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http://news.yahoo.com/s/nm/20110331/lf_nm_life/us_energy_hydrogen_fuel
By Stuart McDill – Thu Mar 31, 5:21 am ET
LONDON (Reuters Life!) – A new technology that allows hydrogen to be stored in a cheap and practical way, could make its widespread use as a carbon-free alternative to petrol a reality, according to its developers.
The technology is based on a new way of producing nano-fibers from hydrides, materials that soak up hydrogen like a sponge, and then encapsulating them in tiny plastic beads so small they behave like a liquid.
The process is being developed by Cella Energy, a spin-off from Britain's Rutherford Appleton Laboratory, who say that the technique allows hydrogen to be released at a much faster rate and at lower temperatures than before.
"What we've been doing is taking these materials and encasing them in plastic and making them into a very fine powder and that improves their properties," Cella Energy Chief Scientific Officer Stephen Bennington said. "It also means you can pump it like a fluid and it's safe. It is not gong to easily burst into flames," he said.
Hydrogen produces only water when its burned and is considered an ideal solution to cutting carbon emissions from petrol or diesel vehicles, which are estimated to cause 25 percent of all carbon release.
But until now, attempts to store hydrogen have not been consumer-friendly so this has not been a viable option. Cella Energy Ltd say their technology would allow people to use the carbon-free fuel with their existing car after a few modifications.
"You would pump it into your petrol tank of your car -- that would go off, be heated, drive the hydrogen off, which would go and run your vehicle and then the waste little beads that we have created you store in the car. And when you go and refuel your car you have two nozzles. One which puts in the new beads and one which takes out the old beads which goes off to be recycled and the hydrogen added to it again," Bennington said.
The development has been to turn hydrides into fibers or beads, 30 times smaller than a human hair, through a process of electro-spinning. This produces a white tissue-like material that can be controlled to capture and release hydrogen.
The encapsulation process protects the hydrides from oxygen and water, prolonging their life and making it possible to handle them safely in air and because it behaves like a liquid, current infrastructure will need minimal modification.
"You can use tankers to carry the material around," said Bennington. "You can take it to forecourts and then you can pump it into the vehicle and give the customer the same kind of experience they have now."
All part of the reason Cella Energy believe their process could herald a new era of carbon-free motoring.
"The experience that most people have now is using regular liquid fuels where it takes three minutes to fill your vehicle and then you can travel 300 miles," said Stephen Voller, Cella Energy's CEO. "Now you can have exactly the same experience with hydrogen but you can't have that experience with an electric car."
The company said hydrogen could be an economically viable alternative to fossil fuels if the gas is produced with renewable energy sources like wind or solar. It has three times more energy than petrol per unit of weight and could power cars, planes and other vehicles that currently use hydrocarbons.
It said it is also attracting interest from large established companies in the energy and transportation sectors.
(Editing by Paul Casciato)
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Cella Energy
Safe, low-cost hydrogen storage
Cella Energy Ltd makes safe, low-cost hydrogen storage materials. Our materials use nano-structuring to safely encapsulate hydrogen at ambient temperatures and pressures. This sidesteps the requirement for an expensive hydrogen infrastructure.
Cella Energy wins Shell Springboard Award 2011 See the video here
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http://www.cellaenergy.com/index.php?page=technology
Our technology
Complex chemical hydrides now exist that store hydrogen in concentrations that are well above 10 wt%. For example, ammonia-borane is 19.6 wt% hydrogen, 12 wt% of which is released at temperatures below 150°C. However, these materials have slow desorption kinetics and can release other chemicals such as ammonia or borazine which could poison a fuel cell.
Many are also difficult to handle in that they degrade rapidly in air. These issues can be solved using our nanotechnology.
Cella Energy has developed a method using a low-cost process called coaxial electrospinning or electrospraying. This traps a complex chemical hydride inside a nano-porous polymer, speeds up the kinetics of hydrogen desorption, reduces the temperature at which the desorption occurs and filters out many if not all of the damaging chemicals. It also protects the hydrides from oxygen and water, making it possible to handle it in air.
The coaxial electrospinning process that Cella uses is simple and industrially scalable, it can be used to create micron scale micro-fibres or micro-beads nano-porous polymers filled with the chemical hydride. Cella believes that this technology can produce an inexpensive, compound material that can be handled safely in air, operates at low pressures and temperatures and has sufficiently high hydrogen concentration and rapid desorption kinetics to be useful for transport applications.
Our current composite material uses ammonia borane NH3BH3 as the hydride and polystyrene as the polymer nano-scaffold. Ammonia borane in its normal state releases 12wt% of hydrogen at temperatures between 110°C and 150°C, but with very slow kinetics. In our materials the accessible hydrogen content is reduced to 6wt% but the temperature of operation is reduced so that it starts releasing hydrogen below 80°C and the kinetics are an order of magnitude faster. Although ideal for our proof-of-concept work and potentially useful for the initial demonstrator projects it is not currently a viable commercial material: it is expensive to make and cannot be easily re-hydrided or chemically recycled.
Cella is now working on other hydride materials, these have slightly lower hydrogen contents but it is possible to cycle them into the hydride phase many hundreds of times and we are encapsulating these in hydrogen permeable high-temperature polymers based on polyimide.
Use of the technology
There are two ways to use these materials:
Pure hydrogen solution Zero carbon emissions
as a way of storing and delivering hydrogen safely for use in an internal combustion engine or a fuel cell
Fuel additive Lower carbon emissions
For use as a fuel additive to reduce the carbon emissions from a hydrocarbon fuel such as gasoline, diesel, JP-8, jet-fuel or kerosene
Pure hydrogen solution, how it would work in a vehicle
Cella can manufacture the materials in the form of micron-sized beads. This makes it possible to move the beads like a fluid. This opens up a number of opportunities:
It is no longer necessary to try and rehydrogenate the material within the vehicle. For most hydrogen storage materials this releases megajoules of energy. If the refuelling is to be done in a few minutes, this requires cooling to remove several hundred kilowatts of power. To facilitate rehydrogenation in the 3-4 minutes that the DOE targets stipulate, the thermodynamics require high temperatures and pressures of around 100bar. This requires substantial engineering and as such we don't believe that on-car rehydrogenation is reasonable. With a fluidized hydride, it is possible to quickly fill or remove the material from the vehicle so that it can be recycled or rehydrided elsewhere.
It is possible to move the material within the vehicle making it possible to separate the storage from thermolysis. A schematic for the kind of idea that we have to achieve this is shown in figure 1. The beads are stored in a fuel tank, which does not need to contain high pressures or be heated and cooled, therefore it can be a simple lightweight plastic tank of complex shape similar to that used in current vehicles. The hydride beads are then pumped to a hot cell where waste heat from the engine exhaust is used to drive the hydrogen into a small buffer volume. The hydrogen buffer is maintained at a pressure suitable for the internal combustion engine ICE or fuel cell and which is sufficient in volume to be able to restart the vehicle. Once the hydride has been heated and the hydrogen driven off, the waste beads are stored in another lightweight plastic tank.
Since the material is removed from the vehicle, large scale chemical recycling routes are available to regenerate the hydride, making a wider range of potential hydrides available.
As the thermolysis, hydride regeneration and storage functions are now separated it is possible to keep the system weight to a minimum.
Pure hydrogen solution, how it would work in a vehicle
There is also the possibility to make encapsulated hydrides that can be added to hydrocarbon fuels to reduce the emission of carbon dioxide CO2. The encapsulation makes it possible to suspend the hydride in the fuel and stops it degrading or making the suspension dangerously pyrophoric.
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(if you having troubles, try posting your comment on this page or send an email to chronicle @ itbhuglobal.org)Institute of Technology, Banaras Hindu University
Varanasi 221005, UP