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Quantum Dots Could Double Solar Energy Efficiency
dptalia notes the recent publication in Science of research demonstrating a way to use hot electrons in solar cells, resulting in an overall energy conversion efficiency of 66%. Here is the abstract in Science; access to the full article requires a subscription. "A team of University of Minnesota-led researchers has cleared a major hurdle in the drive to build solar cells with potential efficiencies up to twice as high as current levels, which rarely exceed 30 percent. ... Tisdale and his colleagues demonstrated that quantum dots — made not of silicon but of another semiconductor called lead selenide — could indeed be made to surrender their 'hot' electrons before they cooled. The electrons were pulled away by titanium dioxide, another common inexpensive and abundant semiconductor material that behaves like a wire."
These [blink]dots[/blink] are all nice and well, bu how long until the consumer market sees all the improvements?
this: http://raincoaster.files.wordpress.com/2007/07/lil-werner.jpg
Okay so we can make more efficient solar cells, the question that I want to know is what kind of over all energy increase will this provide?
Seems like I keep hearing of breakthroughs, but nothing ever seems to fucking change!
Will they save the Earth by using these higher efficiency solar panels, or will they hurt the Earth by using lead?
"The next step is to construct solar cells with quantum dots and study them. But one big problem still remains: “Hot” electrons also lose their energy in titanium dioxide. New solar cell designs will be needed to eliminate this loss, the researchers said."
If I had a tribble for every time one of these solar energy articles came out with their pages full of nothing.... I could make a lot of fur coats.
Could someone in the research field please hold on to their excitement until they can post a report that has words like "WILL, SHALL, DEFINITELY, HAS, IS" instead of the wimpy "could, may, might, has potential to, in 5 years if all goes well....."
I got sucked in by one years ago and pestered the company for information about their new "product" which was due out "soon".... and that was nearly 10 years ago.
So many advances in tiny little cells on a research bench, and so many promising advances. Yet none of them seem to show up at the local hardware store.
I understand that advances in quantum materials science is cool, and can change everything just like the invention of the transistor did once. But seriosly folks - the number of speculative postings based on
these barely germinated lab experiments seem a little bit like the kid who cried "Solar revolution", or was that wolf?
I wrote a paper on this idea last semester, and as interesting a find as it is, I don't think it's ever going to lead to enhanced power conversion efficiencies (PCE). The "Double Solar Energy Efficiency" is actually a theoretical doubling of the thermodynamic limit on PCE, and it doesn't take non-radiative losses into account. These losses have been minimized in the record breaking silicon and multi-junction solar cells, but quantum dots bring lots of problems with them.
It's definitely worth further investigation, but currently I'm not convinced that it will ever bring improvements.
It's messy.
If you're lucky, you have a clear goal, and that goal is reachable though no one knew it beforehand of course. Also far from assured is that no one else has already done it. Not at all easy to find it out either, as others may have approached some problem from a completely different direction, and you will not be looking in the right places when you try to find out what others have done. And you could discover something entirely unrelated while in pursuit of your objectives, something worth taking a massive detour to pursue. Reporting on science skips over the difficulties to the point that it's like the joke about how to put an elephant in a refrigerator. You open the door, put the elephant in, and close the door, duh! Even scientific journals omit "extraneous" details about wrong turns taken, because "thinking is vulgar". Researchers naturally don't want to look dumb, and neither do journals. Plus, journals are always trying to save space and time. Streamlining articles to talk of only the successful experiments is an obvious cut to make. There's a STNG episode that touches on the problem. Lore mocks Dr. Noonien Soong, calling him "Often Wrong", but there it is clear that Lore's criticism is unfair. Science is all about doing things that will probably turn out to be mistakes, and learning from them.
Most people think science is about finding answers. That's only half of it. More important is asking good questions. Finding out which questions to ask and hopefully answer. Yes there are bad questions, don't believe that dogma about there being no such thing as a dumb question. They're still worth asking if you don't know or can't know they're bad. What they aren't is worth answering, and discovering that is the problem. There are questions that turn out to make no sense, or are too simple, or too complicated, or pointless, or misleading, or are based upon or arise from inferior modelings or from misunderstandings, or are predicated on assumptions that actually aren't valid, or are unanswerable. Math is full of shifts in representation to avoid such problems.
For instance, how do you deal with infinity in, say, the slope of a line? Vertical lines have infinite slope. You could pull out calculus and limits to handle these infinities, but if you do, you've just been sucked into doing things in a much harder way, been pulled down a rabbit hole to figure out all kinds of problems with working with infinities and division by 0. So much easier to use vector representations from linear algebra and avoid those infinities. All those questions about handling infinities turn out to be pointless for this problem. Mind you, infinites crop up in plenty of other places, so having ways to handle them is still useful, it just isn't necessary for this problem of representing a line. That's an old, well known problem for which we've known good answers for a long time now. There are also things like the famous Fourier Transform, and Lagrangian basis, not to mention Calculus itself to handle problems that are very nasty in classical geometry. But in new, unexplored territory it's not so easy to tell which questions will turn out to be bad.
Most things that scientists try turn out to be wrong. History has a few famous ones, such as "Squaring the Circle". The public hears little more than the 1% that turned out right.
Intellectual Property is a monopolistic, selfish, and defective concept. It is "tyranny over the mind of man"
In the rest of the world "the breakthroughs" are being embraced and fast-tracked.
Remember, the U.S. is still stuck in a fossil-fuel love affair.
Every time one of these solar cell tech. stories come out, I look forward to digging up the specific details of the technology and am left wanting. It seems like no researchers offer any insight into the lifetime of their new, super-duper technology. They very rarely list a W/kg or W/m^2 figure. Hell, they don't even talk about the largest/smallest wafers that can be cut using the new technology. It's extremely frustrating. As an engineer that wants to look into, 'What could new solar tech actually do for my design?' In terms of mass, area, design lifetime, etc, we are never given the opportunity because the only technical details published is the efficiency factor. /Yawn
Motorcycles, Robots, Space Gossip and More!
Is when it matters, otherwise it's just a curiosity.
Really, these releases of "Ahh YES! We've discovered X" is nothing more than the scientists, engineers, Universities and Labs making a press release so they can get more grant money.
If I can't buy it then I'll spend exactly 20 seconds thinking about it.
I doubt a semiconductor called "Lead Selenide" is going to go far if, as it's name implies, it is comprised of lead and selenium.
who cares about efficiency?
If you make a solar cell that is 100% efficient but costs $10billion / watt to make, who cares?
On the other hand if you make one that is only 1% efficient but only cost .01c / watt to make, that would change the world.
By replacing benign silicone with a toxic heavy metal like lead, we're guaranteed full Republican support for a roll-out!
It's not the environment, either. It's that yet again we have a "breakthrough" that uses difficult to obtain elements and compounds. Large scale adoption would lead to a incredible shortage of yet another rare earth and as a result, large price increases. Not to mention, of course, the problems with mining and refining the stuff.
What we really need is a way to be able to make these out of common, cheap materials that don't deplete our already stressed rare earth supplies.
Note - my personal favorite solar power plant design is a simple updraft tower. It is about as efficient as a typical large solar array - and about the same size as well. But the environmental impact is very slight. In fact, the greenhouse type environment underneath it is a great place to grow crops.
http://en.wikipedia.org/wiki/Solar_updraft_tower
Most working prototypes to date have been under 500 ft tall, and have as a result been fairly easy to design and build, being held up by wires and supports like a radio tower. Talk of a half mile high one is quite silly - they just don't need to be that large to work. ie - it's better to build hundreds of 300-400ft tall ones that need a few dozen acres to run, and 5-10 million dollars each(land cost in a desert for 10-20 acres is assumed to be fairly negligible) than a massive multi-billion dollar monstrosity.
A small scale test was done in 2005 in Botswana as well, with a ~75 foot tall tower and a collection area of 160M^2. This scale would be perfect for a typical small farm, as an example.
So, If I want to make my existing solor cells more efficient, I just need to stick my existing panels into a crock-pot?
Who would win this election: Andrew Weiner vs Andrew Weiner's weiner.
Is there anything it CAN'T do?
I've abandoned my search for truth; now I'm just looking for some useful delusions.
If I worked there, I would definitely avoid the cafeteria.
Fuckin' quantum dots, how do they work?
NEED MOAR DOTS!!!
It must be time for me to cut back on my WoW. All I could think of when I saw the headline, was "MORE DOTS! MORE DOTS!"
For your security, this post has been encrypted with ROT-13, twice.
Seems like I keep hearing of breakthroughs, but nothing ever seems to fucking change!
Prices have changed. According to Solarbuzz per watt costs have dropped from about 5.40 euros or a little over that in US dollars in December 2001 to about 4.20 euros or a little less US dollars for June 2010. Further it says "there are now 488 solar module prices below $4.00 per watt (3.24 euros per watt)". Efficiency has also increased. In 2001 conversion efficiency pushed 12%, in 2009 SunPower sold panels with conversion efficiencies of 19.3%, the highest in the industry.
Falcon
Should there be a Law?
If I had a tribble for every time one of these solar energy articles came out with their pages full of nothing....
Your starship would be full of tribbles. Then it's tyme to call Klingons.
Falcon
Should there be a Law?
come out, I look forward to digging up the specific details of the technology and am left wanting. It seems like no researchers offer any insight into the lifetime of their new, super-duper technology.
Perhaps that's because they are research papers and the tech has not reached practical application yet. And perhaps that's the difference between scientists and engineers, scientists want to know what's possible whereas engineers want the practical application. Without the other neither one gets very far.
Falcon
Should there be a Law?
I seriously wonder why people keep promoting micro-generation. Electricity distribution is very efficient ( you lose maybe 10% of the electricity on average ) , and you lose a lot of economies of scale when going micro. Even assuming you'd manage to make some super cost-efficient solar cells, why would you go destroy it by putting them on poorly aligned roofs, as opposed to building a designated plant where they can be made to track the sun throughout the year?
Seriously , for EVERY energy source centralized generation will come out on-top. It's a consequence of how easy electric power is to transport, as well as the fact that most energy generation schemes scale very well. The only real exception is where you're burning something for combined heat and power, thereby allowing you to recover the spill heat from the power-plant. However, even in that case district-heating will probably work out better, and does in many regions. We use it extensively in Sweden.
Essentially the only way micro-generation is going to be competitive with centralized generation is if government fucks up big time to make centralized generation inefficient. Granted that is of course plausible, and I'm sure there's many people who are willing to say that it is happening many places, but this is a political problem that could just as well ( and probably will ) hit micro-generation. It does nothing to alter the fact that on technical merits, micro-generation is inferior for all places that are connected to the electric grid. It just doesn't make any sense to take technologies that scale very well and deploy them in as small units as possible.
This is good, solid condensed matter physics research, and it is important. But, the 66% efficiency they're quoting comes from an old calculation of what is effectively a perfect solar thermal converter where the electrons are "hot" and the temperature of the crystal doesn't really matter because there's no interaction between the electrons (or photons) and the crystal. This theory has been the motivation for the hot electron transfer work on quantum dots, but at some point it should come up that they can't get hot electron transfer to work at much above around 100 K. That's kind-of really important (not to mention impractical). The device they're *trying* to make shouldn't need to be cooled at all. That's a giant clue that the theory they're basing this amazing 66% on is more than a little oversimplified for what they actually have. It's annoying that people are using an out of date 28 year old paper to sell the direction of their research; it makes life hard on their competition using more honest efficiencies.
I skipped the yearly trip to Vegas and invested some time and money in small scale solar for the house. Best 1K I ever spent. Running the entire outdoors media system and lights on solar.
DIY Solar project.
http://www.flickr.com/photos/nsaspook/sets/72157622934371746/show/
In GOD we trust, all others we monitor.
"Competitive" takes many forms. Decentralized systems lose on efficiency and cost, but often win big in terms of stability and resilience. Also, depending on your political system, you may not have much trust in the politicians or the corporations who deliver your power. Or you might not trust that the national grid won't fail (temporarily or permanently). We had a massive blackout in the northeastern U.S. a few years back (arguably because our privatized energy companies tend to underinvest in the infrastructure under their care).
Transmission losses aren't huge, and some forms of renewable really require big scale (wind, concentrating solar) just based on their physics. But solar panels don't change much in efficiency whether they're properly sited on your roof or sitting next to a million siblings in the desert.
You want the truthiness? You can't handle the truthiness!
Basically the way I see it that home or microgeneration is like a massive UPS device for my house. I have a big battery of batteries that keep everything running when all hell breaks loose in the world around me. I'll have to cut my consumption a bit when I get cut off from the grid but at least I'll have warm showers, TV, radio, lights etc... when various forms of armageddon strike down upon me. The eventual aim is to be personally energy independent home and for commuting purposes (say 20km each way per day).
Even Shakespeare used an Apple, albeit slowler and tastier than todays Macs.
Solar PV is the exception. There is no inherent efficiency advantage to scaling up, so you save a bit on transmission. But the big win is siting -- it's relatively easy to get approval to put something on your own roof, while it is relatively harder and more expensive to find a big piece of unused land, buy it, and get all the necessary approvals. We're seeing this play out in California with rooftop solar.