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Solar Cells That Emit Light Break Efficiency Record

samzenpus posted more than 2 years ago | from the shine-on dept.

Science 139

benfrog writes "Researchers at the University of California-Berkeley say they have come up with a counter-intuitive way of making solar cells more efficient — making them emit light. In a press release the scientists claim to be the first to demonstrate that the better solar cells are at emitting photons (the more LED-like they are), the more efficient they are at generating electricity. However, 'unlike an LED, the electrons in a solar cell are absorbing photons from an exterior source as well as emitting their own.'"

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Break out the mirrors... (0)

HydraSwitch (184123) | more than 2 years ago | (#39799807)

And polish them up.

Re:Break out the mirrors... (-1, Troll)

Anonymous Coward | more than 2 years ago | (#39799843)

And take a long look at this phony green religion going on.

Idea (5, Funny)

busyqth (2566075) | more than 2 years ago | (#39799825)

Why don't they just funnel the emitted light back to the solar panels and thus make them independent of an external light source?
This would be great for space colonies and sea-floor dwellings.

Re:Idea (5, Funny)

X0563511 (793323) | more than 2 years ago | (#39799853)

In this seafloor habitat dwelling we obey the laws of thermal dynamics!

Re:Idea (-1)

Anonymous Coward | more than 2 years ago | (#39800321)

YHBT. HAND.

Re:Idea (3, Funny)

geekoid (135745) | more than 2 years ago | (#39801223)

And that's why we can't have nice things.

Re:Idea (-1)

Roger W Moore (538166) | more than 2 years ago | (#39802727)

In this seafloor habitat dwelling we obey the laws of thermal dynamics!

Really? Everyone else usually obeys the laws of thermodynamics...at least on average.

Re:Idea (1)

YodasEvilTwin (2014446) | more than 2 years ago | (#39799885)

"Independent" is a bit strong of a term, given that even if they were perfectly efficient they would need an external source to actual *generate* electricity instead of just maintain their energy. That said, I would assume they would funnel the light back unless (1) it interfered with letting the external light in or (2) it was of a wavelength that was poorly absorbed by the panels anyways.

Re:Idea (0)

hvm2hvm (1208954) | more than 2 years ago | (#39804335)

Trolls trolling trolls that troll trolls.

Re:Idea (3, Insightful)

mooingyak (720677) | more than 2 years ago | (#39799907)

Why don't they just funnel the emitted light back to the solar panels and thus make them independent of an external light source?

This would be great for space colonies and sea-floor dwellings.

Thermodynamics and all that. But you could probably sit a couple of these facing each other and recapture some of that light. Also, I'd expect space colonies to have relatively easy access to an external light source.

Re:Idea (5, Informative)

Daniel_Staal (609844) | more than 2 years ago | (#39799967)

Because the light will be of lower energy (and therefore of a different wavelength) than that which the solar cells absorbed.

Basically, instead of heating up, these cells emit the energy in a controlled manner, in semi-directed infrared (probably) radiation. No laws of thermodynamics are being bent: The waste product is just closer to the type of the input than in other solar cells.

You could similarly say that a water turbine is more efficient if it lets water flow out: It is. The water will just have less flow strength than it did when it went in. The difference is what the turbine is collecting as energy. In this case, instead of letting the light 'back up' in the solar cells (as heat), it's released.

Re:Idea (-1, Troll)

busyqth (2566075) | more than 2 years ago | (#39800479)

You bring up an interesting point.
It seems like someone ought to be able to use a water turbine to generate electricity which would be used to pump the water back up behind the turbine. It could all be done in a big factory or power station without impacting the environment.
It would be a really green source of energy.

Re:Idea (0)

Anonymous Coward | more than 2 years ago | (#39800629)

Except for the part where you get, theoretically, the exact same energy from the generator as you do into pumping the water, and practically, it's half or less.

Re:Idea (1)

NatasRevol (731260) | more than 2 years ago | (#39800703)

But it uses gravity! /sarcasm
(just in case)

Re:Idea (4, Insightful)

Intrepid imaginaut (1970940) | more than 2 years ago | (#39800571)

This is so cool. Every day brings us closer to glowy alien crystal energy technology.

Re:Idea (2)

CaptainLugnuts (2594663) | more than 2 years ago | (#39800137)

Once this [engadget.com] gets worked out tailoring the waste output into the IR could be quite useful.

LIght emission is negative absorption [Re:Idea] (2)

Geoffrey.landis (926948) | more than 2 years ago | (#39800847)

Light emission is the converse of light absorption, so any solar cell that absorbs light must, by the same mechanism, emit light, unless other loss mechanisms prevent it. Obviously light emission is a loss mechanism-- light emitted is clearly not turned into electricity. However, all other loss mechanisms can be eliminated by sufficiently clever design, but light emission is a loss required by the laws of thermodynamics. Thus, a solar cell is optimized when there is no other loss mechanism other than light emission, which is to say, when the light emission is maximized.

(In fact, it is optimized when the light emission back toward the source is maximized; all emission that isn't back toward the source could in principle be retroreflected and reabsorbed. This would be known as "light trapping".)

Ehh (0)

Anonymous Coward | more than 2 years ago | (#39799867)

Sounds like troll-physics.

Re:Ehh (3, Informative)

uigrad_2000 (398500) | more than 2 years ago | (#39800033)

Well, Physicists from MIT beat 100% efficiency a month ago. [slashdot.org] (of sorts).

The MIT team called it a LED that functions much like a heat pump. It emitted more optical power than the electrical power it consumed. Apparently the trick is that it results in a lower entropy state, and only works on extremely small scales, so it will never lead to a practical device.

This story, however, doesn't seem to say at all that they have broken 100% efficiency. They are trying to get the total efficiency up above 30%. The amount of light given out by the cell and the electrical energy given out add up to less than 100%. The slashdot headline leads you to believe that they broke 100%, but that is not what "efficiency record" means in this case.

Re:Ehh (0)

PopeRatzo (965947) | more than 2 years ago | (#39800369)

The slashdot headline leads you to believe that they broke 100%

Please explain how the headline to this story, "Solar Cells That Emit Light Break Efficiency Record" would "lead you to believe" that they broke 100%.

Re:Ehh (3, Informative)

Khyber (864651) | more than 2 years ago | (#39802239)

Go read the article, maybe? The entire LED world is abuzz right now with that news. The only issue is that it requires a HOT ENVIRONMENT, where the LED seems to utilize by converting some of that energy into visible-wavelength emissions, beating the power input/optical power output ratio of 1:1.

Re:Ehh (1)

PopeRatzo (965947) | more than 2 years ago | (#39802583)

I was joking.

Re:Ehh (1)

ceoyoyo (59147) | more than 2 years ago | (#39803687)

Beating the ELECTRICAL power input to optical power output ratio of 1:1.

Re:Ehh (0)

Anonymous Coward | more than 2 years ago | (#39800821)

Read FAIL

Stands to reason (1)

squidflakes (905524) | more than 2 years ago | (#39799945)

Just like a good reflector of thermal energy also makes an excellent insulator, a good design for converting voltage to photons can be referenced to do the opposite.

Re:Stands to reason (3, Informative)

KlomDark (6370) | more than 2 years ago | (#39800179)

Just like how a speaker can be used as a microphone. It make noise when you run signal-carrying voltage through it, but also makes electricity when you scream into it.

Re:Stands to reason (2)

squidflakes (905524) | more than 2 years ago | (#39800297)

Yep, you can use larger speakers to make really good low frequency mics. Hell, in a pinch you could use your ear buds as a mic for your PC, if that sort of thing ever came up.

Re:Stands to reason (3, Funny)

Eponymous Hero (2090636) | more than 2 years ago | (#39800763)

sure, rage quit a game, throw the mic across the room and realize the plug didn't come with it, and pretty soon you're wearing headphones around the side of your head over your mouth.

Re:Stands to reason (2)

RenderSeven (938535) | more than 2 years ago | (#39801095)

Which is why we should have installed speakers in Congress years ago. Screaming politicians could generate scads of Green Energy!

Re:Stands to reason (3, Funny)

djlowe (41723) | more than 2 years ago | (#39801409)

Which is why we should have installed speakers in Congress years ago. Screaming politicians could generate scads of Green Energy!

I'd think that some sort of thermal conversion would be more in order. After all, Congress generates a LOT of hot air ...

Regards,

dj

What's counter-intuitive about it? (5, Informative)

SirGarlon (845873) | more than 2 years ago | (#39799949)

If you've taken sophomore college physics, it's not counter-intuitive at all [wikipedia.org] that an efficient absorber is also an efficient emitter.

Re:What's counter-intuitive about it? (4, Insightful)

Wraithlyn (133796) | more than 2 years ago | (#39800341)

Um, if someone needs the relevant college-level courses to understand this, then by definition it is NOT intuitive.

What do you think "intuitive" means exactly?

Re:What's counter-intuitive about it? (5, Funny)

gman003 (1693318) | more than 2 years ago | (#39800483)

What do you think "intuitive" means exactly?

Intuitive (adj.) - Anything I already know.

Re:What's counter-intuitive about it? (5, Insightful)

Eponymous Hero (2090636) | more than 2 years ago | (#39800885)

as a slashdotter, the rest of us slashdotters presume that you're a more-than-competent physicist, chemist, biologist, astronomer, economist, engineer, gamer, proofreader, and Dr. Who/BSG/Star Trek/Star Wars/Matrix/LOTR archivist. if you're not, someone who is will pull your card.

plus, isn't sophomore college physics, like, a facebook app or something by now?

Re:What's counter-intuitive about it? (1)

hacksoncode (239847) | more than 2 years ago | (#39800981)

Readily apparent to one's intuition.

The intuition of a person that has taken (and paid attention to) college-level courses is *of course* more efficient at comprehending things that are the topics of the courses.

Perhaps you were thinking of common sense?

The vast majority of people have *crappy* intuitions.

Re:What's counter-intuitive about it? (4, Insightful)

robot256 (1635039) | more than 2 years ago | (#39801281)

The vast majority of people also have crappy common sense. Saying something is intuitive without stating what background is required for it to be intuitive is just a dick move trying to make everyone else look stupid for not knowing everything you know. I learned a long time ago that things I think are obvious are frequently not to other people.

Of course, some of those things include not posing for photos on railroad tracks and making your kids ride with their seat belts buckled. The "bowling ball and a feather falling in a vacuum" question decidedly takes the back seat compared to the lack of intuition some people exhibit.

Re:What's counter-intuitive about it? (3, Informative)

Wraithlyn (133796) | more than 2 years ago | (#39801371)

Nice circular definition? "Something is intuitive if it's intuitive to me"?

Intuition is direct, a priori, instinctive comprehension of a concept, NOT relying on experience, and "without inference or the use of reason".

It is counter-intuitive that a solar cell "throwing away" light will result in higher energy output.

If you have facts/knowledge/education on your side that counter this "layman's expectation", you're no longer relying on intuition.

Claiming you develop a better "personal intuition" as a result of education/experience/whatever is simply an incorrect use of the word.

Re:What's counter-intuitive about it? (1)

geekoid (135745) | more than 2 years ago | (#39801255)

Well, it should be obvious to even the most dim-witted individual who holds an advanced degree in hyperbolic topology, ng-bwui, that Homer Simpson has stumbled into....the third dimension.

Re:What's counter-intuitive about it? (1)

Khyber (864651) | more than 2 years ago | (#39802259)

You don't need college courses.

Newton's third law of motion, which anyone should have learned in MIDDLE SCHOOL, is enough to understand this. For any action, there is an equal, and opposite reaction. Light absorbed, light emitted. Dead fucking simple.

Re:What's counter-intuitive about it? (0)

Anonymous Coward | more than 2 years ago | (#39802593)

I've got to post anon because I've been moderating. You've got that dead wrong. The preconceived notion that people have is that there's light absorbed, because the electromagnetic energy is converted to heat or electrical energy. Light absorbed =/> light emitted. Not at all.

Re:What's counter-intuitive about it? (1)

Khyber (864651) | more than 2 years ago | (#39803083)

You need to stop moderating if you can't read and think critically. There is nothing wrong with what I've stated. This is entirely a classical issue we're discussing, sonny.

Re:What's counter-intuitive about it? (1)

eugene ts wong (231154) | more than 2 years ago | (#39803631)

"intuitive" is explained in Physic 301.

Re:What's counter-intuitive about it? (0)

Anonymous Coward | more than 2 years ago | (#39800579)

Planck's law does not apply to band-gap related emission/absorption.

It's Older and More General Than That (2, Interesting)

Anonymous Coward | more than 2 years ago | (#39802433)

Thermodynamics teaches us that the most efficient cyclical process is one that can be run in reverse the same way it is run forward. The more irreversible the process, the more it strays from equilibrium, the more it runs uncontrolled (all synonyms) the farther it is from being maximally efficient.

Re:What's counter-intuitive about it? (0)

Anonymous Coward | more than 2 years ago | (#39802919)

Question: does an emitter radiate or does a radiator emit?

Re:What's counter-intuitive about it? (0)

Anonymous Coward | more than 2 years ago | (#39803131)

Yep. Have you ever seen a fat person take a dump?

Well, kind of (5, Informative)

Anonymous Coward | more than 2 years ago | (#39799959)

Ideally, you would want all of your electron-hole pairs to never recombine (which would keep them from emitting photons). Since that's obviously not possible, this would be the best possible outcome of internal recombination.

Photosynthesis (0)

Anonymous Coward | more than 2 years ago | (#39800023)

Is this why plants fluoresce in near infrared?

Re:Photosynthesis (-1)

Anonymous Coward | more than 2 years ago | (#39800791)

No, that's be cause they are afraid of your fat ugly momma.

Re:Photosynthesis (3, Informative)

Khyber (864651) | more than 2 years ago | (#39802273)

No, they fluoresce in near-UV (unless you're watching with an IR scope when using 680-700nm light.) Light conversion always works DOWN from higher energy potential to lower energy potential when there's no amplifier or booster present. We can take one blue photon and emit 7 or 8 red photons, roughly. This is why plants have this odd purple/red glow with certain near-uv wavelengths. They absorb blue, emit yellow/red photons as a result.

Re:Photosynthesis (0)

Anonymous Coward | more than 2 years ago | (#39804351)

naw thats cause they valence level is angry

The bigger problem (5, Interesting)

cirby (2599) | more than 2 years ago | (#39800079)

Sure, it would be nice to have much more efficient solar cells, but there's another issue keeping costs up.

It's the home infrastructure.

Right now, it costs more to install the solar cells on a roof than it does to make them, and once you add in the cabling and battery/storage system for balancing the load or for nighttime use, the actual power generating part of the system is much less than half of the whole system cost. Increasing efficiency is great, and will let you cut the overall size of the system for a similar capacity, but the big issue is making a solar system that's easy to install, with cheap storage, for a lot less.

Cheap batteries and inexpensive support systems are the things we need now...

Re:The bigger problem (4, Insightful)

cpu6502 (1960974) | more than 2 years ago | (#39800151)

Make the solar cells part of modular homes where the roof and panel are built as one in a mass-production factory.

Re:The bigger problem (3, Informative)

ArhcAngel (247594) | more than 2 years ago | (#39800807)

You still have to convert the energy from DC to AC so your DC appliances with AC2DC converters can plug into the wall. Damn you Tesla! [wikipedia.org]

Re:The bigger problem (2)

Khyber (864651) | more than 2 years ago | (#39802283)

No you don't.

I've got plenty of 12V native devices. Stereos, monitors, rack servers, guitar amps, and much, much more.

I would only need a battery bank and perhaps some power-smoothing circuitry.

And FYI, these devices have existed for almost longer than my three decades of life.

Re:The bigger problem (1)

ArhcAngel (247594) | more than 2 years ago | (#39802429)

WOW!

Even with the "Damn you Tesla!" hint that it was a lighthearted joke you managed a major league WHOOOOSH

I don't know of any electronic device that isn't DC based. Most, however, are designed to accommodate the AC delivery system we've used for the last century.

BTW...Is your house wired for DC or would you need to run all new outlets for the 12V native devices? If, I suspect, it's the latter which is easier, converting DC to AC and running through the existing wiring in the house or running a separate line to every place in the house an outlet is already located? Because both are going to be equally expensive but one will be substantially more invasive and time consuming.

Don't get me wrong...I'm an advocate for DC in the home I'm just realistic when looking at existing infrastructure.

Re:The bigger problem (1)

Khyber (864651) | more than 2 years ago | (#39803101)

Wires are wires are wires if you're pushing enough power through them. 12V @ roughly 200A is not going to lose too much over a few dozen feet. You just drop the circuit breaker onto a DC storage supply, and hook charging panels + charge controller to the power supply.

I did it with warehouses in Memphis (822 Rozelle) houses are much simpler of a matter.

Re:The bigger problem (0)

Anonymous Coward | more than 2 years ago | (#39803803)

While I dont dispute that wires are in fact wires, to be a little more technical about it, the amount of voltage drop along a wire depends on how much current travels through it. To get the same amount of power with a 12V power supply you would need about 10X thicker wire than with 120V. This is exactly why powerlines run at high voltage; you can send a lot of power in relatively thin cables. Existing home wiring is generally rated around 30A so that means at 12V you could only get about 360W of power out of each household circuit. This is probably fine for all your electronic devices, but wouldn't be enough for a space heater, toaster, oven, clothes dryer, or any other power hungry device.

Re:The bigger problem (1)

Neil Boekend (1854906) | more than 2 years ago | (#39804011)

Pushing 200A through default 2,5mm^2 wires would pose a firehazard (2,5 mm^2 is default in the Netherlands. This is about AWG 16) these wires are rated for 16A over long periods of time. Pushing more than 10 times that power through is a bad idea.
It has a resistance of 13 mOhm/m. A few dozen feet is about 10 meters, so the resistance is 13*10*2 (two wires) = 260mOhm. At a current of 200 A the voltage drop = 52V. This means you couldn't push those 200 A into the cable with a 12V supply if you'd short circuit the end, let alone power a device with it.
With 12V you are going to be able to push 46A into it, max (short circuit). At that current you'd dissipate (46^2)*0.26=550W, in a tube in the wall. That could set your house on fire.

Re:The bigger problem (1)

wagnerrp (1305589) | more than 2 years ago | (#39803549)

Most electric motors are AC based.

Re:The bigger problem (0)

Anonymous Coward | more than 2 years ago | (#39801595)

I recall wind-power exerting more force on those kinda of homes...

Re:The bigger problem (2)

Chuckstar (799005) | more than 2 years ago | (#39800187)

You only need cheap batteries if you are trying to be off grid (or your utility doesn't do net metering). Otherwise, let the grid be your battery.

Re:The bigger problem (1)

PopeRatzo (965947) | more than 2 years ago | (#39800419)

You only need cheap batteries if you are trying to be off grid (or your utility doesn't do net metering). Otherwise, let the grid be your battery.

I just spoke to the Grid and he says, "Fuck you, pay me. I'm in the business of charging you for electricity, not storing your excess. What are you, some kind of German commie?"

Re:The bigger problem (3, Interesting)

Chuckstar (799005) | more than 2 years ago | (#39800561)

I disagree. The grid is in the business of transferring electricity around. The grid doesn't care if it's electricity generated at a plant and sent to your home, or generated at your home and transferred to your neighbors home. And of course you'll pay to be attached to the grid, but that could take many forms, almost any manner of which would be cheaper than buying a bank of batteries.

Re:The bigger problem (1)

PopeRatzo (965947) | more than 2 years ago | (#39801983)

The grid is in the business of transferring electricity around.

The grid is in the business of whatever the corporate entity that owns it says it is. And if you should come up with a way to generate energy without it, you will find out just how fast the Grid can be weaponized.

Re:The bigger problem (1)

Anonymous Coward | more than 2 years ago | (#39802705)

In principle, yes. The grid is just in the business of transferring electricity around, and shouldn't care where that electricity is coming from.

In practice, it doesn't really work that way.

The grid is not a network in the same sense as the Internet. You can't take electricity from one end-point, and route it through the network to other end points. It was built around the idea that you're generating power in large power plants, transmitting that power along the main transmission network, and then dumping it into a distribution network, where it's progressively stepped down in voltage, until it hits your home. It's designed to be mostly one way: power flows from the power plant to your toaster.

You can shove power back into the grid from your home. However, the grid wasn't really designed for this. If you put too much power back into the grid, you could cause some serious damage to the grid equipment (blowing out a transformer, for example). The power can certainly be used by other people close to you in the distribution network, but there's no mechanism to transport that power back up to the transmission network (the distribution network would just be taking less power from the transmission network, rather than sending it back). Even then, energy generally isn't stored anywhere. There are facilities that do store power (sometimes - they're more common in some parts of the world than others), which are used to manage demand surges, but there's no mechanism to get the power from your panels to the storage facility.

You aren't storing power in the grid. You're shifting the demand around instead.

It's quite possible to redesign or augment the grid, so it can handle distributed power generation rather than centralized power generation. It's just bloody expensive and, to the best of my knowledge, nobody's actually done it yet. Remember that the grid we have was built up over something like a century, and it's only very recently that distributed power generation has become viable.

The grid today is foolish (1)

bussdriver (620565) | more than 2 years ago | (#39803521)

Public roads, on public land are the essential infrastructure on which our society functions, it dates back long ago. It is done by the people (aka the government.) Everybody puts money in and everybody benefits.

The electrical grid gets heavy subsidizes and often leverages its monopoly power to corrupt government. The grid should be another public network just like the roads it usually runs next to. City water and sewage is also an old solution we continue. Electricity is now essential and while it is not as important as the traditional grids it is next in line to be made public. We should cast off these crooks who exploit our needs, corrupt our officials, and often poorly manage our power grid. It may cost us the same amount but we have 1 less source of corruption and an open grid to build a larger marketplace around. Private power grids are too cheap to think LONG term while government can build a grid to last longer and run cheaper in the end... such as putting power lines underground near the roads instead of cheaply on poles... higher voltage DC with local DC to AC with plenty of R&D available that no private company can compete with.

Like the roads, water, sewer grids before it, an open public electrical grid will foster competition built upon it and promote a distributed robust marketplace. Grid power storage services that buy cheap and sell high; small distributed power generation and a FAIR payback to individuals who feed to the grid. Many schemes could be devised on such systems, beyond just subsides for example, consumers could choose to pay more for solar and solar producers then get a higher payback. Power rates could be managed automatically down to the second; fostering a whole market of smart devices to save you money.

Power generation can remain private; just as cars, trucks are private but run on the public transportation grid. Although, I can't still see nuclear being possible without huge government intervention as has always been the case.

Re:The bigger problem (0)

Anonymous Coward | more than 2 years ago | (#39800967)

I just spoke to the Grid and he says, "Fuck you, pay me. I'm in the business of charging you for electricity, not storing your excess. What are you, some kind of German commie?"

And a lot of local public utility commissions tell the Grid: "You're a regulated monopoly; you do as we say. Now pay the customer for his extra solar electricity. Full retail price."

Re:The bigger problem (0)

Anonymous Coward | more than 2 years ago | (#39804319)

sheesh that unmaintained be grumpy

Re:The bigger problem (1)

operagost (62405) | more than 2 years ago | (#39800553)

Because the grid never goes down. When the power goes out, so does your grid-tied system.

Re:The bigger problem (1)

Chuckstar (799005) | more than 2 years ago | (#39800683)

As I said "you only need cheap batteries if you are trying to be off grid".

As far as whether batteries are necessary for spurring a broader solar market, it is a small minority of people who would be buying solar panels to avoid power outages. If solar panel costs were finally low enough that you could install a (battery-free) system that would provide signficant net savings over its life, you wouldn't hear a lot of people saying "but if I still lose power when the grid is out, why should I bother".

Re:The bigger problem (1)

robot256 (1635039) | more than 2 years ago | (#39801305)

I looked into this recently, and it is actually pretty close to the break-even point in my area. The cost to install a grid-tie system would be totally paid off by about 15 years of energy savings, assuming the rates don't up drastically, and the panels would have another 5-10 years of life left. It isn't dramatic enough that people are going out and getting solar panels to make a quick buck, but it's enough that people who want to do the right thing aren't penalized in the long run.

Re:The bigger problem (2)

Maxo-Texas (864189) | more than 2 years ago | (#39802611)

And most people do not consider the fact that a saved dollar is tax free while an earned dollar is taxed at 14 to 28%.

Re:The bigger problem (2)

SydShamino (547793) | more than 2 years ago | (#39803603)

Obviously this includes government rebates, but while talking about personal out-of-pocket costs I saw a vendor in Austin, TX selling a 6kW system, installed, for $19.5k. After city of Austin $14,475 rebates (paid directly to the vendor; never out of your pocket), and $1508 federal tax credit (out of your pocket unless you pay quarterly or adjust your W4), the cost for the system was just $3,517. $3,517 is crazy good for a 6kW system, which in Texas supposedly generates about 8400 kW-h of electricity a year. At 10.5 cents per kW-h (a low rate than I pay now), that nets $882 in savings each year.

That's breakeven in less than four years. The remaining 21 years or so of system life are profit.

Re:The bigger problem (1)

Issarlk (1429361) | more than 2 years ago | (#39804679)

Sounds like communism to me: Your neighbor's tax money used to pay for your solar panels. How can this even exist in Texas?

Re:The bigger problem (1)

Jeremi (14640) | more than 2 years ago | (#39801241)

Because the grid never goes down.

Around here, at least, that is more or less true. We get maybe one power outage a year, and it usually lasts for about two seconds until a backup kicks in somewhere.

When the power goes out, so does your grid-tied system.

That's true, but it's not really a problem for most people. Grid-tied systems aren't meant to improve reliability, they are meant to reduce costs and/or emissions.

On the other hand, if reliability is your concern and you're willing to pay extra, buy some batteries for backup.

Re:The bigger problem roxy (0)

Anonymous Coward | more than 2 years ago | (#39800565)

Haven't you heard? Roof mount solar cells are outdated 2-D tech. The new way is 3-D, made like branches and leaves on a tree. Much more efficient also. Instead of all sorts of equipment and manpower to roof mount, they will soon just send a truck with some "solar trees" and cement them in your backyard and run an extension cord to your house/batteries or to the meter to run it backwards. They look like trees from a distance so they are acceptable in more areas than ugly panels. Drill a hole, and put in the new tree. Quick, inexpensive, and more efficient.

Re:The bigger problem (1)

JamesP (688957) | more than 2 years ago | (#39801029)

Well, cost of the support system is something that ends up getting cheaper with scale and technology improvements

And maybe you don't need a battery, or need only a small one.

The key here is efficiency, or better summed up by "bang for the buck".

Energy during the night is cheap, so it makes sense to use from the grid.

It stands to reason then ... (0)

Anonymous Coward | more than 2 years ago | (#39800115)

that the emitted photons could then be absorbed and converted to electricity by other light emitting solar cells?

Logan's Run (3, Interesting)

eggfoolr (999317) | more than 2 years ago | (#39800117)

Who else immediately thought of the solar powered car in the Logan's Run TV series? I could never understand why the solar collector glowed... now I know!

Re:Logan's Run (4, Funny)

cpu6502 (1960974) | more than 2 years ago | (#39800225)

There was a car?
I was too busy watching Jenny Agutter: http://i2.listal.com/image/343660/600full-jenny-agutter.jpg [listal.com] I ought to download and read the Logan's Run book sometime.

Re:Logan's Run (3, Informative)

kimvette (919543) | more than 2 years ago | (#39800495)

She was not in the TV series.

Re:Logan's Run (1)

GuldKalle (1065310) | more than 2 years ago | (#39801149)

That doesn't mean he wasn't busy looking at her.

Re:Logan's Run (1)

lordmetroid (708723) | more than 2 years ago | (#39800727)

The only thing I can concentrate on in this image is that there is a freaking rabbit on the left.

Re:Logan's Run (1)

randy of the redwood (1565519) | more than 2 years ago | (#39801453)

Thanks for ruining it for the rest of us. It was quite pleasant, and now that's ALL I can see also.

Re:Logan's Run (2)

R3d M3rcury (871886) | more than 2 years ago | (#39801635)

In the TV Series, Jessica was played by Heather Menzies [imdb.com] . Nice to look at also, in a 1970s kind of way.

Re:Logan's Run (1)

waltlaw (600062) | more than 2 years ago | (#39801863)

I thought of Heinlein's "Let There Be Light."

Re:Logan's Run (1)

Livius (318358) | more than 2 years ago | (#39802649)

It's funny with the *vast* number of science fiction movies and TV shows that show alien/futuristic technology with strange lights to think that they might have had it right all along.

Yo Dawg! (0)

Anonymous Coward | more than 2 years ago | (#39800129)

We heard you like light...

Hmph... (3, Funny)

PopeRatzo (965947) | more than 2 years ago | (#39800333)

Why are these scientists wasting their time with so-called "solar cells"? Everyone knows solar energy can't possibly work. There's just not enough energy in the sun for it to be useful to us.

Fossil fuels are the result of plant life after millions of years, so they're the real "green" technology. And the sun had absolutely nothing to do with them.

These scientists, who are probably mostly foreign, want to strip us of our birthright: a personal vehicle that weight 6000 lbs. Hell, my wife, Lovey, has a couple of Escalades and she recycles all the plastic wrap that our food comes in. So who's really the "green" one?

Re:Hmph... (1)

busyqth (2566075) | more than 2 years ago | (#39800497)

What kind of food comes in plastic wrap?
All the good stuff comes in cans, well except for dinners. They come in a little tray you can stick in the microwave.

Re:Hmph... (1)

Intrepid imaginaut (1970940) | more than 2 years ago | (#39800617)

Look up desertec. Its good stuff.

Re:Hmph... (1)

PopeRatzo (965947) | more than 2 years ago | (#39801969)

Look up desertec. Its good stuff.

Very good stuff.

No joke (5, Funny)

Memophage (88273) | more than 2 years ago | (#39800413)

Guess I can't tell that joke about a solar-powered flashlight anymore.

Re:No joke (-1, Flamebait)

Onuma (947856) | more than 2 years ago | (#39800819)

And the glow-in-the-dark Sunglasses worn by douchebags like Kanye West (and originally popularized in the 80's) are a joke in themselves.

Re:No joke (3, Insightful)

silentcoder (1241496) | more than 2 years ago | (#39801049)

That joke stopped being funny years ago - solar powered LED flashlights are on the market - I own one.

Sound useless ? It's not. It has a battery - during daytime it charges the battery from solar power, when you use it at night, the battery powers the LED lights.

It's a wonderfully useful tool on camping trips. As a bonus - since the battery isn't replaced during the lifetime of the device it has much less of a pollution (battery-acid) impact (granted this may be less of a consideration in some countries -mine has no systems in place for proper disposal/recycling of battery cells and people just toss them in the trash when they are used up).

That LEDs have become so powerful while remaining so efficient has led to us being able to do a lot of really cool things we weren't able to do even quite recently.
Frankly compared to things like LED based airport runway signal lights a solar powered flashlight isn't even all that impressive :D

heinlein was right again! (1)

circusboy (580130) | more than 2 years ago | (#39801289)

some rolling roads, a life detector, and a massive fundamentalist revolution and we should be all set...

Re:heinlein was right again! (1)

muridae (966931) | more than 2 years ago | (#39804017)

Scudder was elected in 2012, so we may not be that far off.

Direct semiconductors? (1)

Anonymous Coward | more than 2 years ago | (#39802755)

Silicon doesn't emit light because it is an indirect semiconductor. Because of that, it is also less efficient at absorbing light. That's why solar cells have to be so thick (several hundreds of microns), otherwise most photons would just go through the cell.

Direct semiconductors have been used in the past (e.g. GaAs) and they do achieve better efficiency. They are often used in space (they also happen to have wider band-gap, which is better suited to high energy photons, like ultraviolet light). GaAS cells are much thinner (a couple of microns) and lighter as almost all photons with energy above their band-gap are immediately absorbed.

Low cell thickness is good for efficiency - there is less chance that generated electrons will recombine. They simply have shorter distance to travel between the place they were generated at and an electrode. Also, the difference of the photon energy and the bandgap isn't simply converted into heat but rather another electron and is radiated back. It could be then captured by another narrow band-gap cell sandwiched with the main cell.

Perhaps they have found more reasons why direct semiconductors are more efficient, but it is not true that we didn't know it before.

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