Graphene nanoribbons lower power, cooler than copper

[Gizmo]

R. Colin Johnson
EE Times

PORTLAND, Ore.—Graphene will carry nearly 1,000-times more current and run over 10-times cooler than conventional copper interconnects below 22-nanometer line widths, according to researchers at the Georgia Institute of Technology (Georgia Tech).

Read more on the Front Page:
AOA - Graphene nanoribbons lower power, cooler than copper

[Daniel ~]

Well I'm Ready! ":O}

[cloasters]

10 billion Amps per square centimeter? Looks like copper will be ancient history if they can manufacture practical graphene conductors without too much trouble. 10 billion Amps per square centimeter. More than amazing!

[jacksonwalters]

Yea, graphene actually conducted electricity too well so what they just did was add hydrogen atoms on the carbon, a substance called graphane, everywhere they didn't want current to flow in order to create graphene channels within the graphane. Pretty cool stuff.

[cloasters]

Please tell us more if you have the time!

[booman]

does this mean even smaller computers?

[cloasters]

Smaller large transmission lines. Just in time for de-centralized power sources!

[Gizmo]

I'm not convinced we can ever get rid of centralized power generation. There has to be a way to ensure adequate availability to the grid at all times and the economics of power generation (REGARDLESS of how you go about producing; i.e. wind, solar, fossil, whatever) mean that large centralized stations are more efficient.

However, even with de-centralized generation, you still have the problem of getting the power from where it's generated to where it's needed. Given that up to 30% of the generated power is lost in distribution, more efficient power distribution would be a definite improvement.

[jacksonwalters]

You can buy a pallet of 24 130W (about 3kW peak) panels for like 10 grand. add the combiner box, batterys, inverters, etc. and you can probably hop off the grid for like 15 grand. not to mention you can get a couple of windmills depending on where you live.

efficiency is on the rise every day. group at MIT broke 50%.

[Gizmo]

Last I read, the average home consumed about 31 KWh/Day. You also have to allow for the fact that the peak rating on those panels assumes ideal conditions (which no one in the U.S. will ever achieve).

In reality, you're looking at AT LEAST twice that to get 3 KWh of output, plus having to do a lot of other things (like use solar hot water heating, solar cooking, etc) in order to get your energy consumption down so that you can actually get by with 3 KWh of capacity.

[Daniel ~]

I'd still be willing to bet that we crack this and give ourselves energy independence from one an other in the next 20 years...

We all know we want this! ":O}

[jacksonwalters]

Read a little closer Gizmo. 3kW. Not 3 kWh. 1 kWh is just a roundabout way of writing 1000 Joules of energy. I wasn't talking capacity, I was talking dE/dt, power, rate of energy gain, whatever you wanna call it. Also notice I said 3kW peak, I wasn't assuming that you'd get the same power at 6PM as 12 noon. That being said, if you integrate the power you're getting from the panels over the course of 24 hours, you would probably find it's close to 1.5kW*14hours = 21kWh = 21kJ. Also remember on days you don't use the all that energy it is being stored in batteries... Also consider the fact that you wouldn't have a house running on solar panel with all the bells and whistles, you would have to make a few exceptions here and there and be efficient with your power. I wonder if that 31kJ energy per day you quoted was a house running on all CFL's with a few window AC units or if it happened to be a common suburban household without efficient washer/dryer/fridge/pc's/etc. Again, add a few windmills, maybe a water wheel, and you would be good to go.

[cloasters]

I don't think we'll be able to do away with centralized generating stations. Just sayin' that super efficient conductors can make getting generating excess power from households easier to distribute. Bad grammar, brain broken, sorry.

[Gizmo]

Originally Posted by jacksonwalters

you would probably find it's close to 1.5kW*14hours = 21kWh = 21kJ.

Well, ok.

Let me start out by saying that I'm not trying to say we shouldn't pursue solar technology. We absolutely should. But we need to be realistic in our expectations, given the current state of technology.

First, I'll stipulate your point about 3KW. However, if you generate 3KW for one hour, then you've generated 3KWh of capacity, and for an apple-to-apples comparison, that's the figure we need to work with. (BTW, as a point of reference, your average hair dryer can consume upwards of 1KW, meaning that these panels would only be able to power the equivalent of 3 hair dryers).

Second, I DID mention that you would have to do several other things in order to get your house to the point where you could actually get by with 3KW. Solar water heating and solar cooking were among the things I mentioned. One thing you WOULD NOT be doing is running a central air system.

Now, with that out of the way, let's do some basic math:

They don't give a measurement on the Kyocera panels mentioned here, however Kyocera's web site indicates the panels measure 56.1 * 27.6 inches. That's just shy of 1 square meter. By the time you take into account the mounting frame and other miscellany, we can call it 1 square meter, which is a pretty typical size and also makes the rest of our math easier.

The amount of radiation falling on the earth's surface at the equator on March 22 at high noon (when the sun is directly overhead (I think, I'm pulling the exact conditions from memory) amounts to just over 1KW per square meter.

The U.S. doesn't get that much.

Depending on where are you are at in the U.S., and time of year, you will get anywhere from 600 watts (in the desert southwest) down to about 200 watts (in the Pacific Northwest) (this is for the lower 48, Alaska and Hawaii are a whole 'nuther matter).

And bear in mind these figures are assuming 100% efficiency.

These panels, according to Kyocera, are about 16% efficient.

So, where does that leave us?

1. Those 24 panels are going to require roughly 24 square meters of space to generate their power.
2. Their rating assumes ideal conditions. In real-world conditions, in the United States, the BEST you can hope for is about 1.5 KW averaged over the course of a 14 hour day. Since a 14 hour day only exists for about a month out of the year, the rest of the time you'll get less than that, and potentially a LOT less than that.

And we still have to consider clouds, dust, etc.

Oh, and that efficiency figure for those cells assumes that they are running at 25C. Their nominal operating temp is 47C. Although Kyocera don't provide de-rating data as a function of temperature, experience suggests that there will be SOME loss of efficiency as the temperature increases.

As I said, I don't want to discourage the use of solar energy; it's a technology we NEED to pursue. But to simply state that you can generate a peak output of 3KW for $10G ignores a LOT of real-world restrictions. The only place you'll EVER see 3KW of output from that array is in a laboratory.

[jacksonwalters]

I mean, look, we're pretty much on the same page. You quoted a bare minimum 200W/m^2. With 24 panels, I was only assuming 130W, which is what they're quoted at. I really can't go any further with this without knowing the efficiency of the panels. Although, I do think it's possible and would be pretty amazing to be able to live comfortably anywhere you like.

edit: here's a page showing a bunch of complete off grid systems and it actually gives the average kwh produced on a typical day in florida. it looks like you get the equivalent of 4 peak hours over the course of the day. thus, a system rated at 3120W (24 130W panels) seems to be producing roughly 12-15 kWh of capacity per day, real world restrictions considered.

http://sunelec.com/index.php?main_page=off_grid_systems

[noob]

So coupled with this: Nano 'kites' may lead to nanotube growth and several million square kilometres of solar panels in space we should be good for power generation on this planet? Then each time a panel is replaced it can be done with the latest tech. As long as efficiency is as fast as usage growth, we should be good without expanding, but its a big solar system out there.

But personally this looks like it will have applications in computing. Allowing much greater efficiency and higher currents in small scale electronics. But my question is, what is the resistivity compared to copper? While its thermal conductivity if greater, what is its I^2R losses like, and therefore the amount of heat dumped into the system.

[jacksonwalters]

Wikipedia excerpt:

Thermal properties:
The near-room temperature thermal conductivity of graphene was recently measured to be between (4.84±0.44) ×103 to (5.30±0.48) ×103 Wm−1K−1. These measurements, made by a non-contact optical technique, are in excess of those measured for carbon nanotubes or diamond. It can be shown by using the Wiedemann-Franz law, that the thermal conduction is phonon-dominated.[61] However, for a gated graphene strip, an applied gate bias causing a Fermi Energy shift much larger than kBT can cause the electronic contribution to increase and dominate over the phonon contribution at low temperatures.[62]
Potential for this high conductivity can be seen by considering graphite, a 3D version of graphene that has basal plane thermal conductivity of over a 1000 W/mK (comparable to diamond). In graphite, the c-axis (out of plane) thermal conductivity is over a factor of ~100 smaller due to the weak binding forces between basal planes as well as the larger lattice spacing.[63] In addition, the ballistic thermal conductance of a graphene is shown to give the lower limit of the ballistic thermal conductances, per unit circumference, length of carbon nanotubes.[64]
Despite its 2-D nature, graphene has 3 acoustic phonon modes. The two in-plane modes have a linear dispersion relation, whereas the out of plane mode has a quadratic dispersion relation. Due to this, the T2 dependent thermal conductivity contribution of the linear modes is dominated at low temperatures by the T1.5 contribution of the out of plane mode.[64] The ballistic thermal conductance of graphene is isotropic.[62]

Too technical for me. Maybe y'all can make some sense out of that.