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Domain: upei.ca
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Comments · 13
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Re:Who will eat whatever is grown there?
I'm talking about the full krebs cycle efficiency. Meaning the effiency of the process creating sugars on the edge of the chloroplast.
Those efficiency ratings differ from species to species (depending e.g. on their height : trees are vastly more efficient than grass, but at the obviously rather high cost of maintaining an enormous support structure which is not deducted from their photosynthesis efficiency ratings)
So this figure has to be divided by a factor between 100 or 10000 before we're talking about a potato on your plate (and if you want to get anywhere near 100, you'd best be a farmer in congo, without access to fertilizer), and by a factor of at least a 100000 if we're talking meat.
That said, the efficiency of using sunlight to create sugars in plants ranges between 0.2% and 6%. Here are a few sources :
http://www.upei.ca/~physics/p261/Content/Sources_Conversion/Photo-_synthesis/photo-_synthesis.htm
http://en.wikipedia.org/wiki/Photosynthetic_efficiencyThis is the "theoretical number". What electrical food production would need to attain to beat out plants for food on people's plates, is obviously much less. To beat out plants it would need an efficiency of less than 1/1000th of a percent, especially if this could be done at the place of consumption. To beat out meat
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Low pressure by design
A CANDU reactor still has a large steel Calandria surrounding the pressure tubes....the reason why the CANDU was designed was because it runs on natural, unenriched uranium. It had nothing to do with the design of the pressure vessel.
From the Wikipedia article on CANDUs:At the time of its design, Canada lacked the heavy industry to cast and machine the large, heavy steel pressure vessel used in most light water reactors. Instead, the pressure is contained in much smaller tubes, 10 cm diameter, that contain the fuel bundles. These smaller tubes are easier to fabricate than a large pressure vessel. In order to allow the neutrons to flow freely between the bundles, the tubes are made of zircaloy, which is highly transparent to neutrons. The zircaloy tubes are surrounded by a much larger low-pressure tank known as a "calandria", which contains the majority of the moderator.
So posters are quite right that plenty of reactor designs are unaffected by the capacity problems at this steel plant. Indeed, the only effect on CANDU reactors is likely to be a potential increase in customers.
Also:When the first CANDU's were being built, the US was still manufacturing PWR pressure vessels and there was no problem in that area.
The CANDU design had started by 1958, and the first commercial PWR in the US was opened in 1957 - and was just 60MW - making it somewhat unlikely that Canada could have simply purchased PWRs even if it had chosen to. Work started on the first CANDU in 1960, the same year the US started operating only its third nuclear power plant. It appears unlikely that US-built nuclear plants would have been highly available outside the US at that point. -
Re:TFA is worthless.That gives me 23% not 6.6%. Anybody have any more insight into this? From the source cited in Wikipedia: 1. At least eight photons are required to store one molecule of CO2 which means 1665 kJ of light energy are required to store 477 kJ in the plant. Max efficiency is 0.286 or 28.6 %
2. Only light in the range 400-700 nm can be used. This amounts to 43% of total solar incident radiation.
3. Canopy limits absorption to 80 %
4. Respiration required for translocation and biosynthesis requires about 33% of the energy stored which leaves 67%
The overall efficiency is then -
15% would be pretty good
15% efficiency would actually be pretty good considering by some calculations photosynthesis efficiency is around 5 to 20%.
Here is one calculation showing ~6.6% photosynthesis efficiency
It takes into account things like canopy shading, which wouldn't necessarily apply to this, but here's the link:
http://www.upei.ca/~physics/p261/Content/Sources_Conversion/Photo-_synthesis/photo-_synthesis.htm
I tried to find a peer reviewed one, but can't find one right now(I'm at work, break almost over... -
Re:How efficient are they?"Solar power? Would be cheap, but the production of those solar cells is creating a horrible amount of waste and they're far from efficient. Wind power? Even worse."
Could you specify how much is "a horrible amount of" please? From what I have known, they are much cleaner than a horse or a donkey. Also the efficiency of commercial solar power cells are much higher than that of the grass or trees.
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Re:ThermodynamicsNow, here's the rub: Where are you going to get energy conversion efficiency that high?
No where. According to this site, the efficiency of photosynthesis is just 6.6%. So, to capture 100 watts of energy in plants, you need more than 15 square metres of plants. I don't know what the efficiency of human digestion is, but I suspect you'd be looking at closer to 100 square metres or more of plants to get enough energy for one person.
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100% efficient, say what?
I found it difficult to believe the "near 100% efficient" comment. A simple google search found this...
http://www.upei.ca/~physics/p261/Content/Sources_C onversion/Photo-_synthesis/photo-_synthesis.htm
Now, is this a legit website? I don't know, but intuitively it makes more sense to me than "near 100% efficiency" -
Re:Power Company Web Worth a Visit
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Re:Not Found
First of all, it wasn't the first Google result, it was the second
Second of all, somehow an "l" got added to the end which shouldn't have been there.
The real link should be
http://www.upei.ca/~physics/p261/projects/flywheel 1/flywheel1.htm
Thirdly, lighten up. -
Re:Power Company Web Worth a Visit
How about just using a large scale underground flywheel to store the energy?
http://www.upei.ca/~physics/p261/projects/flywheel 1/flywheel1.html -
Re:High Mileage Cars
You're still talking about swapping out hundreds of pounds of batteries; even if they're designed for the swap I don't really see that happening all that easily. Lith-ion batteries have approached 150 WH/kg energy density in test batteries. Assuming we want to drive the same range as a full tank of gas (call it 300 miles), and using the figure of 160 WH/mi (which is correct for an electrified Geo Metro), you wind up with the requirement for 300 kg of battery. Using lead-acid batteries like most EVs currently do, you'd wind up with 900kg. Swapping out 700 pounds of equipment that frequently is a non-starter.
Also, charge-discharge cycles - batteries fail after a few thousand, flywheels see no degradation after hundreds of thousands.
The last point I would make is related to this image. You need to worry about energy storage and power storage. Batteries are okay at energy storage, but miserable at power storage.
Flywheels do have problems (eddy induction, vacuum containment, magnetic bearings not being perfect, etc) but are certainly likely to be as reasonable an option for ZEV as batteries are. -
Re:can't you tell by my ridiculous accent?
Do you think we'd all start using the arabic word? Ignore the fact that there are different alphabets. Just think of the way the arabic word sounds. Again, do you think we'd use the word? Hell, no. Americans wouldn't stand for it.
Hmm... You mean a word like "Algebra"? Nah, we'd never do anything like THAT. Then again, there was the book "Al Gebr We'l Mukabala" by Al Khwarismi. You can find a reference here or here.
Now as for the French, who are you calling naive? If this was America pulling this stunt (can you say "Freedom Fries") we wouldn't hear some lame ass crap about messing up the language. This is just more anti-Anglo behavior from France. Or do you consider it conicidence that they also have restraints on how much American music can be played on radio stations? That's been around for ages.
Wow, talk about naive. -
Re:That's just an A-
No, no! There's still Hawking radiation. Some folks think that it could be reconstructed. 'Course, Hawking doesn't. But he's not in computer security, either.
