Skip to comments.Nanotubes Crank Out Hydrogen
Posted on 01/31/2005 11:44:25 AM PST by anymouse
Pure hydrogen fuel is non-polluting. Current methods of extracting hydrogen, however, use energy derived from sources that pollute. Finding ways to use the sun's energy to split water to extract hydrogen would make for a truly clean energy source.
Several research efforts are using materials engineered at the molecular scale to tap the sun as an energy source to extract hydrogen from water.
Researchers from Pennsylvania State University have constructed a material made from titanium dioxide nanotubes that is 97 percent efficient at harvesting the ultraviolet portion of the sun's light and 6.8 percent efficient at extracting hydrogen from water.
The material is easy to make, inexpensive, and photochemically stable, according to the researchers. The 97 percent efficiency is the highest reported, according to the researchers. There is one catch -- only five percent of the sun's energy is ultraviolet light.
The researchers are working to find a way to shift the response of the nanotube arrays into the visible spectrum.
The key to making titanium dioxide nanotubes that efficiently harvest the energy from light is controlling the thickness of the nanotube walls, according to the researchers. Nanotubes 224 nanometers long with 34-nanometer-thick walls are three times more efficient than those that are 120 nanometers long with 9-nanometer-thick walls.
The researchers made the titanium dioxide nanotube material by mixing titanium with acid and electrifying the mixture, which caused the tiny tubes to grow, then heating them to cause the material to crystallize.
The material could be ready for practical use in two to five years, according to the researchers. The work appeared in the January 12, 2005 issue of Nano Letters.
I think this will be OBE, specifically thermal depolymerization.
later read bump
The flux capacitor in my DeLorean has been doing this for twenty years.
I still think hydrogen is a non-starter. No matter how efficient you get at producing it, the low energy density and near-impossibily of storing it for any significant length of time (it seeps through damn near everything) makes it no match for other fuels.
How many grams to the mile does that Delorian get? :)
Those wonderful "zero emission" electric cars and fuel cell vehicles really aren't "zero emission" at all. They just move their emissoions from where they're operated to to electric power plants producing the electricity required to charge their batteries or manufacture the hydrogen by electrolysis.
Actually it makes lots of sense. It is much easier to put scrubbers on one plant than to maintain emissions on millions of cars.
Of course, it still suffers from the same problem that all solar sources do, namely, the low power density of sunlight. At 1 kW per square meter, it would take 1 square kilometer of a 100% conversion efficiency process, at the equator (when the sun is directly overhead) to generate 1 GW - at noon. Away from the equator, away from noon, and if your process isn't 100% efficient, it would take more land area than that to make 1 GW. That's a lot of land for only a modestly powerful power plant.
One point of the conversion is to move our oil dependency over to natural gas dependency.
TDP OH YEAH!!!!!!!
What kind of emissions is produced by hydrogen fuel?
You are forgetting about the efficiency loss at each step. After all the conversions you are probably at a whopping 3% efficiency
I'd bet that your average 1000 MW coal or nuclear station has a bigger footprint than 1 square km. But those darned "sun angle", "nighttime", and "cloudy day" issues...those are tough indeed to overcome.
Actually, keeping it at the equator still wouldn't maintain maximum capture. You'd have to continuously migrate it between the two tropics. /nitpick
In less-biased engineering terms, we would say that this process for converting sunlight to an alternate form of energy is 5% efficient. But why let realistic calculations get in the way of a good story.
Even when compressed a thousand times atmospheric pressure, hydrogen occupies 5 times the volume of gasoline. Where do you propose storing it in a vehicle?
Depending on how big, how cheap and how resistant to contamination these gadgets are in practice, burning the hydrogen to make water might be a useful method of desalinization.
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