Well, yes, but I chose to paraphrase a different part of the article, since it emphasized the surprising impermeability to helium. Either way the conclusion is the same, and that information was not mentioned in the link in the/. summary.
Perhaps "standard" was included to exclude gases that would react with graphene, as I suspect fluorine would.
The article is unreachable, so I can't see what it says.
Should we be boycotting niobium products now (niobium == columbium, which got its name from being the key element in columbite)? I see it's used in prosthetics, jet engines and superconducting wires [so it's probably used in MRI imaging]). Expecting people to avoid all these products looks impossible.
My comment and the only other comment to it both claim the mirrors are true parabolas, and I have a link to a physics proof that this is so rather than to a side comment in a Wikipedia article.
Excellent choices. I thought Dodd was the pick of the litter among the Democratic presidential candidates, and I only now support Barak as the lesser evil.
If you just throw away the heat generated during the compression, which I think is what is done in current large installations, I have read that you can get about 50% efficiency. The fact that natural gas is used in conjunction with the compressed air to regenerate the stored power confuses the issue, which leads to much higher efficiencies sometimes being claimed.
Here they are proposing to capture the compression heat and use it (with an "adiabatic generator"), which should help the efficiency. I'm a bit surprised the energy savings are worth enough to cover the capital costs of tapping such a low grade heat source, especially since this is also excess energy that will also need to be stored for later.
...but I heard one report that ice levels right now are higher than at the same time last year.
According to http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png that is true, but not by a significant amount. Last year was an unusual anomaly, but the question is whether the feedbacks from that will be enough to tip us into a new regime where that level of ice loss is normal. I think it's too early to know, but so far this year isn't a strong argument against that happening.
What surprises me is that there has not been any significant change in sea level...
Depends on what you mean by significant. In your link the rate of sea level rise was estimated as 1.5 mm/y, over the last few years it's averaged about twice that. By the end of the century the rate of rise should be quite impressive, if you're still around to see it.
Unfortunately, that article is quite misleading in claiming 80% efficiency for compressed air storage. What they can actually do is burn natural gas with 80% efficiency if they use compressed air as an oxidizer. In the online comments on the article they eventually responded to someone called "DaveMart" that the energy-out/energy-in for compressed air is about 50%. That may still be good enough to be practical, but personally I think CSP with heat storage is currently more promising.
Re:Stupid terraforming..
on
Water Ice On Mars
·
· Score: 2, Informative
There is less water in the Martian atmosphere oxygen while the water is more massive... Really? I see the atomic mass of an oxygen molecule as 16 + 16 = 32, while water is 16 + 1 + 1 = 18.
But you're right, either way the dissociated hydrogen is way lighter.
Would something have to shed mass or slam into an orbiting body or something similar, in order to be bound? That could work, but a more reasonable process is that a binary (or multiple) star system interacted with the pulsar system, then the excess energy could be carried away by the stars not captured. Or a single star could displace another star (or perhaps even a large planet) that was already there. In most of the galaxy it is very rare for star systems to come close enough to interact like that though. It is much more likely that the pulsar was part of a multiple star system when it formed, and the system held together through the supernova that created it.
***
It should be easy to tell from doppler shift that a pulsar is in a tight binary with another star, unless the axis of the orbit points almost right at us. What's missing from the article is how closely constrained that alignment is, and therefore what the odds against it are. If the odds against that are many times the number of millisecond pulsars we've see it would make people suspect some other mechanism to create millisecond pulsars might exist.
Thats a four fold increase in something you have to store within the aircraft. But it does weigh less, which is very useful in airplanes. Liquid hydrogen might not be the best alternative to oil based fuels for airlines, but I think it is a workable one. Current jet fuel is almost ideal for its purpose, so I think this is the last place we should be looking to change to alternatives. But, eventually, liquid hydrogen could be a replacement.
-cooling/insulation could not be perfect so 1.7% per day of the hydrogen would leak! Which wouldn't much matter to an airline, but that's one reason that liquid hydrogen looks terrible for cars.
Hydrogen might eventually work out fine for airline fuel (where liquid seems a feasible option), but so far I haven't seen any storage scheme that looks good for automobiles. Hydrogen barely gets you better range than a modern battery would, and yet it may require a whole new infrastructure to distribute it.
We have martian rocks on Earth, and so there surely are a lot of earth rocks on Mars. That doesn't really follow. It is much harder to blast debris out of Earth's gravity well than the smaller one of Mars, and the greater atmospheric pressured here adds another serious difficulty. Perhaps some material from the larger impacts on Earth made it to Mars, but I'd expect the quantity to be minuscule compared to the amount going the other way.
I agreed that the aluminum engines would be larger, but they would also be lighter. Both issues are important, and I'm not sure if the two issues combined make would make aluminum perform better or worse than copper.
Aluminum is less forgiving than copper, and when it was being used in houses not all the issues were understood (and some may not be today, but we can learn). When you combine that with do-it-yourselfers it is somewhat unsafe. Still, it's not like all those houses have had there wiring replaced - with an informed owner they are safe enough to be lived in. An engine is much less likely to have someone poking around inside them, and I would be very surprised if a safe aluminum motor is impossible.
Not that know that copper will be too expensive for a large fleet of electric cars. But if it does cost too much, I am confident aluminum can be a satisfactory replacement.
Aluminum has the best conductivity per unit weight of all the metals, so the amount of aluminum needed for a motor weighs less than the equivalent copper would. This might make aluminum the better choice overall. The volume of the motors would have to be larger because of larger wire needed, but they would still be much smaller than gasoline motors.
Al is 63% the conductivity of Cu, but only 30% of the density. It is at least good enough.
Start construction on a 500 sq mile solar farm in a sunny, remote location.... This is enough power for the entire world during the day. One square mile in a sunny location will get you about 500 megawatts peak output at 20% efficiency. Scaling to 500 sq miles gets you 250 gigawatts, while in 2000 the USA alone had a total electrical generating capacity of 819 gigawatts.
Perhaps you meant 500 miles square, or 250,000 square miles, which would be more that enough energy for all the world's needs, not just electrical.
Slashdot Mirror
Well, yes, but I chose to paraphrase a different part of the article, since it emphasized the surprising impermeability to helium. Either way the conclusion is the same, and that information was not mentioned in the link in the /. summary.
Perhaps "standard" was included to exclude gases that would react with graphene, as I suspect fluorine would.
The linked article claims the graphene is impermeable to gases, but didn't say exactly which gases. This article says that even the smallest gases can't get through, not even helium: http://www.photonics.com/content/news/2008/August/8/92805.aspx
You need salt in the mix to get electrolysis to occur with any efficiency at all. It won't work with distilled water.
You need something to make the water conductive, but NaCl isn't a good choice. Usually, at least for demonstrations, sulfuric acid is used.
My experience is that when you try to use electrolysis on salt water you get NaOH and chlorine.
The article is unreachable, so I can't see what it says.
Should we be boycotting niobium products now (niobium == columbium, which got its name from being the key element in columbite)? I see it's used in prosthetics, jet engines and superconducting wires [so it's probably used in MRI imaging]). Expecting people to avoid all these products looks impossible.
And our reason for going to Venus is...?
Well, it sounds like a nice place to visit, but I wouldn't want to live there.
Are you claiming my comment is wrong? If so, why?
My comment and the only other comment to it both claim the mirrors are true parabolas, and I have a link to a physics proof that this is so rather than to a side comment in a Wikipedia article.
That question immediately came to mind, since as wild guess I would expect something more like a catenary. At http://www.math.iupui.edu/m261vis/LMirror/mirrorproof.html they show that it really is a parabola.
Arlen Specter ... Chris Dodd or Joe Biden
Excellent choices. I thought Dodd was the pick of the litter among the Democratic presidential candidates, and I only now support Barak as the lesser evil.
How Efficient is It?
If you just throw away the heat generated during the compression, which I think is what is done in current large installations, I have read that you can get about 50% efficiency. The fact that natural gas is used in conjunction with the compressed air to regenerate the stored power confuses the issue, which leads to much higher efficiencies sometimes being claimed.
Here they are proposing to capture the compression heat and use it (with an "adiabatic generator"), which should help the efficiency. I'm a bit surprised the energy savings are worth enough to cover the capital costs of tapping such a low grade heat source, especially since this is also excess energy that will also need to be stored for later.
...but I heard one report that ice levels right now are higher than at the same time last year.
According to http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png that is true, but not by a significant amount. Last year was an unusual anomaly, but the question is whether the feedbacks from that will be enough to tip us into a new regime where that level of ice loss is normal. I think it's too early to know, but so far this year isn't a strong argument against that happening.
What surprises me is that there has not been any significant change in sea level...
Depends on what you mean by significant. In your link the rate of sea level rise was estimated as 1.5 mm/y, over the last few years it's averaged about twice that. By the end of the century the rate of rise should be quite impressive, if you're still around to see it.
Unfortunately, that article is quite misleading in claiming 80% efficiency for compressed air storage. What they can actually do is burn natural gas with 80% efficiency if they use compressed air as an oxidizer. In the online comments on the article they eventually responded to someone called "DaveMart" that the energy-out/energy-in for compressed air is about 50%. That may still be good enough to be practical, but personally I think CSP with heat storage is currently more promising.
But you're right, either way the dissociated hydrogen is way lighter.
***
It should be easy to tell from doppler shift that a pulsar is in a tight binary with another star, unless the axis of the orbit points almost right at us. What's missing from the article is how closely constrained that alignment is, and therefore what the odds against it are. If the odds against that are many times the number of millisecond pulsars we've see it would make people suspect some other mechanism to create millisecond pulsars might exist.
Hydrogen might eventually work out fine for airline fuel (where liquid seems a feasible option), but so far I haven't seen any storage scheme that looks good for automobiles. Hydrogen barely gets you better range than a modern battery would, and yet it may require a whole new infrastructure to distribute it.
Unpossible!
Geothermal and hydroelectric.
I agreed that the aluminum engines would be larger, but they would also be lighter. Both issues are important, and I'm not sure if the two issues combined make would make aluminum perform better or worse than copper.
Aluminum is less forgiving than copper, and when it was being used in houses not all the issues were understood (and some may not be today, but we can learn). When you combine that with do-it-yourselfers it is somewhat unsafe. Still, it's not like all those houses have had there wiring replaced - with an informed owner they are safe enough to be lived in. An engine is much less likely to have someone poking around inside them, and I would be very surprised if a safe aluminum motor is impossible.
Not that know that copper will be too expensive for a large fleet of electric cars. But if it does cost too much, I am confident aluminum can be a satisfactory replacement.
Aluminum has the best conductivity per unit weight of all the metals, so the amount of aluminum needed for a motor weighs less than the equivalent copper would. This might make aluminum the better choice overall. The volume of the motors would have to be larger because of larger wire needed, but they would still be much smaller than gasoline motors.
Al is 63% the conductivity of Cu, but only 30% of the density. It is at least good enough.
Aluminum wiring could certainly replace copper in electric cars. I don't think we'll run out since the Earth's crust is about 8% Al.
Perhaps you meant 500 miles square, or 250,000 square miles, which would be more that enough energy for all the world's needs, not just electrical.