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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."
90% of slashdot just simultaneously realized that these solar panels havent been developed because they are too busy looking at porn and playing warcraft.
There's nothing Intelligent about Intelligent Design.
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
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?
For simplicity we take the solar energy density falling onto a window to be 1000 kWh/m2 yr. This is regarded as a typical number for a south-facing window, and more correct values for south-facing/north-facing/horizontal surfaces would be 850/350/920, 1400/450/1700, and 1100/560/1800 kWh/m2 yr for Stockholm, Sweden, Denver, USA, and Miami, USA.
This is from Here
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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.
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.
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
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.