Where are the 70% Efficient Solar Cells? 798
VernonNemitz asks: "Back in 1984 a patent was granted for silicon chip micro rectennas, which would convert visible photons into electricity in the same way that ordinary rectennas convert microwaves into electricity, at perhaps 70% or greater efficiency. Nobody could make such solar cells back in 1984, but we certainly can today, with sizes of antennas that would capture everything from infrared to the edges of UV -- and the patent has expired. So, where are they?" Currently the most popular type of solar technology is photovoltaics, however PV technology only has an efficiency of about 7-17%. With the potential gains claimed by the technology in the cited patent, has anyone even tried to build one of these units to see if it can live up to the given promise, or at least prove to be a technology than we should be exploring?
Beats me (Score:5, Funny)
Heres a company - up to 80% efficiency. (Score:5, Interesting)
Also there was a story about 2 weeks ago, mentioning solar energy breakthrough using full-spectrum layering. Does anyone know anymore about this. I was unable to find it in Google News.
Nanotech material, once they arrive, will of course make 90% efficient material practical.
Planet P Blog [planetp.cc] - Liberty with Technology.
Re:Heres a company - up to 80% efficiency. (Score:5, Funny)
What kind of nanotech material are you talking about? Little nano robots that run around catching photons IN their nano baseball gloves and pitching them into nano furnaces that run nano generataors?
If you want people to take you seriously, a statement like, "nanotech materials _may_ be able to produce 90% efficient material," is more reasonable. "of course" is just silly.
Re:Heres a company - up to 80% efficiency. (Score:4, Funny)
Re:Heres a company - up to 80% efficiency. (Score:5, Funny)
Re:Heres a company - up to 80% efficiency. (Score:4, Informative)
Re:Heres a company - up to 80% efficiency. (Score:3, Informative)
Have a look here [lbl.gov]. It even comes with references to papers (not that I've read them, but y'know).
Re:Heres a company - up to 80% efficiency. (Score:3, Funny)
Lets see. They claim thier stuff is theoretically capable of efficiencies of up to mumble mumble.
Wow.
Now I know it's got to be an oil industry conspiricy repressing this stuff. With credibility like that...
Re:Heres a company - up to 80% efficiency. (Score:3, Interesting)
To be honest, I don't quite understand what role polarization plays in this ... can anyone clear this up?
Re:Beats me (Score:3, Funny)
Brought to you by the folks who gave you cold fusion in a jelly jar.
Rectenna? (Score:5, Funny)
Anyone else get a sorta shifty feeling when they look at that word and picture the consequences of such an invention?
Where the sun don't shine (Score:5, Funny)
Re:Where the sun don't shine (Score:3, Funny)
Re:Where the sun don't shine (Score:5, Funny)
Re:Where the sun don't shine (Score:4, Funny)
</cartman>
Re:Where the sun don't shine (Score:4, Funny)
Re:Rectenna? (Score:3, Funny)
Seriously, I wouldn't be surprised if there are a few grad students who've been toiling away on this project but can't get any funding. Or... maybe the idea just doesn't work out in practice.
We also can't overlook the fact that lots of important stuff is, well, overlooked. Any comments from anyone in the field?
Re:Rectenna? (Score:3, Funny)
The goatse.cx guy [goatse.cx] can generate over 800 megawatts with his rectenna.
Re:Rectenna? (Score:5, Funny)
I asked her, "Are you sure you want to know?"
"Yes, show me."
So I covered my eyes and shift-clicked.
"Eeewwwww," she said, "is that real?"
"Yes dear, it's real and the burning sensation in your eyes will clear in a few days."
It's scary shared-experiences like these that really solidify a relationship.
Why we have to have 80%+ (Score:5, Interesting)
You can read about here on my website [floatingplanet.net] for more info. Some in the oil industry are thinking that peak will be hit within the next two years. This might explain our rush to invade Iraq.
Either way, as oil reserve dwindle and demand goes up, it will create a highly destabilized politic - and if you think the repression we've all been feeling lately is bad, it will only get worse... UNLESS:
We wean ourselves (QUICKLY!) off of Oil. The Hydrogen economy is just waiting in the wings. All of the technology is essentially there. The cost factors will become not only competitive, but cheaper and cleaner than oil, once we start migrating our energy infrastructure over to Hydrogen.
Lets hope this happens before we end up in some kind of nigthmarish Oil Fedual/Fascist Global New World Order.
Planet P Blog [planetp.cc] - Liberty with Technology.
Re:Why we have to have 80%+ (Score:4, Insightful)
My worry is the health of the planet in the mean time. I live in central Minnesota, USA. Our average high temperature this time of year is about 9 degrees F. Yesterday it was 55 degrees F. I know full well one warm winter does not global warming make, but we've had several bizzarely warm years lately. We're s--tting where we eat and it worries me.
Re:Why we have to have 80%+ (Score:3, Interesting)
We're suffering a major drought now and people who study the environment tell us that we'll need 2 years of record hard precipitation to get the ground moisture back to normal.
I'm not a big believer in global warming being all our fault, but I do know it's going to be a real ugly summer on the western prairies.
El Nino (Score:3, Insightful)
Hell, there was no Spring 2002 here - the trees didn't bud until well into June - THAT'S how cold it was.
Then again, in 1997 we had the 'blizzard of the century' followed by the 'flood of the century', but suddenly no one can remember any years with snow since they were a kid? Give me a break.
Re:Why we have to have 80%+ (Score:3, Insightful)
The weather not consistant any where. Globably, the client changes every year. There's no reason to panic or think something screwy is going on. When did people start getting the idea that every year should be predictably the same? I would guess probably around the same time global warming and global cooling wackos starting showing up.
Shock of all shocks we have hot and cool summers in AZ. There's nothing to see here, move along.
Ben
Hydrogen? (Score:3, Informative)
I suspect that once we have employed solar, wind, geothermal and etc to limits of any forseeable technology there will still be shortfall. Once it sinks in that the 15 minute hot showers and the SUV will are out, a new energy supply debate will ensue: When is the uranium going to run out?
Re:Hydrogen? (Score:3, Interesting)
Not likely.
According to this site: http://www.nmsea.org/Curriculum/7_12/The_Solar_Re
You need 33,400 square km to produce enough energy, now their efficiency estimate is about 2x what we are acepting here. So, double that to 66,800 square kilometers. The US has 9,158,960 of total area. So, to produce all of our electricity at 17% efficiency requires 0.7% of the total land area. Which is of course a meaningless number without some other reference. So, the mojave desert is about 65000 sq km, the sonoran desert in Arizona, California, and Mexico is 310,000 sq kilometers.
So, figure between rooftops, and god forsaken places in the middle of nowhere there is definitely enough room to put enough solar to power the entire US. Storage is a problem, but that is what hydrogen is for.
Of course, without fossil fuels to rail against rabid environmentalists will be pissed about covering large stretches of land with PV.
On the hubbert curve and hydrogen (Score:3, Informative)
Pople have been predicting we will run out of oil within 10 years for at least 30 years. It hasn't happened yet and shows few signs of happening too soon. Even if it does happen, hydrogen is unlikely to replace oil because far superior fuels (both renewable and non-renewable) exist
The U.S. Departmetn of energy has a very detailed presentation [doe.gov] describing different scenarios for world oil consumption including the work of Hubbert and of Laherre along with their prediction that we have more than a decade of cheap oil left.
Even if the earlier projections of running out of oil come true, there are enormous amounts of "oil" that can be extracted from oil shale (at $80/bbl) and liquid fuels can be produced from coal (methanol is especially easy) and plants (ethanol, biodiesel). All of these become practical with $3/gallon gas
All this suggests to me that hydrogen, which is difficult and dangerous to handle, and very expensive to produce may not have that much of a future as a fuel in the near term. Even Natural gas is a better choice because it is less expensive and can be used with fuel cells (sort of)
The problem with oil shale and other deposits... (Score:3, Interesting)
Even if the earlier projections of running out of oil come true, there are enormous amounts of "oil" that can be extracted from oil shale (at $80/bbl) and liquid fuels can be produced from coal (methanol is especially easy) and plants (ethanol, biodiesel). All of these become practical with $3/gallon gas
The problem is that it doesn't matter how much per gallon you get. If it takes more energy than is in a gallon of oil to extract a gallon of oil from the shale, for example, you are not producing energy. The same problem exists for coal: At some point, it takes more energy to dig it out of the ground than you get from burning it. When this happens, you can continue to produce at a net energy loss, but you need to get energy from somewhere to do it. Where are you going to get that energy without oil?
That's the real, serious problem we're going to be facing in the short term. It's not going to be lifethreatening in my productive lifetime. Sucks to be growing up now though. The sad fact is people won't change, but hey, I get to fiddle while it goes down! (sarcasm)
Re:Why we have to have 80%+ (Score:3, Insightful)
You are right that hydrogen technology is nearly there, and you're absolutely right about the need to wean ourselves off of oil. They're starting to get the kinks out of the development cars. And Every day we rely on oil, we are putting money in the pockets of dictators in the Middle East and other countries.
Hydrogen, as a general rule, likes to bond to things. As a result, it always takes more energy to separate Hydrogen from what it's bonded to compared to the energy you get when you put it back together.
And the energy for that first process comes from fossil-fuel burning power plants.
Right now, it takes less energy to pull oil out of the ground compared to what we get out of it.
What this means is that the Hydrogen economy is a losing proposition. We will have to pull even more oil out of the ground -- or rely on nuclear power -- and since producing Hydrogen fuel cells costs more energy than it generates, the end result is that this Hydrogen economy will fail. Or it will end up using more petroleum products in the end than if we just dump the stuff directly into our cars.
You can't defeat the laws of thermodynamics with any amount of technology, particularly when the technology is based on the very thing you're trying to replace. The facts suggest that Hydrogen is not the answer, and would only worsen our situation. Hydrogen will ironically hasten our pace towards the Oil Feudal/Fascist Global New World Order you fear. So I am not looking to Hydrogen to be the all-powerful Saviour from our oil dependency.
Let's look to technologies that do work. Even PV solar panels are more efficient in the end than Fuel Cells. It's good to look to the end of the oil cartels; but why abandon knowledge and reason in favor of pseudoscience to do it? Doesn't that just defeat the cause in the end?
Re:Why we have to have 80%+ (Score:5, Insightful)
Oil demand grows at 1-2% per year. Oil production capacity (current and estimated undiscovered) grows at about the same rate, because that's how economics works. They work just hard enough to keep the demand supplied.
However, at some point the reserves (current and estimated undiscovered) run out. At current rates of growth, that's expected to be somewhere between 2039 and 2066, with a 65% confidence level.
There's no peak. We just run into a wall and it's over.
But that assumes demand will be constant. It won't. As the visible end approaches, the surviving producers will start gouging on the scarcity. Consumption will drop, stretching out the date at which the oil dries up. Possibly indefinitely, since at that point other energy technologies become feasible. But still at a much higher $/kWh than we now pay for oil. There's your peak: when the consumption curve turns down due to market economics and substitution of alternatives and deprivation.
Petroleum will become a minor energy product, like whale oil is now (whale oil used to be a major energy product; go look it up).
Which is something the oil companies see coming, but know they can't profit from, so they deprecate alternatives and then secretly work to develop them, so they can continue to control your energy supply after the oil finally becomes deprecated itself.
Re:What about Biodiesel? (Score:5, Insightful)
Honestly, bioethanol has much more short term potential than biodiesel. Lignocellulosic feedstock is available in bulk, and the baseline economics are pretty good - a modest scale facility using existing technology could be built today that would make ethanol at a total cost of probably 1.30-1.60 per gallon if feedstock availability is good and cost is cheap (this works out to probably 1.70-1.90 per gallon equivalent of standard gasoline). In other words, with another 15-20% efficiency improvement followed by scale increases to reduce the amortized fixed cost of plant+facilities per gallon, it could be price competitive with gasoline. And there are already well over 1 million FFVs (Flexible Fuel Vehicles) on the road today that could burn E85 (85% ethanol, 15% gasoline mix) without modification - most people who own these cars don't even realize it.
Ethanol has real potential and some of us are working on making it into a business reality.
Re:What about Biodiesel? (Score:3, Informative)
-ant
--the most common song of all time is not "Happy Birthday", but "king of the castle", or more infamously "nyah-nyah-ne-nyah-nyah".
Ethanol is not good (Score:3, Interesting)
The motivations for the promotion of ethanol seems to be to provide a subsidy to corn farmers under the guise of an alternative fuel source so as to not encurr the wrath of international trade organizations like the WTO.
Re:Ethanol is not good (Score:4, Informative)
What my post talks about if you read it, is what is generally referred to as "bioethanol". Of course, ethanol from corn sugars is biological in origin, but what most people call bioethanol is ethanol produced from biomass or lignocellulosic feedstock.
That means _waste_ cellulose. Such as corn fibers, not the corn iteself, or pulp/wood chip byproducts from the milling/cardboard industries, and "waste" crops such as bagasse in Louisiana that grow in swamp land (i.e. land not arable for production of more valuable crops and that grow with very little external water and energy input and thus are very low in terms of actual feedstock cost including any energy input).
The cellulosic chains are broken down and the constituent glucose and xylose sugar molecules are fermented - there are several processes such as SSF (Simultaneous Saccharification and Fermentation), steam-cracking weak acid hydrolysis, and recirculating strong acid hydrolysis, which are all more-or-less viable for this process.
I shall not defend the corn ethanol industry - you are correct in saying that they exist because of federal subsidies. I am promoting a process for taking otherwise "valueless" biomass that would end up in land fills or lie unused elsewhere that can be obtained at relatively low cost and converted into a relatively high value energy product.
Re:Ethanol is not good (Score:3, Insightful)
or pulp/wood chip byproducts from the milling/cardboard industries, If you have any furniture that was "put it together yourself", It's probably a pulpwood product. Does it have a laminated surface? Then it's definately a pulpwood product. The fiberboard (cardboard) industry? The first thing they do is turn their source material into cellulose. Then they make paper out of it. Then they make cardboard. Or did you really think cardboard was made from playing cards?
and "waste" crops such as bagasse in Louisiana that grow in swamp land (i.e. land not arable for production of more valuable crops and that grow with very little external water and energy input and thus are very low in terms of actual feedstock cost including any energy input).
Do you know what you're talking about here? Swamps are the most biodiverse regions in the world. Does that make them not valuable? Or are you just an MBA? Almost all domesticated crops require a huge amount of water to grow properly. That is why so many farmers irrigate their fields. They don't have enough water for their crops to grow! In the first three feet of soil, at least. And that is where soil moisture is important for commercial crops!
My aunt's farm has a "swamp" on it. It supports deer, bear, raccons, squirrels, crawfish, several species of edible fish, snails and a shitload of migratory birds. As well as mice, rabbits, hawks and eagles. The stream feeding into her "swampland" supports turkeys.
And you're saying that just because a two thousand pound tractor (and attachments) gets stuck, her "swampland" is not valuable?
You must be an MBA.
Re:how about sewage to energy? (Score:3, Informative)
Separating out the useful components of sewage (perhaps waste cellulose in human fecal matter... ewwww) to produce energy probably would undoubtedly use a lot more energy than you could extract from it. Though I think there are anaerobic digestion systems in use in some sewage plants to extract methane and burn it in a turbine, pumping the generated electricity back into the grid.
Re:Rectenna? (Score:5, Funny)
Here's the best that Google could come up with for picturing a rectenna [google.com], but the exact image I wanted wasn't found. As demonstrated in episode 101, rectennas are powerful, but also put out a lot of heat.
Re:Rectenna? (Score:3, Informative)
4Rectena.jpg [univ-reunion.fr]
Re:Rectenna? (Score:3, Funny)
Goverment rebates (Score:3, Informative)
It seems someone is working on them... (Score:5, Informative)
Re:It seems someone is working on them... (Score:3, Informative)
They look neat. The researchers think that they'll be cheap and efficient. But where are the microarrays of silicon rectennas?
I know where they are (Score:5, Funny)
Is it here yet? How about now? How about now? (Score:5, Funny)
But is it real? (Score:3, Interesting)
Research (Score:5, Insightful)
Who elected George Bush anyway?
Re:Research (Score:4, Funny)
Re:Research (Score:5, Funny)
Notice anyone threatening the Netherlands lately, Wisebeing?
Re:Research (Score:5, Insightful)
So even a "Manhattan Project" style affair will be worthless unless we also make a concerted effort to dramatically improve the energy efficiency of our society -- our cars, our appliances, our homes, etc.
With not much effort, by not a huge percent of the population, California was able to fairly significantly reduce its energy needs during the whole Enron-initiated "power crisis." Not to sound polyannaish, but just imagine what would happen if we all actually did some simple, painless, things that saved energy.
The problem is that most people need a real incentive -- dramatically higher costs -- before they will conserve.
Re:Research (Score:3, Insightful)
Nuclear reactors + fuel cells seem like a solution that would allow a similar level of consumption. It just wouldn't work for Berkeley.
Re:Research (Score:3)
Enron's (and other energy company) lobbyists wrote the rules of California energy deregulation. Thank the Pete Wilson administration. This is why its so scary when Dick Cheney sets energy policy via private meetings with energy company executives, and won't tell what went on. If the energy co's greed hadn't made such a public spectacle in California they might have been able to pull off price-fixing on a national scale.
Re: Who elected George Bush anyway? (Score:3, Interesting)
These guys [archive.org] did.
(And I STILL think it's funny that the guy who did the map colored the Bush counties red, rather than the Gore counties. B-) )
U-235 vs. U-238 (Score:5, Informative)
Then there's a wide variety of other radioactive substances that can be burned in reactors. For example, breeder reactors can actually breed plutonium from the very common U-238 (U-238 is one of the most common elements in the Earth's crust), creating an almost infinite supply of fuel. Military breeder reactors work fine for producing lots of plutonium for atomic bombs. Research on commercial breeder reactors (basically the military reactors tied to turbines to power electric generators) was stopped by worries about arms proliferation (it is much easier to seperate Pu-239 from U-238 than it is to seperate U-235 from U-235 in raw uranium ore, thus makes it easier to get enough fissile material to crete atomic bombs), but could be re-started pretty swiftly if necessary. Which would not be for 50 or 100 years, as you mention.
Regarding 100 and 400 years of oil, my own best estimates are somewhat lower than that. My estimates are that we will experience shortages within 20 to 25 years, and that within fifty years we will have basically exhausted all economically accessible oil resources (i.e., there will be oil out there, but it will take more energy to extract it than can be obtained by burning it). However, hopefully by that time the current taboo regarding nuclear power will have eased, and we will be able to replace the lost petrochemical resources with synthetic hydrocarbons or other such creations. (Don't laugh, we use petroleum as feedstock for chemical plants because it's cheap, available, and readily "cracked", but there are certainly other feedstocks that could be "cracked" into various petrochemicals if necessary, including coal, for that matter -- after all, both the Nazis and the South Africans did it).
Re:U-235 vs. U-238 (Score:3, Interesting)
These sources may keep hydrocarbons around for a long time.
Another trend is the end of the population explosion. Many contries in the world are now at negative population growth rates, and that trend is increasing rapidly.
Currently, it's cheaper to get gas - it costs Kuwait only $2/barrel for oil (the difference between that and the world price is all profit). Oil, as has been pointed out, is just too darn good, from an economic standpoint.
The biggest problem with alternative energy (including nuclear, which we *should* use a lot more of) is storage - especially for automotive uses. I simply do not foresee an adequate battery technology coming down the line. Fuel cells may eventually reach the cost, density and safety needs, and we could produce fuel using nuclear generated electricity.
All of this assumes enormous investments and drastic changes in very expensive infrastructure, so it is not going to happen any time soon.
Personally, I am for continuing the large levels of research into these techologies, but not for rationing (by price or any other way) oil for automotive use. The global warming arguments, even if valid, leave decades in which to start changing, and it would be foolish to destroy our economies (with the unpredictable political consequences - such as the rise of anti-environmental or even fascist governments).
Re:U-235 vs. U-238 (Score:3, Insightful)
The "Warning to Humanity" top scientists had very few climatologists in its ranks, so it is utterly and completely meaningless.
Your problem is that you assume that we *can* change, and that we can do so in a beneficial way.
So let me throw just a couple of problems at you...
1) You say the environment is too complex for us to understand the effects we are having on it. That is true. And that means that any action we take is just as likely to be beneficial or not, considering we don't understand the consequences. So why should we choose the one that will cause massive economic dislocation, ultimately killing the millions of people who have such a marginal life right now that they can't *afford* any diminuation in the economic situation.
2) If you look at what the real scientists say (say, for example the IPCC report - and not the politician written summary, but the real thing), you will realize that the Kyoto recommendations, which are supposed to help with global warming, will, IF THE MODELS ARE RIGHT, make such a tiny change that it will be unmeasurable 100 years into the future.
3) If you look at how much change is reputedly needed to make a difference (again, assuming the models are correct), you would realize that Kyoto is just a Trojan horse... a way to get us used to economic sacrifice so that the REAL changes can be done - cutbacks of 30% or more on CO2 emissions which translate, with TODAYS technology, to massive economic disaster.
4)Those who want to follow some plan of change are arrogant enough to believe that they can determine how mankind will behave for the next 100 years (the normal timeline for most scientists studying the issue). They were also that arrogant in the first decade of the 20th century. They thought they had the problems of government solved. Of course, since then there were a few unanticipated events like like World War I, World War II, the rise of communism (which resulted in the worst environmental damage of any system, along with 100,000,000 murders), the invention of the computer, powered airplanes, nuclear power and bombs, quantum theory, the relativity theories, electronics, Social Security, antibiotics, modern genetics, information theory,.... But I'm sure that you believe that things like this won't happen this century, right? Or that minor things like how people really think and act won't get in the way of our punitive solutions? Pardon me if I don't take seriously those people who think they know enough to effect a solution to some vague issue (gasp, we are hurting poor mother earth), and if I am not willing to make economic sacrifices on behalf of their poorly considered ideas.
5) It is interesting that people who put out radical environmental rants tend to be anti-western. Usually this is because they haven't taken a look at how *other* societies treat the environment - which is on average with considerably less respect than we in the west do. Oh, and every one of the inventions I mentioned above... took place in the evil west.
6) The "vicious cycle of consumerism" is an unintended codeword for people exercising their economic freedoms. It is usually uttered by people who are sure they are smarter than these "consumers" - people who justify their beliefs by thinking that consumers are somehow deluded into making their choices by evil capitalist advertisers.
Finally, let me comment that your rant is a perfect example of what I find so objectionable about modern environmentalism: it encourages illogical people with little grasp of the facts and no grasp of history to act and speak as if they knew something.
Why don't you really learn something and read
THIS [tinyvital.com].
Re:Research (Score:3, Informative)
Nope, breeder reactors [netcom.com] take care of that problem. It'll give quite enough fuel to last much longer than a century
silicon chip micro rectennas? (Score:3, Funny)
Production all goes to... (Score:3, Funny)
Where are they? (Score:5, Interesting)
The patent just expired. It takes a while to develop and prove out a new technology.
I see lots more work on windmills for alternative power. Many have shelved solar panels because the current ones have poor performance.
Re:Where are they? (Score:5, Interesting)
Re:Where are they? (Score:5, Interesting)
Re:Where are they? (Score:5, Interesting)
The downspout on an office building is going to produce proportionally less electricity. Let's assume you have a 4000 square meter roof 100 m high and you get 100 cm per year of rain. That's 4 million kg of water dropping 100 m. Since E = mgh, you get a potential annual power yield of 4 gigajoules. Over the whole year, this comes out to an average of 126 watts. Factor in unavoidable generation losses, and you'd be lucky to power a single light bulb with the rainwater from an entire office building.
cost? (Score:5, Insightful)
Re:cost? (Score:3, Insightful)
Now these converters are a different story. Even if they were that efficient, they cost would be so large, like you pointed out, it would be prohibitive for the average consumer. However, with efficiencies that high, eventually lots of people would want one and probably bring the cost down.
Check your math. (Score:3, Insightful)
Ask yourself... (Score:3, Insightful)
Re:Ask yourself... (Score:5, Funny)
90% of slashdot just simultaneously realized that these solar panels havent been developed because they are too busy looking at porn and playing warcraft.
Possibly overlapping Patents? (Score:4, Interesting)
Re:Possibly overlapping Patents? (Score:3, Informative)
Perhaps impractical to actually build? (Score:4, Informative)
Assuming the applicant built a prototype and proved this device works, creating metal coatings in the exact thicknesses he mentions with the detail he describes is still something that would be very expensive to do now. That technology hasn't improved very drastically in the last decade or so.
What, or rather Who keeps this off the market? (Score:5, Funny)
Who keeps the metric system down?
We do, we do.
Who keeps Atlantis off the maps?
Who keeps the Martians under wraps?
We do, we do.
Who holds back the electric car?
Who makes Steve Guttenberg a star?
We do, we do.
Who robs cave fish of their sight?
Who rigs every Oscar night?
We do, we do!
Not with semis (Score:5, Informative)
E=hw
Silicon is actually a rather poor photomaterial, being an indirect material, it's limited to about 60% effeciency at any wavelength. The electron must not only gain energy, but also move a slight bit within the crystal in order to reach the conduction band. Direct materials, such GaAs, being direct, can be > 95%
Perhaps the are other techniques??
Re:Not with semis (Score:5, Informative)
Whoops, I think you're confused. w (which is actually an omega) is angular frequency, not wavelength. And h is really h-bar, which is Planck's constant over 2 Pi, not Boltmann's constant.
But the actual equation is correct :-)
Anyone know the energy in sunlight? (Score:3, Insightful)
Re:Anyone know the energy in sunlight? (Score:5, Informative)
This is from Here [electrochem.org]
Re:Anyone know the energy in sunlight? (Score:4, Interesting)
if you take all the unused building space in america and covered them with solar cells (of today's technology and efficiency) you could generate (more than) all the power we use (even if we convert all cars to electric cars). the neat thing is that the "unused building space" doesn't mean "cover the desert with solar cells" is just means to put solar cells on every roof top, on the top of the medians along the highways. granted this is a difficult task, but what if every residential house that was built had to have it's roof coated in solar cells and put on the grid. after a while you'll be generating quite a lot of power.
another cool thing that is in development is turning the huge windows of office buildings into solar panels. in high-rise office buildings, it's not uncommon to have 10 foot tall windows that span the entire room. usually these windows are tinted and the office generally has blinds or curtains to keep all the sun out (to reduce cooling costs in the summer, and having that much sun in the office would make it to bright anyway). so rather than just using some type of tinting that reflects the light partially, i've seen some cool work with dithering (very) small solar cells in the windows, these will absorb light and turn it into electricity. so you'll get two benefits: tinted window and extra electricity for the building.
just simple solutions like that could help our upcoming power crisis when we run out of oil.
Here it is. The inventor calls it lepcon. (Score:5, Informative)
It looks as if this is all still very blue-sky, and there is no reason to think that these nifty ideas will work in practice. The first page I linked to tells us: ``Dr. Marks is in negotiation with U S. government to fund Lepcon research and development.'' Probable translation: ``He's applying for grants, because he can't sell it to the venture capitalists.''
PVs can exceed 35% efficiency (Score:4, Interesting)
This article mentions Tecstar--apparently the leading supplier of high-output PV cells for space missions. They made the cells for the Mars lunar rover, among other projects.
The difficulty is that manufacturing the cells is very difficult and expensive, requiring multi-million dollar Metal Oxide Chemical Vapor Deposition (MOCVD) machines. Due to variations in the rather elaborate manufacturing process, the yields vary greatly, and also produce cells that have widely varying efficiencies. Some cells fall below a given spec, while others exceed the spec.
In order to achieve a given power output for a space system, they are able to mix the under and overperforming cells into an array that provides the necessary power.
So, although some cells may only provide 30% output, a few will exceed specs, and thus provide > 35% efficiency. The challenge is delevoping manufacturing processes that improve yield and thus reduce costs.
Why aren't we ever going to see these type of cells on earth? Cuz they cost millions of dollars to produce, and there is a multi-year order backlog for them for planned space missions. Unless hundreds of millions of $ gets directed towards making them a commodity, well, you know the story...
The folks at NREL are fixing photovoltaics... (Score:3, Informative)
But as to making micro-antennas that work in a broad enough bandwidth to beat solar cells, no I don't think they're playing with that. But you're talking something painfully small, even at current technologies, I would think. Those 17% efficient solar cells work up at the blue/ultraviolet range. If you look at the spectrum [electric-words.com] that tells you the wavelength of UV is 10**-8 meters, or 10nm. Now a current transistor on a chip is about 180nm; so to get that bandwidth with an antenna you need a component about 1/10th the size of current chip components, and if you want to do one of those fractal, broad-spectrum antennas, you need sections of antenna at least 1/8 that size... So given Moore's law, you're still 10 years off.
Solar cells (Score:4, Informative)
The cost and deposition speeds already eliminate a number of materials from practical application; and, there are a number of other issues that must be taken into account (especially among modern solar cell materials):
1) For sunlight, the maximum intensity occurs at 550nm, which means that a device bandgap of 1.35eV is needed to give a maximum electron/hole pair generation rate. One of the best known solar cell materials, c-GaAs, has an Eg = 1.4eV, but its high cost makes it prohibitive. c-GaAs can be grown by epitaxy, but requires high temperatures for deposition -- it can be difficult to grow uniformly over large surface and on more desirable substrates (like plastics).
2) c-Si, which is cheaper than c-GaAs, must be deposited in very thick layers for max efficiency, and has an Eg = 1.1eV, making it difficult to deal with and not that efficient. Like c-GaAs, impurities in the crystalline latice can have large, detrimental performance effects.
3) a-Si is a great material as it can be grown over large areas very inexpensively, but it has a number of disadvantages. Being amorphous, it suffers from metastability (the Stabler-Wronski effect), which means that its performance degrades over time as more light hits it. It also has Eg = 1.8eV, which makes it less than perfect for sunlight-based solar cells.
There are other issues facing solar cell designers, such as:
1) reflection at the surface
2) series resistance due to impurities and scattering within the semiconductor
3) non-radiative recombination (phonon recominbation) in the semiconductor
4) incomplete extraction of carriers in the semiconductor
5) interface and contact losses in the p-i-n or Schottky barrier structure
Triple-tandem solar cells made of p-i-n structures of a-SiGe, uc-Si, and a-Si:H (which have bandgaps like 1.2eV, 1.45eV, and 1.85eV in the same package) can be used to target as much of the solar spectrum as possible, and can still be grown "relatively" cheaply by PECVD reactors. They get somewhere around 17% efficiency in sunlight.
Performance of solar cells would undoubtedly be better if cost were not an issue, and if single-wavelength light were being used, as exotic material devices could then be targeted for these specific conditions. Alas, real life is not so ideal.
-kris
Comment removed (Score:5, Insightful)
Theoretical problems with optical rectennas (Score:5, Informative)
Sunlight at the earth's surface has a power flux density of about 1 kilowatt per square meter. To convert that to an electric field strength, we take the square root of the power flux density times the impedance of free space, 377 ohms. This gives 614 volts/meter.
Yellow light has a wavelength of 570 nm. That means the electric potential over that distance is only about 350 microvolts. This is approximately the voltage you'd see at the terminals of a 50 ohm half wave dipole, and it's far below the voltage needed to switch a rectifier. Silicon rectifiers take about 600-700 millivolts of forward bias to begin conducting, even if one could be constructed to work efficiently at optical frequencies. Germanium takes about 300 mV, and silicon Schottky diodes take about the same.
It is not possible to construct a diode that doesn't require a forward bias, otherwise we could rectify the noise from room-temperature resistors and convert ambient heat to useful work. This is specifically prohibited by the second law of thermodynamics.
Re:Theoretical problems with optical rectennas (Score:3, Interesting)
IIRC, the rate of attenuation of an electromagnetic wave in a conductor is
sqrt(2/wus),
where
w = 2*pi*f = frequency of the wave, in radians
u = permeability of the conductor, maybe 4*pi*10^(-7) Henry/m for copper
s = conductivity of the conductor, maybe 6*10^7 mhos/m,
meaning that 1/e or about 37% of the wave decays in this distance into the conductor.
If my numbers are right, f = 5.2*10^14 Hz for yellow light, and the skin depth in copper for yellow light is then 2.8*10^(-9) m, or 2.8 nm.
Since the wavelength is 570 nm but the skin depth is only 2.8 nm, it seems that a copper antenna would instead act more like a mirror, reflecting the radiated energy rather than absorbing it.
It's a transverse wave (Score:3, Interesting)
The problem here is likely timescales: light has a VERY high frequency (10^17 Hertz roughly, if I did my math right). At that frequency one doesn't push the electrons back and forth like a kinetic particle in the usual diode treatments so much as one excites interband transtions, which is how a regular solar cell works.
Re:It's a transverse wave (Score:3, Interesting)
Photovoltaic cells work on a very different principle. Because there's a significant amount of energy in each photon, enough to dislodge an electron from silicon's valence band into the conduction band (about 1eV), current can be generated.
If the photon lacks enough energy (has too long a wavelength), nothing happens except that the silicon heats up. If the photon is too energetic, it will still dislodge the electron but it won't impart all of its energy; the rest will again be wasted. These two effects account for much of the poor efficiency of PV cells on sunlight, which has substantial energy across the visible spectrum and into the near infrared.
Oil is solar power! (Score:4, Interesting)
I think it is a good idea, anyway. The only energy that is not solar is geothermal and nuclear.
The real problem with solar cells... (Score:3, Funny)
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:4, Insightful)
If GWB is so concerned about keeping the Texas oil economy going and appeasing the Texas oil companies, wouldn't he want to avoid increasing the supplies of oil, especially foreign oil? If GWB annexed Iraq and started sucking out all the oil for US use, that would just tank the prices of oil and lower the demand for Texas oil.
Plus he's POTUS now, not Governer of Texas, he has more people to appease then just the Texans. (And if it was so easy to invent alternative energy he'd score far more points across the board then he would lose in Texas)
Bush & Cheney both sold off their stocks (at a loss at the time), to limit their conflict of interest with the oil companies.
It isn't GWB holding up electric cars in some oil conspiracy, it's the population as a whole - who collectively don't seem all that interested in alternative fuel vehicles or higher fuel usage vehicles. Then there's the money for whatever new infrastructure is required by alternative energy...
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:5, Insightful)
t0qer's argument is correct, though, just not formulated quite accurately. It's not support for Texan oil. There really isn't any more Texan oil. What oil the US produces is mostly offshore or Alaskan, but even so it's small fraction of what we use.
Bush isn't trying to support pumping of oil; imported crude goes straight into the US petrochemical industry. Many of the refineries are in Texas, but even where they aren't, GWB is a friend of the industry. It's where he made his millions, and it's all he knows.
It's not simple selfishness and wanting to pad his wallet. It's just that that industry is where he grew up. He's conditioned to think of it as central to US wealth and prosperity, the driver of the economy. In his mind, whatever is good for the oil companies is good for every American. He really honestly believes he's doing the right thing for all of us by suppressing alternative technologies and making war with Iraq.
Bush is not smart and worldly enough to see the bigger picture, or to take the long view.
Getting the Iraqi oil fields under a friendly regime means the US has more *control* over oil prices and fewer "bad guys" to worry about messing up the economics for his favorite companies.
It isn't GWB holding up electric cars in some oil conspiracy, it's the population as a whole - who collectively don't seem all that interested in alternative fuel vehicles or higher fuel usage vehicles.
Yes and no. US consumers don't want a wimpy EV1, for the most part. They want the bulk, power, and capacity of an SUV. Thus, the consumer is to blame.
But... The government spends many billions on petroleum research, exploration, and foreign policy to support the petroleum economy. The cost of just the first war with Iraq and the subsequent decade-long airspace occupation is estimated in the back hall of congress to be in the range of $100 to $200 billion [washingtonpost.com]. Billions more are spent every year to subsidize activities (research and exlporation) that benefit the oil companies. I've seen figures (can't find them right now) that estimate you pay $5 to $8 per gallon of gas in income taxes to support petroleum
Now... if over the last fifteen years the government had spent that same half a trillion dollars on electric, fuel cell, and hybrid vehicle research, don't you think we'd already have big powerful SUVs that don't depend on oil? We'd have a cleaner country, consumers just as happy, and fewer foreign policy messes. What if we'd been doing that since 1920? Shouldn't we start now so we're not asking the same question again in 2040?
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:3, Insightful)
While in the end it is consumers who purchase SUVs, the situation is a bit more complicated than that.
Auto companies have to produce cars such that the average fuel economy of what they sell meets a certain federal standard. The car companies are notriously bad at doing this, but even though they ignore the law, promissing to make it up in the future (right...) they are always looking for ways around it.
Now light trucks are exempt from these regulations. But consumers outside of Wyoming (I love Wyoming btw) don't want to drive around in a truck, they like their cars. Enter the SUV. Very few people NEED an SUV, but the auto industry loves them because they are more appealing to consumers than trucks but are classified as light trucks for the purposes of federal fuel economy standards.
So the car company can put a big 'ole engine in there and not worry about the expense and bother of fuel efficiency. Now if only consumers wanted to drive a jacked up station wagon (which is what your typical SUV is, admit it.) Since station wagons are soooo cool...
But wait! That is what marketing is for, to tell consumers what to buy and what to want! So car companies market the crap out of SUVs since they are more profitable than cars and don't hurt their fuel economy averages. Bingo! SUVs are popular because consumers "want" them.
So yes you can blame consumers, but I choose to blame poor legislation that gave car companies incentive to make SUVs as well. While I'm at it I blame the car companies too. Especially Toyota for making a 4Runner with a removable hardtop up until 1989. Wish I still had that car, I mean truck...
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:3, Insightful)
No, actually I don't think we would have that. This is a classical mistake - equating rate of spending money with the rate of resulting technological progress. One could argue, with exactly the same logic that you are using, that if we had invested all that money in medical research, we would all live forever. Or, we could argue that if we invested it all in telekinesis, we could all transport ourselves with no energy at all!
In other words, your argument makes a very dangerous assumption: more money can solve physical problems in a given period of time, regardless of whether they are ever solvable, or if they are solvable without the appearance of another Einstein.
Actually, governments and lots of private industry interests have spent huge amounts of money on alternative transportation energy systems. The reason is the potential enormous profits.
For exmaple, if a company could come up with a viable battery technology for electric cars, the other advantages of electric cars (very low cost and very low maintenance, outside of the battery; very good performance; mechanical simplicity) would cause them to fly out of the show-rooms! Everyone would wnat one, and everyone would buy one, and the car makers would immediatebly build a zillion of them.
With those sorts of profits at stake, the issue isn't the lack of investment, it's the difficulty of the technology!
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:3, Insightful)
DOn't forget, it's not texans, but Powerfull texans that have nothing to gain from shanging the status quo.
However, I do not believe in a conspiracy. I gaurntee you if there was a an alternate source of power i.e. NOT oil. the people in these energy companies would find a way to Globally capitalize on it. That would be far more money, with less over head. If there was a conspiracy, I would look a OPEC.
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:5, Interesting)
Do you have a URL for Bush's guidelines on electric vehicles?
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:4, Informative)
What would happen if all the major automakers decided tomorrow to start building electrics?
We would burn about the same amount of oil, and increase our use of coal.
We would burn about the same amount of oil, because you wouldn't be replacing very many gasoline powered cars on the roads; electrics are still too small and have too short a range to be useful for the majority of Americans. None of this is going to change until there is a dramatic improvement in the stored energy densities of batteries, and/or a reduction in the toxic waste produced in the creation and disposal of the batteries themselves. The last time I saw statistics, the sum total of all the "alternative fuel" vehicles sold in the world over any time period you choose to look it was LOWER than the increase in the number of vehicles in the world ... that is, even with increased sales, we continue to fall further behind.
We would burn more coal because electric cars need to get the electricity to recharge their batteries from somewhere, and the cheapest source of electricity generation (that can be built today in North America and Asia (and even Europe, I believe)) is coal.
This is not to say that there aren't loads of technologies available to improve efficiency of fossil fueled vehicles, but most of them make vehicles MUCH more expensive (by almost any metric you choose) ... and the vast majority of people (Americans AND non-Americans) have little incentive to spend more when they can get the same capabilities for less, EVEN IF it would be to their benefit in the long run (why else would people be willing to lease instead of buy vehicles? It is far far more cost effective in the long run to buy than to lease ... ). Some of these technologies include hybrids, light composite frame and body materials, ceramic and aluminum engine blocks, high efficiency diesels, exhaust scrubbers, biofuels, superconducting electricity distribution grids, etc. etc. etc.
But none of them are perfect, and none of the forseeable technologies will eliminate our reliance on petroleum ... not even that "holy grail" of environmentalists, the "Hydrogen Economy". Hydrogen isn't free after all ... there are no large supplies of the stuff to drill or mine for, and there is none in the atmosphere to distill. You have to generate it by cracking water ... using electricity, that you have to generate by some other means. And currently, the only good way to do THAT is to produce the electricity using nuclear (which the environmentalists ALSO hate and also has a time horizon before the exhaustion of the fuel), hydropower (environmentalists hate this too) or fossil fuels ... and the inefficiencies involved in the seperation, storage, shipment, and sale of hydrogen currently would would require just about the same amount of fossil fuel usage as currently for the same energy extracted by the automobile (although we might be able to use different forms, such as more coal and less oil, and there would be far fewer plants to police). In other words, we'd be burning the same amount of fossil fuel to make the hydrogen as we currently burn to make the cars go in the first place.
There are no simple answers and very few real conspiracies, and I don't understand why otherwise intelligent people continue to believe that there are.
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:3, Insightful)
Re:Where are the 70% Efficient Solar Cells? ask GW (Score:3, Interesting)
Innovation my ass. The work the GM researchers did was excellent, and the GM EV1 v2 would have been even better. However, it doesn't change the fact that the EV1 program was all PR fluff, that was quickly flushed down the toilet once the cars started coming off lease (and this was before GWB was elected.) No EV1 was ever sold to my knowledge - because they were only leased, never sold. Now, how much innovation can you have when you take back the product that was supposed to be innovative? Toyota has done more for alternative fuels (RAV4 EV, which can be purchased, but only in California, and of course, the Prius) than GM's EV1 ever did.
IIRC Clinton even made it a law that all US automakers would have to have an electric vehicle on the market by 2008, and that these cars would have to be built along strict goverment guidelines.
That's news to me. Perhaps you were thinking about the California ZEV mandate instead?
I'm all for electric (I have a 1KW array I'm going to be putting up during spring break), but don't give credit where credit isn't due. After all, people started buying SUVs under the Clinton administration, and only now, are people turning against them (conservative christians and environmentalists alike now decry the excessive fuel consumption.) SUVs = terrorism is the new message. I never saw the Clinton-Gore people say that, probably because they were just as addicted to the oil/car industry as the Bush people are.
Re:It would certainly be nice. (Score:3, Interesting)
Re:Where? I'll Tell You Where.... (Score:3, Insightful)
What is the problem with these? You can go out and buy either of these today.
Of course you will find that for long life incandescent bulbs the cost of electricity to generate the same amount of life is much higher - see to make the blb last longer you need to make the filament thicker, and that cuts down on the buld efficiency. The typical incandescent light bulb is actually optimized to give the most light per kwh.
If you are really interested in long life bulbs and low cost light, you need to go to a different technology altogether - like compact fluorescent.
As far as electric cars, there are of course tradeoffs - simple things like running a heater on a cold winter day reduce your miles between charges a lot. But we already have a much better solution, already on the roads in large numbers - hybrid gas-electric.
Same thing probably goes for efficient solar energy.
Yes, it exists. The problem is capital cost to collect it, and what do you do to get power when the Sun is down or it is cloudy. Right now solar power is 2x to 5x more expensive than fossil electricity because of the capital costs. However the installed solar power wattage is growing rapidly, primarily in areas that are a mile way from conventional power grids where the cost to run the lines outweghs the cost of the solar power system.
Re:OK, which forests do we cut to make solar farms (Score:3, Interesting)
1) One geographic source means that one heavy cloud day would eliminate all production.
2) Once the electricity is produced, you have to send it over transmission lines to the load (customers). Too much energy over one set of lines will melt it.
3) Build more transmission lines, and your local communities will complain about all the electric lines in the area, driving down the local value.
4) Natural disaster. One hurricane, tornado, hail or earthquake, and you've broken all of the glass in the whole plant.
So, the key to PV is decentralization. This means many many installations spread over hundreds (to thousands) of miles) at about 1 station per square mile. Each one would need its own DC to AC converter (to put energy on the grid), not to mention voltage regulators, plus telemetry so you can get the reading from the devices, all of which drives up the costs.
Re:The key to adoption is distributed power (Score:3, Interesting)
The United States & Canadian power grids (of which there are 3 AC systems running in parallel) is currently controlled by a number of Regional Transmission Companies, also working in parallel, and I happen to work for one of them. Fortunately, California & everything west of the rockies are AC-isolated from our Eastern Interconnection, so we east coast fellows (who happen to be running things correctly, not to mention profitably) won't have to suffer if they crash out.
But to your comments, you might want to take a look at recent distributed generation projects, like what's being built in APS territory. Secondly, anyone in the deregulated markets can form an electric co-operative, and buy/sell power to the bulk market. The rules are already in place. (aren't you curious why so many states are fighting deregulation?) The only problem is telemetry... the more distributed you get, the harder (and more costly) it is to collect the individual meters. PP&L is experimenting with automated meter reading using the telephone network, so there is progress in distributed data collection...
The next phase is demand-side response, which is the ability for the customers to adjust their load, and get paid locational pricing for decreasing their consumption. The key here is, you can't play in the spot market only when it's profitable, you have to play 100% of the year. Show me the public utility commission who's willing to risk raw pricing for its citizens...
As for the article, almost every example given was the Midwest-ISO & California-ISO version of how things are done, and frankly, they are in 2nd & last for a reason. And you're correct, the infrastructure does not exist for us to monitor everyone's generation in real-time. But then again, that's what state estimators are for.
p.s. EPRI doesn't exactly have the best reputation, which makes me wonder what agenda Wired had in chatting with them