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January 26, 2011

UK Cella Energy develops hydrogen based fuel in microbeads that can lead to US$1.50 per gallon fuel compatible with existing cars

 UK-based Cella Energy has developed a synthetic fuel that could lead to US$1.50 per gallon gasoline. It is hydrogen based fuel and produces no carbon emissions when burned. The technology is based on complex hydrides, and has been developed over a four year top secret program at the prestigious Rutherford Appleton Laboratory near Oxford. Early indications are that the fuel can be used in existing internal combustion engined vehicles without engine modification. Cella can manufacture the materials in the form of micron-sized beads it is possible to move the beads like a fluid. It looks a practical way to introduce hydrogen fuels that is mostly compatible with existing engines and fuel service station infrastructure.

UPDATE : EADS (Airbus) is working on a conductive storage system for hydrogen

Liquid hydrogen has a specific energy density of about 143MJ/Kg (megajoules per kilogram) compared to regular jet-fuel or kerosene at about 43MJ/Kg. This has big potential for rockets and airplanes and for military applications. Liquid hydrogen is very cold, and has to be stored at -253°C(-423°F). This means keep rockets on launch pads on standby is technically difficult and expensive. Cella's hydrogen micro-beads are also a liquid hydrogen fuel but can be stored at normal temperatures. This means rockets can be kept on permanent stand-by at significantly reduced cost. So the beads would not be used in the rockets since they 6% hydrogen but for safer and cheaper storage.

Cella Energy uses the benefits of nano-structuring to encase hydrides using coaxial electrospinning. Cella Energy replaces the high pressure cylinders with a conventional shaped fuel tank that can be more easily packaged within an existing vehicle chassis design. Refuelling takes place form a regular fuel pump and requires no high pressure or very-low temperatures. This fits easily within the existing refueling infrastructure and means hydrogen could be provided for a billion existing road vehicles immediately.




Cella Energy have developed a method using a low-cost process called coaxial electrospinning or electrospraying that can trap a complex chemical hydride inside a nano-porous polymer that 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 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 for Zero carbon emissions or as a fuel additive.

The pure hydrogen solution is a way of storing and delivering hydrogen safely for use in an internal combustion engine or a fuel cell.

Fuel additive for 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 we can manufacture the materials in the form of micron-sized beads it is 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.

Some Calculations from Nextbigfuture reader Goatguy


   FIGURE COMPONENT         COMMENT
--------- ----------------- ---------------------------
    147.0 MJ/kg             Hydrogen gas
      6.0 kg                in Test vehicle
    882.0 = MJ              in Test vehicle
    431.0 mi/6kg            of driving test
      2.0 = MJ/mile         …yielded
--------- ----------------- ---------------------------
 67,200.0 L of H2           @STP (300K, 14.2PSI)
     96.0 L of H2           @ 10,000 psi
     24.8 gal               @ 10,000 psi
      80%                   gas-in-tank volume
     31.0 gal               of gas bottles
--------- ----------------- ---------------------------
  3,000.0 mol H2            converting kg to moles
    750.0 mol CH4 to make   assuming 4:1 mol production
     12.0 kg CH4            therefore…
 50,700.0 BTU/kg            looked up for methane
608,400.0 BTU/load          therefore…
    $8.50 per 1,000,000 BTU looked up 2008, new england
    $5.17 for methane       therefore…

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