Track your comments!
[x]


When you register, comments on your articles and replies to your comments appear here. Register Now!

Sign in to your account
[x]

Not a Scientific Blogging member yet?

Register Now for a Free Scientificblogging.com Account

  • Customize your profile with pictures, banner, a blogroll and more.
  • Leave comments on articles, add other members to your friend lists, chat with people on the site.
  • Write blog posts that can be seen by hundreds of thousands of readers.

It's free and it only takes a minute!

Already a Scientific Blogging member?

Sign In Now

Banner
By News Staff | August 22nd 2007 07:50 AM | 2 comments | Track Comments
Hydrogen is an interesting idea for a clean, renewable fuel but storage and refueling issues present challenges. A new and attractive storage medium being developed by Pacific Northwest National Laboratory scientists may provide the “power of pellets” to fuel future transportation needs.

The Department of Energy’s Chemical Hydrogen Storage Center of Excellence is investigating a hydrogen storage medium that holds promise in meeting long-term targets for transportation use. As part of the center, PNNL scientists are using solid ammonia borane, or AB, compressed into small pellets to serve as a hydrogen storage material. Each milliliter of AB weighs about three-quarters of a gram and harbors up to 1.8 liters of hydrogen. Researchers expect that a fuel system using small AB pellets will occupy less space and be lighter in weight than systems using pressurized hydrogen gas, thus enabling fuel cell vehicles to have room, range and performance comparable to today’s automobiles.



“With this new understanding and our improved methods in working with ammonia borane,” said PNNL scientist Dave Heldebrant, “we’re making positive strides in developing a viable storage medium to provide reliable, environmentally friendly hydrogen power generation for future transportation needs.”

A small pellet of solid ammonia borane (240 mg), as shown, is capable of storing relatively large quantities of hydrogen (0.5 liter) in a very small volume.

PNNL scientists are learning to manipulate the release of hydrogen from AB at predictable rates. By varying temperature and manipulating AB feed rates to a reactor, researchers envision controlling the production of hydrogen and thus fuel cell power, much like a gas pedal regulates fuel to a car’s combustion engine.

“Once hydrogen from the storage material is depleted, the AB pellets must be safely and effi ciently regenerated by way of chemical processing,” said PNNL scientist Don Camaioni. “This ‘refueling’ method requires chemically digesting or breaking down the solid spent fuel into chemicals that can be recycled back to AB with hydrogen.”

Comments

Why not pelletize Methane which is reformed off Natural Gas derived from a Coal source so that it can fuel a furnace by shooting the pellets into the furnace to produce steam, collecting the pellets each day from a vehicle would make the distribution to a collection point ever so useful when a fleet of ten or more taxi cabs or a truck fleet contributes to the pellet distribution. If and when a Methane Fuel-Cell is provisioned this pellet form would then be like a Hydrogen form for refueling issues. Creating small frozen pellets would enable petri dish storage in cylinders and through automation these are extracted one at a time. Even a donut style would suffice better. Ammonia Fuel Density: 0.604 g/cc Fuel Freezing Point: -78 deg C Fuel Boiling Point: -33 deg C Ammonia is toxic, and will dissolve easily in water Ammonia does form flammable and explosive mixtures with air Anhydrous Synthetic Ammonia is cheap per ton Liquid Oxygen as a Oxidizer Oxidizer Density: 1.140 g/cc Oxidizer Freezing Point: -219 deg C Oxidizer Boiling Point: -183 deg C LOX is obtained from air by fractional distillation LOX is stable but mixtures of fuel and LOX are shock-sensitive fuel vapours that can be exploded by static electricity, electric spark, or flame. Cryogenic not suitable for military uses where storage of the fuelled missile and quick launch are required See the United States by Military Specification MIL-P-25508 Rocket Engines are not allowed on Americas highways, classified as illegal. Ammonium Hydroxide is Severely Poisonous, may be fatal if swallowed or inhaled (higher concentrations can cause burns, pulmonary edema and death), and vapor causes burns to every area it is exposed to, Extremely Corrosive with a rating of 4. Hydrocyanic Acid (or "Hydrogen Cyandide") (HCN) can be commercially produced by reacting Ammonia with Natural Gas (Methane) and an Oxygen-containing gas at an elevated temperature in a converter in the presence of a suitable catalyst. The exit gas from the converter contains unreacted Ammonia together with small amounts of Oxalic Acid and Formic Acid (or precursors of Oxalic Acid and Formic Acid). The Oxalic Acid and Formic Acid end up in the aqueous solution, where they are converted to oxalates and formates. A concentration of oxalate greater than 1% and a concentration of formate greater than 3% are undesirable causing a overhead expense to purge it. The oxalate and formate compounds present in the ammonium phosphate solution are continuously decomposed to carbon dioxide and hydrogen using electrochemical cell. Decreasing the concentrations of formate and oxalate compounds should enable the use of increased concentrations of ammonium phosphate in the ammonium phosphate solutions, and hence an increase in the capacity of the process. A Rocket Engine use was for the XLR-99, USAF Rocket Engine First Stages and is Out of production. The X-15 Rocket Engine use as first stage options were, Bell XLR81-BA-1, Aerojet XLR73-AJ-1, and the Reaction Motors XLR30-RM-2 while the XLR30 rocket engine to be inadequate and a new design was initiated and designated as the XLR99-RM-1 Rocket Engine. The XLR-99 was used in the X-15 manned research rocketplane. The X-15A improved the version in a stage two engine use, while the X-15A-2 added another stage for the LOX/Ammonia use in the improved XLR99. The LR30 Rocket Engine was cancelled in favor of the XLR99. The flow rate of more than 4,500 kg per minute for both propellants were liquid oxygen (LOX) and Anhydrous Ammonia. XLR-99, USAF Thrust(vac) = 262.400 kN Thrust(sl) kN = 227.300 Isp = 276 sec Isp (sl) = 239 sec Designed for = First Stages Status = Out of production
Just a bit of an issue here. I am no expert, but I just wanted to point out no matter how you look at it, any fuel must be a reactive substance in some way or another and therefore not safe and neutral. Whether it is corrosive, flammable, poisonous, whatever, is a given. To criticise the pellets for this reason is unfair, as surely, it won't be healthy to swallow gasoline or diesel either, would it? inert substances just do not make good fuel, sadly.

Add a comment

The content of this field is kept private and will not be shown publicly.
  • Allowed HTML tags: <sup> <sub> <a> <em> <strong> <center> <cite> <code> <TH><ul> <ol> <li> <dl> <dt> <dd> <img> <br> <p> <blockquote> <strike> <object> <param> <embed> <del> <pre> <b> <i> <table> <tbody> <div> <tr> <td> <h1> <h2> <h3> <h4> <h5> <h6> <hr> <iframe>
  • Lines and paragraphs break automatically.
  • Web page addresses and e-mail addresses turn into links automatically.

More information about formatting options

CAPTCHA
If you register, you will never be bothered to prove you are human again.
Image CAPTCHA
Copy the characters (respecting upper/lower case) from the image.