Technical, environmental and exergetic aspects of hydrogen energy systems

This thesis deals with airplanes using solar energy as their only source of energy for more than 24 hours flight. Using solar panels, they collect it during the day for immediate use but also store the remaining part for the night flight. This work presents a new analytical methodology for the conceptual design of such airplane. Its major advantage lies in the fact that it is simple and versatile, which makes it applicable to a large range of airplanes of different wingspans, from the small MAV to the large manned aircraft. The design methodology is based on power and mass balances occurring during level flight. An extensive study was done on the mathematical modeling of the subparts, for example concerning electric motors the question being to know how their mass and their efficiency vary with power. Empirical data over a large range were used in this study. Finally, the analytical method contains 5 mission parameters and 25 others linked to the various technologies involved that the user can vary in order to see on a graph the dependencies between the 3 layout variables (aspect ratio, wingspan and total mass) for all the feasible solutions. The final selection can then be easily made. Sky-Sailor, a 3.2 meters wingspan solar powered airplane, was then designed using this methodology. A prototype, with an ultra lightweight structure covered by silicon solar cells was built in order to validate the process. We also developed in this framework dedicated electronics for the autonomous navigation and the efficient solar power management. The final 2.44 kg airplane was tested with success during several autonomous flights, showing capabilities that were very close to the one calculated in theory. The longest flight achieved lasted more than 27 hours within a circuit length of more than 874 kilometers and proved the feasibility of solar powered continuous flight. In addition to the first application example on Sky-Sailor, other designs are presented and discussed, like the case of a 70 cm solar UAV but also a 60 m manned solar airplane. It is then very interesting to see how things evolve with scaling. In fact, going in each direction removes and adds its batch of

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Design of Solar Powered Airplanes for Continuous Flight

A microprocessor packaging architecture using a modular circuit board assembly that provides power to a microprocessor while also providing for integrated thermal and electromagnetic interference (EMI) is disclosed. The modular circuit board assembly comprises a substrate, having a component mounted thereon, a circuit board, including a circuit for supplying power to the component, and at least one conductive interconnect device disposed between the substrate and the circuit board, the conductive interconnect device configured to electrically couple the circuit to the component.

Method and apparatus for providing power to a microprocessor with integrated thermal and EMI management

An electrically powered device includes a shell, and a battery integrated with the shell. The electrically powered device also includes a trace, and a site adapted to receive an electrically powered component, wherein the battery, the trace and the electrically powered component form a portion of a circuit. The electrically shell may be a portion of an enclosure. The battery is formed within the shell and may be comprised of one or a plurality of deposited layers.

Device enclosures and devices with integrated battery

High thermal conductivity composite of diamond particles with tungsten coating in a copper matrix for heat sink application

A method for fabricating polycrystalline thin films on low-temperature (or high-temperature) substrates which uses processing temperatures that are low enough to avoid damage to the substrate, and then transiently heating select layers of the thin films with at least one pulse of a laser or other homogenized beam source. The pulse length is selected so that the layers of interest are transiently heated to a temperature which allows recrystallization and/or dopant activation while maintaining the substrate at a temperature which is sufficiently low to avoid damage to the substrate. This method is particularly applicable in the fabrication of solar cells.

Fabrication of polycrystalline thin films by pulsed laser processing

Unitized regenerative fuel cells for solar rechargeable aircraft and zero emission vehicles

A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper The composite material can be fabricated in small or relatively large sizes using inexpensive materials The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost

Composite material having high thermal conductivity and process for fabricating same

High power density electronic components such as fast microprocessors and power semiconductors must operate below the maximum rated device junction temperature to ensure reliability. function temperatures are determined by the amount of heat generated and the thermal resistance from junction to the ambient thermal environment. Two of the Largest contributions to this thermal resistance are the die attach interface and the package base. A decrease in these resistances can allow increased component packing density in MCMs, reduction of heat sink volume in tightly packed systems, enable the use of higher performance circuit components, and improve reliability. The substrate for high power density devices is the primary thermal link between the junctions and the heat sink. Present high power multichip modules and single chip packages use substrate materials such as silicon nitride or copper tungsten that have thermal conductivity in the range of 200 W/mK. We have developed Dymalloy, a copper-diamond composite, that has a thermal conductivity of 420 W/mK and an adjustable coefficient of thermal expansion, nominally 5.5 ppm/C at 25 C, compatible with silicon and gallium arsenide. Because of the matched coefficient of thermal expansion it is possible to use low thermal resistance hard die attach methods. Dymalloy is a composite material made using micron size Type I diamond powder that has a published thermal conductivity of 600 to 1000 W/mK in a metal matrix that has a thermal conductivity of 350 W/mK. The region of chemical bonding between the matrix material and diamond is limited to approximately 1000 A to maintain a high effective thermal conductivity for the composite. The material may be fabricated in near net shapes. Besides having exceptional thermal properties, the mechanical properties of this material also make it an attractive candidate as an electronic component substrate material.

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Dymalloy: A composite substrate for high power density electronic components

A reusable grinding tool consisting of a replaceable single layer of abrasive particles intimately bonded to a precisely configured tool substrate, and a process for manufacturing the grinding tool. The tool substrate may be ceramic or metal and the abrasive particles are preferably diamond, but may be cubic boron nitride. The manufacturing process involves: coating a configured tool substrate with layers of metals, such as titanium, copper and titanium, by physical vapor deposition (PVD); applying the abrasive particles to the coated surface by a slurry technique; and brazing the abrasive particles to the tool substrate by alloying the metal layers. The precision control of the composition and thickness of the metal layers enables the bonding of a single layer or several layers of micron size abrasive particles to the tool surface. By the incorporation of an easily dissolved metal layer in the composition such allows the removal and replacement of the abrasive particles, thereby providing a process for replenishing a precisely machined grinding tool with fine abrasive particles, thus greatly reducing costs as compared to replacing expensive grinding tools.

Nicholas J. Colella

Papers

Fabrication of polycrystalline thin films by pulsed laser processing

Unitized regenerative fuel cells for solar rechargeable aircraft and zero emission vehicles

Composite material having high thermal conductivity and process for fabricating same

Dymalloy: A composite substrate for high power density electronic components

Precision replenishable grinding tool and manufacturing process