They made the Electron Volt a unit of energy when they needed a way to describe how much energy difference there is between two particle states, for example the amount of energy needed to electrolyse a single molecule.
Why? Don't you incur a net loss in efficiency by converting mechanical power to electrical and back to mechanical?
Yes, you do. However, as conversions go, it's not that bad - 90 to 98% (better for larger motors). It's possible to lose more by running an engine at suboptimal speeds (idle, for example) or by letting braking energy go to heat instead.
Battery energy density has increased by 4.5x in the past 20 years, and only appears to be speeding up.
You're starting at a 75x density disadvantage (your article's numbers) and bragging about a 4.5x increase? That still leaves you at a 17x density disadvantage. Also, it's not at all clear that batteries will continue to improve much farther. The progress we have already made has been through switching to lighter, more reactive metals. A quick glance at the periodic table will show there isn't much more room there.
ICEs only harness a fraction of the energy in their fuel
This is true; that fraction has also steadily increased (much more gradually) over time. The 20% in your article is pessimistic. Since we're talking about present and near-term future tech, not existing stuff on the road, 35-40% is more reasonable (traditional ICEs achieve the former number - Stirling or Kalina cycle engines regularly achieve the latter and could be integrated into a series hybrid today). Methanol-fed fuel cells are also a more long-term future possibility.
EVs are perhaps 10 years of battery tech away from being on par with your average ICE vehicle in terms of range per vehicle systems mass/volume.
I also expect EVs with several hundred miles of range in ten years. What I have no basis to expect is for such a vehicle to be anywhere near as affordable as the average vehicle today. Lithium-ion batteries are already in widespread mass production (just, not so much for cars yet) - and they are still quite expensive. Batteries will still be the major cost of a long-range EV in 10 years.
So having such huge ranges is pointless.
For a lot of people, most of the time, sure. The true test of that will be how many of them buy plugin hybrids vs. EVs with short-range battery packs vs. EVs with expensive battery packs. I've already listed many other large users of hydrocarbons - batteries will never be a substitute for airliners, ships, long-haul trucking, etc. You can't double the weight of a plane, so an electric airliner would have to have significantly less energy available on takeoff instead. This would drastically (impractically) limit range.
The two main "100% solutions", which require new infrastructure, are rapid charging and battery swapping.
Huge amounts of progress has been made in allowing batteries to rapidly charge/discharge (mostly through creative anode/cathode design) and we're just about at the point where they can be charged as fast as we can throw electricity at them. Some grid improvements would be in order - a charging station with a dozen cars charging at 300kW would be several megawatts, or as much as a decently-sized high-rise building or datacenter, crammed into much less space.
I'm not going to hold my breath on battery swapping stations. The standardization and infrastructure requirements are too much of a chicken and egg problem.
Anyway, I didn't write any of this to say that renewable hydrocarbons are an easy, universal answer. My point is simply that EV+solar isn't easy or universal either. (Nothing is.) You can argue over specific quantifications of 'easy' or specific fractions of 'universal', but I'll let you do that with someone else. I'm done here.
What sort of surplus of fertile farmland with ample rain do you think we have sitting around waiting to be farmed?
"Farmed" apparently conjures up misleading imagery for you. You basically want stuff that will grow on land considered less than 'fertile' using only the rain that lands there - grasses, weeds, etc. There's a lot more of that than there is farmland.
And even algae biodiesel is dwarfed in terms of vehicle miles per acre by solar + EVs (plus, it's basically hydroponics on a massive scale -- i.e., expensive).
You're missing an expensive step in your comparison, since the facts are that right now most vehicle activity can't be powered from batteries (which aren't cheap either), and even in the future only a fraction of it could be. That step is: how efficiently can you make fuel from surplus electricity?
Solar's efficacy is measured in cents per kWh. Biodiesel's efficacy is measured in dollars per gallon. Translating both into a sensical unit such as joules per dollar is a fun little thought experiment but can't by itself get you anywhere. Translating both into a fudgeable unit that describes only part of the costs, like vehicle miles per acre, is silly.
Growing plants for fuel is far, far more destructive and less efficient than just turning the solar energy directly to electricity and operating off of that.
Your selection of links suggests an assumption that such a fuel source needs to be fertilized and irrigated. I think most people recognize at this point that such feedstocks won't be economically attractive, and are looking towards things like algal biodiesel and cellulosic ethanol.
In any case, it would help to recognize the current dichotomy between grid and portable power. People (generally) don't burn gasoline to power their homes. People (generally) don't plug their car into the wall (although that will certainly become more common). Only hydrocarbons are currently practical for planes, car/truck road trips, ships (wind can help here), etc - the energy densities of everything else is just too low.
The two efforts serve (and will continue to serve) two largely independent needs. Yes, there is a lot of room to improve both, and there is a lot that can be done to displace oil use for grid power. But no, photovoltaics will never be a complete answer.
Still, there should be a big efficiency using a mains converter that brings it down to 12 rather than many smaller supplies that bring it from line voltage to 12 and lower.
Not really. Remember the 99.9% efficiency number you read is only the power supply's efficiency on battery. It's not the power supply's efficiency when on AC power and it's not the motherboard's power regulation efficiency. Google's setup is better than most, perhaps even optimal, but I'd be very surprised if the chips and hard drives received more than 80% of the power drawn from the power cord.
Most of their gains are from avoiding an extra AC->DC->AC conversion from a centralized UPS. A typical server has its power converted like this:
AC Line Power
DC UPS batteries
AC UPS Inverter
DC Power Supply Rectification
AC (High Frequency) Power Supply Inverter
AC (High Frequency) Transformer
DC Power Supply Output Rectification
AC Motherboard Voltage Regulator Inverter
DC Motherboard Voltage Regulator Rectifier
Note that additional separate voltages are parallel paths in the last half of this chain - not additional steps in it. Google's setup has a few less steps:
AC Line Power
DC Power Supply Rectification
AC (High Frequency) Power Supply Inverter
AC (High Frequency) Transformer
DC Power Supply Output Rectification (Battery hookup)
AC Motherboard Voltage Regulator Inverter
DC Motherboard Voltage Regulator Rectifier
Google just realized that the motherboard has its own power supply on it anyway, so why not make it official and have it do the final voltage regulation. The bulk of the 12V power gets converted to very low voltages, so there's no reason why the buck regulator that accepts that 12V power can't accept a fairly wide voltage range from a battery.
I think they run AC to the row or rack of servers, then they have just one super efficient PSU powering all the servers in a rack rather than 42 separate power supplies (plus UL enclosures, connectors, extension cords, etc, etc)
No, they don't. They use motherboards built to their own specification that require only 12V power. This power is supplied by the server's own PSU, which takes 240V input. The PSU hooks into a 12V sealed lead acid battery, implementing UPS functionality (there is no centralized UPS).
This is exactly why I got a Canon SX10 last year instead of a CoolPix P80, Lumix DMC-FZ28K, Olympus SP-565UZ, or Sony DSC-H50.
Yes, Li-Ion batteries have about twice the power-to-weight ratios of NiMH, and yes they will last longer. But there's two big reasons to get equipment that uses standard AAs:
1. AAs are fungible. When hiking, I can get a flashlight and GPS receiver that take the same batteries, and if I run out of spares, I can transfer one to the other. When in town, I can quickly find a store that sells them.
2. AAs will be around in 5+ years. Li-Ion batteries die in an average of 4 years whether you use them or not. You can get them to last a little longer if you put them half-charged in the fridge. When the manufacturer stops making your model of camera, they'll stop making your model of camera battery. Now, whether or not they or anyone else keep spares sitting on the shelf for all eternity just in case you need to buy one is irrelevant - if you manage to get your hands on a "new" one, it'll be dead out of the box.
It's quite likely that I will either accidentally kill my camera in that timeframe (that's why I didn't buy a really expensive one) or that I won't care because future cameras will be even cheaper and even more wonderful. But it's not a certainty - and I'd still like something I paid a few hundred bucks for to have a chance of working 5 years after I buy it.
That's Frozen Cold (as in, ice is less slippery because it has less of a tendency to melt and refreeze when you walk or drive on it, snow stays 'dry' and drifts around instead of caking up, and lakes and rivers ice over).
This article doesn't mention anything about mass energy storage. Without that, if we try to increase wind's share of power generation too much, it'll destabilize the grid (I've heard figures of 20-30% for this previously, but can't find a convenient reference).
That appears to be an 80GB drive for $314. For that price I purchase at least 5 80GB magnetic disks. I think his point was valid, and Im not sure how you thought you were refuting it.
Pick any set of magnetic disks + controller hardware that you can get for $314. Now make it do 23MB/sec in random writes. Or anything close to that.
Yeahhh... give me the one that costs 36 times more, takes up 4 times more space, requires 8 times more controllers and is guaranteed to wear out in a few years. If your I/O patterns are so messed up that today's horrendous SSDs actually lower your cost per I/O, you need to rethink your information architecture.
Yes, but I doubt if they use a significant amount of helium.
You're right, it isn't very significant. I just hope the world starts treating it as if it were precious before it becomes very expensive. We've only been using helium for a century, but it would be quite a shame for all of its uses to be lost to future generations forever.
I don't think anyone's done it yet, which of course isn't to say it can't be done. I think such a structure, if buildable, would be very costly and fragile (more so than any balloon).
It would be easier if you were able to deploy it from its target altitude. Otherwise you have three conflicting requirements:
That the entire thing (payload and all) be lighter than ~175 grams per cubic meter displacement (air density at 15000 meters)
That it withstand pressures of 10000 kilograms force per square meter (sea level air pressure), or that the air can be pumped out slowly as the structure rises (but 175 grams/cubic meter density difference is still 1240 kg/m^2 of pressure difference)
That it withstand wind deformation pressures (enough to handle ascent and gusts)
Remember chemistry class and hydrogen balloons? Those were fun times.
Honestly, I hope they use hydrogen for this. Helium is uniquely non-replaceable. It's the product of very slow alpha particle decay, trapped in natural gas fields and such. We'll eventually empty those natural gas fields. There are lots of other ways to make energy, and we can make natural gas if we need methane, specifically, for whatever reason. But we can't make helium except through nuclear fusion. Even then, if fusion delivered 100% of earth's electricity needs, it'd only create a small fraction of what we currently use per year.
We'll always have plenty of hydrogen because it bonds to everything. Helium doesn't, so once you crack open that helium tank, it's just a matter of time until it floats off into space, where it's as good as gone.
I find it highly unlikely that a jet in mid journey above the ocean would be SO far below cruising speed to be anywhere close to "a very narrow margin above stall speed". We're not talking about a Cessna.
Let's run some numbers, because I'm curious myself. An aircraft's stall speed increases as air density decreases - the air is much thinner at 35000 ft.
(figures rounded for simplicity) Wing area: 362 m^2 Weight: 120000 (empty) to 230000 (max takeoff) kg
35000ft is roughly 10600m. Plugging that into this calculator, we get 0.38 kg/m^3
I don't have numbers on the Airbus wing's lift coefficient with flaps up, so I'll estimate between 1 (conservative) and 1.5 (optimistic).
The lift equation is
Lift (in Newtons) = 0.5 * Density (in kg/m^3) * Area (in m^2) * LiftCoefficient * Velocity (in m/s)^2. One Newton is 0.10197 kilogram force.
With the Airbus at takeoff weight and a conservative lift coefficient, it has to be going 181 meters/second to generate 230000kg of force. With the Airbus at minimum weight and an optimistic lift coefficient, it has to be going 107 m/s to generate 120000kg of force.
The real numbers are probably somewhere in the middle, but either number is a good fraction of the cruising speed (0.86 mach at that altitude is 255 meters/second).
Ultimately, you stall when your wing exceeds a certain angle of attack, not when you go below a certain speed. Stall speed only refers to the speed at which a wing can no longer maintain 1G of lift (to maintain level flight). At speeds above stall speed, you can develop more and more G forces before you stall. Lift increases with the square of speed, so at twice stall speed you can pull 4 Gs before stalling. This is important because airframes are only built to take a certain number of Gs. I believe most airliners are built for +/- 2.5Gs (I don't have a reference for this and would love to see one). 2.5Gs means only 1.58 times stall speed - 181*1.58 = 285 m/s, 107*1.58 = 169 m/s. This speed where you are inherently protected against pulling more Gs than the structure will take is called "maneuvering speed", and if the pilot slowed down, this is likely the number they wanted to hit. It would be quite a ways above stall speed, even taking into account 30m/s gusts.
The second is that the data lines are single-ended, meaning that there's only one wire per signal.
Well, this may not be exactly what you were getting at, but I'd like to split hairs here anyway, and divide this into two separate issues that SATA/SAS resolved.
For best results it's important to model the cable as an RF transmission line, with a specific impedence.
An ideal transmission line has the important qualities that all the energy you send from one end will arrive at the other, and none will be reflected back to you. To get reasonably close to this ideal, we space the wires we use a fixed distance apart (in relation to the wire's diameter), choose our dielectric (insulating material) carefully, use terminating resistors at both ends, and keep the line a simple line (no tees, etc.)
For those of you who cut your teeth on parallel SCSI, 10base2/10base5 Ethernet, or Apple LocalTalk, you'll wax nostalgically at just how much of a pain in the ass this was.
For those of you who have only messed with parallel IDE, you'll wonder why you never had to deal with this. The reason is that IDE cheated a little bit - they only terminated the controller (motherboard) side of the bus, and let the signals reflect off the other end. This left only a master/slave/cable-select jumper to infuriate you - but it also limited how long an IDE cable could be and prevented them from jacking up the clock rates on it.
SATA/SAS fixes this for good by limiting you to one device per cable ("port", not "bus"). Both ends are hard-wired to always terminate and any cable problems are limited to a single drive.
The other issue you may have been referring to is balanced (differential) vs. unbalanced signalling (where one wire is held to ground and the voltage read off the other wire). Electrical engineers do commonly call unbalanced signalling one wire because ground is so boring that they never bother to connect it on their schematics, but it does have to be connected in real life and coax Ethernet/most old SCSI/Parallel IDE/RS-232/VGA still used two wires per signal. Balanced/differential signalling (LVD/HVD SCSI, SAS, SATA, 10/100/1000baseT, USB, telephone lines, T1 lines, LocalTalk, etc.) allows for the can't-imagine-life-without-it common-mode noise rejection technique you describe.
Two sine waves of the same frequency and amplitude will, when added together, result in a single sine wave of the same frequency. The amplitude of that sine wave depends on the phase angle (0 to 360 degrees) and will range from 0 (flat line) at 0/360 degrees to 2 at 180 degrees.
Heck, you may need a new building to put all this in. Which will need an HVAC system, of course.
Oh, and those machines won't run themselves. So you'll need to hire a few people; fairly qualified admins.
That's right, these would be new expenses, because it's all new functionality - as we know, the US military does not currently use email. And there's no possible way they would have a datacenter already.
Slashdot Mirror
They made the Electron Volt a unit of energy when they needed a way to describe how much energy difference there is between two particle states, for example the amount of energy needed to electrolyse a single molecule.
Yes, you do. However, as conversions go, it's not that bad - 90 to 98% (better for larger motors). It's possible to lose more by running an engine at suboptimal speeds (idle, for example) or by letting braking energy go to heat instead.
You're starting at a 75x density disadvantage (your article's numbers) and bragging about a 4.5x increase? That still leaves you at a 17x density disadvantage. Also, it's not at all clear that batteries will continue to improve much farther. The progress we have already made has been through switching to lighter, more reactive metals. A quick glance at the periodic table will show there isn't much more room there.
This is true; that fraction has also steadily increased (much more gradually) over time. The 20% in your article is pessimistic. Since we're talking about present and near-term future tech, not existing stuff on the road, 35-40% is more reasonable (traditional ICEs achieve the former number - Stirling or Kalina cycle engines regularly achieve the latter and could be integrated into a series hybrid today). Methanol-fed fuel cells are also a more long-term future possibility.
I also expect EVs with several hundred miles of range in ten years. What I have no basis to expect is for such a vehicle to be anywhere near as affordable as the average vehicle today. Lithium-ion batteries are already in widespread mass production (just, not so much for cars yet) - and they are still quite expensive. Batteries will still be the major cost of a long-range EV in 10 years.
For a lot of people, most of the time, sure. The true test of that will be how many of them buy plugin hybrids vs. EVs with short-range battery packs vs. EVs with expensive battery packs. I've already listed many other large users of hydrocarbons - batteries will never be a substitute for airliners, ships, long-haul trucking, etc. You can't double the weight of a plane, so an electric airliner would have to have significantly less energy available on takeoff instead. This would drastically (impractically) limit range.
Huge amounts of progress has been made in allowing batteries to rapidly charge/discharge (mostly through creative anode/cathode design) and we're just about at the point where they can be charged as fast as we can throw electricity at them. Some grid improvements would be in order - a charging station with a dozen cars charging at 300kW would be several megawatts, or as much as a decently-sized high-rise building or datacenter, crammed into much less space.
I'm not going to hold my breath on battery swapping stations. The standardization and infrastructure requirements are too much of a chicken and egg problem.
Anyway, I didn't write any of this to say that renewable hydrocarbons are an easy, universal answer. My point is simply that EV+solar isn't easy or universal either. (Nothing is.) You can argue over specific quantifications of 'easy' or specific fractions of 'universal', but I'll let you do that with someone else. I'm done here.
Yes. Energy density.
"Farmed" apparently conjures up misleading imagery for you. You basically want stuff that will grow on land considered less than 'fertile' using only the rain that lands there - grasses, weeds, etc. There's a lot more of that than there is farmland.
You're missing an expensive step in your comparison, since the facts are that right now most vehicle activity can't be powered from batteries (which aren't cheap either), and even in the future only a fraction of it could be. That step is: how efficiently can you make fuel from surplus electricity?
Solar's efficacy is measured in cents per kWh. Biodiesel's efficacy is measured in dollars per gallon. Translating both into a sensical unit such as joules per dollar is a fun little thought experiment but can't by itself get you anywhere. Translating both into a fudgeable unit that describes only part of the costs, like vehicle miles per acre, is silly.
Your selection of links suggests an assumption that such a fuel source needs to be fertilized and irrigated. I think most people recognize at this point that such feedstocks won't be economically attractive, and are looking towards things like algal biodiesel and cellulosic ethanol.
In any case, it would help to recognize the current dichotomy between grid and portable power. People (generally) don't burn gasoline to power their homes. People (generally) don't plug their car into the wall (although that will certainly become more common). Only hydrocarbons are currently practical for planes, car/truck road trips, ships (wind can help here), etc - the energy densities of everything else is just too low.
The two efforts serve (and will continue to serve) two largely independent needs. Yes, there is a lot of room to improve both, and there is a lot that can be done to displace oil use for grid power. But no, photovoltaics will never be a complete answer.
The B-52 is roughly comparable to the A330 and spring tab controls were used on it.
Not really. Remember the 99.9% efficiency number you read is only the power supply's efficiency on battery. It's not the power supply's efficiency when on AC power and it's not the motherboard's power regulation efficiency. Google's setup is better than most, perhaps even optimal, but I'd be very surprised if the chips and hard drives received more than 80% of the power drawn from the power cord.
Most of their gains are from avoiding an extra AC->DC->AC conversion from a centralized UPS. A typical server has its power converted like this:
Note that additional separate voltages are parallel paths in the last half of this chain - not additional steps in it. Google's setup has a few less steps:
Google just realized that the motherboard has its own power supply on it anyway, so why not make it official and have it do the final voltage regulation. The bulk of the 12V power gets converted to very low voltages, so there's no reason why the buck regulator that accepts that 12V power can't accept a fairly wide voltage range from a battery.
No, they don't. They use motherboards built to their own specification that require only 12V power. This power is supplied by the server's own PSU, which takes 240V input. The PSU hooks into a 12V sealed lead acid battery, implementing UPS functionality (there is no centralized UPS).
I think it's a very elegant design.
This is exactly why I got a Canon SX10 last year instead of a CoolPix P80, Lumix DMC-FZ28K, Olympus SP-565UZ, or Sony DSC-H50.
Yes, Li-Ion batteries have about twice the power-to-weight ratios of NiMH, and yes they will last longer. But there's two big reasons to get equipment that uses standard AAs:
1. AAs are fungible. When hiking, I can get a flashlight and GPS receiver that take the same batteries, and if I run out of spares, I can transfer one to the other. When in town, I can quickly find a store that sells them.
2. AAs will be around in 5+ years. Li-Ion batteries die in an average of 4 years whether you use them or not. You can get them to last a little longer if you put them half-charged in the fridge. When the manufacturer stops making your model of camera, they'll stop making your model of camera battery. Now, whether or not they or anyone else keep spares sitting on the shelf for all eternity just in case you need to buy one is irrelevant - if you manage to get your hands on a "new" one, it'll be dead out of the box.
It's quite likely that I will either accidentally kill my camera in that timeframe (that's why I didn't buy a really expensive one) or that I won't care because future cameras will be even cheaper and even more wonderful. But it's not a certainty - and I'd still like something I paid a few hundred bucks for to have a chance of working 5 years after I buy it.
That's Frozen Cold (as in, ice is less slippery because it has less of a tendency to melt and refreeze when you walk or drive on it, snow stays 'dry' and drifts around instead of caking up, and lakes and rivers ice over).
Metric isn't too much worse. I think about it in terms of 0-40 instead:
0: Freezing cold
10: Cold
20: Normal
30: Hot
40: Crazy Hot
One more exception: Tidal power comes from the earth's rotation in the presence of the sun and the moon.
This article doesn't mention anything about mass energy storage. Without that, if we try to increase wind's share of power generation too much, it'll destabilize the grid (I've heard figures of 20-30% for this previously, but can't find a convenient reference).
Has anything panned out on that front? (i.e. been cheap enough for wide-scale use?) Pumped-storage hydro, Sodium-sulfur batteries, etc?
Pick any set of magnetic disks + controller hardware that you can get for $314. Now make it do 23MB/sec in random writes. Or anything close to that.
There are two schools of thought regarding SSDs:
You're right, it isn't very significant. I just hope the world starts treating it as if it were precious before it becomes very expensive. We've only been using helium for a century, but it would be quite a shame for all of its uses to be lost to future generations forever.
I don't think anyone's done it yet, which of course isn't to say it can't be done. I think such a structure, if buildable, would be very costly and fragile (more so than any balloon).
It would be easier if you were able to deploy it from its target altitude. Otherwise you have three conflicting requirements:
Good luck!
Honestly, I hope they use hydrogen for this. Helium is uniquely non-replaceable. It's the product of very slow alpha particle decay, trapped in natural gas fields and such. We'll eventually empty those natural gas fields. There are lots of other ways to make energy, and we can make natural gas if we need methane, specifically, for whatever reason. But we can't make helium except through nuclear fusion. Even then, if fusion delivered 100% of earth's electricity needs, it'd only create a small fraction of what we currently use per year.
We'll always have plenty of hydrogen because it bonds to everything. Helium doesn't, so once you crack open that helium tank, it's just a matter of time until it floats off into space, where it's as good as gone.
Let's run some numbers, because I'm curious myself. An aircraft's stall speed increases as air density decreases - the air is much thinner at 35000 ft.
(figures rounded for simplicity)
Wing area: 362 m^2
Weight: 120000 (empty) to 230000 (max takeoff) kg
35000ft is roughly 10600m. Plugging that into this calculator, we get 0.38 kg/m^3
I don't have numbers on the Airbus wing's lift coefficient with flaps up, so I'll estimate between 1 (conservative) and 1.5 (optimistic).
The lift equation is Lift (in Newtons) = 0.5 * Density (in kg/m^3) * Area (in m^2) * LiftCoefficient * Velocity (in m/s)^2. One Newton is 0.10197 kilogram force.
With the Airbus at takeoff weight and a conservative lift coefficient, it has to be going 181 meters/second to generate 230000kg of force. With the Airbus at minimum weight and an optimistic lift coefficient, it has to be going 107 m/s to generate 120000kg of force.
The real numbers are probably somewhere in the middle, but either number is a good fraction of the cruising speed (0.86 mach at that altitude is 255 meters/second).
Ultimately, you stall when your wing exceeds a certain angle of attack, not when you go below a certain speed. Stall speed only refers to the speed at which a wing can no longer maintain 1G of lift (to maintain level flight). At speeds above stall speed, you can develop more and more G forces before you stall. Lift increases with the square of speed, so at twice stall speed you can pull 4 Gs before stalling. This is important because airframes are only built to take a certain number of Gs. I believe most airliners are built for +/- 2.5Gs (I don't have a reference for this and would love to see one). 2.5Gs means only 1.58 times stall speed - 181*1.58 = 285 m/s, 107*1.58 = 169 m/s. This speed where you are inherently protected against pulling more Gs than the structure will take is called "maneuvering speed", and if the pilot slowed down, this is likely the number they wanted to hit. It would be quite a ways above stall speed, even taking into account 30m/s gusts.
Apparently. At the very least you are making "perfect" the enemy of "damn good".
Well, this may not be exactly what you were getting at, but I'd like to split hairs here anyway, and divide this into two separate issues that SATA/SAS resolved.
For best results it's important to model the cable as an RF transmission line, with a specific impedence. An ideal transmission line has the important qualities that all the energy you send from one end will arrive at the other, and none will be reflected back to you. To get reasonably close to this ideal, we space the wires we use a fixed distance apart (in relation to the wire's diameter), choose our dielectric (insulating material) carefully, use terminating resistors at both ends, and keep the line a simple line (no tees, etc.)
For those of you who cut your teeth on parallel SCSI, 10base2/10base5 Ethernet, or Apple LocalTalk, you'll wax nostalgically at just how much of a pain in the ass this was.
For those of you who have only messed with parallel IDE, you'll wonder why you never had to deal with this. The reason is that IDE cheated a little bit - they only terminated the controller (motherboard) side of the bus, and let the signals reflect off the other end. This left only a master/slave/cable-select jumper to infuriate you - but it also limited how long an IDE cable could be and prevented them from jacking up the clock rates on it.
SATA/SAS fixes this for good by limiting you to one device per cable ("port", not "bus"). Both ends are hard-wired to always terminate and any cable problems are limited to a single drive.
The other issue you may have been referring to is balanced (differential) vs. unbalanced signalling (where one wire is held to ground and the voltage read off the other wire). Electrical engineers do commonly call unbalanced signalling one wire because ground is so boring that they never bother to connect it on their schematics, but it does have to be connected in real life and coax Ethernet/most old SCSI/Parallel IDE/RS-232/VGA still used two wires per signal. Balanced/differential signalling (LVD/HVD SCSI, SAS, SATA, 10/100/1000baseT, USB, telephone lines, T1 lines, LocalTalk, etc.) allows for the can't-imagine-life-without-it common-mode noise rejection technique you describe.
And everything inbetween, actually.
Two sine waves of the same frequency and amplitude will, when added together, result in a single sine wave of the same frequency. The amplitude of that sine wave depends on the phase angle (0 to 360 degrees) and will range from 0 (flat line) at 0/360 degrees to 2 at 180 degrees.
That's assuming there's nothing in the document itself that only a particular author would write. That's how they ended up identifying the unibomber.
That's right, these would be new expenses, because it's all new functionality - as we know, the US military does not currently use email. And there's no possible way they would have a datacenter already.