Power Generation With Nanotubes

NubKnacker writes "Business World is carrying an article about how an Indian scientiest at IIT, Bangalore has come up with a new innovative method to produce power by blowing gases over carbon nanotubes. The underlying physics of the idea is quite simple yet no one had thought of it until today."

Comments

Very cool, related story in Nature

[tao_of_biology]

The journal Nature just ran a seperate news story a couple weeks ago about carban nanotubes' properties with regards to temperature. That story can be found here.

From the Nature article:

Ortwin Hess from the University of Surrey, Guildford, UK and colleagues say that if you took the temperature at one end of a 10-micrometre nanotube, it would not necessarily have the same temperature as the other end, no matter how long it was left to reach a thermal equilibrium. Such a nanotube is about as long as a sheet of paper is thick.

Now, I'm definitely no physicist so please pardon my ignorance--maybe someone can help me out. Does this mean that the temperature differential created on the carbon nanotube wire that causes the current to flow won't ever reach equilibrium? Doesn't this seem too good to be true? Just keep blowing gas over the wire, and you'll have limitless energy.

Re:Very cool, related story in Nature

[ToshiroOC]

It costs energy to blow gas over the wire.

Gedanken experiment:
You have two tanks of air at equal pressure, and a nanotube setup like the one described in the article in the valve connecting the two tanks. You open the valve - and no air moves across the nanotube, since the tanks are at equal pressure. Now, you pump air from tank 1 to tank 2, and the nanotube will generate energy - but only an equal or lesser amount of energy than it took to pump the air across the tanks.

Re:Very cool, related story in Nature

[hawkbug]

Fortunately, that's why we are able to use the sun to heat one tank of gas (Aka green house) and then open the valve - so during the day, solar power heats the gas so we can use it to generate electricity.

Re:Very cool, related story in Nature

[mdielmann]

And at night, when the tank cools down, you can generate energy again, from the air going in the opposite direction. This system generates energy in much the same way as a stirling engine does - moving heat to generate kinetic energy vs. moving air to generate electric energy.

I haven't read the article (I'm not that new here), but if there was an issue with the direction of flow, a simple system with 2 bi-directional valves and a little extra pipe could guarantee the gas flowed in a given direction that section of pipe, regardless of which tank was the source and which was the destination.

Re:Very cool, related story in Nature

[arete]

probably not.

Mechanical work (wind-power, hydroelectric, bicycle generator, regenerative braking) is already a low-entropy source... it's easy to capture it, and while it can't be lossless we have techniques that can generally come pretty close to the theoretical values for capturing it.

(which doesn't mean it can't be better, lighter, cheaper - but they're basically pretty good)

A pressure differential is somewhat worse - and a heat source (solar heating, gasoline, diesel, natural gas, coal, heating oil...) is very high entropy and very hard to get the energy out of.

Usually we use the heat source to generate a pressure differential that generates mechanical work. (which may or may not then generate electricity)

So that's more likely where this is applied - where you have a heat source that can be used to create a pressure differential.

Arete

Cost prohibitive for non-sensing applications

[ToshiroOC]

Unfortunately, nanotubes are still so expensive, velocity sensors are probably all these would be good for - larger power generating variants would be cost prohibitive. I also wonder how robust any velocity sensor made with nanotubes could be; sure, you could probably put one in a steam pipe or a LNG line and get reasonable data (in fact, in any nanotube-friendly chemical you could probably get good data from this sensor), but if you wanted to put one on the outside of a car or an airplane for velocity measurements, I can see nanotubes being easily damaged; either pulled from their moorings/leads in the device or simply snapped - nanotubes may be strong, but that's not going to help if you have a 500mph tiny sharp projectile impact just a few nanotubes. Also, in 'dirty' environments such as those outside of a car or a plane, you would probably start getting buildup of different pollutions at a reasonable rate, causing a need for either a) constant recalibration or b) sensor replacement.

Re:Cost prohibitive for non-sensing applications

[Delf]

RTFA, it's not just nanotubes that demonstate the effect:

Ajay Sood, professor of physics at the Indian Institute of Science in Bangalore, and his student Shankar Ghosh blew a gas over a piece of wire and watched it generate electric current. Two years ago he had blown water over ultra-tiny wires - carbon nanotubes - and watched them generate a current too. Carbon nanotubes are bits of exotica for the layperson; you expect them to behave in ways that you had not known before. Some of the wires in the second experiment (apart from the nanotubes) were semiconductors, not too different from the ones inside your the ubiquitous personal computer. They are the stuff of everyday life. You could build the device with a few thousand rupees.

SCO will be saved!

[SpaceLifeForm]

Yep, all of the smoke they have been blowing can finally be put to good use.

Efficiency?

[Anonymous Coward]

Does anyone know how efficient this system is? Depending it could become even more widespread than the article suggests.

That was amazing.

[Randolpho]

It is exactly what they've mentioned: so simple nobody ever thought of it.

Seriously, the potential applications to this just for minute gas-flow sensing are astounding; if this were ever exploited for consumer energy..... I think the guy deserves a Nobel prize for it.

IISc and not IIT

[florist]

It is Indian Institute of Science Bangalore and not IIT

How was this "unknown"?

[RealErmine]

According to this the Seebeck Effect (current flow from temperature difference) is just the reverse of the Peltier Effect (temperature difference from current flow). It's been known that the semiconductor material of a Thermoelectric cooler (or Peltier cooler) works in reverse, generating current from a temperature difference between sides. The story seems to imply that this is a new discovery both for nanotubes and other semiconductors and it's been known that nanotubes can act as semiconductors. It does not exlplain how doing this with a wire and a moving gas is new.

Re:How was this "unknown"?

[Randolpho]

It's not "unknown", it's just "undone" before. It's been known that you could get a current by creating a temperature differentiation on both wires and nanotubes. It's just that nobody had ever tried to create a temperature difference through the Bernoulli Principle. Nobody did it before this guy, the guy deserves credit for it for thinking of it first, even though it seems so damn obvious to us now.

Think of it this way:

We knew about peanutbutter. We knew about chocolate. We knew they both taste good. But we didn't know they tasted so damn good together until they came out with Reese's Peanutbutter Cups. Thank you Mr. Reese, whomever you are. ;)

Caption

[DavidNWelton]

High school physics meets nanotech: Ajay Sood (R) with student Shankar Ghosh passed gases over carbon nanotube wires to generate measurable electric current

Well... that's a lab I wouldn't want to work in.

Lower your shields

[kdark1701]

Resistance is futile