Yup, you're right. Sorry about that. I'll now revise it to 4 times the original. Now it's 2.5% efficient ((1 KW/sq.mt flux) / (200 MW/ 8M sq. mt.)
You're still fighting against 12-13.5%, from solar panels that are available *now*. That's five to six times the power at the same area. Yes, the cost is higher. I'm not arguing that at all. I'm just arguing efficiency, and that's all.
Now you're assuming that the words "2 mile wide" is a circle, and that it's the radius and not the diameter of the circle (though that doesn't tie up with your 25km^2 either).
It said radius in the document. Did you read it? And a 2 mile radius is 12.56 square miles, which is 32,530,250 square meters (I said square meters, not square kilometers) - Google is your friend. 200 MW means 200,000,000/32,530,250 = 6 watts per square meter, or 0.6% efficiency.
And making assumptions about the generation time.
Yah. Generous assumptions. Considering the method of power generation, power is generated for more than the sun is up, which means it's *worse* than 4%. I'm assuming that the 200 MW number is average power generation, not peak. If it's peak, it's far worse. If it's average, then the solar efficiency goes up by the fraction of the generated power time. You mean to tell me that it's only generating power from solar flux for less than 5 hours?!?! Solar cells generate peak power without tracking for more time than that!
Yeah, that's solar flux to DC. Which is damned near useless on a large scale. Invert it and lose 10-20%.
10-20% of 15% is 12-13.5%. Still much higher than 4%. And there are inverters out there that are 95% efficient, not 80-90%. I can give you more quotes if you want.
You're making assumptions about the heat being lost as waste heat after it's used, the very fact you mention the Carnot efficiency assumes this (hint: it isn't lost)
What are you talking about? Carnot efficiency is conversion of heat to mechanical (and mechanical to electrical, which is near perfect). If you use a heat engine, this is the best you will ever get. If the heat isn't lost, then the conversion efficiency is lower, because it's the heat transfer to the baths that matter. The "hot bath" in this case is the hot water (not the sodium, as the sodium doesn't run through the engine to do work - it's simply heated and cooled) and the "cold bath" is the cooling of the steam to recondense to water. If the cold bath isn't cold, then the maximum conversion efficiency gets worse.
These aren't assumptions. It's thermodynamics, that's all. You're using a heat engine. You're going to be bound by thermodynamics.
Photoelectic cells which are 30%, 40%, 50% efficient are fairy stories, they don't exist.
Labs are fairy stories? Neat. They do exist, and they will make it to market. It will take time, but it will happen.
So call me a crank, but notice that Lovelock has been opposed to wind energy because it just ain't pretty, and is a notorious flake that posits the Earth as a self-aware and self-healing organism (getting rid of us pests). Occam's razor, anyone?
I won't address point A (that opposing wind energy is crazy) because I believe that you're probably right, but of course you have to be very careful before massively deploying wind turbines to make sure it won't adversely affect the area's climate. Of course, you have to do the same thing for nuclear plants, but nuclear plants are a known, and the impact studies are done things.
But I really can't stand people misusing Occam's Razor, and unfortunately, you are. Positing that the Earth is a self-aware organism can't be disproved with Occam's Razor, because stating that anything is self-aware is axiomatic - you can't prove it - it must just simply be an axiom of the framework. Outside of the being in question, "will" is unprovable. I can't prove that anyone besides me has will - I just simply have to accept it as an axiom of my existence. (Otherwise Occam's Razor would suggest that every other person on the planet is not self-aware, because it requires 6 billion "wills" on the planet, where only 1 - my own - would suffice to satisfy my own experiences, so clearly only "myself" being self-aware is simpler)
Occam's Razor helps in disproving hypotheses or theories based on their complexity. It does not do anything with regards to axioms, because it can't. They're unprovable assertions.
The self-healing thing is clearly correct, though. Otherwise the biosphere of the Earth wouldn't be masking solar flux variations so well.
I'm guessing that was meant to be to me, as the parent didn't mention a temperature.
Anyway, the thermodynamic "temperature" is the only thing that really matters - that is, what's the hot bath, and what's the cold bath? If you're using steam to generate the electricity, and you're cooling the steam to room temperature and pressure (via a standard cooling tower), then the temperature of the sodium really doesn't matter - it's the temperature of the steam that matters. I can't find out what temperature they ran the water at. It looked like 550 F on a diagram I saw, which would give a Carnot efficiency of like 48%, and probably a real efficiency of like 35-40%, which is consistent with what they were claiming for "efficiency", so maybe that's right. But that's *definitely* not the solar flux->electricity efficiency, which is what solar panels are talking about when they talk about efficiency. My extremely poor, massively optimistic "flux to electricity" efficiency, only considering the mirror area, seemed to say ~10-15%, which is consistent with solar panels. Which is not bad, but it's definitely not "much better than solar panels."
Mirrors (lots of small mirrors, not one large one) are cheap - for a given area, mirrors will be orders of magnitude cheaper than solar cells, and can be made a good deal more robust
Yah, but you can use mirrors for solar cells as well to increase their effective collection area. Plenty of people do that already.
I would need to do lots of plumbing to get my superheated steam from the obelisk to the turbine
Plus you need the cooling tower as well, and you know how large those are. Plus you need the water in the first place (which, in any place with high solar flux is actually moderately hard to come by!). I really wish I could find what the cost of Solar II was.
you would need to do lots of wiring to get lots of small direct currents to your converter and into something that could be used by a consumer device
Absolutely, but you'd need to do the same thing as well - turbines don't exactly produce ultra-high voltage power. It's the exact same cost as a power plant, so you've got the advantages of economies of scale. But I've been ignoring the incidentals because incidentals are probably roughly equivalent in both cases, cost wise.
Plus, you've got to think about future potential - even if the panels are expensive now, all of the incidentals will last you through successive panel generations, each of which will have improved conversion efficiency, which means your power generation can go up easily over time. With a solar power tower, that's not possible - thermodynamics is your main bottleneck, and you basically have to design your system for a specific efficiency - the temperature of the hot bath compared to the temperature of the cold bath.
Like I said, power towers can make sense as a low-cost solution for *right now*, but I don't see how any intelligent long-term analysis would favor them. Yes, the initial cost is higher, but the long term cost is lower. (This is actually true for home panel usage as well in high-sunlight areas, but most people still don't use them, because the initial cost is just too high.)
Basically, Power Towers are cheaper, more efficient, scale better and are environmentally more friendly than photovoltaics. The only advantage I can see for photovoltaics is that they work on a small scale.
The only question I addressed here was the "more efficient". The rest - cost, environmental friendliness - I never argued with (though the 'scale better' I would argue with as well, as photovoltaics scale with no effort, as they're fundamentally a small technology, scaled huge).
So I found the total mirror area of Solar II finally, and it's ~85,000 square meters. That means that if you *only* take into account the area of the mirrors, it'd be 114 watts/meter^2, which is less than available solar panels (150 watts/m^2). Even if you assume that that 10 MW was generated for slightly more than the time that the sun was up (I saw numbers of 3 hours or so?) that's not going to be much better than already available solar panels, and panels available in the lab are 2 to 3 times better than that.
Solar panels will not generate that power all the time during the day, of course, but the area of Solar II was greater than 85000 m^2 - you have to take into account the area in the middle, for instance. The fiducial area of both is probably equivalent.
The only efficiency number that matters is solar flux to electrical power, and I think in a lot of cases they're misreporting the efficiency. Nothing I've seen convinces me that an equal size array of solar panels wouldn't generate *more* power than a power tower. This does not mean they're better. I'm strictly speaking in terms of conversion efficiency, which was the original argument.
However, I wasn't trying to argue cost effectiveness. The point was made that solar power towers are more efficient than solar panels, and they're simply not. Even in terms of *just* mirror area, Solar II would only be maybe 11%-15% efficient in converting solar flux to energy, which is what commercial solar panels already do.
Efficiency is not helpful for considering cost-effectiveness, but it is helpful for considering scaling effectiveness and future potential. Solar power towers can't operate much more efficiently than they already are - thermodynamics is the bottleneck. Any improvements will be incremental, and very small. So you'd be wasting your time trying to improve the conversion efficiencies - just try to get the cost down, and it'd be fine.
Solar panels are different, because they don't have that bottleneck - theoretically, their efficiencies can go much higher (and have - up to 34% or higher) and so it's a good idea to spend your time trying to improve their conversion efficiencies rather than trying to get the cost down (which is what they're doing).
Ultimately, however, solar panels have a brighter future (if you'll forgive the pun) because they don't have a thermodynamic wall in their path. The only roadblock is the cost to manufacture, which economies of scale can defeat.
Build a solar panel plant of the same area, and .. it will generate significantly more power. It'll cost a lot more, too, of course, but we're talking about efficiency, not cost-effectiveness.
Sigh. Should've looked more carefully before I hit reply.
838K would only be ~65% Carnot efficient against room temperature, and that's *just* the thermodynamic efficiency. I can't imagine you'd beat 50%, just thermodynamically (all of the losses from heating the air, for instance). And those losses would *scale* with area, so making it larger (and hotter) would make it less efficient as well.
From the description on the webpage, it looks like the steam generator runs at 550 F? It's a little tough to tell where the "550" is. If that's true, the thermodynamic efficiency could be, at best, 48%.
Plus you're just supporting my point more when you say they have to defocus the mirrors - that's lost energy right there.
None of the web pages I've seen so far tout the towers as advantageous over solar panels. The main advantage is that you can store energy very efficiently, but there are other methods of doing this which aren't specific to this method and could be used with solar panels (like pumping water uphill, which is also 90+% effective!). Have there been any studies on this?
Remember that solar panels right now are ~15-20% total efficiency - that is, straight from the solar flux to electricity. I don't see any numbers on the total efficiencies of those towers, though here suggests a 2-mile radius (25 km^2 or so) needed for, say, 200 MW. So that's 25 million m^2, per for 200 MW, so that's 8 watts per square meter, or less than 1% efficiency. Even being nice, and assuming that the power generation occurs 5 hours out of a day, so that the actual efficiency is ~5 times higher, it's still only ~4% efficient.
The only advantage I see is that it's probably cheaper than a solar panel plant would be, right now. But it's in a thermodynamic bottleneck. You can't increase the efficiency without increasing the heat, and you can't increase the heat without causing more problems, as you stated (they had to defocus the mirrors). Photovoltaics don't have that bottleneck. Lab solar panels now hit 34% or better efficiency, and as we've seen recently, there's a lot of work being done to improve it. Build a solar panel plant of the same area, and
I fully admit the possibility of being wrong, but thermodynamics doesn't lie. Use a heat engine to generate electricity, and fundamentally, any process which avoids it will probably beat you in efficiency eventually. No one denies that hydroelectric plants are the undisputed kings of energy efficiency, and that's because they aren't heat engines.
Well, no-one's built a full-size one yet, but the Spanish got good results from their little 50KW testbed (don't have a link to it to hand). Note that a coal-fired station is only about 40% efficient now anyway (slightly more with CHP, but you can do that with an obelisk too), and they're considered very viable.
Absolutely, with regards to the coal station's efficiency - but its efficiencies are highly controlled (very litle heat leakage, etc.) to reach that, and you simply can't do the same with the design you're talking about. But I don't see any advantages over photovoltaics, other than the initial deployment costs. When you couple in the solar efficiency - that is, the percentage of the solar flux they're converting, I can't imagine that obelisks would scale as well as photovoltaics would.
I'm just missing the advantages. Put a lot of photovoltaics on a motorized rail and have them track the sun. You also get advantages because mirrors won't do anything if the sun's behind clouds, but the solar panels will still generate *some*.
The only advantage I can see is the initial cost advantage, but considering the durability of the panels (breaking a mirror would destroy the entire mirror - braking a solar panel would reduce the energy output only by the destroyed cells, if they're in parallel), any reasonable long-term cost estimate would have to scream in favor of the panels.
A 50 KW solar panel generator would require about 400 m^2 of panels. This isn't that big (it's only 20x20 meters!). I just *really* would like to see some details.
My preferred technique would be the "black obelisk". It requires a large, open space, which you fill with mirrors on motorized bearings, and in the middle you build a huge black obelisk, filled with pipes. The mirrors rotate througout the day focussing the sun's energy on the obelisk, superheating water that is pumped into it, the steam coming out the other end is used to run the kind of turbine that exists in an ordinary coal or oil fired station. It's very efficient, and reuses existing technology, existing power stations in suitable climates could simply be converted in-place.
This can't fundamentally be more efficient than photovoltaics. First off, it's a heat engine - it's limited in efficiency by thermodynamics. I can't imagine that the heat reservoir would be higher than a nuclear reactor, so you're already limited to efficiencies of 60% by Carnot (this would mean that the obelisk reaches temperatures of order 750K!) There's, of course, no way you're actually reaching Carnot, so thermodynamically you're even less than that.
Second off, you'd be heating both the mirrors and the surrounding area of the obelisk, which is all wasted heat, and wasted energy. Any attempt to seal off the "reactor" area for better efficiency would, of course, prevent solar flux from coming in!
The kicker, in my mind, is that you could've built this in the early 1900s. So why didn't they?
Photovoltaics are semiconductor devices, so they're not limited by the "thermodynamic bottleneck". I'd expect in the next 50 years to see photovoltaics hit 40-50% efficiency, which I doubt a "black obelisk" would *ever* hit. So I'm skeptical. Proof?
No, it doesn't. If it did, then the MPAA couldn't be said to "censor" films, which it, of course, does. The fact that the censoring is backed with the threat of lower sales (with an R or NC-17 rating) rather than criminal prosecution doesn't change the fact that it's censorship.
But just to drill the point beyond all recognition,
The lunch box was tightly sealed, had an overlaping lip for the lid. Unless the hole was microscopically thin but an inch long I don't see how it had any holes. And it would have to do 2 90 degree bends to get in.
Oddly enough, the bends aren't not a problem. The overlapping lip wouldnt' work - there needs to be a conductive path, or else it's not a Faraday cage. The physical structure of it means nothing - it's all about the electrical structure. Are you sure the lunchbox surface was electrically conducting? Was it painted?
So an overlapping lid would act as a slot antenna out of (and into) the Faraday cage. Easily enough for a cellphone to work, but I imagine the signal strength was down several dB.
But if you do have one, see how much work you have to do to make a faraday cage that will prevent the phone from ringing.
Actually, I've already done just that, which is why I said it was easy. Copper tape is your friend.
My point is that the electronics on a plane are no more sensitive then those on devices on the ground.
That's correct. But electronic interference on the ground doesn't kill people, which is why they're a tad paranoid, and I can agree.
They're mainly worried about devices which broadcast with power (like cellphones, walkie talkies, radio controlled stuff, WiFi, and Bluetooth stuff) because those can definitely cause problems. Plus cellphones have other problems, namely jamming the cellphone network. But 300 people all using cellphones on a plane could definitely cause interference.
As a matter of fact, no, I haven't. It strains my eyes.
Good for you. There are many who have - including me. We should all take better care of ourselves. Thankfully there are also ways to play video games without straining your eyes, also. Just because most people don't do them doesn't make the activity bad.
Count the number of people who primarily play such games. Then count the number of people who play things like Doom, Quake, Super Mario, or Tetris. Come back when you've compared the two populations.
That's like saying reading isn't valuable because there are more people who read those crap harlequin novels than who read Hemingway.
Don't blame the medium for the existence of chaff.
but have equal efforts been made to discover planets which could house lower forms of life[?]
Absolutely! In fact, tons more effort has been put into discovering planets which could house lower forms of life.
There's just one problem we can't do it yet. It's *much* harder to do! The only way to do it would be by spectroscopy on light from the planet, and we can't do that yet, but it's being worked on. That's what the Terrestrial Planet Finder is for, and it will cost huge amounts more than SETI@home ever did.
SETI is basically no money for huge gain. That's why it's worth supporting. For everyone who thinks "well, I'm Folding, because I think that's more important" - here's a hint: your CPU cycles won't make or break the project. SETI@home has far, far exceeded the computing power that they wanted, so sure, go ahead, do whatever you feel like doing. I would actually suggest doing some of the DC projects that have less members, simply because SETI@home is doing fine.
The entire universe crammed into a small space would have one hell of a Swartzchild radius, and nothing within this radius could escape unless it were moving faster than the speed of light. Therefore, all Big Bang theories that I am familiar with introduce the notion that space itself was expanding, effectively allowing matter to move (relative to other matter) faster than the speed of light and therefore escape the gravitational pull at the center. Without (effective) faster-than-light travel, how could the universe ever have expanded with that sort of gravity present?
The Schwarzschild metric assumes that the boundary conditions are flat space, at infinity. In the early universe, this is not true.
More importantly, nothing did escape the Schwarzschild radius of the Universe at the time (there was nowhere for it to go, anyway). The space inside it expanded, pushing matter along with it (well, kindof - the space inbetween matter expanded, so it might've 'seemed' like a push).
The Universe didn't have to expand faster than the speed of light. It probably did, but there were theories out there that worked without it.
I admit that I am not a cosmologist, but I certainly thought that this was the reasoning behind the theory of inflation.
Main reasoning nowadays is that it's the only way you can flatten out the Universe. Inflation pushes omega to equal 1, which is what we see.
It was a gps receiver connected to a Palm Pilot. It worked just fine. I think the pilot was just rounding since he only gave 1 significant digit of accuracy. It was just fun to watch.
It's the GPS receiver that won't give out values exceeding 18,000 meters (60K feet) and 515 m/s (1000 knots), not the interface. I thought the altitude restriction was lower, so it doesn't actually matter for plane flight, but whatever.
This could be - but do pilot really give altitude to ground? So if they are flying in an altitude corridor they constantly need to go up and down as the ground does?
Yes. Watch the altitude reported by a plane with an onboard nav system (like United's passenger jets) when you land. It hits zero.
(More importantly, think about it- it's the altitude with respect to ground that actually matters for a plane, now isn't it?)
And besides, making a Faraday cage is harder then it sounds. I once put a cell phone in a metal lunch box - totally sealed everywhere - it still rang. Someone told me it was the tiny seams where the lid met the box that allowed it to leak. (I always thought that if the hole was less then 1/4 of the wavelength it didn't coun't.)
Sigh. Making a faraday cage is simple. A conductive wire mesh is a faraday cage - to wavelengths ~ longer than the spacing between them. Cellphones use frequencies either in the 800 MHz range (foot-ish) or 1500 range (half-foot). The hole would need to be an inch long. It's also important to realize that a hole in a faraday cage acts like an antenna in open space, so those slots were slot antennas.
That doesn't mean it wasn't a faraday cage (it just had slot antennas). Put multiple sources inside the box, and the field strength increases much more than in free space.
Anyway, the only study I know that the FAA did was to see if there had been any documented problems caused by cellphone usage, not if there could be in any situation.
Placing cellphones next to monitors can screw them up, for crying out loud. Yes, it's miniscule, but if everyone ignored them, it could be a problem.
Well, think about the starting condition for the big bang: all of the matter in the universe crammed into a small space. Now, think about how much gravity the ENTIRE UNIVERSE has. Even if every particle in the universe were flying away from the center at 99.9999999% the speed of light, the gravity would be so unbelievably strong that the universe would near-instantaneously re-collapse into the biggest black hole imaginable. Remember, light itself, the fastest thing in the universe, can't escape from a black hole weighing a measly 10 solar masses. Surely a mass of 10 billion trillion solar masses would somewhat more difficult to get away from.
This isn't true. The energy that a particle contains has no upper bound, even if its velocity does. Its velocity is simply asymptotic to c.
Just because there was a particle of matter smaller than an atomic nucleus containing all the matter in the Universe now doesn't mean it would collapse into a black hole - because space itself was only that big. The metric for the Universe was certainly extremely complicated!
There have been theories which did not require inflation, but which allowed for a Big Bang. I think one or two are still around (but I don't pay that much attention to fringe cosmology).
Out of curiosity, how does one measure the motion of space? Or how does one even define that? With respect to what are you going to measure that motion?
With respect to space that's not moving. It's precisely the same as measuring the curvature of space, it's just curvature in time as well.
What will result is two paths that have wildly different proper times to take them, based on the path you take. You can equate this to travelling near a star, rather than traveling just a few parsecs away - travelling near a star will take you longer, because the space there is stretched.
See Alcubierre's first paper for a bit more detail. The metric is actually quite simple - the dynamics (and stress-energy tensor that causes it) are not.
PS. As a side note - have you ever watched your GPS as a plane was taking off? It's really! cool to watch those speed and altitude numbers. I remember one time the pilot announced that we were cruising at a altitude something - I looked at my GPS and he was off!:) By about 20%. But of course he was probably just rounding.
2 answers:
Answer one:
Commercial GPS won't work properly at high altitudes and high velocities - read the spec sheet of the GPS receiver device. This is to prevent cheap GPS-driven missile tech. It's possible the GPS stopped working at that cutoff height, and you were flying about 20% higher.
Answer two:
GPS gives altitude to sea level. The pilot is likely giving altitude to ground.
Final comment:
Stop playing around with electronics onboard planes when they ask you not to. One person doing it is not a problem - they can't prevent everyone, and they know that there are going to be people who do it specifically because they've been told not to. The problem is when everyone does it - then interference can become a real issue. That's why they ask you not to - it can be a real significant concern. Many planes have what, over a hundred people on them, all within a few feet of each other, and all inside a Faraday cage? Not exactly the world's best RF environment.
Did I assume incorrectly? You do seem like a liberal Christian. Get off your "I'm offended!" high horse.
Yes, you did assume incorrectly. What I believe is far, far more complicated than what "liberal Christian" would indicate. And I am offended - and it's not a high horse. You've placed beliefs on me that I don't have, nor did I ever claim to have. That's the worst kind of prejudice.
This whole "interpretation" nonsense is your platform, not mine.
But you're interpreting to present your platform - that's the problem. Jesus didn't state 5 specific things you need to do to get into heaven - not in those extremely specific words that you're quoting. Definitely not, as he didn't speak modern English!
Nor did he never use hyperbole and metaphor, both of which require interpretation. I did note you never responded to the question of whether or not you think that Christ meant you must forgive people 490 times, and then you can give up on them?
Of course you think this is silly: my arguments do not fall underneath your premises
No, I think it's silly because you're saying that I can't interpret an interpretation. You keep quoting scripture (I'm not even sure from which *version*) and asking for specific examples, and then when I give them, saying that's not what was said there. Clearly there's no possible way to have a discussion here - everything I say is tautologically wrong, because it's not the same statements that you read into it, therefore I'm interpreting, and that's not okay.
Notice that I haven't referred to scripture and verse - that's because I mentioned it once, and you claimed that's not what it said. I don't see how this is different than the people who say "that's not what it means" except you used the word "said", even when neither of us are actually using the specific words being referred to, nor are we using them in the original language, nor the original context. That's why it's silly.
Explain: why must I necessarily have the same beliefs as someone who has similiar works?
Because that's what the belief means. Half the problem here is the fact that you're never stating what belief - or better yet, faith - means at all. Nor what "Christ" is. What does "to have faith in a person" mean?
And that's where you and I will probably disagree - because to me, you can have faith in Christ without being a Christian. Just like you can belive in Buddhism without being Buddhist, et cetera.
This is the stupidest thing you've written yet.
Man, your comments are just getting harsher and harsher. Not exactly encouraging a forum for intelligent conversation.
The "divine" exists in the imaginations of humans.
That's your opinion of "divine" - not mine. Divine, to me, would come from the dictionary definition - "having the nature of or being a deity." The question then, becomes "what is a deity?" or "what is God?"
That's again an arguable definition - again, a dictionary definition would be "the perfect, omniscience, omnipotent creator of the Universe". Relax the "creator" portion, and replace it with "an omniscient, omnipotent object", and God must exist by construction - it's the Universe itself, because the Universe, by construction, is omnipotent and omniscient. It's only the replacement of "object" with "being" - that is, the imbuing of will - that's unprovable.
So a "divine truth", then, would be a universal truth. But that's my opinion.
Occam's razor does apply, and that's why my explanation is better.
No, it doesn't - you haven't given any reasons why it does, and I've given reasons why it doesn't - the implied frames of references are different. Placed in equal frames of reference, the "emergent property" argument requires the strong anthropic principle, which requires just as many unprovable assertions as divinity does. There's no reason it had to be an emergent property. We would
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Yup, you're right. Sorry about that. I'll now revise it to 4 times the original. Now it's 2.5% efficient ((1 KW/sq.mt flux) / (200 MW/ 8M sq. mt.)
You're still fighting against 12-13.5%, from solar panels that are available *now*. That's five to six times the power at the same area. Yes, the cost is higher. I'm not arguing that at all. I'm just arguing efficiency, and that's all.
Dangit! I'm a doof. It is 25 km^2, not 25k m^2. It's 25M m^2. Sigh. Square units. (It's actually 32 km^2)
Whoops - that was supposed to be 25k m^2, not 25 km^2. Sorry about that. Anyway, the efficiency number doesn't change.
Now you're assuming that the words "2 mile wide" is a circle, and that it's the radius and not the diameter of the circle (though that doesn't tie up with your 25km^2 either).
It said radius in the document. Did you read it? And a 2 mile radius is 12.56 square miles, which is 32,530,250 square meters (I said square meters, not square kilometers) - Google is your friend. 200 MW means 200,000,000/32,530,250 = 6 watts per square meter, or 0.6% efficiency.
And making assumptions about the generation time.
Yah. Generous assumptions. Considering the method of power generation, power is generated for more than the sun is up, which means it's *worse* than 4%. I'm assuming that the 200 MW number is average power generation, not peak. If it's peak, it's far worse. If it's average, then the solar efficiency goes up by the fraction of the generated power time. You mean to tell me that it's only generating power from solar flux for less than 5 hours?!?! Solar cells generate peak power without tracking for more time than that!
Yeah, that's solar flux to DC. Which is damned near useless on a large scale. Invert it and lose 10-20%.
10-20% of 15% is 12-13.5%. Still much higher than 4%. And there are inverters out there that are 95% efficient, not 80-90%. I can give you more quotes if you want.
You're making assumptions about the heat being lost as waste heat after it's used, the very fact you mention the Carnot efficiency assumes this (hint: it isn't lost)
What are you talking about? Carnot efficiency is conversion of heat to mechanical (and mechanical to electrical, which is near perfect). If you use a heat engine, this is the best you will ever get. If the heat isn't lost, then the conversion efficiency is lower, because it's the heat transfer to the baths that matter. The "hot bath" in this case is the hot water (not the sodium, as the sodium doesn't run through the engine to do work - it's simply heated and cooled) and the "cold bath" is the cooling of the steam to recondense to water. If the cold bath isn't cold, then the maximum conversion efficiency gets worse.
These aren't assumptions. It's thermodynamics, that's all. You're using a heat engine. You're going to be bound by thermodynamics.
Photoelectic cells which are 30%, 40%, 50% efficient are fairy stories, they don't exist.
Labs are fairy stories? Neat. They do exist, and they will make it to market. It will take time, but it will happen.
So call me a crank, but notice that Lovelock has been opposed to wind energy because it just ain't pretty, and is a notorious flake that posits the Earth as a self-aware and self-healing organism (getting rid of us pests). Occam's razor, anyone?
I won't address point A (that opposing wind energy is crazy) because I believe that you're probably right, but of course you have to be very careful before massively deploying wind turbines to make sure it won't adversely affect the area's climate. Of course, you have to do the same thing for nuclear plants, but nuclear plants are a known, and the impact studies are done things.
But I really can't stand people misusing Occam's Razor, and unfortunately, you are. Positing that the Earth is a self-aware organism can't be disproved with Occam's Razor, because stating that anything is self-aware is axiomatic - you can't prove it - it must just simply be an axiom of the framework. Outside of the being in question, "will" is unprovable. I can't prove that anyone besides me has will - I just simply have to accept it as an axiom of my existence. (Otherwise Occam's Razor would suggest that every other person on the planet is not self-aware, because it requires 6 billion "wills" on the planet, where only 1 - my own - would suffice to satisfy my own experiences, so clearly only "myself" being self-aware is simpler)
Occam's Razor helps in disproving hypotheses or theories based on their complexity. It does not do anything with regards to axioms, because it can't. They're unprovable assertions.
The self-healing thing is clearly correct, though. Otherwise the biosphere of the Earth wouldn't be masking solar flux variations so well.
I'm guessing that was meant to be to me, as the parent didn't mention a temperature.
Anyway, the thermodynamic "temperature" is the only thing that really matters - that is, what's the hot bath, and what's the cold bath? If you're using steam to generate the electricity, and you're cooling the steam to room temperature and pressure (via a standard cooling tower), then the temperature of the sodium really doesn't matter - it's the temperature of the steam that matters. I can't find out what temperature they ran the water at. It looked like 550 F on a diagram I saw, which would give a Carnot efficiency of like 48%, and probably a real efficiency of like 35-40%, which is consistent with what they were claiming for "efficiency", so maybe that's right. But that's *definitely* not the solar flux->electricity efficiency, which is what solar panels are talking about when they talk about efficiency. My extremely poor, massively optimistic "flux to electricity" efficiency, only considering the mirror area, seemed to say ~10-15%, which is consistent with solar panels. Which is not bad, but it's definitely not "much better than solar panels."
Mirrors (lots of small mirrors, not one large one) are cheap - for a given area, mirrors will be orders of magnitude cheaper than solar cells, and can be made a good deal more robust
Yah, but you can use mirrors for solar cells as well to increase their effective collection area. Plenty of people do that already.
I would need to do lots of plumbing to get my superheated steam from the obelisk to the turbine
Plus you need the cooling tower as well, and you know how large those are. Plus you need the water in the first place (which, in any place with high solar flux is actually moderately hard to come by!). I really wish I could find what the cost of Solar II was.
you would need to do lots of wiring to get lots of small direct currents to your converter and into something that could be used by a consumer device
Absolutely, but you'd need to do the same thing as well - turbines don't exactly produce ultra-high voltage power. It's the exact same cost as a power plant, so you've got the advantages of economies of scale. But I've been ignoring the incidentals because incidentals are probably roughly equivalent in both cases, cost wise.
Plus, you've got to think about future potential - even if the panels are expensive now, all of the incidentals will last you through successive panel generations, each of which will have improved conversion efficiency, which means your power generation can go up easily over time. With a solar power tower, that's not possible - thermodynamics is your main bottleneck, and you basically have to design your system for a specific efficiency - the temperature of the hot bath compared to the temperature of the cold bath.
Like I said, power towers can make sense as a low-cost solution for *right now*, but I don't see how any intelligent long-term analysis would favor them. Yes, the initial cost is higher, but the long term cost is lower. (This is actually true for home panel usage as well in high-sunlight areas, but most people still don't use them, because the initial cost is just too high.)
Basically, Power Towers are cheaper, more efficient, scale better and are environmentally more friendly than photovoltaics. The only advantage I can see for photovoltaics is that they work on a small scale.
The only question I addressed here was the "more efficient". The rest - cost, environmental friendliness - I never argued with (though the 'scale better' I would argue with as well, as photovoltaics scale with no effort, as they're fundamentally a small technology, scaled huge).
So I found the total mirror area of Solar II finally, and it's ~85,000 square meters. That means that if you *only* take into account the area of the mirrors, it'd be 114 watts/meter^2, which is less than available solar panels (150 watts/m^2). Even if you assume that that 10 MW was generated for slightly more than the time that the sun was up (I saw numbers of 3 hours or so?) that's not going to be much better than already available solar panels, and panels available in the lab are 2 to 3 times better than that.
Solar panels will not generate that power all the time during the day, of course, but the area of Solar II was greater than 85000 m^2 - you have to take into account the area in the middle, for instance. The fiducial area of both is probably equivalent.
The only efficiency number that matters is solar flux to electrical power, and I think in a lot of cases they're misreporting the efficiency. Nothing I've seen convinces me that an equal size array of solar panels wouldn't generate *more* power than a power tower. This does not mean they're better. I'm strictly speaking in terms of conversion efficiency, which was the original argument.
You're absolutely correct.
However, I wasn't trying to argue cost effectiveness. The point was made that solar power towers are more efficient than solar panels, and they're simply not. Even in terms of *just* mirror area, Solar II would only be maybe 11%-15% efficient in converting solar flux to energy, which is what commercial solar panels already do.
Efficiency is not helpful for considering cost-effectiveness, but it is helpful for considering scaling effectiveness and future potential. Solar power towers can't operate much more efficiently than they already are - thermodynamics is the bottleneck. Any improvements will be incremental, and very small. So you'd be wasting your time trying to improve the conversion efficiencies - just try to get the cost down, and it'd be fine.
Solar panels are different, because they don't have that bottleneck - theoretically, their efficiencies can go much higher (and have - up to 34% or higher) and so it's a good idea to spend your time trying to improve their conversion efficiencies rather than trying to get the cost down (which is what they're doing).
Ultimately, however, solar panels have a brighter future (if you'll forgive the pun) because they don't have a thermodynamic wall in their path. The only roadblock is the cost to manufacture, which economies of scale can defeat.
Build a solar panel plant of the same area, and
.. it will generate significantly more power. It'll cost a lot more, too, of course, but we're talking about efficiency, not cost-effectiveness.
Sigh. Should've looked more carefully before I hit reply.
838K would only be ~65% Carnot efficient against room temperature, and that's *just* the thermodynamic efficiency. I can't imagine you'd beat 50%, just thermodynamically (all of the losses from heating the air, for instance). And those losses would *scale* with area, so making it larger (and hotter) would make it less efficient as well.
From the description on the webpage, it looks like the steam generator runs at 550 F? It's a little tough to tell where the "550" is. If that's true, the thermodynamic efficiency could be, at best, 48%.
Plus you're just supporting my point more when you say they have to defocus the mirrors - that's lost energy right there.
None of the web pages I've seen so far tout the towers as advantageous over solar panels. The main advantage is that you can store energy very efficiently, but there are other methods of doing this which aren't specific to this method and could be used with solar panels (like pumping water uphill, which is also 90+% effective!). Have there been any studies on this?
Remember that solar panels right now are ~15-20% total efficiency - that is, straight from the solar flux to electricity. I don't see any numbers on the total efficiencies of those towers, though here suggests a 2-mile radius (25 km^2 or so) needed for, say, 200 MW. So that's 25 million m^2, per for 200 MW, so that's 8 watts per square meter, or less than 1% efficiency. Even being nice, and assuming that the power generation occurs 5 hours out of a day, so that the actual efficiency is ~5 times higher, it's still only ~4% efficient.
The only advantage I see is that it's probably cheaper than a solar panel plant would be, right now. But it's in a thermodynamic bottleneck. You can't increase the efficiency without increasing the heat, and you can't increase the heat without causing more problems, as you stated (they had to defocus the mirrors). Photovoltaics don't have that bottleneck. Lab solar panels now hit 34% or better efficiency, and as we've seen recently, there's a lot of work being done to improve it. Build a solar panel plant of the same area, and
I fully admit the possibility of being wrong, but thermodynamics doesn't lie. Use a heat engine to generate electricity, and fundamentally, any process which avoids it will probably beat you in efficiency eventually. No one denies that hydroelectric plants are the undisputed kings of energy efficiency, and that's because they aren't heat engines.
Well, no-one's built a full-size one yet, but the Spanish got good results from their little 50KW testbed (don't have a link to it to hand). Note that a coal-fired station is only about 40% efficient now anyway (slightly more with CHP, but you can do that with an obelisk too), and they're considered very viable.
Absolutely, with regards to the coal station's efficiency - but its efficiencies are highly controlled (very litle heat leakage, etc.) to reach that, and you simply can't do the same with the design you're talking about. But I don't see any advantages over photovoltaics, other than the initial deployment costs. When you couple in the solar efficiency - that is, the percentage of the solar flux they're converting, I can't imagine that obelisks would scale as well as photovoltaics would.
I'm just missing the advantages. Put a lot of photovoltaics on a motorized rail and have them track the sun. You also get advantages because mirrors won't do anything if the sun's behind clouds, but the solar panels will still generate *some*.
The only advantage I can see is the initial cost advantage, but considering the durability of the panels (breaking a mirror would destroy the entire mirror - braking a solar panel would reduce the energy output only by the destroyed cells, if they're in parallel), any reasonable long-term cost estimate would have to scream in favor of the panels.
A 50 KW solar panel generator would require about 400 m^2 of panels. This isn't that big (it's only 20x20 meters!). I just *really* would like to see some details.
My preferred technique would be the "black obelisk". It requires a large, open space, which you fill with mirrors on motorized bearings, and in the middle you build a huge black obelisk, filled with pipes. The mirrors rotate througout the day focussing the sun's energy on the obelisk, superheating water that is pumped into it, the steam coming out the other end is used to run the kind of turbine that exists in an ordinary coal or oil fired station. It's very efficient, and reuses existing technology, existing power stations in suitable climates could simply be converted in-place.
This can't fundamentally be more efficient than photovoltaics. First off, it's a heat engine - it's limited in efficiency by thermodynamics. I can't imagine that the heat reservoir would be higher than a nuclear reactor, so you're already limited to efficiencies of 60% by Carnot (this would mean that the obelisk reaches temperatures of order 750K!) There's, of course, no way you're actually reaching Carnot, so thermodynamically you're even less than that.
Second off, you'd be heating both the mirrors and the surrounding area of the obelisk, which is all wasted heat, and wasted energy. Any attempt to seal off the "reactor" area for better efficiency would, of course, prevent solar flux from coming in!
The kicker, in my mind, is that you could've built this in the early 1900s. So why didn't they?
Photovoltaics are semiconductor devices, so they're not limited by the "thermodynamic bottleneck". I'd expect in the next 50 years to see photovoltaics hit 40-50% efficiency, which I doubt a "black obelisk" would *ever* hit. So I'm skeptical. Proof?
Actually, it does.
No, it doesn't. If it did, then the MPAA couldn't be said to "censor" films, which it, of course, does. The fact that the censoring is backed with the threat of lower sales (with an R or NC-17 rating) rather than criminal prosecution doesn't change the fact that it's censorship.
But just to drill the point beyond all recognition,
censorship n.
1. The act, process, or practice of censoring.
And, censoring...
tr.v. censored, censoring, censors
To examine and expurgate.
and, expurgate,
expurgate
tr.v. expurgated, expurgating, expurgates
To remove erroneous, vulgar, obscene, or otherwise objectionable material from (a book, for example) before publication.
Certainly removing all of the material (by preventing its publication) is censorship. Anyway, where was the government listed here?
The lunch box was tightly sealed, had an overlaping lip for the lid. Unless the hole was microscopically thin but an inch long I don't see how it had any holes. And it would have to do 2 90 degree bends to get in.
Oddly enough, the bends aren't not a problem. The overlapping lip wouldnt' work - there needs to be a conductive path, or else it's not a Faraday cage. The physical structure of it means nothing - it's all about the electrical structure. Are you sure the lunchbox surface was electrically conducting? Was it painted?
So an overlapping lid would act as a slot antenna out of (and into) the Faraday cage. Easily enough for a cellphone to work, but I imagine the signal strength was down several dB.
But if you do have one, see how much work you have to do to make a faraday cage that will prevent the phone from ringing.
Actually, I've already done just that, which is why I said it was easy. Copper tape is your friend.
My point is that the electronics on a plane are no more sensitive then those on devices on the ground.
That's correct. But electronic interference on the ground doesn't kill people, which is why they're a tad paranoid, and I can agree.
They're mainly worried about devices which broadcast with power (like cellphones, walkie talkies, radio controlled stuff, WiFi, and Bluetooth stuff) because those can definitely cause problems. Plus cellphones have other problems, namely jamming the cellphone network. But 300 people all using cellphones on a plane could definitely cause interference.
As a matter of fact, no, I haven't. It strains my eyes.
Good for you. There are many who have - including me. We should all take better care of ourselves. Thankfully there are also ways to play video games without straining your eyes, also. Just because most people don't do them doesn't make the activity bad.
Count the number of people who primarily play such games. Then count the number of people who play things like Doom, Quake, Super Mario, or Tetris. Come back when you've compared the two populations.
That's like saying reading isn't valuable because there are more people who read those crap harlequin novels than who read Hemingway.
Don't blame the medium for the existence of chaff.
but have equal efforts been made to discover planets which could house lower forms of life[?]
Absolutely! In fact, tons more effort has been put into discovering planets which could house lower forms of life.
There's just one problem we can't do it yet. It's *much* harder to do! The only way to do it would be by spectroscopy on light from the planet, and we can't do that yet, but it's being worked on. That's what the Terrestrial Planet Finder is for, and it will cost huge amounts more than SETI@home ever did.
SETI is basically no money for huge gain. That's why it's worth supporting. For everyone who thinks "well, I'm Folding, because I think that's more important" - here's a hint: your CPU cycles won't make or break the project. SETI@home has far, far exceeded the computing power that they wanted, so sure, go ahead, do whatever you feel like doing. I would actually suggest doing some of the DC projects that have less members, simply because SETI@home is doing fine.
The entire universe crammed into a small space would have one hell of a Swartzchild radius, and nothing within this radius could escape unless it were moving faster than the speed of light. Therefore, all Big Bang theories that I am familiar with introduce the notion that space itself was expanding, effectively allowing matter to move (relative to other matter) faster than the speed of light and therefore escape the gravitational pull at the center. Without (effective) faster-than-light travel, how could the universe ever have expanded with that sort of gravity present?
The Schwarzschild metric assumes that the boundary conditions are flat space, at infinity. In the early universe, this is not true.
More importantly, nothing did escape the Schwarzschild radius of the Universe at the time (there was nowhere for it to go, anyway). The space inside it expanded, pushing matter along with it (well, kindof - the space inbetween matter expanded, so it might've 'seemed' like a push).
The Universe didn't have to expand faster than the speed of light. It probably did, but there were theories out there that worked without it.
I admit that I am not a cosmologist, but I certainly thought that this was the reasoning behind the theory of inflation.
Main reasoning nowadays is that it's the only way you can flatten out the Universe. Inflation pushes omega to equal 1, which is what we see.
Except that reading isn't (as) bad for your eyes
.
You've never read in low light conditions? How is that worse?
reading encourages thinking and imagination
reading expands knowledge, reading . .
This is different from any videogame with a decent plot... how?
though I have to admit getting kids to interact with other people through online games is probably better than having them playing alone . . .
... reading.
Yah, playing alone. It's dangerously close to that silly activity
It was a gps receiver connected to a Palm Pilot. It worked just fine. I think the pilot was just rounding since he only gave 1 significant digit of accuracy. It was just fun to watch.
It's the GPS receiver that won't give out values exceeding 18,000 meters (60K feet) and 515 m/s (1000 knots), not the interface. I thought the altitude restriction was lower, so it doesn't actually matter for plane flight, but whatever.
This could be - but do pilot really give altitude to ground? So if they are flying in an altitude corridor they constantly need to go up and down as the ground does?
Yes. Watch the altitude reported by a plane with an onboard nav system (like United's passenger jets) when you land. It hits zero.
(More importantly, think about it- it's the altitude with respect to ground that actually matters for a plane, now isn't it?)
And besides, making a Faraday cage is harder then it sounds. I once put a cell phone in a metal lunch box - totally sealed everywhere - it still rang. Someone told me it was the tiny seams where the lid met the box that allowed it to leak. (I always thought that if the hole was less then 1/4 of the wavelength it didn't coun't.)
Sigh. Making a faraday cage is simple. A conductive wire mesh is a faraday cage - to wavelengths ~ longer than the spacing between them. Cellphones use frequencies either in the 800 MHz range (foot-ish) or 1500 range (half-foot). The hole would need to be an inch long. It's also important to realize that a hole in a faraday cage acts like an antenna in open space, so those slots were slot antennas.
That doesn't mean it wasn't a faraday cage (it just had slot antennas). Put multiple sources inside the box, and the field strength increases much more than in free space.
Anyway, the only study I know that the FAA did was to see if there had been any documented problems caused by cellphone usage, not if there could be in any situation.
Placing cellphones next to monitors can screw them up, for crying out loud. Yes, it's miniscule, but if everyone ignored them, it could be a problem.
Well, think about the starting condition for the big bang: all of the matter in the universe crammed into a small space. Now, think about how much gravity the ENTIRE UNIVERSE has. Even if every particle in the universe were flying away from the center at 99.9999999% the speed of light, the gravity would be so unbelievably strong that the universe would near-instantaneously re-collapse into the biggest black hole imaginable. Remember, light itself, the fastest thing in the universe, can't escape from a black hole weighing a measly 10 solar masses. Surely a mass of 10 billion trillion solar masses would somewhat more difficult to get away from.
This isn't true. The energy that a particle contains has no upper bound, even if its velocity does. Its velocity is simply asymptotic to c.
Just because there was a particle of matter smaller than an atomic nucleus containing all the matter in the Universe now doesn't mean it would collapse into a black hole - because space itself was only that big. The metric for the Universe was certainly extremely complicated!
There have been theories which did not require inflation, but which allowed for a Big Bang. I think one or two are still around (but I don't pay that much attention to fringe cosmology).
Out of curiosity, how does one measure the motion of space? Or how does one even define that? With respect to what are you going to measure that motion?
With respect to space that's not moving. It's precisely the same as measuring the curvature of space, it's just curvature in time as well.
What will result is two paths that have wildly different proper times to take them, based on the path you take. You can equate this to travelling near a star, rather than traveling just a few parsecs away - travelling near a star will take you longer, because the space there is stretched.
See Alcubierre's first paper for a bit more detail. The metric is actually quite simple - the dynamics (and stress-energy tensor that causes it) are not.
PS. As a side note - have you ever watched your GPS as a plane was taking off? It's really! cool to watch those speed and altitude numbers. I remember one time the pilot announced that we were cruising at a altitude something - I looked at my GPS and he was off! :) By about 20%. But of course he was probably just rounding.
2 answers:
Answer one:
Commercial GPS won't work properly at high altitudes and high velocities - read the spec sheet of the GPS receiver device. This is to prevent cheap GPS-driven missile tech. It's possible the GPS stopped working at that cutoff height, and you were flying about 20% higher.
Answer two:
GPS gives altitude to sea level. The pilot is likely giving altitude to ground.
Final comment:
Stop playing around with electronics onboard planes when they ask you not to. One person doing it is not a problem - they can't prevent everyone, and they know that there are going to be people who do it specifically because they've been told not to. The problem is when everyone does it - then interference can become a real issue. That's why they ask you not to - it can be a real significant concern. Many planes have what, over a hundred people on them, all within a few feet of each other, and all inside a Faraday cage? Not exactly the world's best RF environment.
Did I assume incorrectly? You do seem like a liberal Christian. Get off your "I'm offended!" high horse.
Yes, you did assume incorrectly. What I believe is far, far more complicated than what "liberal Christian" would indicate. And I am offended - and it's not a high horse. You've placed beliefs on me that I don't have, nor did I ever claim to have. That's the worst kind of prejudice.
This whole "interpretation" nonsense is your platform, not mine.
But you're interpreting to present your platform - that's the problem. Jesus didn't state 5 specific things you need to do to get into heaven - not in those extremely specific words that you're quoting. Definitely not, as he didn't speak modern English!
Nor did he never use hyperbole and metaphor, both of which require interpretation. I did note you never responded to the question of whether or not you think that Christ meant you must forgive people 490 times, and then you can give up on them?
Of course you think this is silly: my arguments do not fall underneath your premises
No, I think it's silly because you're saying that I can't interpret an interpretation. You keep quoting scripture (I'm not even sure from which *version*) and asking for specific examples, and then when I give them, saying that's not what was said there. Clearly there's no possible way to have a discussion here - everything I say is tautologically wrong, because it's not the same statements that you read into it, therefore I'm interpreting, and that's not okay.
Notice that I haven't referred to scripture and verse - that's because I mentioned it once, and you claimed that's not what it said. I don't see how this is different than the people who say "that's not what it means" except you used the word "said", even when neither of us are actually using the specific words being referred to, nor are we using them in the original language, nor the original context. That's why it's silly.
Explain: why must I necessarily have the same beliefs as someone who has similiar works?
Because that's what the belief means. Half the problem here is the fact that you're never stating what belief - or better yet, faith - means at all. Nor what "Christ" is. What does "to have faith in a person" mean?
And that's where you and I will probably disagree - because to me, you can have faith in Christ without being a Christian. Just like you can belive in Buddhism without being Buddhist, et cetera.
This is the stupidest thing you've written yet.
Man, your comments are just getting harsher and harsher. Not exactly encouraging a forum for intelligent conversation.
The "divine" exists in the imaginations of humans.
That's your opinion of "divine" - not mine. Divine, to me, would come from the dictionary definition - "having the nature of or being a deity." The question then, becomes "what is a deity?" or "what is God?"
That's again an arguable definition - again, a dictionary definition would be "the perfect, omniscience, omnipotent creator of the Universe".
Relax the "creator" portion, and replace it with "an omniscient, omnipotent object", and God must exist by construction - it's the Universe itself, because the Universe, by construction, is omnipotent and omniscient. It's only the replacement of "object" with "being" - that is, the imbuing of will - that's unprovable.
So a "divine truth", then, would be a universal truth. But that's my opinion.
Occam's razor does apply, and that's why my explanation is better.
No, it doesn't - you haven't given any reasons why it does, and I've given reasons why it doesn't - the implied frames of references are different. Placed in equal frames of reference, the "emergent property" argument requires the strong anthropic principle, which requires just as many unprovable assertions as divinity does. There's no reason it had to be an emergent property. We would