Hybrid-electric propulsion for aircraft

Against a background of increasing energy demand and rising fuel prices, hybrid-electric propulsion systems (HEPS) have the potential to significantly reduce fuel consumption in the aviation industry, particularly in the lighter sectors. By taking advantage of both Electric Motor (EM) and Internal Combustion Engine (ICE), HEPS provide not only a benefit in fuel saving but also a reduction in take-off noise and the emission levels. This research considers the design and sizing process of a hybrid-electric propulsion system for a single-seat demonstrator aircraft, the experimental derivation of the ICE map and the EM parameters. In addition to the experimental data, a novel modeling approach including several linked desktop PC software packages is presented to analyze and optimize hybrid-electric technology for aircraft. Further to the analysis of a parallel hybrid-electric, mid-scale aircraft, this paper also presents a scaling approach for a 20 kg UAV and a 50 tonne inter-city airliner. At the smaller scale, two different mission profiles are analyzed: an ISR mission profile, where the simulation routine optimizes the component size of the hybrid-electric propulsion system with respect to fuel saving, and a maximum duration profile; where the flight endurance is determined as a function of payload weight. At the larger scale, the performance of a 50 tonne inter-city airliner is modeled, based on a hybrid-electric gas-turbine, assuming a range of electric boost powers and battery masses.

A quantum dot sensitized solar cell based on vertically aligned carbon nanotube templated ZnO arrays

We report on a quantum dot sensitized solar cell (QDSSC) based on ZnO nanorod coated vertically aligned carbon nanotubes (VACNTs). Electrochemical impedance spectroscopy shows that the electron lifetime for the device based on VACNT/ZnO/CdSe is longer than that for a device based on ZnO/CdSe, indicating that the charge recombination at the interface is reduced by the presence of the VACNTs. Due to the increased surface area and longer electron lifetime, a power conversion efficiency of 1.46% is achieved for the VACNT/ZnO/CdSe devices under an illumination of one Sun (AM 1.5G, 100 mW/cm2). © 2010 Elsevier B.V.

Integrating vertically aligned carbon nanotubes on micromechanical structures

The integration of high yield, uniform and preferential growth of vertically aligned carbon nanotubes (VACNT) on low stress micromechanical structures was analyzed. A combination of electron-beam crosslinked surface micromachining and direct current plasma enhanced chemical vapor deposition of electric field aligned carbon nanotubes was used for the analysis. The selective placement of high yield and uniform VACNTs on a partially suspended Ni/SiO2/Ti microstructure was also demonstrated.

Growth of ultrahigh density vertically aligned carbon nanotube forests for interconnects.

We present a general catalyst design to synthesize ultrahigh density, aligned forests of carbon nanotubes by cyclic deposition and annealing of catalyst thin films. This leads to nanotube forests with an area density of at least 10(13) cm(-2), over 1 order of magnitude higher than existing values, and close to the limit of a fully dense forest. The technique consists of cycles of ultrathin metal film deposition, annealing, and immobilization. These ultradense forests are needed to use carbon nanotubes as vias and interconnects in integrated circuits and thermal interface materials. Further density increase to 10(14) cm(-2) by reducing nanotube diameter is possible, and it is also applicable to nanowires.