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## Hairy Solar Cells Could Mean Higher Efficiency203

Posted by ScuttleMonkey
from the warm-fuzzy dept.
kitzilla writes "Two research groups working independently have come up with what they say are cheap processes for growing nanowires to be used with solar cells. The 'hairy' cells provide a direct path for electrons collected at the panel face to reach an electrode, something which has the potential to dramatically improve system efficiency."
This discussion has been archived. No new comments can be posted.

## Hairy Solar Cells Could Mean Higher Efficiency

• #### Anonymous Coward (Score:2, Informative)

by Anonymous Coward
solar cells are pn junctions and DO NOT Collect electrons. i am to lazy to get into solid state theory right now. so go figure how exactly pv cells work.
• #### Re:Anonymous Coward (Score:5, Informative)

on Monday May 19, 2008 @05:00PM (#23467922)
AC's got it right. For those who are TLTRTFM (Too Lazy To ...), what the poster should have said is that they help channel charge carriers away from the junction so that they don't immediately recombine. *That* is one of the holy grails of PV design, and one of the reasons that current production cells are incredibly inefficient.
• #### Let me guess... (Score:5, Funny)

on Monday May 19, 2008 @04:47PM (#23467806)
They expect to have something ready in 3 to 5 years.

If every solar cell advance that was announced actually led to improvements of solar cells you could actually buy, then they would be 99.9999999% efficient and cost less than crackers.

But I'm not bitter, nooooooo.

• #### Re:Let me guess... (Score:4, Informative)

on Monday May 19, 2008 @04:56PM (#23467894)
Slight problem at the moment is band gap, and tuning a semiconductor to have the appropriate bandgap that will cover the visible spectrum. Currently there is no single device that is sensitive to the whole visible spectrum, but there is research into this. This is one of the major reasons for the low efficiency in solar cells.
• #### Re:Let me guess... (Score:5, Insightful)

<tepples@gmail . c om> on Monday May 19, 2008 @05:01PM (#23467934) Homepage Journal

Currently there is no single device that is sensitive to the whole visible spectrum
Then why not have some sort of dichroic reflector [wikipedia.org] pass specific wavelengths to specific PV cell banks?
• #### Re:Let me guess... (Score:4, Interesting)

on Monday May 19, 2008 @05:39PM (#23468296) Homepage Journal

Currently there is no single device that is sensitive to the whole visible spectrum
Then why not have some sort of dichroic reflector pass specific wavelengths to specific PV cell banks?
Good idea, but someone beat you to it [uspto.gov]
• #### Re: (Score:3, Insightful)

Thus proving something everyone on Slashdot already knew: when it comes to rapidly advancing technology, patents do nothing but move the state of the art back 10 or 20 years.
• #### Re:Let me guess... (Score:4, Insightful)

on Tuesday May 20, 2008 @04:25AM (#23472716)

Thus proving something everyone on Slashdot already knew: when it comes to rapidly advancing technology, patents do nothing but move the state of the art back 10 or 20 years.

I don't see its proved anything of the sort to be honest. Unless the poster who made the original suggestion is in a position to bring this product to market himself, and was willing to make what I assume would be a large investment to do so without the benefit of any patent protection, then no one has lost anything. On the flip side the patent holder may be able to find an investor willing to back development of the technology; it would be considerably harder to do so if the investor knew that if the product was a success, they'd have to very quickly face competitors selling identical products who didn't have to make as large an initial investment.

Disclaimer: I know crap all about solar power or the validity or utility of this particular patent; I'm just trying to make a distinction between the development of software and that of physical inventions.

• #### Re: (Score:2)

Because reflectors can cause energy loss. better way to tune a semiconductor is using controlled dimensionality- use Quantum Dots.
• #### Re: (Score:2)

Wouldn't micro (nano?) bands of prisms and repeating strips of particular frequency sensitive solar panels work as well?
• #### Re: (Score:2)

too much effort to tune the directionality of the prisms. best way would to have a repeating pattern of Quantum Dots receptive to a particular frequency, and then just pack as many on to the surface as possible. even though a given particle could only absorb a given frequency, the reflection off of the particles could cause radiation to disperse through the surface. this method is better as it's a) simpler and b) doesn't leave surface real estate taken up by crystals.
• #### Re:Let me guess... (Score:4, Informative)

<charles.d.burtonNO@SPAMgmail.com> on Monday May 19, 2008 @04:57PM (#23467900) Journal
Personally I love solar voltaic panels with a little of that canned cheese on them. On a more serious note, why do people not focus on the tech that we have now? For instance if you want solar the solar thermal systems are pretty cheap to build and have decent efficiency. I just don't get why everyone is so stuck on solar voltaic which is as someone else said in a perpetual early adoption stage when a good chunk of baseline power could be provided by solar thermal.
• #### Re: (Score:2)

because solar thermal is even more of a joke than PV is....
• #### Wow, are u clueless or what (Score:4, Informative)

by Anonymous Coward on Monday May 19, 2008 @05:45PM (#23468358)
Thermal solar is the lowest costs of all AE except for hydro. At this time, it is the same costs as a recent coal plant i.e. a plant that is cleaner than average. Of course, the solar thermal is clean all the way around.
In addition, it is fairly easy to store the heat in salts and generate during the night. Spain, Arizona, New Mexico, Northern Africa, etc. are all headed in GW size of solar thermal. Spain expects to sell power back to its northern neighbors at a tidy profits. Arizona has a 1/4 GW install going in. In addition, another group is close to building a 1/2-3/4 GW in NM or southern CO (possible to take advantage of 3 different power companies and 5 states incentives).

All in all, the only joke is a fool like you.
• #### Re: (Score:2)

solar thermal has a number of problems, though, not the least of which is that pipes that are gotten very hot by the sun tend to burst or at least fracture much more frequently than in other applications...

in systems large enough to generate megawatts of electricity there are solutions to this problem, but systems meant to be installed on top of a residential roof are notoriously bad for needing to be repaired every season, for some unlucky souls...

• #### Re: (Score:3, Interesting)

..and I'll believe it when I see it.

Planned installations chasing incentives are a far cry from power plants installed to meet grid needs.

24h power (storage and retrieval of energy) is unnecessary system complexity when you are not looking to replace the current grid, and at their current level of deployment (nil, pretty much) this is not a concern. You might want to co-fire with natural gas to avoid thermal cycling of your plant like they do at Kramer Junction in CA, but that's beside the point.

Furthermor
• #### Re: (Score:2, Informative)

nonsense. the largest thermo solar power plant is just 64 mega watt - enough for 15,000 homes. compared to coal fired stations that can supply 700,000 homes, yes it's a JOKE.
• #### Re: (Score:2, Informative)

The first coal plants couldn't even supply one modern home with power... They have plans to build 'em much bigger, such as 553MW for Mojave Solar Park: http://media.cleantech.com/1522/pg-e-solel-in-553-mw-solar-deal [cleantech.com]
• #### Re: (Score:2)

The SEGS is the largest at 354 MW, but larger ones are soon
to come online as other posters have mentioned.

http://en.wikipedia.org/wiki/SEGS [wikipedia.org]

Total Solar Thermal for just 10% of the Sahara is over
3 times all power used on Earth in 2005 at 40% Efficiency.

So for those who disdain Solar thermal, it could make
all the hydrogen for fuel cells for earth easily.

Setting up the system and managing it will be a Herculean
• #### Re: (Score:2)

Solar Thermal. You mean the stuff that is widely used in China, providing hot water to at least 30 million households there? Yep, sounds like a joke to me....
• #### Re: (Score:2)

Thermal is currently 40% in some units,
and a prototype achieved 60%.

http://en.wikipedia.org/wiki/Solar_thermal#High-temperature_collectors [wikipedia.org]

Excerpt:

As the temperature increases, different forms of conversion become practical. Up to 600ÂC, steam turbines, standard technology, have an efficiency up to 41%. Above this, gas turbines can be more efficient. Higher temperatures are problematic because different materials and techniques are needed. One proposal for very high temperat
• #### Re: (Score:3, Informative)

36% in concentrator cells, but they'll be stuck in the lab for quite a while, and will probably be infeasible for large installations.

Thermal is currently 40% in some units, and a prototype achieved 60%.

That's the efficiency of the turbine itself. The plant will have some additional losses (not all of the sunlight hitting the area of the plant will actually be collected, etc).

• #### Re: (Score:2)

This new technology has a liability in that it breaks down when exposed to air, but if they could be manufactured and deployed in space, they might prove very effective. I find that a lot more interesting than the liquid salt solutions, personally. Cool shit.
• #### Re:Let me guess... (Score:4, Insightful)

on Monday May 19, 2008 @06:19PM (#23468716)

a good chunk of baseline power could be provided by solar thermal.
Baseline power is the minimal power required during the day, so it has to be supplied constantly. Solar thermal plant output drops to 0 watts at night unless you use some means of energy storage, and is severely reduced during the winter or when there are thick clouds, so they're not suited to supplying baseline power unless a reliable means of storing huge amounts of energy with little loss is developed. For now, the only feasible baseline power plants are hydro, nuclear and fossil.

Generally solar is good as long as the sky is clear. Imagine what would happen to a 100% solar economy hit by a month of thick clouds. I don't think relying on something as random as the weather for your main energy supply is a good idea. It's OK e.g. when you want to power farm machines, because if there's no power you can wait, but powering cities with it doesn't seem wise. I also think that green activists should stop pretending they can do without nuclear power (at least those of them that do), because right now they can't, and telling everybody not to invest in nuclear and wait until we come up with adequate energy storage technology is making the global warming worse by preventing substantial CO2 emission reductions.
• #### Effort actualy has to be put in (Score:4, Interesting)

on Monday May 19, 2008 @10:49PM (#23470780)
Nuclear always comes up in discussions like this. The answer for nuclear is to put as much effort into research as is going into solar research - instead the money has gone into lobbying to build antiquated plants. If more research was done pebble bed might be furthur along, accelerated thorium might be at the full prototype stage and synrock might have been developed in less than thirty years. Note that the three major developments come from South Africa, India and Australia on fairly small budgets from begrudging governments - think what the USA could have done on venture capital alone. There should be more to civilian nuclear energy than 1960s white elephants painted green.
• #### I have 2 words for you (Score:2)

1. batteries

2. deserts
• #### Re: (Score:2)

Super heated oil storage is being used now.

Super heated molten salt is being developed now.

http://en.wikipedia.org/wiki/Molten_salt_battery [wikipedia.org]

http://www.ornl.gov/sci/scale/pubs/SOL-05-1048_1.pdf [ornl.gov]

A hybrid of ORNL plans and the prior link could be the
super solution to night energy storage.

Especially if you could use something like a giant empty salt mine.

http://simple.wikipedia.org/wiki/Salt_mine [wikipedia.org]
• #### Re: (Score:2)

For instance if you want solar the solar thermal systems are pretty cheap to build and have decent efficiency.

If you're talking about passive solar heating... They're an okay option, but don't provide any cooling (which is needed most when it's sunny out). What's more, as PV panels keep getting more efficient, so too do heat-pumps, which require electricity, not heat (...ignoring inefficient and expensive gas absorption units).

If you're talking about generating electricity via steam or the like, the laws

• #### Re: (Score:2)

Mmmmm, hairy crackers...

</Homer Simpson>
• #### Re: (Score:2, Funny)

by Anonymous Coward

Mmmmm, hairy crackers...
Fantasizing about us white guys again?
• #### Re:Let me guess... (Score:5, Interesting)

on Monday May 19, 2008 @05:32PM (#23468208)
Remember, solar power is generally available HERE and NOW.

I just invested in a PV system for my house (in sunny SoCal). As a computer geek, I asked our guy if it was stupid to invest, since there always seem to be efficiency breakthroughs on the horizon.

He reminded me that efficiency generally meant "smaller" and perhaps "cheaper". But since my roof was plenty adequate for what I needed, "smaller" wasn't really an issue. Cheaper will ALWAYS be the case, as it always has been.

Don't get frozen by the thought that solar power isn't worth investing in today. It totally is.

• #### Re:Let me guess... (Score:4, Funny)

on Monday May 19, 2008 @06:06PM (#23468548)
Sounds just like computers. I need to get one of those one of these days. Just as soon as they stop getting smaller and cheaper.
• #### Re: (Score:2, Interesting)

by Anonymous Coward
Not only here and now. I started homesteading in 1979 and been off the grid, but not without power since then -- the tech was already good enough insofar as solar panels go. Batteries, on the other hand...we do OK with what there is. What makes good panels (such as I have) expensive is not the silicon part. It's all the rest, which has made my panels last from then until now, still performing like new -- I couldn't guess the eventual lifetime. All it's going to take is more people putting their money w
• #### Re: (Score:2)

Waiting for cheaper can be a fallacy too tho, if you buy today and then in 5 years time, the price drops, well, you have been selling electricity for 5 years already, so how much did you make in the meantime?
• #### Re: (Score:2)

This is almost exactly the argument I used to convince some people to finally jump on the computer wagon.

Sure, it'll be cheaper and more powerful in the future. But they were running a business and the expected savings would pay for the systems in less than two years with an expected lifespan of at least five.
• #### Re: (Score:2, Interesting)

by Anonymous Coward
Thank you thank you thank you! I've lost count of the number of times I've heard the "solar is almost ready, but it's only x% efficient, so best to wait a little longer when it'll be cheaper/smaller/whatever" argument repeated over the years. Yes, just like any other technology solar cells will get better as time goes by... so the "don't buy until we reach nirvana in $\lim n \to \infty$ years time" argument can be equally applied to pretty much any technology. Like, say, computers, cars, refrigerators, h
• #### Re: (Score:2, Funny)

... then they would be 99.9999999% efficient and cost less than crackers.
Yes, but would they be individually wrapped?
• #### Sheeit Negro, that's all you had to say! (Score:2, Interesting)

What's really awesome is that PV cells have undergone constant improvement in lab performance for 20 years, but since nothing ever gets put into production, the industry is held in a constant state of "early adoption" and we get screwed like perpetual "early adopters".

Know what would rawk? A 5 year moritorium on new PV cell research so we could get some actual PV cell production going.

• #### Lab advancements != commercially viable (Score:5, Insightful)

on Monday May 19, 2008 @04:56PM (#23467892)
The problem is that a large portion of the lab performance-enhancing techniques are so insanely expensive that they *can't* go into production. Many of them - particularly exotic materials or multi-junction cells - are prohibitively expensive to make, given the meager performance improvements. I think Nanosolar has the right idea for now - craptastic cells made cheap. Who cares if they're large if they're incredibly inexpensive?
• #### Re: (Score:3, Insightful)

Yeah but this is like any technology. A few days ago there was an article on why touch table tops are just now coming around. Thats because 30-40 years ago when they were developed they were developed in labs and were extremely expensive. Now with the advancement in technology that produced them its feasible for this technology to be manufactured/developed/sold.

Give this technology another 20-30 years, maybe even less, and the advancement of production will drop the price.
• #### Re: (Score:2)

And by golly, nuclear reactors are so cheap!

• #### Re: (Score:2)

Pretty lucky here as well, 7.68 cents a KWh and it is
natural gas here in Oklahoma.

• #### Lots of NG electricity for you... (Score:2)

I find it interesting that you're 40% NG(20% cola) and that you're getting 7.68 c/KWh.

NG generally has cheap construction costs and expensive running costs. But you probably have substantional cheap NG deposits.
• #### Re: (Score:2)

Oh yeah, Oklahoma has massive natural gas wells.

Some were so massive when they came in they caused minor earthquakes.

There are literally dozens if not hundreds of them.

Oklahoma is the 3rd largest Natural Gas producer in the US.

Suprised we use any coal at all.
• #### Re: (Score:2)

hydro isn't 100% tapped, there are tons of places around the world where new hydro electric plants are going up, maybe in America the market was saturated early, but if we put in hydro plants in many countries in Africa, those countries won't have to put in as many coal fired plants at technology gets cheaper, etc.

wind is nowhere near tapped.... i think the Department of energy once found in a study that wind power plants could provide up to 40% of the energy needs of the US, overall, the problem though, i
• #### Re: (Score:2)

High power tornadoes are extremely rare.

I live in the center of tornado alley, and my house
is 55 years old, and my friend's house is 70+ years old.

Neither of these houses have been hit by a F0-F5.

Some day that will happen, but I may not be alive to see it.

There are lots of homes around me that are over 50 years
old and none of them have been hit.

A few areas in central Oklahoma seems to be a tornado magnet
Moore and Edmond, some areas almost never get hit,like Norman.

I have no idea why, just a observation of t
• #### Re: (Score:2)

Since solar is currently 4X, that means it will drop to .2-.8X of CURRENT power costs.

Do you happen to have a source on this? All the times I've figured it, it's around 10X as much.

4X might be with some of the high levels of subsidies and such. Or a large solar thermal installation, which photovoltiacs don't figure into.

Or maybe it's compared to retail electrical prices, and doesn't include support equipment such as the inverter.
• #### Re: (Score:2)

I was quoting the parent of my comment.

However with nanosolar's thin film cells the price can drop to about 1.5X coal (although space could become an issue).

Currently the payback period for a full off-grid residential solar system is on the order of 7-10 years. (Cited all over the place) This is in line with the roughly 4X for conventional silicon cells.
• #### Re: (Score:2)

Even given your calculations (and I don't think I'm really happy with all the assumptions) solar power is often usable where wind power isn't, and vice versa, so it's not an "either or" situation.
• #### Re: (Score:2)

If you're talking strictly about the monetary economics, then I think what we really need to do is rethink the world's concept of economics.

At SOME point the bullet has to bitten as far as cost goes somewhere. Oil and coal aren't going to stick around for ever.
• #### Re: (Score:2)

While increasing the efficiency of a solar cell can indeed make it cheaper, in that if the increase in efficiency doesn't significantly increase the cost of a cell, making it so you need half as many, half as much mounting equipment, etc... It doesn't really matter.

I agree with you, the significant obstacle isn't the efficiency of solar panels. It's the cost of them, more so than the space they take up.

If we could produce solar panels that were half as efficient as current panels for the cost of a ream of
• #### Re: (Score:2)

so even assuming the 100% efficiency, efficiency gains alone cannot make solar economical.

Add the long term cost of the Iraq war, and the future
war in Iran onto the cost of your petro power.

It is not so cheap anymore.

If the long term projected trillions of dollars went to a
Solar Thermal array like the SEGS system we could
power the earth with 10% of the Sahara Desert
3 times over replacing all forms of power including
oil, coal, nuclear, wind, hydro.

In 2005 total world energy usage was 15 Tera Watts,
the 10% se
• #### Fraud alert ... (Score:5, Funny)

on Monday May 19, 2008 @06:46PM (#23468940)
These guys are scammers ... it's the old When Hairy Met Sili Con.
• #### Wow, ANOTHER solar cell breakthrough (Score:5, Insightful)

on Monday May 19, 2008 @07:39PM (#23469368)
Wake me up when there's actually a cheap product. These articles need their own icon; maybe Bigfoot, the Easter Bunny, Santa Claus, the Loch Ness Monster, or La Chupacabra.

Breadth-first search is the bulldozer of science. -- Randy Goebel

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