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.
Here are some numbers on land use for different energy sources, based on a 1000 MWe design:
nuclear: 1-10 km2
solar: 20-50 km2
wind: 50-150 km2
biomass: 4000-6000 km2
Obviously, some of those are extrapolated based on scale-up of smaller systems, since we don't have any 1000 MWe solar or biomass power plants out there.
But those darned "sun angle", "nighttime", and "cloudy day" issues...those are tough indeed to overcome.
Not to mention the one that I always bring up to the sun worshippers that I have yet to hear a satisfactory answer for, that pesky old natural phenomenon called night.
... or tilt it slightly, if you can afford the increased slant path through the air. I didn't mention clouds either.
Not to mention the one that I always bring up to the sun worshippers that I have yet to hear a satisfactory answer for, that pesky old natural phenomenon called night.
It was mentioned...
Not much you can do if your primary energy source goes away for 50% of the time. Those nanotubes get their rest then, I suppose.
How about six times the solar capacity, combined with ten times the storage (battery) capacity, plus a backup soure for the third cloudy day?
You'd get more ultravilot if you widened the ozone hole.
H2O Water. That's all. Seems like a perfect solution doesn't it?
BTTT
Even with only 3%, that's a lot of energy. Coal could be the staple again. The benefit comes in with the fact that you can use any kind of kinetic energy to turn a turbine and produce electricity. You would only need to centralize the emissions control at one location. There are other problems than efficiency that stand in the way at this time but the world's finest engineers(The Americans) are working on it. If their track record remains, they will find a way.
They will have to make the system more efficient. Not all problems are solved but the major problem we have now, fossil fuels controlled by unstable nuts causing dangerous emissions, would be solved. The problems it creates may take a while to be economically feasible. But they are worth looking into.
The only conversion that really matters is the H2 Chemical energy to kinetic motion conversion. That's the problem to solve. All the rest would be large enough tomake it work. What's the efficiency rate for a coal fired electrical plant?
I second that.
Just noting that the terrorists go to great lengths to turn a vehicle into a car bomb.
Just think the power they would have from readily made car bombs manufactured for them carrying 10,000 lb PSI hydrogen tanks in them. Really good boom.
Kilometers? We don't need no stinkin' kilometers!
That's what I thought. I misunderstood what you wrote. I thought you were saying something else.
Ok, a couple of things here.First, why not store the hydrogen as a Hydride? that way, you do not have to deal with a huge, ultra-high pressure tank. If a high-density storage hydride can be developed, that could be the answer, couldn't it?
Second, the fuel-cell cars would be the best users of this technology, as the storage problem is currently the only major hurdle preventing elecric-powered cars, from reaching the mass market.
And, instead of using pure hydrogen, why not methanol, or something, similar, to use in a fuel cell, that does not need a reformer? you will still get the benefits of clean-emissions-free operation, and the ease of a"quick, easy fill up", at the "gas" station, that everyone is already used to now.
Thermodynamic efficiency is about 40% for large central stations. But that is just at the point of conversion, i.e., at the plant itself. It doesn't include the whole cycle, such as mining and transport of fuel, construction of the station, waste disposal, etc.
Any kind of practical process is going to have losses. A key consideration is converting something that was not in "useful" form into a kind of energy that can be used effectively. Crude oil underground contains energy. You use a lot of energy getting it out and refining it into gasoline, but once you do that you have a source of energy that is quite useful in that it has high energy content, is readily transportable, and has an important end use. Likewise there is a lot of energy locked up in uranium nuclei that can be exploited in a relatively straightforward manner to produce an energy form that is transportable and probably has the widest range of uses of any energy source we currently have. Sure, you had to expend energy to get it into that form, but now you have it to use whereas before when it was bound up in the nucleus, you didn't.
But that is just one part of the picture. There are others, I know, so we should not be too narrowly focused on the efficiency aspects. Certainly those play an important role, especially on the economics side of the equation, but other issues, like availability, projected lifetime of the resource, environmental effects, etc., may have significant bearing.
I can guarantee that if hydrogen fuel catches on, the watermelons will start condemning it because water vapour is an alleged "greenhouse gas". That's what they started saying about carbon dioxide when gas-fired plants got cleaner.
Metal hydrides have been touted as a storage solution for at least 25 years- they release the hydrogen when heated. So far, the best they've been able to do has still not matched the efficiency of rechargeable batteries.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.