Silicon Nanoparticles Could Lead To On-Demand Hydrogen Generation

cylonlover writes "Researchers at the University of Buffalo have created spherical silicon nanoparticles they claim could lead to hydrogen generation on demand becoming a 'just add water' affair. When the particles are combined with water, they rapidly form hydrogen and silicic acid, a nontoxic byproduct, in a reaction that requires no light, heat or electricity. In experiments, the hydrogen produced was shown to be relatively pure by successfully being used to power a small fan via a small fuel cell."

Comments

Re:The key question becomes

[R_Ramjet]

Significant. From the article: "Though it takes significant energy and resources to produce the super-small silicon balls, the particles could help power portable devices in situations where water is available and portability is more important than low cost."

Re:The key question becomes

[Stirling Newberry]

Both this question and the next one roll into what is called the "Life Cycle Analysis" the net output per unit input.

Remember, there is energy extraction, and energy packaging. Petroleum is a huge win, because it is both - refining is relatively cheap, and it packages the result. This is not energy extraction - there is a large input, but it makes a convenient fuel cell package that gets around the problem of storing hydrogen. Since hydrogen is very chemically reactive, it's a big problem in having a hydrogen based energy chain.

The input cost is essential, especially the theoretical efficiency, against other forms of energy storage. This would include how stable the nano-particles are, because water is ubiquitous.

However it could be great for renewables, because the onsite wind farm or what have you, could be used to generate the silnaparts and this stores them. It could also be good for nuclear power, which runs continuously, and thus reduce the need for peak capacity, which is heavily carbon dominated. Even if not very efficient it could significantly reduce carbon footprint, because there would be no concern about the major problems of current bulk energy storage: gravity is environmentally destructive, and batteries have rather low cycle limits.

10nm particles...

[BLKMGK]

What's the health impact of these getting into the ecosystem? Pass right thru a human? Cause serious disease? What happens when it hits the water IN a human? If this becomes in any way widespread these are going to be issues.

What's left after the reaction? Must the water be pure or can we produce power from dirty water and do what with what's left? Could this be used to clean dirty water by simply using the water for power? Is oxygen also produced from this - I'd think so right since water is H2O. Are the particles completely consumed in the reaction? No reuse? How much water is used in the manufacturing process to create these particles? What are the waste byproducts for the process of creating these particles?

Re:The key question becomes

[DeathToBill]

Um, no. It typically takes around 4MJ/L (just over 1kWhr/L) to refine petrol, while the energy content is 35MJ/L. Drilling and transport add a little to that, but it's negligible compared to refining it. If it wasn't so, using it would have a net negative impact on our energy supply and no-one would use it.

Re:The key question becomes

[VortexCortex]

If your pathetic genome had better redundancy and error correction you wouldn't care about the radiation.

Oh wook at da poor wittle hue-mans, can't come out an pway in the milky way because them scawed for cosmic rays. Have fun being grounded dork!

Re:The key question becomes

[mapsjanhere]

This is strictly for military applications. The US forces in Afghanistan use 28 gallons of fuel to deliver one gallon of fuel to an outpost where a 3 gal/h generator charges an Ipod (don't laugh, that's from an US Army presentation). So, if I can charge my devices of a fuel cell fed by something like this silicon hydrogen generator I might save money not because it's energy efficient in production but energy efficient at the point of use. The reason they use silicon is that it gives you 1 gram of hydrogen per 8 grams of silicon. You could use other, cheaper, metals, but the weight ratio isn't as favorable (iron would require something like 20 to 1). As 1 kg of hydrogen gives you 127 MJ of energy, 1 kg of silicone powder gives you about 15 MJ. Compare that to a battery that gives you less than one MJ/kg, and you see the attractiveness if weight is at a premium.

Re:The key question becomes

[rgbatduke]

Where does silicon come from? Silicon dioxide, a.k.a. "sand". How tightly is it bound? Very, very, very tightly. Indeed, a whopping 910.86 kJ/mole. So it requires at LEAST this much energy to turn sand into silicon and oxygen, except that one cannot electrolyze or reduce it until it is molten, so add to this enough energy to melt sand, after raising its temperature to some 1500 C. Then, one has to engineer "nanoparticles" out of the purified silicon metal. At a guess -- only a guess, of course -- this involves heating the silicon to the vaporization point and either vapor depositing it on a suitable substrate and scraping off the nanoparticles or spraying silicon vapor into a suitable medium that causes it to condense out small particles and then filtering or otherwise separating out the 'nano' particles from those that are merely small. Sounds like more energy to me.

At the end of the day, you can get at most the 250 or so kJ/mole back from the hydrogen gas produced after the silicon nanoparticles steal the hydrogen back from water. I think it would be an absolute miracle if it this is as much as 10% of the energy invested in making the nanoparticles, and the energy costs are probably at most half of the total manufacturing costs. Down to 5%. Multiply by roughly 50% again (efficiency of fuel cell).

This "Fermi estimate" of the probable economic efficiency is on the order of 2.5%, then, compared to the cost of just buying electricity or any other form of concentrated energy. Even if I'm too aggressive in my pessimism, 10% is a pretty safe upper bound. I'm not seeing this as a game changer. Gasoline or other hydrocarbons are still the gold standard for readily available energy density at ballpark 35 MJ/liter, and don't require investing 20 times the energy eventually recovered in their preparation.

rgb