Metal Hydrides
Powders of certain metal alloys, under certain conditions, form relatively loose chemical
bonds with hydrogen, permitting them to act as ‘sponges’ for the gas. In theory, these metal
hydrides appear to be the idea storage medium for hydrogen as they permit the storage of
relatively large volumes of gas in a relatively small volume and yet at comparatively modest
pressures (30% atmospheres or 435 psi), and with relatively good energy efficiency. For
example, certain metal hydrides store 80% or so hydrogen in the same volume as liquid
hydrogen without the associated challenges of ultra-cold temperatures.
Unfortunately, most metal hydrides are rather dense, and the weight of hydrogen stored is
only 2% of the weight of the metal hydride. Therefore, while a metal hydride storage system
capable of carrying 5 kg of hydrogen would only occupy around 90 litres, it would weigh
around 575 kg (over 1,200 pounds) not counting the pressure tank.
Hydrides based on alkali metals have considerably better energy densities, and can deliver
about 5% of the combined weight of reactants in hydrogen. In other words, 5 kg of hydrogen
could be produced from just under 100 kg of alkali hydride and water, which is a weight not
much different from that of a full fuel tank of gasoline in a small truck. Unfortunately, the
process of storing hydrogen in alkali hydrides is not very energy efficient. The process
requires around 60% more energy than that which can be extracted from the resultant hydrides.
While the efficiency of alkali hydrides storage appears to be less than that for compressed or
liquid hydrogen, this may be offset by the relatively simple storage systems required to hold
the product, and the inherent losses associated with storing cryogenic or compressed hydrogen.
Some schemes for using alkali hydride storage propose refueling by simply loading a
new set of fuel canisters, which are transported back to the manufacturers for recharging. The
change out process, which could be automated, would probably speed the refuelling process
considerably, and is one of the main drawbacks to gaseous storage.
The "hydrogen" is stored at ambient conditions in a non-flammable liquid "fuel" - an aqueous solution of sodium borohydride, NaBH4. Sodium borohydride is made from borax, a material that is found in substantial natural reserves globally. The process supplies pure hydrogen for energy applications without the need (and associated energy penalties) for compression or liquefaction. Hydrogen produced by this system can be used for numerous applications, addressing a wide range of power requirements.
Last night I was at a lecture by Dr. Ballard, CEO of Ballard Power Systems who are giving fuel cells their damndest try. The key points of his hour long lecture (skipping the technical details) were:
(* points are the most important)
-Moving to a hydricity (hydrogen/electricity) economy lets you use a multiplicity of primary energy sources. Right now, oil HAS to be the original energy resource. By under hydricity you can generate the power any way you want, according to your country's strengths.
-There are (at least) 5 basic fuel cell models. But, I took a quick look at this chart, only about 2, maybe 3 could be used as vehicles. Some were power plant-only, if anything (run over 1000°C and has a minimum constant output).
-Hydrogen, like oil, lets you scale power and energy. So you can have a big tank and a weak engine, or a large engine and a small tank, whatever you need. This is a plus for marketing
*He doesn't believe the corner gas station is going to set up the hydrogen infrastructure. There's a catch 22: no one will make any profit setting it up without hydrogen cars to service, and no one will make cars unless there is a NETWORK. Who'll buy a car if they can only fill it up at one place?
His plan right now is to try and sell hydrogen forklifts to "big-box" companies like Walmart and Target, with gigantic shipping yards. They can do it in a way that will save money. Then, once every gigant shipping yard has a hydrogen pump, try and get a few big rig trucks to switch (2% of the vehicles in LA produce 60% of the pollution: the giant shipping trucks). Start with niche markets like that. Then, once the automakers see this network in place, they can offer cars, get Walrmart to retool the pumps for cars and sell it, and we beat the catch 22.
*In order to be economical, the technology has to drop at least an order of magnitude in price. Drop from ~$500/kW to...well most people will tell you under $50/kW, but it's really under $37. Or, to look at it another way, you need to get $0.01/kWh, and we can't do much better then $10.
He doesn't believe "economies of scale" and incrementally improving our current designs will work: if you run the numbers, you can't even buy the raw materials by the parking lot load, magically turn them into product for free, and sell them at no cost while still beating the price for the family car. You cannot put a car onto the streets of America without a totally new engine geometry: a "quantum leap" in the technology. Every major automaker in the world is trying.
-Public cars will be the last thing to get fuel cells. They've got to be proven safe. I mean, just think about recalling a 1000s of cars when you accidentally misplace a bolt on an engine or screw up a tire, even though normal cars are century-old technology. Not gonna happen for awhile
-By the third generation of technology (out kids, grandkids?), you should be able to just go home and plug you car into the grid to fuel it for the next day. Or, in a power outtage plug the car in to power your house. Or drive to the cottage, run it a week from just your car (no power lines), and drive home.
*Where will the hydrogen come from? Realistically, water cracking with nuclear power is the only way that makes sense to him. Nothing else can do it on the incredible scales needed.
-Trend prediction is usually impossible, so "you can be sure what I'm telling you will end up wrong." Life doesn't follow a linear projection
Oh, and just out of interest, he actually studied as a geological engineer and did his thesis on volcanoes, so, you never know where you'll go in this world.
For example, nuclear Plant Hatch in Georgia withdraws an average of 57 million gallons per day from the Altamaha River and actually "consumes" 33 million gallons per day, lost primarily as water vapor, according to the U.S. Nuclear Regulatory Commission.
Aaron wrote:If we accept cracking seawater for hydrogen,
OilBurner wrote:Devil, I'd be interested to see those calculations and I guess others might too.
How about popping them up on here?
Thanks.
Really? Are there currently any Hydrogen powered airplane, trains, ships, submarines, electrical generators, tractors, semis, bulldozers, and other modern machines besides the personal horseless carriage in existence? Will hydrogen make a feedstock for plastics? Will Hydrogen be able to be fuel for camping lights? Can I use hydrogen in my camping stove? Can I use hydrogen to produce Nitrogen to use in fertilizers when it is 6 elements away? Can I use Hydrogen to fuel my lighter so I don't have to quit smoking and also have a portable source of fire? Can hydrogen heat my house like LNG can? Can I cook with Hydrogen? Can I use Hydrogen to lubricate a squeaky hinge? Can I use Hydrogen for a lubricant in my car? Can I as easily transport Hydrogen in a 5 gallon jug for possibly 1000's of miles like I can with oil based products? Is Hydrogen as dense in energy as oil is? Can Hydrogen be a complete solution to all uses that petroleum has?
Dustin wrote:
Technical Problems aside, like storage and cooling and production, it makes a decent energy carrier.
Don't say wind and solar panels, because electrolysers need to work at 100% capacity 24/7/52 to remain efficient.
fecteau wrote:Devil wrote:Don't say wind and solar panels, because electrolysers need to work at 100% capacity 24/7/52 to remain efficient.
Not according to Stuart Energy (http://www.stuartenergy.com/main_our_products.html), one of the leading producer of Hydrogen infrastructure. Their hydrogen generation is suitable for production from wind farms.
Devil wrote:
I didn't say it wouldn't produce H2. I said it would do it efficiently only if run at full capacity 24/7/52, which is true.
Sorry, Aaron, but seawater, per se, is unsuitable for hydrogen generation: you will get a lot of caustic soda and chlorine (so much you couldn't use it!) but precious little hydrogen. Sodium chloride dissociates preferentially to dihydrogen monoxide.
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