Electric power

About: Electric power is a research topic. Over the lifetime, 73036 publications have been published within this topic receiving 636991 citations.

A quantum-dot heat engine operating close to the thermodynamic efficiency limits.

Abstract: Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs1,2. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines3–6, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine’s steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency η. We find that at the maximum power conditions, η is in agreement with the Curzon–Ahlborn efficiency6–9 and that the overall maximum η is in excess of 70% of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics10, on-chip coolers or energy harvesters for quantum technologies.

Comparing the Topological and Electrical Structure of the North American Electric Power Infrastructure

Abstract: The topological (graph) structure of complex networks often provides valuable information about the performance and vulnerability of the network. However, there are multiple ways to represent a given network as a graph. Electric power transmission and distribution networks have a topological structure that is straightforward to represent and analyze as a graph. However, simple graph models neglect the comprehensive connections between components that result from Ohm's and Kirchhoff's laws. This paper describes the structure of the three North American electric power interconnections, from the perspective of both topological and electrical connectivity. We compare the simple topology of these networks with that of random, preferential-attachment, and small-world networks of equivalent sizes and find that power grids differ substantially from these abstract models in degree distribution, clustering, diameter and assortativity, and thus conclude that these topological forms may be misleading as models of power systems. To study the electrical connectivity of power systems, we propose a new method for representing electrical structure using electrical distances rather than geographic connections. Comparisons of these two representations of the North American power networks reveal notable differences between the electrical and topological structures of electric power networks.

System and method for transferring electrical power between grid and vehicle

Abstract: The present invention discloses a system for transferring electrical power between a grid and at least one vehicle. The vehicle can be Battery Electric Vehicle (BEV), Plug-in Hybrid Electric Vehicle (PHEV) or Fuel Cell Vehicle (FCV). The type of vehicle will be recognized and controlled by the system to support demand response and supply side energy management. Vehicle recognition can be carried out by load signature analysis, power factor measurement or RFID techniques. In an embodiment of the invention, the grid is a Smart Grid. The present invention also discloses a method for facilitating electrical power transfer between the grid and the vehicle.

General Steady-State Analysis and Control Principle of Electric Springs With Active and Reactive Power Compensations

Abstract: This paper provides a general analysis on the steady-state behavior and control principles of a recently proposed concept of “electric springs” that can be integrated into electrical appliances to become a new generation of smart loads. The discussion here is focused on how different real and/or reactive load powers can be canceled or altered using the electric springs. Mathematical derivations supporting the theoretical framework of the concept are detailed in the paper. Experimental results validate the theoretical discussions and solutions proposed. It is demonstrated that the electric spring is capable of providing different types of power/voltage compensations to the load and the source.

Separable inductive coupler

Abstract: A separable inductive coupler for transferring electrical power across a dielectric medium using magnetic induction. Its coil geometry allows for easy disassembly of primary and secondary circuits. When primary and secondary coils are mated, an extremely low leakage inductance transformer is formed. This provides for good high frequency operation at high power density. The coupler allows electrical power transfer without metal-to-metal contact. The design allows easy removal of the primary or secondary coil from the transformer. The coil geometry has very low leakage inductance and very low high-frequency resistance which allows high frequency operation. The power transfer density is much higher than previously achieved with separable inductive couplers. Approximately 6000 watts has been transferred through a version of the present separable inductive coupler having a volume of 25.8 cubic inches, yielding a power density of 230 Watts/cubic inch. The coupler is adapted to provide a safe, convenient and weatherproof device for coupling power to a load, such as an electric vehicle to recharge its propulsion battery.