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Where are the 70% Efficient Solar Cells?
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?
They keep me in the dark about these things :-)
All my previous sigs now look like this one, I wish they were permanetly recorded when used.
Anyone else get a sorta shifty feeling when they look at that word and picture the consequences of such an invention?
Any sufficiently well-organized Government is indistinguishable from bullshit.
What the US needs is a Manhattan Project for alternative energy to oil. Solar, wind, geo, fusion, whatever. Something but burning simple chain hydrocarbons and because the waste product is mostly invisible, pretending it doesn't exist.
Who elected George Bush anyway?
I don't think that rectenna is going to be in much sunlight.
I have know about this company for years. Lumeloid Solutions claims their technology is theoretically capable of efficiencies of up to 80%.
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 - Liberty with Technology.
www.enthea.org
Why haven't you built one of these things? Chances are that's the same reason that they haven't yet been built.
Could it be that the effect in question has been patented for some other use? I'm not familiar with the patent quagmire, but multiple similar uses for the same physical phenomenon (light absorbtion into silicon) might be the issue...
This device may be fabricated upon a transparent slab by the deposition of one or more metal coatings in a known manner. The various rectifier elements are first prepared by opening appropriate windows in the metal coating utilizing an electron beam and suitably coating and doping the rectifying areas. An electron or ion beam cuts the shape and connections shown. The connections are completed after deposition of the insulating coating 9. The circuit is then the same as that shown in FIG. 1.
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.
Who controls the British Crown?
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!
Semiconductor photocells can easily be >90% effecient, but over a rather small range of wavelengths. This is due to the bandgap. An electron is freed if the electron gains enough energy from the photon(s) to overcome the bandgap. the energy of several photons can be combined to free and electron, but is lossy. If the photon has more energy than is required to free the electron, the extra will mostly be dumped as heat. The equation governing wavelength, energy, and Boltzmann's constant is
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??
I don't get a shift feelign at all. We are already direly close to Hubbert Peak, when oil demand starts to outstrip production. In fact Hubbert, himself an oil man, said that Hubbert Peak, even considering undiscoverd reserves (which is fairly predictable with satellite reconaissance) will come sometime between 2002-2009.
You can read about here on my website 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 - Liberty with Technology.
www.enthea.org
I know this is a dumb question. I remember hearing the answer back in high school but I have since forgotten it. I want to know the total energy in sunlight. I know it varies widely depending on location and weather but an average or a range per square foot, square yard, acre or whatever would be interesting. I ask because I think some people overestimate the value. If you can produce a 1 inch square solar cell that's 100% effecient but it costs $1000, then it's never going to pay for itself except in space applications. The big payoff for solar cells will come when you can produce them for almost nothing and plaster them over everything. When that cool, one way billboard plastic wrap stuff that covers busses also acts as an 80% effecient solar cell, then we'll see more of this stuff.
Okay here's my problem with your argument:
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...
For a time, I lived in a so-called Texas oil town during the late 80's and early 90's. A family member worked on oil rigs there. The town itself was a ghost-town (and is much worse within the last few years) because the government paid the oil producers to shut down the wells. Texas oil is more expensive to drill, retrieve and refine than just buying tanker-full shipments of imported oil. If anything, the "Texas oil economy" probably revolves more around importing and off-shore drilling. Just a detail there for ya, "partner".
Do you have a URL for Bush's guidelines on electric vehicles?
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.
Hydrogen is only an energy storage mechanism. It is an attractive one to be sure but it is not itself an energy source. What to you propose to generate Hydrogen with once the hydrocarbon tap is turned off? To be sure, Hydrogen's role as an energy transport and storage mechanism will be important whenever oil does run out but that isn't what I'm asking. What fills the large petroleum shaped hole in energy production once it's depleted?
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?
Right... There's a soccer mom picking up her kids in a big giant suv that GWB made her buy. This is about our collective dependance on oil. Don't like what Ford is pawning off as an electric car? Blame Ford, the current standards for what constitues a "Car" are probably not much more than that golf cart either but you don't see them wasting any time on turning out ex(plorers\scursions) like they were going out of style. The first company that makes a serious mass market attempt will probably succeed provided infrastructure supports it.
When it was clinton/gore presidency, everything was dumped into technology, the GM EV1 is a classic example of the innovations that occured under a goverment that supported research that would cut out our dependance on foriegn (read Iraq) oil.
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.
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.
... so that you can think you're filling for $1.79/gallon. (based on the cost of drilling, wars, local goverment concessions to bring industry to the area, etc.)
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. 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?
I stole this sig from someone cleverer than me.
because texas oil companies make money from overseas oil. Look how Enron made money, it sure wasn't from pumping texas oil.
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.
The Kruger Dunning explains most post on
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).
Send mail here if you want to reach me.
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...
Lasers Controlled Games!
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.
I see alot of people here want cheap solar cells that can cover their entire roof for a "few hundred dollars". Are you nuts? Standard roofing materials (made from asphalt) aren't that cheap and all they do is keep water out!
Maybe the price needs to come down to a few THOUSAND dollars...with some government tax credits and utility savings, it might be worth it.
-ted
We already went through this during the last big El Nino, then we (well, us in Manitoba anyway) had several really shitty/cold/wet years.
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.
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.
I see a serious theoretical difficulty here that may explain why the optical rectenna was never built.
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.
Plants stored energy from the Sun, then died and were burried for a long time. That energy still came from the Sun. If we can just figure out a way to go from plants to oil more quickly, we can plant fields and basically they would be giant solar pannels.
I think it is a good idea, anyway. The only energy that is not solar is geothermal and nuclear.
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
Diesel creates PM10 pollution. This stands for "particles less than or equal to 10 microns in size". It may produce less CO2, but the PM10s have the most dramatic effect on lungs. A tuned diesel engine produces less, but if you see that plume of black smoke, your normal dust filtering ability in the nose and throat is letting the tiny particles deep into your bronchi.
-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".
...is that they only work when we don't need to turn the lights on anyway.
Take electric cars and ultra-ultra long life lightbulbs.
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.
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?
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!
The only good weather is bad weather.
Hmmm. The electric field of EM radiation is transverse (perpendicular) to the direction of propagation (i.e. wavelength) so the potential difference doesn't build up in that direction.
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.
Curtains for windows?
Having one centralized solar farm would almost guarantee the project's failure. Because..
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.
Reading that Wired article, I feel like the brain cells were dying under the weight of mis-information (not to mention opinion being reported as fact) contained in that article.
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
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.
Ethanol is a bit of a sham solution. It seems fine at first glance, but when you look under the cover, it in fact requires much more energy per gallon to produce than many other energy sources. The majority of ethanol fuel is derived from corn, and the quantity of energy expended in the tilling & harvesting, etc. of that corn exceeds by far the energy expended producing most other fuels. Usually this expenditure is in the form of burning other fossil fuels in tractors & combines.
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.
There are a thousand forms of subversion, but few can equal the convenience and immediacy of a cream pie -Noel Godin
I did my PhD on polarization effects, so know a bit about them. Whether I can explain in layman's terms is another matter, but here goes...
Light may be considered to act as both a particle and a wave, but for our purposes we'll stick to waves.
Imagine looking at an unfiltered, unpolarized light source. The light is travelling towards you but each little bit of light is a wave which may be orientated up and down, or side to side, or anywhere inbetween, as it travels. (I'm ignoring what is known as circular polarization for now.) You can consider a polarization filter as a grill. Only the waves which line up with the grill will get through intact. Waves which are partly aligned will pass through the amount that does line up. Waves which are at right-angles to the grill will not get through at all. The light which does not get through is absorbed. If you take evenly distributed unpolarized light, which is what solar cells pretty much get from the sun, then you can only get 50% of the light through into linear polarization with a single filter. You can change one polarization into another efficiently, but the initial conversion from unpolarized to fuly polarized causes 50% loss.
However, a 50% polarization followed by an 80% conversion within the solar cell still gives you an overall 40%, which is much better than current cells.
Here's something to think about: If you shine light through 2 polarizers which are crossed at right-angles then no light gets through. This is because the light coming through the first polarizer is all aligned at 90 degrees to the orientation of the second polarizer and is hence completely blocked. If you now add a third filter at 45 degrees between the other two then you start getting light through. Adding a filter has increased the amount passing through. Explaining why, I'll leave as an exercise for the reader.
This sig is a figment of your imagination.