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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