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Creating Hydrogen With (Very) Hot Water
carbonman writes "NYTimes is reporting that a public-private research team will announce on Monday that they have discovered a new technique to produce pure hydrogen that is far more efficient than conventional methods. The advance could be a significant development in attempts to realize the dream of the hydrogen economy in taking gasoline-powered vehicles off the road, and without releasing carbon dioxide emissions that are linked to climate change. It does, however, require the use of advanced high-temperature nuclear reactors, none of which have been built on a production scale before."
swiftstream adds a link to the same story at the no-reg Indianapolis Star, and summarizes the method as "electrolysis of very, very hot water."
A pot of boiling water on your stove will probably not reach a higher temperature. This is because of the surrounding air pressure. If they put this in a closed system like a "pressure cooker", it could get hotter.
That's why a pressure cooker works faster than an open pot. The increased pressure allows the water to boil at a higher temperature.
Is it just me or water can't be very very hot? At about 100 degrees Celcius, it vaporize...
Yes it does at standard temperature and pressure. If you were to increase the pressure it would require a higher temperature to vaporize, just as lower pressures require lower temperatures.
Water can be superheated as much as you please, it simply has to be at a high enough pressure. Past water's critical point (about 650 K and 22 MPa), it becomes a supercritical vapor, indistinguishable from liquid or vapor. Additionally, the boundary between liquid and gas dissapears, and the properties of the substance are somewhat different.
Already invented:
Mini nuclear reactor could power apartment blocks
A nuclear reactor designed to generate power in the basement of an apartment block is being developed in Japan
It has been known for some time that blowing hot steam across coke results in hydrogen, which is how most commercial hydrogen is made.
Here's the reaction
Generation IV Nuclear Reactors
Very high-temperature gas reactors. These are graphite-moderated, helium-cooled reactors, based on substantial experience . The core can be built of prismatic blocks such as the Japanese HTTR and the GTMHR under development by General Atomics and others in Russia, or it may be pebble bed such as the Chinese HTR-10 and the PBMR under development in South Africa, with international partners. Outlet temperature of 1000C enables thermochemical hydrogen production via an intermediate heat exchanger, with electricity cogeneration, or direct high-efficiency driving of a gas turbine (Brayton cycle). There is some flexibility in fuels, but no recycle. Modules of 600 MW thermal are envisaged
The fellas at Ballard Power Systems seem to have an interesting vision in this regard. (I'm trying to recall what I heard on a CBC interview with one of the company's founders, so what I describe here may be partly my own fabrication). Anyway, they describe an electrical grid in which individual cars help generate and store electricity for the entire system. Something about micro power plants. You may choose to sell your power to the grid (when your car is unused), benefitting from the current market price of the power. Similarly, you can purchase electricity and store it in your car (in hydrogen form) hopefully taking advantage of a cheap power rate. Buy low, sell high. Anyway it all seems very interesting to me, an idea of millions of micro power plants contributing to the greater power grid. One big distributed storage and generation system, probably better at absorbing peak power demands too -- you see that it's 1 pm on a hot summer day and the grid will pay big $$ for your power, you take advantage of that.
This isn't really correct - although pretty much all the power reactors in the USA are water cooled (primarily due to the Navy's interest is nuclear propulsion), there are plenty of gas cooled reactors elsewhere. Most of our (Britain's) nuclear generating capacity is from either AGR (Advanced Gas-cooled Reactors) or Magnox (named after the Mg-alloy fuel can) reactors, both of which use carbon dioxide as the coolant.
So, the technology may be new to the USA, but there's are wealth of knowledge on designing and running these reactors elsewhere in the world.
Oh yes, they're arguably quite a bit safer than PWRs as well!
I assume you also have touched a cup of microwaved H2o and had it instantly boil over on your hand.
It's an interesting apparent contridiction because the water seems already hot enough to boil, yet it does't until the container is moved.
Anyone care to explain why this is?
To vaporize, water needs something to form a steam bubble around. Coffee grounds, sugar, or ridges on a metal pot will work for this. But, if you heat up pure water in a smooth ceramic cup in the microwave, there isn't anything to induce it to form steam. Thus, when you spoon that instant coffee in, it explodes.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
There were interstate oil pipelines completed or under construction before World War II. U-Boat attacks on coastal tankers accelerated the process. Today, there are 200,000 miles of oil pipelines and 2/3 of US oil is transported by pipeline. Houston to New York, the cost is about $1 a barrel, or 2 1/2 cents a gallon at retail. Association of Oil Pipelines
Nuclear plants are built in places where the conditions are right. Primarily where there is a large source of water for cooling. Usualy big lakes or rivers, sometimes oceans. You need a massive amount of water to keap them going without killing all the fish and such in the water source when the hot water is dumped back in.
Since the location of plants is defined by water, it tends to put them in the same regions where cities grew up, next to lakes and rivers. They try to put them in isolated spots, but by the nature of things, areas around them grow up.
You can't put them in the middle of nebraska cause they don't have a place to get anough water for cooling. Also you want your powersource near the place of use to eliminate losses.
Besides, their is nothing wrong with nuke plants in ones back yard, i would be perfectly happy with such a thing. Far better then any coal plant or similar. It's nuclear, their is nothing to fear, unless you are one with that bizare fear that something that is glassified then incased in indestructable storage containers that are then moved to remote areas has even a remote chance of ever harming you.
Has everyone forgotten the Three Mile Island and Hindenburg accidents?
Hmm... an incident (TMI) that happened over a quarter century ago? Another that happened 67 years ago? We've come a long way since these incidents. That's what progress is all about; living and learnign and USING this new knowledge for a better system.
And how is the hydrogen fuel to be transported?
With the use of the Texaco Ovonic Hydrogen Systems metal hydride containment units. It creates a stable form of hydrogen. The US DoT has already approved the system.
I'm afraid we'd be inviting disaster and a sitting target for terrorists.
These same circumstances exist today. We're not creating a new hazard.
(nucular for Dubya types)
This is a fairly wise remark from someone who seems to have posted before they sat and really given any thought on the subject. This is what's called a knee jerk reaction.
Dedicated Cthulhu Cultist since 4523 BC.
I don't think it's that hard actually.
While I can't verify the temperature that the water was at, I had an incident this weekend that indicates this super-heating is not too difficult.
I put a 2 cup pyrex measuring cup in a microwave for about 2.5 minutes. The water appeared very calm and didn't have any bubbles. But as soon as I dropped my tea-bag into the cup, the water flared up and began to boil very vigorously for a few seconds.
The water was filtered drinking water from Walmart, and the pyrex was only cleaned with tap-water (rather "hard" water) and soap.
The 300MW is the net amount of electricity that the reactor produces, not the amount of fuel that was put in. So, a fuel input rate of 600MW and a 50% efficient reactor would produce either 300MW of net electricity or 2.5 kg/s of H2. Basically, they're saying that the efficiency of producing H2 is the same as the efficiency of producing electricity. They are NOT simply using the electricity coming out of the reactor to directly produce H2. The efficiency gains come from using the waste heat of the reactor.
These "spots" of super heated water occur around what are called black smokers. The magma, or more accurately, mantle, is drawn up at mid ocean ridges due to the top-cooled convection of which plate tectonics is a direct result.
Mid Ocean Ridges rarely heat water beyond 400 degress C, but even so there could be potential there, since it's already heated to a great degree, requiring less energy investment. Plus, there's tens of thousands of kms worth of MORs on Earth.
Looks can be deceiving. Or CAN they?
polar h20 molecules are flipped or spun as the microwave passes by them. because the em field emparts energy into the molecules, they can contain enough energy to phase shift. Think about covering a gym floor with basket balls so that none are touching. Then somehow make every ball spin at 10000 rpm. At first the balls would continue to sit on the floor spinning really fast. They have a ton of energy, but are still floor balls. Then a single ball is nudged into it's neighbor. Suddenly a chain reaction would happen with basketballs flying everywhere as the spin energy is converted into movement energy.
same thing happens in a microwave to h20, or any other free floating polar molecule. h20 just happen to absorb the microwave em very efficiently.