies between micro, meso,
and macro-scale. BEV-system is on the verge of experiencing massive growth; however, the system entails a variety of substantial challenges. Observations show the main issues of BEVsystem that require more attention followed by the authors’ recommendations towards an emerging market
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