Why do so many people suggest LED lighting for solar instillations or other high efficiency applications?
CFLs have similar efficiency ratings to LEDs, and a significantly cheaper. The Philips Tornado CFL above me has 75lm/W stamped on it, only the best Cree LEDs exceed this and are rated ~100lm/W when run at below their max power.
I guess you need a slightly more expensive inverter for a CFL system, but it will probably still work out cheaper with CFLs over LEDs.
Even if their units are wrong, the sentiment is sort of correct. The amount of solar energy incident through the circle of the Earth each year is about 100x our current yearly worldwide electricity usage.
I don't have the link handy, but there was a gif posted in the original article about the collision which showed that the satellites were traveling roughly orthogonally to each other.
The problem with the LED Vs CFL efficiency thing is that each are more efficient in certain circumstances.
Lets look at just raw efficiency: The 23W Phillips Tornado in my room is 70Lm/W, 1550lm warm white, (written on the side of the base). The most efficient "high-output" LED I know of is a Cree XR-E which is quoted at just over 100m/W, but only for a cool white at 350mA, by the time you crank them to their 1A max rating the efficiency has dropped to ~60lm/W (calculated from their datasheet)
It is worth noting that as CFL efficiency increases with higher power, whereas LED efficiency decreases with higher power. So, there is a good chance that the small high quality flashing LEDs in the front of your computer case exceed 100lm/W, but this isn't exactly a useful amount of light for room lighting.
All those numbers are all well and good, but there is another issue here: LEDs are trivial to focus due to their small emission area, whereas CFLs are comparably very difficult. This means that the overall system efficiency of, say, lighting up a square foot of your desk would be much higher when using a 200Lm ~3.7W Cree XR-E focused onto the small area than using a 1500Lm 23W CFL which sprays light in all directions. This is why LEDs, although not the most efficient technology in raw Lm/W, is used exclusively over CFLs in torches, pushbike headlights etc.
There are other psychological issues such as continuous spectrum vs discreet spectrum illumination, but that's a rather fuzzy "well, that's just your opinion" argument I don't want to get into. For reference, white LEDs tend to be fairly continuous, nothing like a black body radiator but with far more wavelengths than a CFL.
In addition to being power hungry, plasma TVs also give off a lot of radiation in the HF range, so no doubt a lot of HAMs would be glad to see them go.
...This is going to make me even more employable:).
The biggest opposition to Rudd's "computers in schools" plan has been that he's funding the hardware/software but no the support or training. No doubt this will give more weight to their argument.
Yeah I know that:p. In the OP's context it's fine. I just remember watts being used in place for joules in the context of battery storage articles and the like. Meh, nothing to worry about.
10 to 25c/kwh ignores the connection fee though. My parents are considering solar for a small weekend house on a 40 acre property they own (on the North coast of NSW, Australia). The local provider (Country Energy) recently increased the cost of connection from ~40c to ~60c per day, and since we're there about 4 days a month, and just run an electric fence continuously, this equates to almost all of the bill, making solar power without a grid connection far more attractive, and shortening the payback time significantly.
Obviously this isn't exactly a "normal" situation, but a lot of the rural areas with high connection fees, low reliability, and often lower usage*, are going to be (and have already been) the early adopters.
*Forgive my bias, but only wasteful city types who move to the country build McMansions with ducted air con and the like, your average farmer just runs a fridge/washer/lights, and there's a culture of basically never using a clothes dryer (not that it ever really rains anyway).
>Besides, LEDs have narrow frequency ranges too, you know.
Actually, I beg to differ. If you look at a Luxeon datasheet (page 9) you will see the spectrum graph. The graph shown does have a peak in the blue, but it has a FWHM of ~30nm, as opposed to ~1-2nm for the peaks from CFLs. In addition to that from ~500nm and up it's very continuous, appearing much like a black body spectrum with a peak ~550nm (T = 5300K).
Interesting that you mentioned musical complexity. I find most forms of "popular" music really boring. The "metal" bands I listen to include the likes of Opeth, Therion, Blind Guardian, Nightwish etc, all of which write very interesting and technical (esp Blind Guardian) music.
It would be interesting if the study included classical pieces as well, as in studying how many gifted teenagers like both modern "complex" metal and "complex" classical. A close friend and I like both kinds, it would be nice to know we weren't the only ones who mix Ride The Lightning with Toccata and Fugue in D Minor.
I've only done an undergraduate degree majoring in physics, that guy's work is beyond me:p. I'm really glad that people are thinking about this stuff in ways other than just accepting the existance of dark matter and basing all their maths on that assumption. The "greatest blunder of Einstein's life" was when he assumed the universe was static.
I thought this too for a long time, but it seems that the only evidence for dark matter isn't just galactic rotation curves. I'm having trouble finding it through Google, but while I was studying astrophysics last year we were shown an image of a gravitationally lensed quasar, but without any visible foreground stars. The lensing may have been caused by a clump of baryonic matter that just happened to be cold and not emitting much light, but it may also be dark matter. So unfortunately it's not quite as simple as, say, using general relativity to calculate a galactic rotation curve.
Personally I'm still hopeful that Newtonian gravity doesn't work at large distances, someone discovering some new gravitational physics (like, working out a quantum model for gravity is a good start) would be more exciting to me personally than just knowing that there's something that's mostly undetectable floating around in the universe.
Oh, and very large bodies also obey the laws of quantum physics, just taking them into account is a waste of time as the effects are insignificant. AFAIK there isn't a situation where QM doesn't apply correctly. In the same way as you can take special relativity into account when you're driving in your car, the maths works and it's correct but the effect is so small it is truly insignificant.
LEDs are also slightly more full-spectrum. The FWHM of a coloured LED is ~20-40nm (estimated from a plot in a Luxeon Star module datasheet), and very smooth (albeit with a peak at the blue end) for the white modules. Emission spectra from CFL phosphors (well, any emission spectra really) have peaks a
It's this sort of thing which I feel makes CFLs not as great as one would like. Although their total light output may be equivilant to, say, a 100W incandescent (for a 20W Philips Tornado), the "psychological usefulness" of the light in terms of being able to see clearly seems to be far off the usefulness of a 100W incandescent.
This is all just gut feeling though, I'd love to see a study where people are put in rooms with an unknown light source (say, an incandescent/CFL above a diffuser) and asked to judge how easy it is to read/write/sew/solder/whatever under different light sources. It may be able to quantify results better if a measurement of eye strain could be done (I'm not an eye doctor though, so I've no idea how easy this is to do).
I don't do any serious work on the internet as it stands. It's basically just a source of mindless entertainment, like what TV is for the less nerdy masses. Every now and then over my summer break I spend a month at a country property my parents own. It doesn't have a phone line, or a computer and they've only recently bothered getting a TV. Anyway, whenever I'm there I don't miss technology at all, in fact I enjoy the fact that there's no temptation to waste half my life sitting in front of a screen.
So yeah, I'd probably just end up doing more "real world" activities. Join the local archery club, do more bushwalking, go to the beach more etc.
The only serious effect it would have would be that I would no longer have a convenient place to publish my photography and make it available to the masses, therefore subjecting my family and friends to it more:p.
I think textbooks are a bad example to show where olpc gives a financial gain since the printing cost of a textbook is ~$5-$10, most of the cost is in the copyright.
Exactly. Hell, laptops don't even seem to help students in industrial nations. One of my cousins goes to a private school (in Sydney) where every student is required to have a laptop, from what he says everyone just uses them to waste time gaming:p. I go to the university of Sydney and suprisingly few people carry laptops around. Nobody in my 3rd year physics classes does, and only one (out of 20 or so) in my computational physics class does. However, USYD has ready access to computing facilities for all the students anyway, perhaps if that wasn't supplied students would feel more of a need for their own laptop.
One of the things we need to realise is that we use computers mainly as tools for dealing with a modern world. We need to do banking, so many of us use internet banking, many shop online because the service is available, we type reports on computers because we're involved in work/studies which require them. None of these things are required by a mostly agricultural society attempting to exist without enough clean drinking water.
OLPC is a great idea, but only because the people who came up with it exists in a world where laptops are a usefull tool. If you want to help their education send them books. I've heard reports form people working on a Christian missionary ship the Doulos and quite often when they arrive in a poor country teachers will go to the ships bookshop and whatever they've got end up being that year's material.
Anyway, there's probably someone on Earth who will benefit from OLPC, and it seems a lot of good engineering was achieved through the project, but I believe it's too early for it to be usefull to most of its intended audience.
For hot water we've got one of these. They have temperature control that you "dial in" via a remote control pad. We've only got one in the kitchen but you can install more than one per unit.
Personally I want home appliances that simply *work*. I don't really care how fast the internet is on my fridge, if it stops cooling my food within 5 years I'd be very dissapointed. We went through several dishwashers before getting a Bosch which is fairly featureless, but is very reliable.
In terms of the television diary-like-system mentioned in the summary, it's probably usefull for a house-husband, but it's been my experience that women simply don't have trouble with this sort of thing. Not meaning to be sexist, but women handle the multitasking nature of housework *much* better than men. If they're not they're either in the statistical minority, or too stressed by career responsibilites etc.
*sigh* Maybe I'm just too traditional for "modern life"...I'll crawl back to my hippy commune now.
Why would they build them with filters? I've only seen a couple of new traffic lights around Sydney to use them, and both of them have used red/green LEDs (unless they were really sneaky and put a small filter over each LED individually. Likewise the signal lights used on the Cityrail network are being replaced with LEDs and these are individual reds/greens too. The guard lights (on the station platforms) are an array of white and blue (they replace white globes with Fresnel lensing) for some reason, but still they aren't filtered individually.
Anyway, I find them to be a little *too* bright at times, not strictly a bad thing for seeing the signals, but they can be fairly distracting when you're blinded by a green light and subsequently don't see the pedestrian in black running across the road in front of you. No doubt they over-engineer them to be too bright so that they have some give when it comes to replacing them (ie, they can let more LEDs die before replacement. Yes they *do* die on these things, they're probably a bit over-driven or stressed by the elements).
50Mb/s yes, but only sequentially. As soon as you're seeking you get a few ms of delay on a HDD, but a few us or ns on anything solid state. So basically if you're encoding video a HDD or RAID array would work great, but if you're reading/writing lots of little files (say, in swap, or in a DB server) flash would beat it hands down.
I think more important is that the creation story really just tells us *why* we came about (basically, God's will for humans to be the pinnacle of creation) as opposed to the mechanisms that were used ("...and God said" is a heavanly mechanism, not a physical one).
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Well, the sand is more reflective than a solar panel, so covering all the deserts would warm the Earth up slightly by making it a better black body.
Why do so many people suggest LED lighting for solar instillations or other high efficiency applications?
CFLs have similar efficiency ratings to LEDs, and a significantly cheaper. The Philips Tornado CFL above me has 75lm/W stamped on it, only the best Cree LEDs exceed this and are rated ~100lm/W when run at below their max power.
I guess you need a slightly more expensive inverter for a CFL system, but it will probably still work out cheaper with CFLs over LEDs.
Even if their units are wrong, the sentiment is sort of correct. The amount of solar energy incident through the circle of the Earth each year is about 100x our current yearly worldwide electricity usage.
But yeah, their wording is shocking.
I don't have the link handy, but there was a gif posted in the original article about the collision which showed that the satellites were traveling roughly orthogonally to each other.
The problem with the LED Vs CFL efficiency thing is that each are more efficient in certain circumstances.
Lets look at just raw efficiency: The 23W Phillips Tornado in my room is 70Lm/W, 1550lm warm white, (written on the side of the base). The most efficient "high-output" LED I know of is a Cree XR-E which is quoted at just over 100m/W, but only for a cool white at 350mA, by the time you crank them to their 1A max rating the efficiency has dropped to ~60lm/W (calculated from their datasheet)
It is worth noting that as CFL efficiency increases with higher power, whereas LED efficiency decreases with higher power. So, there is a good chance that the small high quality flashing LEDs in the front of your computer case exceed 100lm/W, but this isn't exactly a useful amount of light for room lighting.
All those numbers are all well and good, but there is another issue here: LEDs are trivial to focus due to their small emission area, whereas CFLs are comparably very difficult. This means that the overall system efficiency of, say, lighting up a square foot of your desk would be much higher when using a 200Lm ~3.7W Cree XR-E focused onto the small area than using a 1500Lm 23W CFL which sprays light in all directions. This is why LEDs, although not the most efficient technology in raw Lm/W, is used exclusively over CFLs in torches, pushbike headlights etc.
There are other psychological issues such as continuous spectrum vs discreet spectrum illumination, but that's a rather fuzzy "well, that's just your opinion" argument I don't want to get into. For reference, white LEDs tend to be fairly continuous, nothing like a black body radiator but with far more wavelengths than a CFL.
In addition to being power hungry, plasma TVs also give off a lot of radiation in the HF range, so no doubt a lot of HAMs would be glad to see them go.
...This is going to make me even more employable :).
The biggest opposition to Rudd's "computers in schools" plan has been that he's funding the hardware/software but no the support or training. No doubt this will give more weight to their argument.
It's kind of annoying for retailers to have to fob off old machines with 512MB of RAM though. I feel really sorry for people who buy them too.
Yeah I know that :p. In the OP's context it's fine. I just remember watts being used in place for joules in the context of battery storage articles and the like. Meh, nothing to worry about.
A quick off-topic question, is the American standard to use "watts" as a substitute for joules and joules/second?
10 to 25c/kwh ignores the connection fee though. My parents are considering solar for a small weekend house on a 40 acre property they own (on the North coast of NSW, Australia). The local provider (Country Energy) recently increased the cost of connection from ~40c to ~60c per day, and since we're there about 4 days a month, and just run an electric fence continuously, this equates to almost all of the bill, making solar power without a grid connection far more attractive, and shortening the payback time significantly.
Obviously this isn't exactly a "normal" situation, but a lot of the rural areas with high connection fees, low reliability, and often lower usage*, are going to be (and have already been) the early adopters.
*Forgive my bias, but only wasteful city types who move to the country build McMansions with ducted air con and the like, your average farmer just runs a fridge/washer/lights, and there's a culture of basically never using a clothes dryer (not that it ever really rains anyway).
>Besides, LEDs have narrow frequency ranges too, you know.
Actually, I beg to differ. If you look at a Luxeon datasheet (page 9) you will see the spectrum graph. The graph shown does have a peak in the blue, but it has a FWHM of ~30nm, as opposed to ~1-2nm for the peaks from CFLs. In addition to that from ~500nm and up it's very continuous, appearing much like a black body spectrum with a peak ~550nm (T = 5300K).
0.001%? Did they even ship enough disks in the first place to get such a small number of complaints as one in 100,000?
:p.
*crosses fingers and hopes my maths is right*
Interesting that you mentioned musical complexity. I find most forms of "popular" music really boring. The "metal" bands I listen to include the likes of Opeth, Therion, Blind Guardian, Nightwish etc, all of which write very interesting and technical (esp Blind Guardian) music.
It would be interesting if the study included classical pieces as well, as in studying how many gifted teenagers like both modern "complex" metal and "complex" classical. A close friend and I like both kinds, it would be nice to know we weren't the only ones who mix Ride The Lightning with Toccata and Fugue in D Minor.
I've only done an undergraduate degree majoring in physics, that guy's work is beyond me :p. I'm really glad that people are thinking about this stuff in ways other than just accepting the existance of dark matter and basing all their maths on that assumption. The "greatest blunder of Einstein's life" was when he assumed the universe was static.
I thought this too for a long time, but it seems that the only evidence for dark matter isn't just galactic rotation curves. I'm having trouble finding it through Google, but while I was studying astrophysics last year we were shown an image of a gravitationally lensed quasar, but without any visible foreground stars. The lensing may have been caused by a clump of baryonic matter that just happened to be cold and not emitting much light, but it may also be dark matter. So unfortunately it's not quite as simple as, say, using general relativity to calculate a galactic rotation curve.
Personally I'm still hopeful that Newtonian gravity doesn't work at large distances, someone discovering some new gravitational physics (like, working out a quantum model for gravity is a good start) would be more exciting to me personally than just knowing that there's something that's mostly undetectable floating around in the universe.
Oh, and very large bodies also obey the laws of quantum physics, just taking them into account is a waste of time as the effects are insignificant. AFAIK there isn't a situation where QM doesn't apply correctly. In the same way as you can take special relativity into account when you're driving in your car, the maths works and it's correct but the effect is so small it is truly insignificant.
LEDs are also slightly more full-spectrum. The FWHM of a coloured LED is ~20-40nm (estimated from a plot in a Luxeon Star module datasheet), and very smooth (albeit with a peak at the blue end) for the white modules. Emission spectra from CFL phosphors (well, any emission spectra really) have peaks a
It's this sort of thing which I feel makes CFLs not as great as one would like. Although their total light output may be equivilant to, say, a 100W incandescent (for a 20W Philips Tornado), the "psychological usefulness" of the light in terms of being able to see clearly seems to be far off the usefulness of a 100W incandescent.
This is all just gut feeling though, I'd love to see a study where people are put in rooms with an unknown light source (say, an incandescent/CFL above a diffuser) and asked to judge how easy it is to read/write/sew/solder/whatever under different light sources. It may be able to quantify results better if a measurement of eye strain could be done (I'm not an eye doctor though, so I've no idea how easy this is to do).
I don't do any serious work on the internet as it stands. It's basically just a source of mindless entertainment, like what TV is for the less nerdy masses. Every now and then over my summer break I spend a month at a country property my parents own. It doesn't have a phone line, or a computer and they've only recently bothered getting a TV. Anyway, whenever I'm there I don't miss technology at all, in fact I enjoy the fact that there's no temptation to waste half my life sitting in front of a screen.
:p.
So yeah, I'd probably just end up doing more "real world" activities. Join the local archery club, do more bushwalking, go to the beach more etc.
The only serious effect it would have would be that I would no longer have a convenient place to publish my photography and make it available to the masses, therefore subjecting my family and friends to it more
I think textbooks are a bad example to show where olpc gives a financial gain since the printing cost of a textbook is ~$5-$10, most of the cost is in the copyright.
Exactly. Hell, laptops don't even seem to help students in industrial nations. One of my cousins goes to a private school (in Sydney) where every student is required to have a laptop, from what he says everyone just uses them to waste time gaming :p. I go to the university of Sydney and suprisingly few people carry laptops around. Nobody in my 3rd year physics classes does, and only one (out of 20 or so) in my computational physics class does. However, USYD has ready access to computing facilities for all the students anyway, perhaps if that wasn't supplied students would feel more of a need for their own laptop.
One of the things we need to realise is that we use computers mainly as tools for dealing with a modern world. We need to do banking, so many of us use internet banking, many shop online because the service is available, we type reports on computers because we're involved in work/studies which require them. None of these things are required by a mostly agricultural society attempting to exist without enough clean drinking water.
OLPC is a great idea, but only because the people who came up with it exists in a world where laptops are a usefull tool. If you want to help their education send them books. I've heard reports form people working on a Christian missionary ship the Doulos and quite often when they arrive in a poor country teachers will go to the ships bookshop and whatever they've got end up being that year's material.
Anyway, there's probably someone on Earth who will benefit from OLPC, and it seems a lot of good engineering was achieved through the project, but I believe it's too early for it to be usefull to most of its intended audience.
For hot water we've got one of these. They have temperature control that you "dial in" via a remote control pad. We've only got one in the kitchen but you can install more than one per unit.
Personally I want home appliances that simply *work*. I don't really care how fast the internet is on my fridge, if it stops cooling my food within 5 years I'd be very dissapointed. We went through several dishwashers before getting a Bosch which is fairly featureless, but is very reliable.
In terms of the television diary-like-system mentioned in the summary, it's probably usefull for a house-husband, but it's been my experience that women simply don't have trouble with this sort of thing. Not meaning to be sexist, but women handle the multitasking nature of housework *much* better than men. If they're not they're either in the statistical minority, or too stressed by career responsibilites etc.
*sigh* Maybe I'm just too traditional for "modern life"...I'll crawl back to my hippy commune now.
Anyway, I find them to be a little *too* bright at times, not strictly a bad thing for seeing the signals, but they can be fairly distracting when you're blinded by a green light and subsequently don't see the pedestrian in black running across the road in front of you. No doubt they over-engineer them to be too bright so that they have some give when it comes to replacing them (ie, they can let more LEDs die before replacement. Yes they *do* die on these things, they're probably a bit over-driven or stressed by the elements).
50Mb/s yes, but only sequentially. As soon as you're seeking you get a few ms of delay on a HDD, but a few us or ns on anything solid state. So basically if you're encoding video a HDD or RAID array would work great, but if you're reading/writing lots of little files (say, in swap, or in a DB server) flash would beat it hands down.
Modern HDD peak transfer rates are probably faster than USB 2.0, but the latency would sure be a hell of a lot lower from a flash drive!
I think more important is that the creation story really just tells us *why* we came about (basically, God's will for humans to be the pinnacle of creation) as opposed to the mechanisms that were used ("...and God said" is a heavanly mechanism, not a physical one).