Sunday, October 30, 2011

Hydrogen SOFC Cells: UAV and future Unmanned submarines, Transport

There is an ever increasing need for  stealthy underwater platforms, unmanned underwater vehicles, ocean research vessels, and mobile counter measure devices.  Hence a need for much quieter and almost undetectable emissions of all types.  There's also a move for all-electric platform concepts for improved underwater fishing. Storing and underwater batteries both for life-saving mechanisms.

The fuel cell integrated into micro UAV designed by two US aerospace research laboratories and with NASA support (Dryden Flight Research Center, US Air Force Scientific Research, National Science Foundation set a new micro-UAV flight distance of 78 miles. 

The flight record was achieved using only 25% of the hydrogen tank capacity stored-on-board the UAV.  The ultra-compact fuel cell propulsion system creates high efficiencyy electrical power by reacting hydrogen and  oxygen from the air without combustion. The Fuel Cells enable longer flight times, quieter operation, less heat signature, and higher reliability than batteries other methods of propulsion for many UAV'

  • A new process is being tested by chemical engineers of Purdue University to get high hydrogen production at fuel-cell temperature-level with no catalyst use. This is full of promise for vehicles powered by hydrogen and other portable electronic items like dig-cams, medical diagnostic devices, defibrillators, cell phones and notebook computers. The research funded by US Department of Energy is ushering in a new process.
  • A team of researchers at the Harvard School of Engineering and Applied Sciences that is headed by Sriram Ramanathan is working on developing fuel cells. If Ramanathan is to be believed, the solid-oxide fuel cells the visionary and specialist in the field is making along with other scientists, will become a highly sought after technology in days to come. How will solid-oxide fuel cells be generated? The solid-oxide fuel cells that are capable of replacing fossil fuel with pollution less fuel are generated with the use of the plentiful fuel resources and low operating temperatures, along with some material that is of low cost, and some other small devices.
Hydrogen Fuel Catalysts

Hydrogen has great potential as a fuel of future because it is an environmentally clean energy fuel and save us from the undesirable side effects of greenhouse gases. Before becoming it a fuel of the masses we need necessary infrastructure to store it and move it. We will also need fuel cells on economical scale. To make hydrogen as a popular alternative fuel some engineers are working on storage factor of hydrogen fuel. They don’t want compressed hydrogen into a tank. They want to store hydrogen fuel into a large molecule. When we want hydrogen out of the molecule we will need a catalyst. Now, researchers have new details about one such catalyst.

New Low cost hydrogen fuel cell theory:

Source of power can be classed into either power generation or energy storage devices. Nuclear submarine (SSN) to cite an example has three power sources. Primary power source is from Nuclear steam raising plant (NSRP); auxiliary power source comes from Diesel generator; Emergency energy storage uses Lead acid battery.

Fuel cells convert a fuel and an oxidant directly into electricity by an electrochemical process, which in theory, up to 100% efficient. Practical limitations lower the fuel cells efficiency typically between 40% and 65%.  The basic fuel cell stack has no moving parts, can generate silently with least maintenance and a long life.

Solid oxide fuel cells operate at high temperatures (c-750-1000 degrees C) using ceramic materials as electrolyte and electrodes.  Utility power generators and naval applications,  uses hydrocarbon fuel directly by internal reformation to hydrogen and carbon dioxide and by direct oxidation. Alkaline fuel cells have been developed in space and automotive applications. Alkaline electrolyte has found uses on submarine in conjunction with direct liquid fuel.

PEMFC  PROTON EXCHANGE MEMBRANE FUEL CELL:  This technology has the greatest potential for submarine applications since it offers gravimetric and volumetric power density (better than 700W/kg and 1100 W/dm3) and operates at up to 80 degree C  with instant start up. The heart of the fuel stack is the membrane-electrode assembly.

METAL-OXIDANT SEMI FUEL CELLS:  Aluminum-oxygen systems are currently in use in the US UUV power.  Asystem has been developed by alupower which uses oxygen stored as a compressed gas and has energy density of 265 Wh/kg and per litre. The developers of the ARCS power source have a specific energy density of 400Wk/g for an aluminum-oxygen system using hydrogen peroxide as the oxidant. Magnesium-hydrogen peroxide system has specific target of 550 Wh/kg currently used by UUv's.

Of the newest AIP power generator, the proto exchange membrane fuel cell (PEMFC) is the most fuel efficient for all sizes of platform. The ideal fuel option would be hydrogen stored in a reversible metal hydride or in compressed form using advance high performing composite cylinder. Carbon nanofibre, aluminum, magnesium or lithium  could be explored and attractive than hydrogen.

Soon we would be using integrated, hybrid, air-independent propulsion system in a full electric architecture for littoral operations and submerged platforms. Its quiet and powerful.

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