Carbon Nanotube Solar Cells On the Horizon

MikeChino writes Carbon nanotube news abounds as of late, and the next application for the up and coming material may be hyper-efficient and economical solar cells. Led by professor Paul McEuen, researchers at Cornell recently tested a simple solar cell (called a photodiode) crafted from a single carbon nanotube. Surprisingly, researchers discovered that more light shined on the nanotube created even more electricity, a huge difference from today's silicon solar cells where excess energy is lost in the form of heat rather than used to create more electricity."

Comments

The technology isn't important

[davidwr]

The question is, it it cost-effective?

New title:

More cost-effective Solar Cells On the Horizon

There, fixed that for you.

Re:The technology isn't important

[Anonymous Coward]

The question is, it it cost-effective?

New title:

More cost-effective Solar Cells On the Horizon

There, fixed that for you.

New solar cells that are "more cost-effective" require new technology.
New technology requires research.
Research is an expensive process.

To make new, more cost effective solar cells, we need to fund _some_ technology. Carbon Nanotubes are promising.
Press releases get a college department more funding, which buys new equipment and affords more people working on a subject area.

So, in short, the fact that this technology is related to Carbon Nanotubes is intrinsically important.

Re:The technology isn't important

[bugnuts]

Considering the energy required to produce crystalline Si cells, if the manufacturing is perfected, it could be both more efficient and cheaper. A solar pv panel today must produce energy for a year or two to recover the energy used to create it. Nanotubes may be much more complex, but they probably need nowhere near as much power to create.

The bottom line Is what generally matters to consumers, but the cells must still be efficient because roof real estate is not unlimited.

Re:The technology isn't important

[show me altoids]

One important application where efficiency (and durability and lifetime, but that's another story) trumps cost-effectiveness by a wide margin is powering satellites and spacecraft, though. So there is room for more than one technology in the mix, depending on the application.

Re:The technology isn't important

[kheldan]

The question is, it it cost-effective?

If someone developed a 99% efficient solar cell, would you really care what it cost?

Re:The technology isn't important

[mapsjanhere]

It's a great finding, but unfortunately, making nanotubes is a HIGHLY energy intensive process, and you will still need some form of substrate to connect these - most likely silicone. To really utilize this effect they have to find that you can get the effect from a macroscopic sheet of woven or non-woven CNTs, or they have to learn how to grow the tubes from one electrode to the other, which isn't trivial.

Re:The technology isn't important

[Idiomatick]

Yes... that's stupid. Of course it matters what it cost.

Re:The technology isn't important

[camperdave]

Yeah, but you can buy tubes of silicone at any hardware store. It ain't exactly rare.

Re:The technology isn't important

[Da Fokka]

If someone developed a 99% efficient solar cell, would you really care what it cost?

You're kidding right?

For everyone who is looking for real solutions (unfortunately that's not quite everyone in the debate), the cost is a crucial factor in the equation. Economic efficiency is more important than energy efficiency.

Re:The technology isn't important

[fifedrum]

could a 99% efficient solar cell even provide enough electricity to cool/warm/light my home? Of course, but how large of a setup would one need?

Let's see.

according to http://www.wunderground.com/calculators/solar.html I have no idea what I'm talking about.

How much electricity do I need in my home? http://tonto.eia.doe.gov/ask/electricity_faqs.asp says the 2007 average was 936 kWh per month. I'll say I'm average in that respect with a gas furnace and clothes dryer.

that's 11,232 kWhs per year?

At my location, upstate NY on a line from Buffalo to Albany, at 99% efficiency, I would need one 10'x10' panel to generate 13,938 kWhr/year.

So, there you go, Yes, I would like one 12'x12' 99% efficient solar cell (larger than I need, to cover for growth and storing for a rainy day), and really, the cost is important so I would like it for free.

Re:The technology isn't important

[drseuk]

It's a great finding, but unfortunately, making nanotubes is a HIGHLY energy intensive process

Obviously we need someone to invent some sort of hyper-efficient, clean and renewable energy source to power the manufacturing process then.

Re:The technology isn't important

[Dare nMc]

Economic efficiency is more important than energy efficiency.

they are both fairly important. As stated above, if your launching this into space for a satellite then the Economics is vastly different than if you putting this next to a nuclear plant. If we could just convert a nuclear plant into a dedicated solar cell manufacturing plant, get rid of all the ugly & terrorist target & high maintenance of the power grid, all the middle men (IE Enron, etc) in favor of wal-mart, that changes overall economics greatly. Adding $50,000 to the cost of a Prius to have a permanent solar charge that fits into the roof, I would have to pass. Adding $70,000 to a high end motor home, that then never needs fuel, grid connection, etc. Even if it just provides say 500 miles of travel a week + complete self sufficiency (ok I still probably need to recycle the waste for clean water) Is well worth considering (would trade my house in as a down payment.)

Re:The technology isn't important

[hesaigo999ca]

I guess that would also depend on how much more efficiency we gain through this method.
I think the present state is 30 to 40% or something minimal like that...if this shot it up to 80-90% then I think regardless of cost, the same panel would yield you twice as much power...just let's hope it does not cost twice as much to produce.

Re:The technology isn't important

[TooMuchToDo]

If I have 100 sq miles of land I can cover with solar panels, do I care how efficient they are if they're dirt cheap?

Re:The technology isn't important

[Aceticon]

Well, if somebody developed a 150% efficient solar cell I wouldn't care about cost.

Then again, you could use such a solar cell to power some high efficiency light producing device (say, a LED) which you would point at the solar cell thus getting back more energy than you used to power the light (i.e. free energy).

Re:The technology isn't important

[CrimsonAvenger]

If someone developed a 99% efficient solar cell, would you really care what it cost?

Yes, I would. If it cost $1,000,000 for enough solar cells to generate 1 kilowatt at 99% efficiency, it would be essentially worthless for anyone but NASA.

What I'm looking for is something that costs $1,000 per kilowatt. That's cheap enough that I could actually make use of it.

Re:The technology isn't important

[Anonymous Coward]

At any price it'd be a steal at only half the cost--and they are only charging double that!

Re:The technology isn't important

[jeffb (2.718)]

Adding $70,000 to a high end motor home, that then never needs fuel, grid connection, etc. Even if it just provides say 500 miles of travel a week + complete self sufficiency (ok I still probably need to recycle the waste for clean water) Is well worth considering (would trade my house in as a down payment.)

Good luck with that. A 20% efficient panel will collect maybe 1 KWh/m^2 over the course of a mid-latitude day, on average. A typical motor home will have somewhere around 15 m^2 of roof area. That means you can collect 15kWh per day with today's panels. That's enough to run an electric motor at 20HP for a bit less than an hour. Or, looking at it another way, that's about the energy you get from burning half a gallon of gas.

This is all from the back of a pretty small envelope, as it were -- your panels won't be oriented optimally toward the sun, but you could also cover the sides and ends, so the total-power-intercepted figure shouldn't be too far off. An electric power train is a lot more efficient than an IC engine and power train. But, bottom line, it's not going to be practical to run an RV on any conceivable solar arrangement, unless it's got big dragonfly wings covered with panels, which would run afoul of DOT regulations.

Re:The technology isn't important

[Locke2005]

The question is, is it complete bullshit from a clueless moron?

researchers at Cornell recently tested a simple solar cell (called a photodiode)

I'm not a Cornell researcher, but I'm fairly certain a solar cell is not the same thing as a photodiode. Once again, proof that the only way we can make science relevant again is to train the people reporting on it to actually understand what the hell they are talking about!

Re:The technology isn't important

[werfu]

Then use produced Solar cell and install them on the top of the factory so the energy for manufacturing the next one will come from the sun.

Re:The technology isn't important

[kheldan]

they are both fairly important..

You see my point; If, say, a few square feet of your roof can supply all of your daily electricity needs for the next 20 (or more) years, then what's that worth to you? If a dozen acres of otherwise useless land can supply a city the size of New York, then what's that worth? Naturally the cost of any technology goes down over time as manufacturing processes are perfected and optimized, and as more manufacturers are producing that technology.

Re:The technology isn't important

[Khyber]

For one, 15kWh is about the average amount a three bedroom house uses in a day. That RV would move just fine off of that, and it could still have huge 'dragon wings' as you know, most RVs have those things called hinges that allow those huge shade spreaders on the sides of RVs to fold against the side of the RV while it is in motion. The only problem would be camping in a forest where a majority of sunlight gets blocked. More efficient solar cells made from this technology would pretty much allow truly solar-powered vehicles.

Re:The technology isn't important

[Anonymous Coward]

Sure you care. Look at the cost and resistive losses associated with wiring 100mi^2.

Re:The technology isn't important

[Artifakt]

The problem with that is, Economic Efficiency is a non-stable and non-quantifiable metric. Trying to calculate economic efficiency results in absurd conclusions.
        In the real world, such calculations have 'proved' that the United States doesn't need high speed cargo rail, it just needs to keep subsidising the airlines. It's 'proved' that shipping from say, Nice to Tuniz by truck, through nations such as Lebanon, in time of war, is 'better' than shipping straight across the sea by blimp. It's 'proved' that communications sattelites could never be successful unless only done by various governments. It's 'proved' that putting small tiles on the belly of your space-shuttle instead of casting large sections could never possibly cause an accident worth getting excited about.
        In more abstract situations, a professional cost accountant will tell you quite literally that NO consequence is bad enough to make you not take an offer, IF the consequence occurs far enough in the future. If a new chemical process will make billions in the next few years, but render all mammalian species totally sterile 200 years from now, we should do it, because the negative consequences are so remote, no matter how devastating or inevitable.
        This was once pointed out by John W Campbell Jr. back in the early 1950's. He put some extreme scenarios to several economic efficiency experts and had them use their usual mathematical tools to analyse just how much immediate profit would justify taking the offer, with accompanying Campbell selected long term consequences described as inevitable. Every one of the subjects found some level of immediate profit that made the offer a good one even though the long term outcome was something such as putting everyone over age 50 into a meat grinder, shooting all males of our species, or other such horrible ultimate outcomes. Several of the respondents said they were only willing to let him have their results because they believed no one would actually act on them, or something else would intervene before we had to pay out. Five of them put something in their responses to the tune of "Thank God Hitler's dead so there's nobody crazy enough to actually try this". (Hope that doesn't Godwin the thread).
        Buckminster Fuller has written quite a bit about why realistic economic rules would always include either energy efficiency or total energy budget values, and from what I gather, he generally expected both were vitally important in all but a few degenerate calculations.
       

Re:The technology isn't important

[Dare nMc]

The thread was more of a hypothetical 99% efficiency what would the value be... It appears with nano tubes a reflector has a bigger benefit, so we could get 20% over not only the panel area, but the reflector area as well. 10meter x 2.2meter motor home roof, with a full length vertical reflector on each side that could automatically rolled out to say 5 meters while parked, tracking the sun would give me 22 m^3 of panel area + 50 m^3 of reflector area (assuming we can choose the optimal parking direction.) with just one reflector panel up at a time we could be close to the 75kwhr@20% efficiency. I could see a 100 hpHr per day, with enough batterys to store that for the week, I could see moving that large of a motor home 60 MPH @ 100HP * 4Hr = 240 miles a week, and still using 1/2 the power for personal non motoring use (make night runs when no traffic, and maximize reflector use by day.)
I think my point is the convenience of not worrying about power (other than a "lets relax another day") in high luxury doesn't need to make the same economic sense to the same degree as a factory just trying to cut costs.
The solar panels on the roof couldn't stay flat, but maybe just a single hinge allowing a full 90 degree tilt and if absorbed solar from both sides, could get this well over 75 m^3, even at difficult sun angles.

Re:The technology isn't important

[Brigadier]

Perhaps, but I promise you this, at 99% in an energy starved world where energy is one of the driving forces for tension between countries, and world dominance (see middle east and russia) cost becomes much much less important. at $10.34 per kw/hr I assure you no matter what cost you charge there will be investors out there who will finance you.

Re:The technology isn't important

[Artifakt]

A solar Cell is definitely not the same as a Photo(emitting)diode. (and most of the time, when someone says photo-diode that's what they mean). Whether you could justly call a photo(converting)diode a solar cell with built in unidirectional output is really a matter of semantics. I'd go with not conflating the two simply because it's potentially confusing, but then, most people say LED instead of photo-diode these days so maybe the usage is legitimate.

Re:The technology isn't important

[Idiomatick]

no.... if it costs 10x current solar prices to ramp it up to 99% then it doesn't really help does it. I mean maybe for some weird science use but not for energy production.

Re:The technology isn't important

[jeffb (2.718)]

For one, 15kWh is about the average amount a three bedroom house uses in a day. That RV would move just fine off of that...

...just not for long.

Most people don't seem to realize that the typical vehicular engine can produce much more power than the typical household electric service. A generous 200A 240V feed equates to about 64 horsepower. At that power level, you consume 15kWh in a bit less than 20 minutes.

Looking at it another way, an RV will typically get around 10 mpg. That means you're using about 3.3kWh of gasoline per mile (energy content of gas is about 33kWh/gal). Assuming you lose about 80% of that to thermodynamics and other losses not present in an electric power train, you'll still need something like 0.8 kWh per mile, giving you a range of maybe 20 miles per day. And that's neglecting all the other things you'd like to do with the power you collect.

The fold-out panels hold promise; see the comment below.

Re:The technology isn't important

[efalk]

Absolutely. If it costs more than twice the price of 50% efficient cells, then its usefulness is limited to a few weight or surface area -critical applications.

Re:The technology isn't important

[jeffb (2.718)]

Yes, this idea of putting down roots and spreading out petals during the peak of the day could buy you quite a bit. However, it also imposes a much greater requirement for batteries, which brings us right back to the other disappointingly stagnant technology. If only we could come up with a high-power-density battery system with a service life much greater than the current few hundred to few thousand cycles, a lot of things would get a lot better.

The best power density I see for current commercial technology is less than 150 Wh/kg. That means the batteries to store 75kWh of energy would weigh half a ton. If you want a week's worth, that's 3.5 tons, about the weight of, well, a motorhome.

Re:The technology isn't important

[henryhayne]

It does not matter about the costs, because even if it were 100% efficient it would require huge tracks of land to replace our current energy sources. That in itself would be more damaging to the environment than the current fossil fuel problems. Only Geothermal and nuclear power offer environmentally sound approaches to replacing fossil fuel.

Re:The technology isn't important

[jonadab]

> Economic Efficiency is a non-stable and non-quantifiable metric.

There are limits to how precisely it can be pinned down, but some arrangements are obviously more reasonable than others.

> In the real world, such calculations have 'proved' that
> the United States doesn't need high speed cargo rail,

That conclusion is correct. The problem with any railroad is that it's only practical when huge amounts of cargo (or passengers for that matter) need to travel exactly the same route all the time. We do use it for things like taking coal to steel mills, but delivery speed doesn't matter there. A high-speed cargo rail would have VERY limited applicability in the United States. If you're from Europe or southern California, you might really have a sense of this until you drive across the Midwestern US in a car a couple of times. Put simply, only a small percentage of our cargo starts or stops at a major city.

> it just needs to keep subsidising the airlines.

That's a separate issue and not significantly related to the rail question. The airlines mostly handle passenger traffic and mail. Almost all cargo goes on eighteen-wheeled semi trucks, because they can deliver to any destination.

> It's 'proved' that shipping from say, Nice to Tuniz by truck,
> through nations such as Lebanon, in time of war, is 'better'
> than shipping straight across the sea by blimp.

Any kind of reasoning can fail of the person applying it fails to take important factors (such as war, for instance) into account. That's neither here nor there.

> NO consequence is bad enough to make you not take an offer,
> IF the consequence occurs far enough in the future

That's a straw man, and not a particularly clever one. Nobody in the history of the universe has ever seriously argued in favor of doing anything that they knew would destroy their entire race a couple of centuries down the road. Nobody. Ever.

Economic efficiency *does* matter for solar cells, and ones that are cheaper to manufacture (for any given level of energy output) are better, and such research is important, because if the solar panels can pay for themselves in a year and continue producing energy for ten or twenty years, people *will* buy and install and use them; whereas, currently most people are not buying or installing or using them, because they don't produce enough energy to pay for themselves fast enough to cover the opportunity cost of whatever else people could buy with the same money.

I don't know whether these nanotubes will lead to the kind of solar cells that are really needed, or whether it's a blind alley. The researchers don't know that either. But in the absence of any knowledge of a *better* technology, it's worth exploring the possibility.

Re:The technology isn't important

[jonadab]

Yeah, but someone living in northeastern Ohio would probably need about ten *acres* of solar cells to meet the energy needs of an average household, unless you can provide enough batteries to store the summer excess to last all winter. (In the fall and winter, NEO can go *months* without direct sunlight, so your panels would be running on the diffused ambient light that filters down through the cloud cover, which is typically about half as bright as a normally-lit indoor room.)

Re:The technology isn't important

[Lloyd_Bryant]

no.... if it costs 10x current solar prices to ramp it up to 99% then it doesn't really help does it. I mean maybe for some weird science use but not for energy production.

TFA is a little light on details, but consider this quote: "Researchers discovered that more light shined on the nanotube created even more electricity, a huge difference from today's silicon solar cells where excess energy is lost in the form of heat rather than used to create more electricity."

So say it's 10x the current price of solar cells, but can utilize cheap mirrors so that you only need 1/10 as many of them as conventional solar cells.

There *is* some potential here (assuming it actually works on a larger scale, of course).

Re:The technology isn't important

[Socguy]

Boys, let's not argue! Cost vs efficiency are both important, it's your application that determines which is more so. If you're planning to launch the things into space, the purchase cost is not going to be terribly important to you but if you're planning on selling solar accent lights through Wal-mart then you want the cheapest cells that you can get your hands on.

Re:The technology isn't important

[Beezlebub33]

As well as the installation, maintenance, and hail damage costs associated with a large area installation.

Most people in this thread really need to understand something about lifecycle costs. If solar panels were completely free, it still would not make sense for most people to install them on their roofs, because of all the other costs.

Re:The technology isn't important

[EvilBudMan]

It just might be cost effective soon. Just a few years ago 100 NM was the longest you could make this stuff in quantity. Now it's up to 1000 NM. That's just barely enough to make fabric and maybe wire.

Re:The technology isn't important

[Dare nMc]

agreed, were not even close. But I can dream of becoming a super Hippie. Were probably closer to gathering the methane from the black water tank to get home, than packing the 2 tons of batteries around.
Although I just want the pedals on my current camper (trailer) so I can run the AC when it's hot (and maybe hook it up to the house at home). I do think making that trailer a hybrid would be nice first. Be able to even out the hills towing, smart braking around corners, and then charge the batteries down the last hill for camping...
I did have a chance to play around with the Zebra batteries, that do meet (barely exceed at times) that 150 Wh/kg, just a bit difficult to overcome that 18% charge loss per day required to keep them at the 300 C they need (and the upfront charge, but I might still be able to get the first set for a 5 finger discount.)

Re:The technology isn't important

[geekoid]

That would be 1 Kilowatt per sqr meter. So, is there a limit to how much you would pay to gte 1 KW for hour, 12 hours a day?

Re:The technology isn't important

[geekoid]

Current price has just about lowered to 1 dollar per Watt.
The optimum conversion of sunlight hitting the earth would be 1 Kw per sqr meter.

That means at 10 times the current cost you would be pating 10K dollars per sqr Meter.

I currently pay about 10 cents per KW.
So, yeah cost is a factor.

Re:The technology isn't important

[geekoid]

a 101% efficiency would drive the cost down to just above 0 per KW.

Of course, if we are talking about magic, we might as well hope for a way top get 10KW of power from body odor.

Re:The technology isn't important

[CrimsonAvenger]

That would be 1 Kilowatt per sqr meter. So, is there a limit to how much you would pay to gte 1 KW for hour, 12 hours a day?

Yes, there is.

My roof is rather larger than 1 square meter. It's enough larger that I can get 1kW per hour, 12 hours per day with 15% efficient panels.

So, if it costs more than about 7 times as much as conventional solar, it's worthless to me.

Re:The technology isn't important

[soundguy]

If you want a week's worth, that's 3.5 tons, about the weight of, well, a motorhome.

That's not a motorhome. THIS is a motorhome. About 16 tons. Bus conversions are closer to 20 tons.

Re:The technology isn't important

[AshtangiMan]

I don't think you've thought that through. While I won't argue that PV is green, the area for putting the PV (as you say, huge tracks of land) is not the problem. For starters, rooftops in urban centers gets you a lot of the way there (there are many other opportunities that won't add to the ecological damage from human development). In SanFran they put up a bunch of PV on tall buildings and found that on the cloudiest/foggiest of times they were still generating 70% of capacity. You are way overstating the area required for PV to meet demand. The usual reasons to say that PV can't handle the entire load are day/night and storage, which are valid. But even with the current state of the technology PV can be a very important part of the energy portfolio, along with solar thermal, geothermal, nuclear, and wind.

Re:The technology isn't important

[marcosdumay]

Wrong, you pay 10 cents per KWh.

Re:The technology isn't important

[Idiomatick]

Ok god, if it was 1000430985109581095x as much it wouldn't matter then. God I thought it was a simple point but I was wrong. Price always matters. Saying it doesn't is stupid. It is like saying human lives are invaluable. Well if ya were it'd cost infinite money to raise a child. You can't use black and white answers was all I was trying to say. Soulsucking /.ers T_T

Re:The technology isn't important

[Tibia1]

Hey I have a solar cell that costs 0.00000001 cent. Sweet. Sure its only 0.00001% energy efficient, but that's not what's important, right?

Re:The technology isn't important

[Anonymous Coward]

So you saying it's fine if they cost 50 times more?

Re:The technology isn't important

[hey!]

It all depends on the application.

If I'm powering a satellite, I *almost* don't care what it costs. If I'm powering a planetary probe, it'd easily be worth its weight in gold.

On the other end of the spectrum, I read last year about a group working on photovoltaic house paint. That's almost certain to be extremely inefficient. However if it costs about the same as regular house paint, and works about as well, the inefficiency *almost* wouldn't matter. I've got to paint my house anyhow, and I were going to throw those photons away in any case. If I got any useful output from it at all, it'd be a win.

Now for selling vast amounts of energy into a commodity "energy" market, a low total amortized cost per watt is the difference between making a profit and losing money. Efficiency is secondary -- we were throwing those watts away anyhow -- but all other things being equal efficient cells reduce costs. For example, imagine land is your limiting factor. You can get twice as many watts per acre from a cell that was twice as expensive. While land is probably one of the least important factors in scaling a photovoltaic installation up just about *any* expense outside the cell itself is going to be reduced by a more efficient cell exactly the same way.

It's the expenses attached to the cell itself that will determine whether the technology is viable: producing the cell, replacing the cell as it wears out, and disposing of the cell.

Re:The technology isn't important

[fifedrum]

absolutely, and I'm roughly parallel to Lake Erie with possibly worse weather than Ohio, the argument above isn't about normal solar cells, it's about 99% efficient magical solar cells made from, apparently, alien technology gathered from Area 51.

Who knows, maybe 99% efficient will happen with carbon nano tubes and pixie dust.

Re:The technology isn't important

[drseuk]

Precisely my point.

Homer says...

[Azghoul]

Carbon nanotubes... is there anything they _can't_ do?

Re:Homer says...

[Anonymous Coward]

They have yet to get me a date with Megan Fox.

Re:Homer says...

[idontgno]

We need a huge ticker-tape parade for our hero, Inanimate Carbon Nanotube.

Re:Homer says...

[Bovius]

Carbon nanotubes can't be mass produced economically.

Re:Homer says...

[kheldan]

Carbon nanotubes can't be mass produced economically yet.

There, fixed that for you.

Re:Homer says...

[Anonymous Coward]

Wow! Did you actually get to _see_ the nanotube??

Re:Homer says...

[lorenlal]

Let's be fair, I doubt anyone perusing these forums has either.

Re:Homer says...

[TooMuchToDo]

Michael Bay can work that into Transformers 3. With some more explosions.

Re:Homer says...

[Locke2005]

"Ye cannae change the laws of physics!"

Re:Homer says...

[werfu]

Well, I guess they did : http://tech.slashdot.org/story/09/09/18/1243244/Bullet-Proof-Sheets-of-Carbon-Nanotubes

Re:Homer says...

[Radtastic]

That's because your tube, while carbon, is still nano.

Re:Homer says...

[Avalain]

Though he can only work that into Transformers 3 if he has enough carbon nanotubes.

Re:Homer says...

[Eudial]

Plenty. In many cases, people just add them to things because it sells. It's increasingly becoming a buzzword. I think Ruby on Rails is carbon nanotube reinforced, and The Cloud consists of up to 20% of carbon nanotubes.

Re:Homer says...

[michael_cain]

But the scope on "yet" may also be important. Those on the "doomer" side of the peak energy debate would argue that "yet" needs to be within the next several years, or it won't matter, because we'll have started down a positive-feedback decline curve. If you knew with absolute certainty that, no matter how much research money you spent, cheap nanotubes were at least 70 years away, would you spend any money on that research, or would you spend it on something else?

Re:Homer says...

[kheldan]

..at least 70 years away, would you spend any money on that research, or would you spend it on something else?

See, it's that sort of thinking that gets humanity in trouble in the first place. We need to, as a race, see beyond the ends of our own noses. Yes, it may be true that spending time and resources on Technology-XYZ won't see any real benefit for X-number of years, but does that mean that it's not worth the effort? I believe the average person would say No, it's not worth it because I won't see any benefit from it in my lifetime, which is the wrong answer.
"Why develop alternative energy? We have plenty of oil!"

Re:Homer says...

[michael_cain]

You misunderstand my complaint. Investments in efficiency/conservation work today. Wind works today. Low-efficiency but cheap dye-sensitized solar panels work today. Kilowatt-class direct carbon fuel cells that can use biomass work in the lab today. Metal-air batteries with fast mechanical replacement and separate recharging appear to have sufficient energy and power densities for traction applications today. It's not that I'm unwilling to fund research that may bear fruit X years down the road, where X may or may not be within my lifetime; it's that we don't have X years.

It's just one person's opinion, but I believe that the limiting factor to deal with the energy problems will be capital; that is, the costs to replace or modify infrastructure and long-lived goods may be larger than we manage and sustain some version of the system. The choices of where we put that capital will be important, and research with uncertain benefits, or benefits that pay off only in the long term, may not be the right place.

Re:Homer says...

[kheldan]

*shrug* somebody's got to blink, because the staring contest can only go on for so long.

Yikes, what an article!

[Maury Markowitz]

Did anyone else conclude that article was written by someone who had little idea what they were talking about? Note that "light" doesn't enter the description until after they talk about running power through it. And not one number.

Re:Yikes, what an article!

[Anonymous Coward]

I agree, especially with the comment about excess light. Traditional solar cells do in fact produce more "electricity" or current, with higher intensity light. Second, a photodiode is a more complex structure than a solar cell in most cases, since a solar cell is just a P-N junction.

Re:Yikes, what an article!

[swanzilla]

No numbers, but they managed to sneak in an exclamation point.

Researchers across the world have attempted to create cells from silicon, plastic and even human hair!

Lacking substance...long on hippy drivel.

Re:Yikes, what an article!

[stokessd]

A photo diode is just a PN junction too.

Re:Yikes, what an article!

[Anonymous Coward]

Photodiodes are also light emmitters, not collectors. The article seemed to be describing some kind of super-efficient electronic PMT, though the science must be different with graphine nano-sheets. Supposedly the carbon nanotubes form a zero-gap semi-conductor somehow, even though the work function of carbon itself is a staggering ~5eV.

That said, heat is typically generated in silicon solar cells by electrons struck by light that doesn't give them enough energy to jump the gap. An externally applied field would give those electrons more energy, and a low resistance zero-gap material would allow them to be carried away before they could recombine. So I can see how these nanotubes might theoretically be capable of converting very high and very low energy photons into electricity...

However, visible light is at about 1eV, so these nanotubes would have to have some mechanism for converting 1eV photons into electricity, other wise it wouldn't matter how efficient they are, since the vast majority of the sun's isolation is visible light.

Re:Yikes, what an article!

[Jeremi]

and even human hair! [...] Lacking substance...long on hippy drivel.

To be fair, it's only the hippies who had hair long enough to be usable in industrial quantities.

Hyper-efficient + economical

[Anonymous Coward]

Neither of these two keywords will ever be available in solar cell tech for private customers. The technology combining these two have existed in several shapes for decades, but the dire reality is that there's much money to be lost in releasing this to the public, and much money to be made in making sure this tech. never reaches the hands of the public market.

Since circa the 60s, when amorphous silicon solar cells became available to anyone, there have been numerous breakthroughs - tried, tested, verified and producable for the same penny - in this field, and still, today, 40 years later, the only thing on the market is just that: inefficient, amorphous silicon, which isn't even cheap.

Ooh, ooh

[russotto]

Another world changing technology that's just around the corner.

Re:Ooh, ooh

[yancey]

This didn't sound "just around the corner" because it's pretty basic research and we still need good ways to mass produce the nanotubes. Still, the science there is now proven and it's "just" an engineering problem. Someone fund this... please!

Re:Ooh, ooh

[H0p313ss]

Another world changing technology that's just around the corner.

Just for fun, if you're old enough, try to remember what things were like 35 years ago in the mid 70's:

• The internet was essentially a private network that most of us didn't hear about until the late 80s...
• No PCs, a portable computer was a dummy terminal PRINTER with a 300 baud modem
• Cell phones the size of lunch boxes
• Giant floppy disks with less that 1MB capacity.

These days the average (new) cell phone is more powerful than all the computing resources used by the Apollo program. Heck I carry my ENTIRE music collection around with me every day!

Now try to imagine the world in 35 years.... it's just around the corner.

Re:Ooh, ooh

[Anonymous Coward]

I think it's pretty amazing, actually, that a cellphone sized computer could be used to perform (and now, perhaps even automate - as in run an autopilot program) all the calculations necessary to control a spacecraft intended to fly to the moon and back. Granted, the launch vehicles themselves are a bit more sophisticated, but all of that number crunching was necessary to control the thing. Now, your laptop could be the flight controller for the entire American space program prior to the 1980's, and probably with power to spare.

It's hard to say what the future will hold, but people take contemporary technology for granted enough as it is.

Re:Ooh, ooh

[seven of five]

I think it's pretty amazing, actually, that a cellphone sized computer could be used to perform (and now, perhaps even automate - as in run an autopilot program) all the calculations necessary to control a spacecraft intended to fly to the moon and back.

There's an app for that.

Re:Ooh, ooh

[H0p313ss]

There's an app for that.

You might be aiming for +funny by tapping that meme, but it turns out you're right.

Re:Ooh, ooh

[russotto]

Just for fun, if you're old enough, try to remember what things were like 35 years ago in the mid 70's:

Nuclear fusion was just around the corner. So were high efficiency solar cells. Some things got a lot better. Some things didn't.

Re:Ooh, ooh

[H0p313ss]

Just for fun, if you're old enough, try to remember what things were like 35 years ago in the mid 70's:

Nuclear fusion was just around the corner. So were high efficiency solar cells. Some things got a lot better. Some things didn't.

Have you read Robert Heinlein's essays on the foolishness of trying to predict the future?

Re:Ooh, ooh

[geekoid]

The moon? you think small. We ahve devices exiting are solar system that were built with technology on the 70s.

Re:Ooh, ooh

[tsotha]

Except that the things we thought were right around the corner turned out not to be. By now we were supposed to have fusion power and sub-orbital passenger ships. Hydroponics for food staples. A cure for cancer. Cryogenics.

It's not the things you expect that turn out to be world changing. Those things tend to not happen at all or not be as important as you thought they'd be. It may be quite a bit harder than people think to produce these things economically, and there are already a few other technologies that may render reasonably efficient solar a negligible increase in cost over the substrate.

Again with the #$##%# solar cells

[McGregorMortis]

Not a week goes by that you don't hear about yet another breakthrough in cheap and efficient solar cells. Every week, without fail, since 1979, I swear to God. Any more grains of salt, and I'll have a heart attack.

Re:Again with the #$##%# solar cells

[MyLongNickName]

And prices have been dropping. I am only a casual observer, but have seen that manufacturing costs have dropped to under one dollar per watt. I'd really be curious to see a chart of the price drop over the past twenty years, but my google-fu has yet to uncover the information.

Re:Again with the #$##%# solar cells

[geekoid]

On the plus side, the cost of solar panel is expected to hit 1 dollar a watt by before the end of 2010, and as cheap as 50 cents a watt by the end of 2012.

Re:Again with the #$##%# solar cells

[PmaxII]

But this one is not like the others! It's hyper-efficient.

Re:Again with the #$##%# solar cells

[MyLongNickName]

Here is an anecdote I found in my search

"Scott,
The price of PV modules has come down in the last year, although not quite as much as the Times article suggests. I don't think there has been any significant drop in the cost of inverters, racks, cable, or installation labor.

My first PV module cost me $8.33 per watt in 1980. I paid $3.97 per watt in 2004, and $3.99 per watt in April 2009. Current PV module prices can be as low as $3 a watt, but only if you buy a whole pallet of modules. Otherwise you're still liable to pay $3.50 to $3.96 a watt"

So, since the year 1979 which the GP references, prices to the consumer have dropped more than 50%, even without adjusting for inflation. After accounting for inflation, you are looking at solar being 5 times cheaper than 30 years ago. Not bad.

I know it is poor form to extrapolate like this, but if we had a similar improvement over the next thirty years, then solar would easily become the number one source of energy worldwide. that may or many not come to pass, but the overall point is that despite the jaded responses from folks, we are seeing dramatic improvement in the price/performance of solar.

Re:Again with the #$##%# solar cells

[Firethorn]

On the plus side, the cost of solar panel is expected to hit 1 dollar a watt by before the end of 2010, and as cheap as 50 cents a watt by the end of 2012.

Do you have a link on that?

If true, the only thing remaining would be to drop the ancillerary costs to a similar level. Right now that's running around $1/watt itself.

For example, a 6kw inverter runs $3.6k. That's $.50/watt right there, without getting into wiring, mounting costs for the panels, paying for the electrician to hook everything up*, etc...

*You can't count on everyone, or even a significant fraction of the population to be able to do this stuff themselves.

Re:Again with the #$##%# solar cells

[plastick]

I totally agree. Article after article and yet we never see a single thing or a single product. I'll believe it when I see it and, until then, it's vaporware.

Re:Again with the #$##%# solar cells

[Kokuyo]

You extrapolate wrong, though. In your own example, the price has actually risen between 2004 and 2009. Even keeping inflation in mind, the price drop during those three years will come out as marginal. So the curve of this price drop has become quite flat, don't you think?

This implies, IMO, that even though manufacturing costs have dropped, the consumer price has not changed all that much. Obviously, someone is finally making a profit... Or rather huge profits all of a sudden, depending on how cynical you want to be.

Re:Again with the #$##%# solar cells

[blueg3]

The shorter a time period you use for extrapolation (or fewer data points), the more wrong you are. You shouldn't be concluding much of anything from the price trends of the last five years.

Re:Again with the #$##%# solar cells

[MyLongNickName]

Not really. Adjusting for inflation, we are still seeing a 14% drop in five years, or nearly 3% drop annually.

Also, we are discussing one guy's experience. I'd still love to see a more formal chart of manufacturing costs and consumer cost per watt.

Re:Again with the #$##%# solar cells

[Idiomatick]

Firstly, 2006 p/w was 8$ (Before gov rebate). Next, it sounds like a logistic graph though i doubt you could ascribe a curve to it. With much more points I bet you would find big drops followed by period of relatively little change. This may be bounded by a logistic curve.

But solar panels are physically limited. Even if they grab 99% of the energy that hits them and they transfer it cheaply we will still have to make they for almost the same price as sheets of hard plastic. At best solar cells can become what 3.5x more efficient from in use ones (physical limitation) and maybe halve in price (more variable). After you take away government rebate then I think in 50?(huge range with diminishing returns) years we could make solar power cost 1/4~1/5th as much.

Current nuclear technology price per watt is nearing that now. It has much much more room to drop in price. And it is better for the environment than current solar panels. The amount of materials raped from the earth is less. The footprint is much less. Uranium is more common than tin. And there is no hard physical limitation on 'plant' style energy production.

I do think that solar will have its place. But saying it will be our number one if folly. Perhaps is we find a rugged cheap version we could eventually replace shingles with them but I don't expect that any time soon. Use in mobile devices sure... if it is paint-able we could be it more widespread. But they will never replace power plants. In the next 50 years, energy demands are going to spike as people leave gas and maybe coal as well. Nuclear is the only technology that can keep pace with that. Plain and simple.

Re:Again with the #$##%# solar cells

[TooMuchToDo]

http://solveclimate.com/blog/20071219/1-watt-itunes-solar-energy-has-arrived

A Silicon Valley start-up called Nanosolar shipped its first solar panels -- priced at $1 a watt. That's the price at which solar energy gets cheaper than coal. Curious that this story is not on every front page.

Note that the article is from 2007. What I love about their process is that when they run the roll of substrate faster, the process becomes more efficient. And while you're correct, the support equipment and installation aren't exactly cheap, the panels will continue to come down in price making the total installation cost cheaper.

Re:Again with the #$##%# solar cells

[drinkypoo]

Show me someplace I can purchase nanosolar at even a competitive price, say, $3.75 a watt for finished panels (ready to glue down or whatever.) I can get seconds-quality panels (cosmetic problems, nothing wrong with them) for $2.75 a watt fairly regularly.

Re:Again with the #$##%# solar cells

[TooMuchToDo]

I can't, because their capacity is sold out for the next year or two, which isn't a bad thing. They're available though.

Re:Again with the #$##%# solar cells

[Anonymous Coward]

Manufacturing a 6KW inverter in large quantities does not cost $3,600.

You can get a 600W PC powersupply for less than $100, or a 600W UPS for $130 - and the latter includes the battery ;-)

Both a PSU (tightly controlled low voltages) and a UPS (an up and a down converter) are electrically much more complicated than an inverter, which is just a big MosFet, a transformer and a couple of diodes and small switches to select the correct phases of the 3-Phase AC mains.

Throw in a $2 microcontroller, and you are done.

If this was manufactured in quantities like small UPSes or PC PSUs, the price would be $360, not $3,600 - even for a part that lives a little bit longer than your average 600W PSU ;-)

 

Re:Again with the #$##%# solar cells

[geekoid]

I'm talking just the panel consumer cost. I.e. you walk into a store and that's your price for the panel.

The panels coming out of China next year are expected to be low cost do to lower manufacturing.

I am not talking about the converter.
Like these:
http://sunelec.com/index.php?main_page=index&cPath=5&zenid=2cb58ed84ab020ff9956e7bcdaa79691

Re:Again with the #$##%# solar cells

[Spoke]

He's talking about panels only.

Thin film manufacturers like FirstSolar have already announced that they are producing panels below $1/watt. NanoSolar is very likely there as well.

Silicon panels have dropped a huge amount in the past 6-9 months with the weak economy. Wholesale prices are close to $2/watt, and you can buy panels retail at $3/watt.

Yes, the rest of the costs to install a system (inverter, wiring, mounts, labor) are quickly becoming the largest cost in a solar system, so expect to see drops in price there as well.

Re:Again with the #$##%# solar cells

[BlueParrot]

I know it is poor form to extrapolate like this

I don't think you realize just how stupid it is. Consider:

Doubling efficiency from 5% to 10% - relatively easy.
Doubling efficiency from 25% to 50% - hard
Doubling efficiency from 55% to 110% - requires breaking the laws of thermodynamics

It is obvious that if you start out with rubbish efficiency you will see some great improvements when you put some effort into it, but that rapid improvement will stall when you are up to par with what the tech is actually capable off.

Or to quote Dilbert: "Are you expecting a room full of engineers to be impressed by a percentage improvement over a trivial base?"

Re:Again with the #$##%# solar cells

[Firethorn]

I'm talking just the panel consumer cost. I.e. you walk into a store and that's your price for the panel.

I think you need to reread my post. I asked for a source on the $.50/watt solar panels, then commented that the next that needs to happen is that the associated costs need to drop - which at that point would be double that of the solar panels themselves, thus a bigger target.

What I said: 'If true, the only thing remaining would be to drop the ancillary costs to a similar level. Right now that's running around $1/watt itself.'

When solar panels themselves were running $4-$5/watt, $1/watt ancillary costs weren't as big of a deal. With panels dropping below $1, they're now a big deal.

Well, unless you want to run everything off of DC, but that has issues in and of itself, and you'll likely STILL need a regulator/storage system except for things like sunfrost fridges that can be off 3/4 the day and still keep your stuff cold.

Re:Again with the #$##%# solar cells

[MyLongNickName]

It is also poor form to pick up on one tangent to the discussion and miss out on the main point, especially when poster already noted that extrapolating was not appropriate. The main point, if you missed it, is that the expense of solar has already dropped a lot despite original poster's belly aching.

Re:Again with the #$##%# solar cells

[hey!]

It's all a matter of timing.

We know at some point petroleum will become impractical to support the energy needs of civilization as we know it. In 1979, people thought the end was nigh, when in fact it was just an oil cartel flexing its muscle. But the ability of the cartel to do this was a harbinger of peak oil. The US was no longer anywhere near energy self-sufficient. The same thing happened in 2008, suddenly the end was nigh. It wasn't.

Let me draw a closer analogy. During the Dot Com boom, lots of individuals made money, but very, very few web enterprises did. VCs were pouring money into startups with nothing more than a name and a PowerPoint presentation -- not a real business plan. There wasn't time. Money had to be spent. Why? Because everyone knew web commerce was coming. And they were right, web commerce was coming. Yet the vast majority of money invested in those days was wasted, at least from the perspective that investments should provide returns to the investors. In part it was classic bubble behavior, but even *solid* business plans had a huge element of uncertainty. If the business plan was timed *right*, it would be like buying Microsoft in 1986.

Some day, if the conditions are right, one of these photovoltaic "breakthroughs" may take the world by storm. The chance of any single "breakthrough" doing it is vanishingly small, but the chance of *some* "breakthrough" doing it is substantial. It has to be the right development at the right time.

There are basically three avenues I can imagine working:

(1) Really cheap cells. If it works and can be produced commercially, this is an almost certain winner, because there are many places we can use power and are throwing away photons. Probably won't change the world if it is really inefficient, because *other* costs around installation will limit success.

(2) Incrementally better cells. If it works with given production infrastructure and doesn't have any significant drawbacks, a nearly certain winner that will expand the utility of photovoltaics to applications that are currently marginal. Certainly not a big winner in the short term, but a step forward for the tortoise in the race.

(3) Radically more efficient cells. Least likely to succeed, IMHO. The best cells on the market are about 23% efficient; given thermodynamic limits there isn't a *great* deal of room for improvement. Super-efficient cells will probably have niche applications, but any "breakthrough" in this area needs to have the proviso "and costs about the same to produce as current photovoltaics" before it's worth sitting up and taking notice of.

Re:Again with the #$##%# solar cells

[Firethorn]

He's talking about panels only.

Doesn't mean that I can't bring up the point that the ancillery costs need to drop as well. Heck, if panels go below $.50/watt, the inverter becomes the new biggest expense.

Hmm... Assuming a 30% power factor, 1 watt of solar should produce 2.6kwh/year. $.26-.39 worth of electricity

At $3/watt installed cost, a 1KW install will produce $260-$390 worth of grid power a year*, $21.66-$32.50. Going on an average 20 year lifespan** and 5% cost of capital/loan, that would cost $19.80/month to service the capital.

$4/watt, cost rises to $26.40/month, no longer making sense in areas with cheap electricity(I pay $.10/kwh), and/or less sunlight. You can still save a moderate amount of money in higher cost areas like California.

$2/watt - monthly loan service is only $13.20 for our $2k investment, making us $8.46 per month, even assuming cheap electricity. I like, but sub-dollar panels and install costs per watt is still restricted to big commercial installs.

*Excepting fancier schemes like time billing and subsidizations.
**I know they're guarenteed for 40, but call it a kinda penalty for the odds of a malfunction, cells failing and the company not making good on warranty, non-warranty damage, etc....

thanks for this

[Anonymous Coward]

wow... nice thanks for sharing....

http://www.techandgizmo.com

On the Horizon? Really

[BJ_Covert_Action]

FTFA:

Though still in the very early stages of development, if perfected, carbon nanotube-based cells could provide a more efficient method of converting light to electricity....

ans

While the device is certainly in its earliest stages of development...

So it uses a rather exotic material and is still in the "earliest stages of development" but is on the horizon? Really? It sounds to me like we probably won't see them commercially available for at least another 10 years...then again, I suppose the truth of the statement depends on one's definition of, "on the horizon," but I wouldn't expect to be seeing these guys in Home Depot anytime soon...

Re:On the Horizon? Really

[blueg3]

It's a strange but not rare material -- essentially limitless, but currently expensive to produce.

Re:On the Horizon? Really

[sgt scrub]

The last working test is sitting in an eastern window. Get it? East... Window... Horizon...

Sorry.

Re:On the Horizon? Really

[Idiomatick]

Really, when was the last time you actually MADE it to the horizon, I think the title is maybe cruel but true.

Re:On the Horizon? Really

[avandesande]

The important thing though is that with the linear response to photons light can be focused on the cells- even if they are expensive they could possibly be cost competitive with Si cells.

I for one...(obligatory)

[Anonymous Coward]

I for one, welcome our Carbon Nano-Tube overlords!

The slow rate of solar cell improvements

[Danathar]

Is it just me or do we get all sorts of stories about this or that breakthrough but I have yet to see ANY of this stuff make it to wide use (or even in specialized cases). What good is all this research if none of it ever gets engineered into something we can use.

Don't get me wrong. I LOVE science and research but I look up in the sky and see that big freaking nuclear fusion ball hanging there and wonder why we can't seem to get enough energy from it.

Re:The slow rate of solar cell improvements

[snspdaarf]

why we can't seem to get enough energy from it.

It's that 8 minute delay. It kills your efficiency.

Re:The slow rate of solar cell improvements

[Anonymous Coward]

well, we are kinda only getting the energy that happens to intersect with earth, and of that only the part that makes it through the atmosphere as light, and of that only about 30-40% at current best makes it into usable energy... I'm sure if we were to encase the sun in a sphere designed specifically to capture all radiation from it, we'd be able to generate as much energy as we'd ever need for a good long while, even if the sphere itself was only 10% efficient.

Re:The slow rate of solar cell improvements

[blueg3]

R&D takes time. If you want to read articles about scientific developments where you can have engineered results "soon", read publications from 15-20 years ago.

Re:The slow rate of solar cell improvements

[timeOday]

Is it just me or do we get all sorts of stories about this or that breakthrough but I have yet to see ANY of this stuff make it to wide use (or even in specialized cases).

I think what you are seeing is all the progress in solar is masked by the fact it still hasn't reached the critical threshold of being cheaper than fossil fuel. Regardless of whether it's 20 percent more expensive or 20 times more expensive, it's still not the cheapest option. However, it has been making progress and getting cheaper, which fossil fuel is headed quickly in the other direction. (Well, not coal... it's the cheap, plentiful, crystal meth of energy production that may just prove the undoing of our environment).

Re:The slow rate of solar cell improvements

[geekoid]

No one will jump.
We can power the US on industrial solar power. It takes room and money, but the technology is well known.

I for one welcome our new carbon-based leaders...

[Anonymous Coward]

I for one welcome our new carbon-based leaders... Oh, wait? They aren't new?

Cool, I can't wait.

[dvh.tosomja]

Nanotubes solar panel will be looking great on our flying cars. Except, articles like these occured every few month or so. Meanwhile, the only available cells in the real shops are those silicon cells with 14-17% efficiency - just like 50 years ago.

Future speak meets now tech.

[ZWarrior]

I, for one, thought the article was good for giving us a look into the future of the tech. Based on teh way things are rapid prototyped and built these days I would expect to see something like this hit the markets in 5-7 years, and the price become reasonable with 2-3 years after that. 10 years to a cheap and cost efficient power source is not bad.

More light = More electricity

[MiniMike]

Surprisingly, researchers discovered that more light shined on the nanotube created even more electricity, a huge difference from today's silicon solar cells where excess energy is lost in the form of heat rather than used to create more electricity.

Great, then we only really need one of these. And one really, really big lens.

Re:More light = More electricity

[Tekfactory]

I know you could be going for funny, but there is a project in Israel that does exactly this they have 1,000x parabolic concentrating reflectors that reflect all their light onto a single PV panel.

http://www.greenmomentum.com/wb3/wb/gm/gm_content?id_content=2365 The image seems to be missing, so here is the Manufacturers site. http://www.zenithsolar.com/

Also this Fresnel Lens gets 1,000x concentration but isn't really a reflector

http://www.technologyreview.com/energy/22204/?a=f

99% != infinite

[jeffb (2.718)]

If it costs less than 10 times as much as a 10%-efficient cell, I'm all over it. If it costs 100 times as much, I have no interest, unless I'm really constrained for space and/or weight, or installation costs per square meter are really high.

No, wait. If "99% efficient" means only 1% of the incident radiant energy gets past it or gets re-radiated as heat, I'm all kinds of interested. But, of course, that's not ever going to happen.

Photoresistive, not photovoltaic

[Ancient_Hacker]

If you read TFA carefully it seems to be describing a PHOTORESISTOR, not a PHOTOVOLTAIC device.

They talk about APPLYING a potential difference across the thingy, and discovering it has a wide dynamic range OF RESISTANCE, not of any ability to generate voltage or current.

We don't need any more resistors, we have enough of them and they don't generate any power anyway.

This article is even more of a major fail than most.

Re:Photoresistive, not photovoltaic

[Anonymous Coward]

If you read TFA carefully it seems to be describing a PHOTORESISTOR, not a PHOTOVOLTAIC device.

But they describe it as a photo-diode. I'm going to take a leap of faith here and assume they know the difference.

Oh, and here is a link to the original page.

Re:Photoresistive, not photovoltaic

[Ancient_Hacker]

>But they describe it as a photo-diode.

Photo-diodes can be used in resistive or voltaic modes. The original page is not any clearer.

In any case it still an answer to a non-existent problem-- photocells do just fine in full sunlight.

Re:Photoresistive, not photovoltaic

[geekoid]

"We don't need any more resistors, "

Sure we do. That allows for smaller and more versatile devices.

Re:Photoresistive, not photovoltaic

[Anonymous Coward]

I attended a colloquium by Dr. McEuen a few months ago where he described this research in some depth. They did actually demonstrate a proof of concept with this, but it was very impractical (ultra low temperature with a focused laser on the tube).

Re:Photoresistive, not photovoltaic

[Anonymous Coward]

"Photo resitance is futlie" eh?

(-:

Re:Photoresistive, not photovoltaic

[Anonymous Coward]

Uh...

It actually just sounds like the cell is biased. They do claim that electrons are freed from the matrix. IANA materials guy, but I imagine that the graphine/nanotube matrix creates "loose" electrons similar to metal matrices. I would expect more of a "falling domino" version of hole (imaginary positive charge particle) transmission to the negative terminal (passed .

The only thing I do not understand is how the tube acts as a "photo-diode", per the article. You would need a non-random direction of transmission for the generated electrons, but I don't know how this is achieved. Simply supplying an outside voltage would mean that any energy gained from a change in potential in generated electrons would be provided by the voltage source, not the light. An EMF would have to be induced by the light for the cell to produce energy, but I don't see how this is possible without some difference in material.shape along the tube (similar to N/P doping required in silicon to create a photodiode).

Any insights?

Re:Photoresistive, not photovoltaic

[Anonymous Coward]

The article linked above is crap. If you read the actual letter published in Science, or even Cornell's press release you would have a better understanding of this research.

They have not created an actual photovoltaic device, but have demonstrated highly efficient electron-hole pair generation when the carbon nanotube is illuminated. In other words, they have created a photodiode, not a photoresistor. Surely you know the difference between a diode and a resistor? Anyways, the neat thing is that this shows that carbon nanotubes could be used to make highly efficient photovoltaic devices, after a lot of further research.

Re:Photoresistive, not photovoltaic

[Ancient_Hacker]

Holy bleepin diety.
>They have not created an actual photovoltaic device, but have demonstrated highly efficient electron-hole pair generation when the carbon nanotube is illuminated. In other words, they have created a photodiode, not a photoresistor.

Respectfully, NO. To have a diode, you need a junction. If you only make electron-hole pairs, you just have a photoresistor. And if you read previous replies, you see people that have actually heard the author state it only works at very low temperatures, and with laser light to boot.

But is it ENERGY-effective?

[Errol backfiring]

What's even more important: is it energy-effective? In other words, does the solar panel generate more energy in its entire life than it takes to build one? At least for a decade ago, that did not seem to be the case for any solar panel.

Bad examples

[Dare nMc]

I can put a dollar value on those easily, and they better make financial sense, little else matters. In the US Cars are generally a 2-3 year investment, and a house is a 5-8 year thing, both generally financed. Both (as a guy) require me to grab a calculator and figure out the math (because it won't change my lifestyle/activities.) And given the choice of eliminating a $150 per month utility bill at the cost of a $300 mortgage will be obvious (same with the car.) The same isn't true about lifestyles, hobbies, security, fun. So a luxury item isn't scrutinized to the same degree. That was why the motor-home analogy, it is a luxury item, it is also a lifestyle changing item throw in a hobbies/fun factor (bring out the toys!!!) Now it is only a matter of "can I afford it?", if yes count me in.

Meaningless

[Geoffrey.landis]

The press release is written in such a way that it is clear that the science reporter who wrote it doesn't understand what was done.

For all solar cells, increasing the intensity (the "amount of light shining on the cell") increases the photocurrent.

It would be nice if the press release had a link to the actual work.

Re:Photoresistive, not photovoltaic (Wrong...)

[Anonymous Coward]

I know this was labeled 'informative', but there should be another label 'disinformation', which applies in this case.

The reason this work in interesting is that they found a behavior in carbon nanotubes that has not been found in other solar cell semiconductor systems: the output electricity scales with the input amount of light. Existing materials saturate and have an upper bound to their output. Carbon nanotubes act differently. Now maybe ther is no way to usefully exploit this effect, but it is still a very interesting result. Perhaps it could be extened to other materials, for example.

The fact that they found this when looking at a different application (photo-diode) is typical of scientific discovery. You are confusing the test where the effect was found with the application of the technonogy.

And I did read TFA, and it does say they they are generating electrons from light, not just changing the resistance. Get you fact right before you rant.
 

More Than You'd think

[linuxpyro]

Well, yes and no, you mention a lot of things that could be grouped as switch-mode power supplies.

Making an inverter isn't really rocket science; basically one way to do it is to get your input voltage to say 170 VDC (maybe up from 12 or 24 volts from a battery, or down from say 600 volts from a solar array) and then use that to power a class D amplifier with a sine wave as the input.

Now, that isn't that hard to build. However, for an inverter of the type you might get to feed power from your solar array into the grid it gets more complicated. First, it has to run in phase with the grid, which isn't that hard. But then of course we want to have safety features in place, and the utilities will require UL listing. The inverter has to be able to sense over- and under-voltage and current conditions on both its input side and output side, not to mention variations in frequency in the AC line.

A possible problem is that of islanding. Say the power goes out on your block during the day. We don't want the inverter to backfeed the downed grid, and attempt to power the neighborhood. It's also possible that a neighbor may have a generator wired improperly, such that when he starts it up, he backfeeds the grid; ideally this should be detected as well so the inverter does not contribute. (Detecting these situations relies on above mentioned safety features; obviously you probably won't be able to juice up your whole neighborhood anyway, so if nothing else the overcurrent protection should shut the inverter off.) Yes linemen are trained to treat all lines as if they are hot, but it is still a safety issue. (There are some inverters that can maintain batteries too, so obviously they would just have to disconnect from the grid so you could still have some backup power for yourself.)

On top of this many modern batteryless inverters implement some form of maximum powerpoint tracking (MPPT), in which they adjust the conversion ration on the input to maximize the power from the array. And a lot of them even keep statistics, I think some even have Web interfaces. (Nice to have, but I suppose it would be a bit excessive.) So a lot more than you would think goes into that $3600 inverter.

The UPS you mentioned probably has a modified square wave output, from a comparatively simpler inverter circuit. (Higher end ones may have a sine wave output, but probably not the $130 one you mentioned.) Your computer PSU probably won't care, but things don't tend to run as efficiently on power of that quality, and you sure as hell can't put it on the grid.

Re:More Than You'd think

[Firethorn]

And a lot of them even keep statistics, I think some even have Web interfaces.

You're right - The one I linked to DOES keep statistics, and has a GUI interface panel.

The smaller ones lack that, but are still around $.50/watt.

Can/will costs drop when even more people go installing them? Sure, but my thing right now is that since I'm just south of Canada I'm going to wait until most of the people below the Mason-Dixon line have installed them because I have cheap electricity and less sunlight. I might have to count on a .2 power factor, instead of .3-.4.

Re:More Than You'd think

[linuxpyro]

Keep an eye on the prices, it should be interesting to see what happens over the next few years with renewable energy. I think it is becoming appealing to more people. Eventually if it came down enough so that a substantial portion of the population would consider using their unused roof space to offset their energy consumption (especially in the summer, when there's a lot of sun and people like to use air conditioning) our energy situation would greatly improve.

I might have to count on a .2 power factor, instead of .3-.4.

What exactly do you mean here? Residential electric customers don't get charged for imperfect power factor, and it shouldn't really affect how much power you put onto the grid via an inverter. (This assumes that the grid behaves as a load with unity power factor, as that's what the utility strives for.)

Re:More Than You'd think

[Firethorn]

What exactly do you mean here?

Terminology goof, I meant to say capacity factor.

Solar power is pretty much limited to a maximum of .5 - IE it produces 50% of it's rated power over the course of a year due to the sun only being up half the time.

Realworld, especially if you're not using tilting panels, is more like 30% even in the desert.

Being in North Dakota, I'd be more at 20%.

Re:More Than You'd think

[linuxpyro]

True. Depending on where you are another option is to use tracking racks; I forget where the cutoff is as to what makes this preferable to say more panels or a more efficient charge control (MPPT), but it is an option.

Re:More Than You'd think

[Firethorn]

There's limits to the more efficient charge control, as for tracking rails - I'm so far north that they matter less as well.

The basic facts of the matter is that any given system will give me around a third less energy for the investment than the same investment down below the mason-dixon line.

Ergo, I'm waiting for solar installs to be more or less standard down in the south before I go installing my own system. I've priced them out several times, just hasn't reached the point of making sense yet, even considering subsidizations.

I've also looked at putting a wind turbine up(I'm in a very small town, so I should be able to do it), but haven't been able to make that math make sense.

Re:More Than You'd think

[linuxpyro]

That's true, at this point chances are from a monetary standpoint renewable energy probably won't make sense for most homeowners. I'm from the Buffalo, NY area, and while we get decent sun I'm not in a rush to cover my roof with the latest PV technology. I do have a few panels, though, and I charge some batteries. My interest in RE is partly our of general curiosity (and partly out of the hope of minimizing my impact on the environment), and having a little bit of backup power should the grid go down. (We had a storm back in '06 that took the power out for 8 days.)

I'm actually planning to build my own inverter (as you may have guess from the other post), and would like to come up with a control scheme whereby I have a couple big deep cycle batteries constantly topped off with excess power here and there diverted to running my mail server. (Of course, with a Web interface for remote monitoring, and for linking to on /. so folks can go count the watt-hours and hit refresh every few minutes while they're bored at work. :))

If you're curious, you should play with it in a small system. You could drop maybe $300 or so (maybe less) and build a little one to run some lights or charge a laptop or whatever. Great way to learn, and great in the event of an emergency too.

Re:More Than You'd think

[Firethorn]

Great way to learn, and great in the event of an emergency too.

I'm in North Dakota. 'Emergencies' that leave a home inhabitable are something that happens in the winter. During Blizzards, when there's a foot of snow on the roof. I'm not getting any solar power then.

I've played around with my electrical systems enough that if I do anything, I'm likely to try for a combined cycle generator - using a generator for both power AND heat.

Re:More Than You'd think

[linuxpyro]

During Blizzards, when there's a foot of snow on the roof.

Well, that's why you start with a small system ;). I have two panels that right now I have set up on the ground outside. (I move them around sometimes for better sun exposure.) Thus the snow's not that much of a problem, and the little bit of power is helpful.

The generator is a good idea though.

WALL-E !

[h00manist]

and EVA! - will finally be possible