Power density

About: Power density is a research topic. Over the lifetime, 9534 publications have been published within this topic receiving 197264 citations. The topic is also known as: volumic power & volume power density.

Performance Comparisons Between Carbon Nanotubes, Optical, and Cu for Future High-Performance On-Chip Interconnect Applications

Abstract: Optical interconnects and carbon nanotubes (CNTs) present promising options for replacing the existing Cu-based global/semiglobal (optics and CNT) and local (CNT) wires. We quantify the performance of these novel interconnects and compare it with Cu/low-kappa wires for future high-performance integrated circuits. We find that for a local wire, a CNT bundle exhibits a smaller latency than Cu for a given geometry. In addition, by leveraging the superior electromigration properties of CNT and optimizing its geometry, the latency advantage can be further amplified. For semiglobal and global wires, we compare both optical and CNT options with Cu in terms of latency, energy efficiency/power dissipation, and bandwidth density. The above trends are studied with technology node. In addition, for a future technology node, we compare the relationship between bandwidth density, power density, and latency, thus alluding to the latency and power penalty to achieve a given bandwidth density. Optical wires have the lowest latency and the highest possible bandwidth density using wavelength division multiplexing, whereas a CNT bundle has a lower latency than Cu. The power density comparison is highly switching activity (SA) dependent, with high SA favoring optics. At low SA, optics is only power efficient compared to CNT for a bandwidth density beyond a critical value. Finally, we also quantify the impact of improvement in optical and CNT technology on the above comparisons. A small monolithically integrated detector and modulator capacitance for optical interconnects (~10 fF) yields a superior power density and latency even at relatively lower SA (~20%) but at high bandwidth density. At lower bandwidth density and SA lower than 20%, an improvement in mean free path and packing density of CNT can render it most energy efficient.

A Modular-Designed Three-Phase High-Efficiency High-Power-Density EV Battery Charger Using Dual/Triple-Phase-Shift Control

Abstract: In this paper, an enhancement-mode GaN high-electron mobility transistor (HEMT)-based 7.2-kW single-phase charger was built. Connecting three such single-phase modules to the three-phase grid, respectively, generates a three-phase ∼22-kW charger with the $>{\text{97}}\% $ efficiency and $>{\text{3.3}}-{\rm{kW}/ \rm{L}}$ power density, superior to present Si-device-based chargers. In addition to GaN HEMTs with fast-switching transitions yielding high efficiency, the proposed charger employs the dc/dc stage to control the power factor and power delivery simultaneously, yielding little dc-bus capacitance and thereby high power density. To secure the soft switching for all switches within full voltage and power ranges, a variable switching frequency control with dual phase shifts was adopted at high power, and a triple phase shift was employed to improve the power factor at low power. Both control strategies accommodated the wide input range (80–260 VAC) and output range (200–450 VDC). A closed-loop control for the three-phase charger was realized to minimize the output current ripple and balance the power among three single-phase modules. Experimental results validated this design.

Enhanced ion transport by graphene oxide/cellulose nanofibers assembled membranes for high-performance osmotic energy harvesting

Abstract: As an emerging potential energy source to address the energy crisis, osmotic energy has attracted increasing attention. Fast ion transport is essential for this blue energy and for other membrane-based energy systems to achieve low membrane resistance and high ion selectivity for power density. However, the current nanochannel membranes suffer from a high energy barrier for ion transmembrane movement because of the narrow channel size and the low charge density, which results in low current and undesirable power density. Here, an elaborate graphene oxide (GO) nanosheets/cellulose nanofibers (CNFs) assembled membrane is reported to improve confined ion transport for high-performance osmotic energy conversion. CNFs, the most abundant natural nanomaterial with highly anisotropic properties and a high density of functional groups, not only enlarge the original narrow channel, which reduces the energy barrier for ion transport, but also introduce space charge between pristine GO nanosheets to maintain ion selectivity. Benefiting from the effective assembly of GO and CNFs, a high power density of 4.19 W m−2 with an improved current is obtained by mixing artificial seawater and river water. Moreover, a power density of 7.20 W m−2, which is higher than the standard for commercialization, is achieved at 323 K. The osmotic energy conversion shows a nonlinear thermal dependence relationship at high temperatures due to bubble nucleation. This material design strategy can provide an alternative concept to effectively enhance ion transport in membrane-based fields such as separations, desalination, flow batteries and fuel cells.