That does not change the fact that the math is pretty solid and it would work.
You haven't done the math or cited any.
There is a big efficiency problem in space-based solar with the double conversion from DC to RF/laser and back to DC. Total efficiency neglecting transmission loss is about 64% (80% twice). Then you have to invert it back to AC usually, but that is also needed for terrestrial solar.
So 35% power is thrown away, but since the sun is stronger in space without atmospheric attenuation, and there are no clouds, some of that will be made up.
So to a first approximation the power per unit of panel area is the same from space as it is on earth.
Now factor in launch costs which are tremendous (even if SpaceX succeeds in yet another 10x reduction in launch costs as claimed) and the difficulty performing maintenance in space versus on land, and I don't see a strong case. Installation costs on land are around $1/watt, I'd like to see you come within a factor of 10 of that in space.
In undoped semiconductor resistance will usually decrease as temperature is raised because a higher temperature excites more electrons into the conduction band where they can carry current.
But for cases where there is already a lot of charge the opposite usually applies. In something like a MOSFET the electrons are supplied by the source contact or in a doped bulk semiconductor there will be lots of charge from dopants. In these cases increasing the temperature doesn't significantly increase the charge. However raising the temperature does increase the electron scattering rate which reduces the electron mobility and slows electrons down, so the resistance actually increases.
Regulation of the coal industry is simply forcing the companies building and operating it to internalize the negative externalities. You can't do a fair analysis without considering the whole picture.
I'm all for exploring space, but the premise of mining the moon sounds pretty shaky and its totally fair for geeks to want realistic goals because that's what attracts sustainable capital investment from public and private sources that are needed to realize the goal. It's not a zero-sum game, but putting private and public money into crazy unworkable ideas takes some money away from realistic ideas.
Moon mining sounds to me a lot like orbital solar power - it sounds great and cool until you actually think for a moment and realize that it has very little to no net benefit per panel area compared to terrestrial solar after you transmit the power back to earth, and the cost is astronomical to boot. What is the benefit of mining the moon aside from sounding cool? It doesn't seem like there's a particularly high concentration of any of these purported mineral riches and with the expense of mining the material in space I'm highly suspicious of it being in any way economical after shipping back to Earth. He-3 is a bust since there's currently no major use for it. Maybe moon mining would be viable for obtaining materials on the moon without launch costs, but the supposed mineral riches are mostly high priced specialty materials and not the boring metals like iron and aluminum that would be needed for building a spaceship or lunar colony.
Fuck off, some of us have dreams.
Some of us like to support our dreams with back of the envelope analyses to ensure viability before getting too invested in them.
Nope, reread your link. Channel capacity (at a given signal to noise ratio) is proportional to bandwidth alone. 1.000GHz to 1.065GHz is as good as 20.000GHz to 20.065GHz.
But as you say higher frequencies often have worse propagation characteristics, especially through buildings, which reduces channel capacity by reducing the signal to noise ratio.
To get tens of watts from solid state in W-band yes you need either spatial or corporate (or both) combining of individual chips. So the amp ends up being of similar size to a mm-wave TWT but you don't need an expensive and large HV power supply or water cooling. Chip level output powers in GaAs I think have been done up to about 500mW, and 1-2W in GaN.
GaN for mm-wave still has some yield and reliability problems (pick at least one depending on supplier), and performance is not yet up to the ideal levels. But that's the same thing that GaN went through at lower frequencies, and mm-wave GaN is improving.
Solid state GaAs is slowly catching up to TWTAs at this frequency. They're not common but it is possible to buy a 30 watt solid state amplifier, probably for the same price you can get a TWTA that has a little bit more power. GaN still has lots of problems at this frequency but it's improving and will likely be competitive with tubes within 5-10 years.
But yes it seems like it would be much easier to do this at Ka band where solid state amps are now a better value than tubes for communication applications.
In addition to penetrating solids the range is challenging (or expensive anyway) just because of limited transmit power levels. Power is important because that gives you your range, your cell phone and home wireless router transmit up to about 1 watt. A 1 watt output solid-state power amplifier at this frequency would cost $5-10k, or at least that was the case about a year ago. This project seems to propose using travelling wave vacuum tube technology which provides lots of drive power (50-100 watts) but at a high price (over $100-250k).
What's wrong with kWh? For industrial processes that's a common energy unit.
It may confuse you but it doesn't confuse other people. In fact it makes more sense to most people since they have some frame of reference for how much energy a kWh but they don't have an intuitive frame of reference for Joules.
Do you know how many solar panels it takes to charge an electric car? You're basically looking at a football field's worth, each.
Ah, to be young and full of made up numbers. Let's do the math.
The large Tesla battery is 85kWh. A solar cell typically has an efficiency of 10-20%, so with about 5kWh/m^2/day of typical solar radiation (check PVWatts for specifics in your town you can produce about 0.5-1kWh/m^2 per day.
If we assume 15% charging losses it will take 100kWh to charge a Tesla battery, which will require 100 to 200 square meters to produce in one day. A football field has about 5300 square meters, so we could expect one football field of tightly packed solar panels to charge around 26 to 53 Tesla's per day.
Graphene in addition to the engineering challenges does have some very fundamental scientific challenges as well.
The most important challenge is its lack of a bandgap meaning that graphene transistors cannot be turned off. That drawback means that while it may have a ~500GHz cutoff frequency on par with silicon and below the InP records it will not modulate current in an energy-efficient way, and while it can create some forms of logic the lack of a bandgap limits its power amplifying frequency to a measly 50GHz, well below the competing technologies. Contrast that with Northrop Grumman's recent 1000GHz amplifier, which is admittedly not a great amplifier since it is run very near its cutoff frequency it has 1dB or less gain per stage, but it works which is still quite impressive.
So far the various methods that can give graphene a bandgap also take away the extremely fast electron transport properties that made graphene so interesting for electronics in the first place. Some of us working on competing technologies wonder why hundreds of millions of dollars have been spent on graphene transistor development without solving the fundamental bandgap problem - of course we just want that money directed to our own research, but some of us try to be realistic about the capabilities of what we are developing;-)
I'm sure graphene will be useful for some things but so far there are still some fundamental problems that need to be solved before using it for high-speed electronics for wireless applications or digital logic. We'll see how it does.
Implemented well it should have a slightly lower latency because the propagation of signals in air is faster than in fiber optics. But the delay from customer to the ISP is probably only a small part of the latency anyway.
Cynical much? One phone does not need to be all things to all people in order to be successful. Not all of us need cases on our smartphones: in my 4.5 years of smartphone usage and two smartphones I have yet to damage my uncased phones in any way.
Since you need a case on your smartphone you should buy a different one, others of us enjoy the beautiful design of a tiny bezel. But I hope to keep my phone at least another 1-2 years so I'm not in the market currently.
Why does the 3D printing matter? Some people do make ultra high frequency waveguide with 3D printing - in the case I'm familiar with they "printed" it on a stereolithgraphy machine out of a polymer, then gold plated all of the surfaces. It may have some applications for complex waveguide circuits which are not possible to make by other methods in a given size constraint. However, getting the plating thickness just right on such a small scale when you have to plate the inside of the long and super narrow waveguide tubes is difficult and conventional machining techniques are often faster and cheaper, and can have higher material quality than a printed or plated material.
The point of the Northrop Grumman work is that the circuit is integrated on a chip, so the waveguide interconnect will be relatively simple and simple objects can generally be made better, faster, and cheaper, by conventional techniques.
If that is the rationale, then the car needs to be 100% automated, under all circumstances, with all liability going to whoever made the damned thing.
I don't see why that would be necessary. Effectively you are saying that insurance over the lifetime of the vehicle should be factored into the purchase price instead of allowing people to buy insurance policies. That's not a bad idea but I don't think that it should be a requirement.
Instead this can be treated like any product: you buy an insurance policy to cover damages and go after the manufacturer in cases of negligent manufacturing or design flaws.
They claim to use far-field power transmission (i.e. radiated power) rather than near field inductive coupling. The transformer analogy only works for near-field transmission but it tends to be difficult to get range. Far-field will be radiating power all over the place.
If power is transmitted using near-field methods such as the direct inductive coupling used in RFID, most cell phone wireless chargers, and electric toothbrush chargers then the power transmission is coupled directly to the recipient device, and if the device is removed and the transmitter is still running then very little power is radiated away. This is potentially quite efficient. If you use far-field transmission then power is being radiated away whether a device is there to receive it or not. In order for it to be efficient you need high antenna gains to focus the power into a narrow beam the size of your receiver antenna aperture and beamforming to actively steer it. Otherwise the antenna is just spraying a broad beam of power in the general direction of the receiver like your sprinkler analogy.
They say it's using far-field transmission of power:
WattUp's RF transmission, which operates at 5.7MHz and 5.8MHz, is referred to in the industry as "far-field" wireless charging. Energous is not the first company to come up with the idea.
At such low frequencies it would be very hard for them to implement high gain antennas and beam forming. Also at such low frequencies I wonder how it can really be far field since the receiver will be well within a quarter wavelength of the transmitter.
More information is needed to fully answer the question, but this sounds like a convenience feature rather than an efficient one.
The blue LED may have been harder than the red LED for the reasons that you give, but Holonyak did make some key accomplishments including the demonstration of a ternary alloy semiconductor and tuning the bandgap and thus color by varying alloy composition which has paved the way for achieving all of the different colors for LEDs in use today and is also used for the InGaN emission layer in the blue LEDs.
An alloy semiconductor instead of having, for example, one group III and one group V element in perfect 50% ratio in a uniform crystal structure mixes it up and uses two or more group III elements and two or more group V elements. In the case of Holonyak he used two group V elements: Arsenic and Phosphorous. At the time at least some people did not think that an alloy semiconductor would even work, and it is a little weird because the crystal structure is now non-uniform where a given group V crystal site contains one element or the other at random. In fact this randomness does slow down the electrons. Holonyak also showed that the bandgap could be tuned by varying the relative concentrations of the group V elements. You can read more about him in a nice IEEE profile.
I don't know enough about the history to say who should have gotten the Nobel, but certainly no matter who they selected somebody would have been snubbed.
There isn't a limit of one prize per invention or discovery. The Physics and Chemistry Nobel prizes are frequently awarded decades after the original work was done.
The Nobel prize announcement did state that the significant impact of this invention was a factor in the selection. In addition to the huge commercial and societal impact of the work these researchers' work had a major scientific impact on the entire field of growth and properties of nitride semiconductors. LEDs are certainly the biggest application of nitride semiconductors but their work has also paved the way for nitride transistors in wireless and power electronics applications.
Yes, it's a very crude estimate, and more of a summertime number too here in the US.
In the US I would refer them to PV Watts which will take examine a database of historical solar data and tell you how much daily energy to expect through the year for different types of setups, even including solar panel fixed angle or angle tracking systems. But it will not take into account your point on the effect of diffuse light on concentrated systems.
It could also be 12kW peak, which with typical sunlight variation over a day would work out to around 60kWh per day.
Most of the time I see a non-technical article about solar with a kilowatt figure it's the peak power available from the cells, and as a first estimate you can multiply the peak solar power by 5 hours to get the daily output.
Slashdot Mirror
You haven't done the math or cited any.
There is a big efficiency problem in space-based solar with the double conversion from DC to RF/laser and back to DC. Total efficiency neglecting transmission loss is about 64% (80% twice). Then you have to invert it back to AC usually, but that is also needed for terrestrial solar.
So 35% power is thrown away, but since the sun is stronger in space without atmospheric attenuation, and there are no clouds, some of that will be made up.
So to a first approximation the power per unit of panel area is the same from space as it is on earth.
Now factor in launch costs which are tremendous (even if SpaceX succeeds in yet another 10x reduction in launch costs as claimed) and the difficulty performing maintenance in space versus on land, and I don't see a strong case. Installation costs on land are around $1/watt, I'd like to see you come within a factor of 10 of that in space.
In undoped semiconductor resistance will usually decrease as temperature is raised because a higher temperature excites more electrons into the conduction band where they can carry current.
But for cases where there is already a lot of charge the opposite usually applies. In something like a MOSFET the electrons are supplied by the source contact or in a doped bulk semiconductor there will be lots of charge from dopants. In these cases increasing the temperature doesn't significantly increase the charge. However raising the temperature does increase the electron scattering rate which reduces the electron mobility and slows electrons down, so the resistance actually increases.
Regulation of the coal industry is simply forcing the companies building and operating it to internalize the negative externalities. You can't do a fair analysis without considering the whole picture.
I'm all for exploring space, but the premise of mining the moon sounds pretty shaky and its totally fair for geeks to want realistic goals because that's what attracts sustainable capital investment from public and private sources that are needed to realize the goal. It's not a zero-sum game, but putting private and public money into crazy unworkable ideas takes some money away from realistic ideas.
Moon mining sounds to me a lot like orbital solar power - it sounds great and cool until you actually think for a moment and realize that it has very little to no net benefit per panel area compared to terrestrial solar after you transmit the power back to earth, and the cost is astronomical to boot. What is the benefit of mining the moon aside from sounding cool? It doesn't seem like there's a particularly high concentration of any of these purported mineral riches and with the expense of mining the material in space I'm highly suspicious of it being in any way economical after shipping back to Earth. He-3 is a bust since there's currently no major use for it. Maybe moon mining would be viable for obtaining materials on the moon without launch costs, but the supposed mineral riches are mostly high priced specialty materials and not the boring metals like iron and aluminum that would be needed for building a spaceship or lunar colony.
Some of us like to support our dreams with back of the envelope analyses to ensure viability before getting too invested in them.
While possible, it could also be something mundane like failure of station-keeping thrusters.
Nope, reread your link. Channel capacity (at a given signal to noise ratio) is proportional to bandwidth alone. 1.000GHz to 1.065GHz is as good as 20.000GHz to 20.065GHz.
But as you say higher frequencies often have worse propagation characteristics, especially through buildings, which reduces channel capacity by reducing the signal to noise ratio.
To get tens of watts from solid state in W-band yes you need either spatial or corporate (or both) combining of individual chips. So the amp ends up being of similar size to a mm-wave TWT but you don't need an expensive and large HV power supply or water cooling. Chip level output powers in GaAs I think have been done up to about 500mW, and 1-2W in GaN.
GaN for mm-wave still has some yield and reliability problems (pick at least one depending on supplier), and performance is not yet up to the ideal levels. But that's the same thing that GaN went through at lower frequencies, and mm-wave GaN is improving.
Solid state GaAs is slowly catching up to TWTAs at this frequency. They're not common but it is possible to buy a 30 watt solid state amplifier, probably for the same price you can get a TWTA that has a little bit more power. GaN still has lots of problems at this frequency but it's improving and will likely be competitive with tubes within 5-10 years.
But yes it seems like it would be much easier to do this at Ka band where solid state amps are now a better value than tubes for communication applications.
In addition to penetrating solids the range is challenging (or expensive anyway) just because of limited transmit power levels. Power is important because that gives you your range, your cell phone and home wireless router transmit up to about 1 watt. A 1 watt output solid-state power amplifier at this frequency would cost $5-10k, or at least that was the case about a year ago. This project seems to propose using travelling wave vacuum tube technology which provides lots of drive power (50-100 watts) but at a high price (over $100-250k).
What's wrong with kWh? For industrial processes that's a common energy unit.
It may confuse you but it doesn't confuse other people. In fact it makes more sense to most people since they have some frame of reference for how much energy a kWh but they don't have an intuitive frame of reference for Joules.
Ah, to be young and full of made up numbers. Let's do the math.
The large Tesla battery is 85kWh. A solar cell typically has an efficiency of 10-20%, so with about 5kWh/m^2/day of typical solar radiation (check PVWatts for specifics in your town you can produce about 0.5-1kWh/m^2 per day.
If we assume 15% charging losses it will take 100kWh to charge a Tesla battery, which will require 100 to 200 square meters to produce in one day. A football field has about 5300 square meters, so we could expect one football field of tightly packed solar panels to charge around 26 to 53 Tesla's per day.
Graphene in addition to the engineering challenges does have some very fundamental scientific challenges as well.
The most important challenge is its lack of a bandgap meaning that graphene transistors cannot be turned off. That drawback means that while it may have a ~500GHz cutoff frequency on par with silicon and below the InP records it will not modulate current in an energy-efficient way, and while it can create some forms of logic the lack of a bandgap limits its power amplifying frequency to a measly 50GHz, well below the competing technologies. Contrast that with Northrop Grumman's recent 1000GHz amplifier, which is admittedly not a great amplifier since it is run very near its cutoff frequency it has 1dB or less gain per stage, but it works which is still quite impressive.
So far the various methods that can give graphene a bandgap also take away the extremely fast electron transport properties that made graphene so interesting for electronics in the first place. Some of us working on competing technologies wonder why hundreds of millions of dollars have been spent on graphene transistor development without solving the fundamental bandgap problem - of course we just want that money directed to our own research, but some of us try to be realistic about the capabilities of what we are developing ;-)
I'm sure graphene will be useful for some things but so far there are still some fundamental problems that need to be solved before using it for high-speed electronics for wireless applications or digital logic. We'll see how it does.
Check your own grammar before pointing out somebody else's mistake. ;-)
Implemented well it should have a slightly lower latency because the propagation of signals in air is faster than in fiber optics. But the delay from customer to the ISP is probably only a small part of the latency anyway.
Cynical much? One phone does not need to be all things to all people in order to be successful. Not all of us need cases on our smartphones: in my 4.5 years of smartphone usage and two smartphones I have yet to damage my uncased phones in any way.
Since you need a case on your smartphone you should buy a different one, others of us enjoy the beautiful design of a tiny bezel. But I hope to keep my phone at least another 1-2 years so I'm not in the market currently.
Why does the 3D printing matter? Some people do make ultra high frequency waveguide with 3D printing - in the case I'm familiar with they "printed" it on a stereolithgraphy machine out of a polymer, then gold plated all of the surfaces. It may have some applications for complex waveguide circuits which are not possible to make by other methods in a given size constraint. However, getting the plating thickness just right on such a small scale when you have to plate the inside of the long and super narrow waveguide tubes is difficult and conventional machining techniques are often faster and cheaper, and can have higher material quality than a printed or plated material.
The point of the Northrop Grumman work is that the circuit is integrated on a chip, so the waveguide interconnect will be relatively simple and simple objects can generally be made better, faster, and cheaper, by conventional techniques.
No, the electron transport in vacuum tubes is in a vacuum. Vacuum is not a solid.
I don't see why that would be necessary. Effectively you are saying that insurance over the lifetime of the vehicle should be factored into the purchase price instead of allowing people to buy insurance policies. That's not a bad idea but I don't think that it should be a requirement.
Instead this can be treated like any product: you buy an insurance policy to cover damages and go after the manufacturer in cases of negligent manufacturing or design flaws.
They claim to use far-field power transmission (i.e. radiated power) rather than near field inductive coupling. The transformer analogy only works for near-field transmission but it tends to be difficult to get range. Far-field will be radiating power all over the place.
If power is transmitted using near-field methods such as the direct inductive coupling used in RFID, most cell phone wireless chargers, and electric toothbrush chargers then the power transmission is coupled directly to the recipient device, and if the device is removed and the transmitter is still running then very little power is radiated away. This is potentially quite efficient. If you use far-field transmission then power is being radiated away whether a device is there to receive it or not. In order for it to be efficient you need high antenna gains to focus the power into a narrow beam the size of your receiver antenna aperture and beamforming to actively steer it. Otherwise the antenna is just spraying a broad beam of power in the general direction of the receiver like your sprinkler analogy.
They say it's using far-field transmission of power:
At such low frequencies it would be very hard for them to implement high gain antennas and beam forming. Also at such low frequencies I wonder how it can really be far field since the receiver will be well within a quarter wavelength of the transmitter.
More information is needed to fully answer the question, but this sounds like a convenience feature rather than an efficient one.
You take one Ampere-second (i.e. 1 Coulomb) of electrons per second, and accelerate them.
The blue LED may have been harder than the red LED for the reasons that you give, but Holonyak did make some key accomplishments including the demonstration of a ternary alloy semiconductor and tuning the bandgap and thus color by varying alloy composition which has paved the way for achieving all of the different colors for LEDs in use today and is also used for the InGaN emission layer in the blue LEDs.
An alloy semiconductor instead of having, for example, one group III and one group V element in perfect 50% ratio in a uniform crystal structure mixes it up and uses two or more group III elements and two or more group V elements. In the case of Holonyak he used two group V elements: Arsenic and Phosphorous. At the time at least some people did not think that an alloy semiconductor would even work, and it is a little weird because the crystal structure is now non-uniform where a given group V crystal site contains one element or the other at random. In fact this randomness does slow down the electrons. Holonyak also showed that the bandgap could be tuned by varying the relative concentrations of the group V elements. You can read more about him in a nice IEEE profile.
I don't know enough about the history to say who should have gotten the Nobel, but certainly no matter who they selected somebody would have been snubbed.
There isn't a limit of one prize per invention or discovery. The Physics and Chemistry Nobel prizes are frequently awarded decades after the original work was done.
The Nobel prize announcement did state that the significant impact of this invention was a factor in the selection. In addition to the huge commercial and societal impact of the work these researchers' work had a major scientific impact on the entire field of growth and properties of nitride semiconductors. LEDs are certainly the biggest application of nitride semiconductors but their work has also paved the way for nitride transistors in wireless and power electronics applications.
Yes, it's a very crude estimate, and more of a summertime number too here in the US.
In the US I would refer them to PV Watts which will take examine a database of historical solar data and tell you how much daily energy to expect through the year for different types of setups, even including solar panel fixed angle or angle tracking systems. But it will not take into account your point on the effect of diffuse light on concentrated systems.
It could also be 12kW peak, which with typical sunlight variation over a day would work out to around 60kWh per day.
Most of the time I see a non-technical article about solar with a kilowatt figure it's the peak power available from the cells, and as a first estimate you can multiply the peak solar power by 5 hours to get the daily output.