The same is true of AC. The technology is called 'grid interactive', and we should be developing it more as it allows for things like co-generation and distributed generation.
You can buy solar panels with a single, standard wall plug which, when you plug in starts pumping energy back into the grid. Perfectly safe too - you can unplug it and stick your tongue on the plug!
Well you need to go back to school. Power is volts*amps (ignoring things like PF for now) for both AC and DC. The only problem was that DC transformers are very hard to build. But we don't care any more because we can build efficient DC->AC generators in each power supply, and tune the AC for conversion, rather than transmission. DC is superior to AC for transmission (hence the high voltage interconnects).
Higher voltages mean lower current for both AC and DC.
Just be careful of ground loops - the device in question may rely on the independant supply to avoid noise problems. Ethernet is fine, but usb, audio and firewire are not isolated and make have trouble. High efficiency wall warts are quite doable, there just isn't any demand. Personally I would like the power block separate from the plug (so they don't get in each other's way) and designed to stack or clip together.
8GA cable (heavy car cable) 0.00252ohms/m assume 10 m between powersupply and computer, 200W power gives 2V drop. So you're wasting about 30% of the input power.
There's a reason that cars are moving to 42V!
250V DC makes more sense technically, but it is far more lethal than 250V AC.
What the hell are you talking about? DC carries more power for a given conductor size and peak voltage (hence RMS). The only significant advantage of AC (besides historical reasons) is the ability to change voltage to current with a simple transformer. As consumer devices are tending towards switchmode power supplies (which generate their own AC on demand and at a much more suitable frequency) DC is actually more useful as it avoids requiring power factor correction.
Almost everything in your house would be better served with DC - lights (compact fluoros rectify the current and produce their own higher freq AC, e.g.), heating, motors, computers, etc.
DC at high voltages are much harder to deal with than AC because you need very high voltage transistors and diodes to deal with them. AC only requires a suitable transformer and isolation. DC is used because it avoids inductive and capacitive losses.
I'm fascinated that my post got moderated overrated. This argument comes up every time there is a discussion of PV panels, yet is has been known to be false for 40 years!
This seems to be one of those memes that floats around, perhaps because the people who believe want to disregard a technology that exists in preference for something that doesn't - in my experience these solar detractors want to believe in fusion as the world's saviour!
Diesel Electric locos can't do regenerative braking because they have no where to put the energy. Instead the electric braking energy is shunted into some very large resistors. The reasons for doing it is to save on brake blocks more than anything.
"Studies have shown that, depending on the type of PV technology, the clean energy payback of a PV system ranges from one to four years. With life expectancies of 30 years, 87% to 97% of the energy produced by PV systems will be free of pollution and greenhouse gas emissions. For more information, see the NREL report, "Energy Payback: Clean Energy from PV""
Except I'm still required to read some headlines for a country that has very little relevance to me. Go and look at Google again and see what minimalist means. (Of course I generally use my toolbar any way:)
Newtonian (dopplerian?) red shift occurs only because the waves are phase shifted/compressed by the motion. With these you wouldn't have trouble if you send the signal to a central receiver because the webcam never approachs the receiver. However, with relativistic doppler you also get a shift due to orbiting sources (I can't remember why though, I think it's because the measuring waves are also affected or something).
To move 310K (body temp) to visible light (at least 3100K) we need a factor of 10 increase in frequency (Wein's law), this corresponds to a shift of (10^2-1)/(10^2+1) = v/c, which is about 98% of the speed of light. That's a very fast wheel:)
Doppler occurs equally in cable and free space from memory (possible with a 0.7 correct for the change in the speed of light).
So I don't think the idea is practical.
Incidently, I think if you want to observe thermal radiation you need cool your sensor significantly below the temperature you want to measure to stop the sensor from light polluting your array. The great Chris Wallace designed the first peltier tree to achieve this.
As in BCD, Boolean Coded Decimal?;) I spose technically Boolean refers to the logic and binary refers to the encoding of numbers, but I've heard the terms used interchangably.
Who cares anyway, it's just bit picking. (nit picking is base e:)
Actually, you can solve the 2->1 folding problem quite easily. You just need to find gates that output as much information as they use. For example, an xor gate produces a single output, but if you invent the gate 'a,b' -> 'a, a^b' (xor*) then it is fully reversible and it is its own inverse.
The trick is to make the electronics themselves fully reversible, rather than emulating xor* using a standard xor and a wire. I don't know how this is done. My basic physics understanding is that it is impossible to do real computation without any energy input as you are creating order, but the amount of energy required for computation is bounded by the change in entropy of the information, which is a very small amount!
There are prototypes, I believe the real problem is size, not existence. As each operation does not destroy information, lots of spare bits pile up when you perform a calculation, and these all need to be stored. Operations tend to be exponential chip size from bits computed IIRC. This means that even relatively simple operations require far more chip size (means more error prone to make) than their inefficient lossy cousins.
(dear sibling,) Not is an unary binary operation. unary refers to the single argument, binary refers to the domain (takes a true or a false as its single input). And is a binary binary operation:)
Re:Things I'd like to see from GNOME.
on
Gnome 2.10 Released
·
· Score: 2, Informative
My wife uses GNOME on Ubuntu. CD's work fine, cameras work fine, printing works, web works. She says "It's subtly different to XP, but really it's perfectly fine." regarding eating itself, I would presume that that is a distribution problem.
What I've never grokked is: where does the beam come from? My basic physics suggests that it comes from the poles, but why would the poles sweep like lighthouses?
My friend recently started using linux (debian, then ubuntu) and his words were "Now that I've got grub I'm not scared of trying a new kernel". If you have grub as your boot loader (default for ubuntu?) then testing a new kernel should just be a matter of installing it using synaptic, then rebooting. You can always select the old kernel, boot up and remove the newer kernel if something goes wrong. Be Bold! (And good luck:)
"Nautilus will not under any circumstance burn a CD for me. It keeps prompting me for a blank CD. Again I believe this is a kernel issue. "
It's a bug in nautilus-cd-burner, which doesn't interpret a flag correctly in gconf. See if cdrecord works correctly for you. I wish they'd fix this.
Incidently Ubuntu warty happily detects my firewire external drive, so you may well be right about the kernel. Look at what dmesg says when you plug it in to determine the sticking point.
Ok, I was grumpy when I wrote that from the sheer idiocy I see on slashdot (makes me wonder why I even read it:). Sorry.
I'm not sure what the model is for your steerable solar dish, are you thinking of having one per household? This seems unlikely as dishes only become reasonable around the 20m diameter mark, which would be too large for any but the largest houses. On the other hand, panels are economic even for 1cm squares for powering calculators. So I very much doubt that people will have their own solar ovens. Solar hot water is already efficiently handled with panel type heaters, which work even without direct sunlight (unlike dishes).
So, that leaves large collectors for solar-thermal systems like the ANU combined heat and power system. You are concerned about the failure mode where the dish points in the wrong direction. In this case the dish will no longer focus to a single point, but rather to a circle along the axis of the incident rays. Hopefully this area is already cleared, as otherwise the sun will not get to the dish. It is possible that a branch is overhanging the dish, but in that cose there is a chance that it will get in the focus even with a working drive, so the real cause is poorly maintained equipment. In that case I imagine the likelyhood of causing a fire is about the same as that of a diesel generator causing a fire from its exhaust.
So I agree that there is a potential problem, but I very much doubt it is as significant as fires caused by broken glass or cigarette butts. Most likely it will never be an issue as large dishes will be maintained professionally, and smaller installations will use panel type systems, which do not concentrate the light significantly.
A parabolic dish has only one focal point, in the obvious spot. Furthermore, an off axis parabolic reflector cannot focus properly, so they only work when they are pointed in the right direction.
The ?irony? is that people who post anti-solar posts invariably demonstrate that they have no clue.
Slashdot Mirror
Wouldn't heatpipes be a lighter and less leaksome solution?
The same is true of AC. The technology is called 'grid interactive', and we should be developing it more as it allows for things like co-generation and distributed generation.
You can buy solar panels with a single, standard wall plug which, when you plug in starts pumping energy back into the grid. Perfectly safe too - you can unplug it and stick your tongue on the plug!
Well you need to go back to school. Power is volts*amps (ignoring things like PF for now) for both AC and DC. The only problem was that DC transformers are very hard to build. But we don't care any more because we can build efficient DC->AC generators in each power supply, and tune the AC for conversion, rather than transmission. DC is superior to AC for transmission (hence the high voltage interconnects).
Higher voltages mean lower current for both AC and DC.
Just be careful of ground loops - the device in question may rely on the independant supply to avoid noise problems. Ethernet is fine, but usb, audio and firewire are not isolated and make have trouble. High efficiency wall warts are quite doable, there just isn't any demand. Personally I would like the power block separate from the plug (so they don't get in each other's way) and designed to stack or clip together.
8GA cable (heavy car cable) 0.00252ohms/m
assume 10 m between powersupply and computer, 200W power gives 2V drop. So you're wasting about 30% of the input power.
There's a reason that cars are moving to 42V!
250V DC makes more sense technically, but it is far more lethal than 250V AC.
What the hell are you talking about? DC carries more power for a given conductor size and peak voltage (hence RMS). The only significant advantage of AC (besides historical reasons) is the ability to change voltage to current with a simple transformer. As consumer devices are tending towards switchmode power supplies (which generate their own AC on demand and at a much more suitable frequency) DC is actually more useful as it avoids requiring power factor correction.
Almost everything in your house would be better served with DC - lights (compact fluoros rectify the current and produce their own higher freq AC, e.g.), heating, motors, computers, etc.
DC at high voltages are much harder to deal with than AC because you need very high voltage transistors and diodes to deal with them. AC only requires a suitable transformer and isolation. DC is used because it avoids inductive and capacitive losses.
I'm fascinated that my post got moderated overrated. This argument comes up every time there is a discussion of PV panels, yet is has been known to be false for 40 years!
This seems to be one of those memes that floats around, perhaps because the people who believe want to disregard a technology that exists in preference for something that doesn't - in my experience these solar detractors want to believe in fusion as the world's saviour!
Any ideas?
Diesel Electric locos can't do regenerative braking because they have no where to put the energy. Instead the electric braking energy is shunted into some very large resistors. The reasons for doing it is to save on brake blocks more than anything.
Why are you maliciously spreading lies, or are you just stupid?
"Studies have shown that, depending on the type of PV technology, the clean energy payback of a PV system ranges from one to four years. With life expectancies of 30 years, 87% to 97% of the energy produced by PV systems will be free of pollution and greenhouse gas emissions. For more information, see the NREL report, "Energy Payback: Clean Energy from PV""
I don't know. Look it up and tell me!
Except I'm still required to read some headlines for a country that has very little relevance to me. Go and look at Google again and see what minimalist means. (Of course I generally use my toolbar any way :)
Newtonian (dopplerian?) red shift occurs only because the waves are phase shifted/compressed by the motion. With these you wouldn't have trouble if you send the signal to a central receiver because the webcam never approachs the receiver. However, with relativistic doppler you also get a shift due to orbiting sources (I can't remember why though, I think it's because the measuring waves are also affected or something).
:)
To move 310K (body temp) to visible light (at least 3100K) we need a factor of 10 increase in frequency (Wein's law), this corresponds to a shift of (10^2-1)/(10^2+1) = v/c, which is about 98% of the speed of light. That's a very fast wheel
Doppler occurs equally in cable and free space from memory (possible with a 0.7 correct for the change in the speed of light).
So I don't think the idea is practical.
Incidently, I think if you want to observe thermal radiation you need cool your sensor significantly below the temperature you want to measure to stop the sensor from light polluting your array. The great Chris Wallace designed the first peltier tree to achieve this.
As my collegue pointed out, this does not work because of the chroot line. It's a good joke though :)
(of course Ubuntu doesn't even require a command line)
As in BCD, Boolean Coded Decimal? ;) I spose technically Boolean refers to the logic and binary refers to the encoding of numbers, but I've heard the terms used interchangably.
:)
Who cares anyway, it's just bit picking. (nit picking is base e
I too was disappointed with the headline choice.
:)
Actually, you can solve the 2->1 folding problem quite easily. You just need to find gates that output as much information as they use. For example, an xor gate produces a single output, but if you invent the gate 'a,b' -> 'a, a^b' (xor*) then it is fully reversible and it is its own inverse.
The trick is to make the electronics themselves fully reversible, rather than emulating xor* using a standard xor and a wire. I don't know how this is done. My basic physics understanding is that it is impossible to do real computation without any energy input as you are creating order, but the amount of energy required for computation is bounded by the change in entropy of the information, which is a very small amount!
There are prototypes, I believe the real problem is size, not existence. As each operation does not destroy information, lots of spare bits pile up when you perform a calculation, and these all need to be stored. Operations tend to be exponential chip size from bits computed IIRC. This means that even relatively simple operations require far more chip size (means more error prone to make) than their inefficient lossy cousins.
(dear sibling,)
Not is an unary binary operation. unary refers to the single argument, binary refers to the domain (takes a true or a false as its single input). And is a binary binary operation
My wife uses GNOME on Ubuntu. CD's work fine, cameras work fine, printing works, web works. She says "It's subtly different to XP, but really it's perfectly fine." regarding eating itself, I would presume that that is a distribution problem.
Check it out sometime!
It opens fine in gpdf for me. gpdf is the default viewer for pdf documents since at least 2.8.
Gnome 2.0 over 1.4. Major featureset reduction.
Of course, thanks. Silly Earthling prejudices :)
What I've never grokked is: where does the beam come from? My basic physics suggests that it comes from the poles, but why would the poles sweep like lighthouses?
My friend recently started using linux (debian, then ubuntu) and his words were "Now that I've got grub I'm not scared of trying a new kernel". If you have grub as your boot loader (default for ubuntu?) then testing a new kernel should just be a matter of installing it using synaptic, then rebooting. You can always select the old kernel, boot up and remove the newer kernel if something goes wrong. Be Bold! (And good luck :)
Are you willing to try a newer kernel?
"Nautilus will not under any circumstance burn a CD for me. It keeps prompting me for a blank CD. Again I believe this is a kernel issue. "
It's a bug in nautilus-cd-burner, which doesn't interpret a flag correctly in gconf. See if cdrecord works correctly for you. I wish they'd fix this.
Incidently Ubuntu warty happily detects my firewire external drive, so you may well be right about the kernel. Look at what dmesg says when you plug it in to determine the sticking point.
Feel free to email me if you need help.
Ok, I was grumpy when I wrote that from the sheer idiocy I see on slashdot (makes me wonder why I even read it :). Sorry.
I'm not sure what the model is for your steerable solar dish, are you thinking of having one per household? This seems unlikely as dishes only become reasonable around the 20m diameter mark, which would be too large for any but the largest houses. On the other hand, panels are economic even for 1cm squares for powering calculators. So I very much doubt that people will have their own solar ovens. Solar hot water is already efficiently handled with panel type heaters, which work even without direct sunlight (unlike dishes).
So, that leaves large collectors for solar-thermal systems like the ANU combined heat and power system. You are concerned about the failure mode where the dish points in the wrong direction. In this case the dish will no longer focus to a single point, but rather to a circle along the axis of the incident rays. Hopefully this area is already cleared, as otherwise the sun will not get to the dish. It is possible that a branch is overhanging the dish, but in that cose there is a chance that it will get in the focus even with a working drive, so the real cause is poorly maintained equipment. In that case I imagine the likelyhood of causing a fire is about the same as that of a diesel generator causing a fire from its exhaust.
So I agree that there is a potential problem, but I very much doubt it is as significant as fires caused by broken glass or cigarette butts. Most likely it will never be an issue as large dishes will be maintained professionally, and smaller installations will use panel type systems, which do not concentrate the light significantly.
A parabolic dish has only one focal point, in the obvious spot. Furthermore, an off axis parabolic reflector cannot focus properly, so they only work when they are pointed in the right direction.
The ?irony? is that people who post anti-solar posts invariably demonstrate that they have no clue.