So called Brushless DC motors are actually permanent magnet rotor, synchronous AC motors?
They are virtually identical, yes. There might be some nuanced differences in their physical construction or drive (sinusoidal vs trapezoidal waveform, for example) but the operational principle is the same.
For fractional horsepower motors there's no cost-benefit to doing sophisticated controls in most cases. You just need it to turn on and off at one, sometimes two or three speeds and the load is more or less constant. I wouldn't expect that to change any time soon. =Smidge=
Flywheels can be charged up lots faster than batteries.
That depends entirely on the design of the flywheel/battery. But you know what flywheels do better than batteries? Leak. An idle flywheel will lose energy much faster than an idle battery.
Supercapacitors are neat but have the worst volumetric energy efficiency of then all. =Smidge=
But for the cost and weight, a battery is better than a flywheel in essentially every aspect. For however much you reduce the required size of a flywheel, you can reduce the battery size as well.
Battery systems are damn close to 100% efficient if you're not too close to fully charged or fully discharged, or not diving the current much higher than 1.0C.
There is no advantage to using a flywheel at all. None. =Smidge=
In 2013, the average price for a new car was $32K. Many EVs available right now are below that even *before* any state or federal incentives, and many more hit that point after incentives.
Meanwhile, the average price for a used car was $16.8K. I don't know where you'd get a sub-$10K used vehicle from a reputable source (versus a cash transaction in someone's driveway...) =Smidge=
Consider replacing the electric commuter-car battery with a flywheel. We have the tech to do this for ranges of 50 miles or so.
Why would you, though? Flywheels have atrocious energy densities.
We should be thinking about replacing batteries with "fuel cells", because, like hydrocarbon engines, only fuel (most agree hydrogen is best) needs to be carried around, and the waste (H2O) can be dumped.
Wrong. A fuel cell car also needs a sizable battery, because a fuel cell capable of providing sufficient output for acceptable performance would be massive and expensive. A battery needs to be included to provide the peak power and the fuel cell basically acts as an on board generator to keep it topped off.
And given that, it's a waste. For all the solar energy you collected to make and process the hydrogen, you could have put that directly into an EV's battery and come out way ahead. =Smidge=
if you're going to have an internal module that "generates whatever voltages are needed" then you're just going through the conversions again, and you're saving nothing on efficiency (and losing a lot on costs).
The only way it'll work is if the DC input, eg solar panels, is matched to the unit's requirements. Anything other than that and you're just running in circles. =Smidge=
Of course you can power everything with heat. Indeed, nearly everything *is* powered with heat; Most conventional power plants use thermal processes, converting heat energy into mechanical energy then into electrical energy.
A solar powered refrigerator (or any refrigeration cycle driven directly by heat) allows the use of fairly low quality heat sources to do useful work without losses converting it to electricity first. Very useful in some circumstances. =Smidge=
And yet, in practice, HVDC is still more efficient than current AC lines in the end, even if still somewhat more expensive at the moment.
Yes and no.
AC power is far more efficient at higher voltage and short to medium distances, and you save a lot of material (and thus money) on conductor sizes. The voltage can be changed easily and it is safer and easier to switch on and off since there's 50 or 60 times per second where the voltage/current is zero - allowing for the circuit to be opened without arcing or inductive voltage spikes. AC arcs also tend to be self-extinguishing for this reason.
But AC systems also have inductance and capacitance to deal with. For very high power, very long distance runs, the capacitive losses start to add up. More current is required to charge/discharge this inherent capacitance, which means more power losses. This is where HVDC really shines. =Smidge=
More and more commercial AC equipment is moving to variable frequency drive compressors for efficiency, so if you can provide sufficient DC current at the necessary voltage to can shave a few percent off of the conversion losses.
That took all of 5 seconds on Google. That's FY2013 but it's hard to imagine anything significant changed for FY2014.
Reports similar to this are available for just about every government agency. The budget omnibus that congress passes is a matter of public record as is the requests that each government agency submits (which the budget omnibus is based on).
Of course they aren't going to just mail these reports to you on a subscription basis - you actually have to get off your ass and find them or... god forbid... ask for them! =Smidge=
Fake acupuncture, where the skin isn't penetrated at all, was found to be much more effective than real penetrative acupuncture and acupuncture improperly applied (needles in the "wrong" locations).
And the tests were done on human volunteers. Citations in the video description. =Smidge=
And it's not just replacing current electrical generation - there would probably have to be a two or three ORDER OF MAGNITUDE expansion of electrical generation capacity.
So at the absolute WORST case, it's a little more than double. But when you figure that an electric vehicle uses that energy nearly three times more efficiently, it's under 50% more.
And that's if you go ahead and replace *everything* that burns gasoline with electric, which of course you wouldn't.
Then after all that, producing ~50% more kWh does not translate into needing ~50% more power plants. You would need to factor in some diversity factor as not all power plants are running all the time nor at full capacity. =Smidge=
Written like someone who's old, bitter and crippled.
So what? The able-bodied people will fill those cars, because there will be fewer passengers in them at the start. And if it's really bad there is already priority seating for people with mobility problems, which is enforced by the train staff. =Smidge=
It's not easy to add cars because you'd have to extend existing platforms to accommodate longer trains, which is usually expensive and time consuming.
It IS possible to move between cars once you're on the train, you know, and from my experience with taking the train to and from NYC, some people seem willing to walk the entire length of the train in search of a seat that doesn't have anyone sitting next to them.
There's even two stops on the line I take where the platform isn't long enough, and there's an announcement explaining that long in advance in addition to the warning being on the schedule itself. At one station the last two cars do not platform, at the other ONLY the last two cars platform.
Not to say there isn't an upper limit to the number of cars you can have, but you can easily have like six cars more than the platform can handle assuming there's another room otherwise. Walking three cars isn't terribly difficult and doesn't take a lot of time. =Smidge=
The tune was written to avoid said copyright, and the writer (Mike Jittlov) allows anyone to use it royalty-free. I don't think it's been properly licensed as such, though, since CC didn't exist at the time. =Smidge=
I've simulated this exact scenario for hours, and I've gotten the same results from this study; moderate increase in usage but not enough to really address inner-city congestion.
They probably spent hundreds of thousands of dollars on their study, too - this only cost me $20 during the Steam Summer Sale. Stupid government! =Smidge=
You evidently didn't read the last line in TFS. FOIAs aren't free to file.
Your UserID is low enough to know that TFS is often dead wrong.
FOIA law does not specify any fees, but it allows each agency to establish its own fee structure for filling requests.
Generally speaking, if filling the request takes minimal effort, there's no fee. This has always been true (in my limited experience) for electronic copies of electronic records; if all someone has to do is copy a file or whatever, no problem.
If you're going to start requesting printed copies of records, they're likely to start charging you at some point. A few pages probably isn't too bad, but the idea is to prevent some jerk from tying up the system asking for 50,000 prints from microfiche archives and not having to invest anything in such a request. Usually the fee is in line with expected costs (e.g. 10-15 cents per page or whatever, plus hourly rate for a worker to do it.)
If your local government whatever is charging a fee simply for filing a request, let alone providing the data, you might have a case for a lawsuit. =Smidge=
But in the dirty air model, the dark veil over the plain soaked up much of the sun's warmth high in the atmosphere, while simultaneously cooling the streets and fields below. This altered thermal structure stabilized the daytime atmosphere and suppressed rainfall.
But as night fell, the moist air mass moved northward toward the Longmen Mountains, which tower some 2000 meters above the basin. The weather system that had been building energy over the plains for 12 hours was driven upward as it collided with the range's steep contours, triggering the postponed convection. A day's worth of rainfall from the plains was focused into a few hours over a handful of mountain valleys.
I know, I know... "Read the article" blah blah... =Smidge=
The [lack of] precision in the bearings is much more significant than angular precision.
You solve that with better manufacturing techniques.
Harmonic drives are already used industrially and commercially. This is essentially a double harmonic drive driven with a planetary gearset. Nothing some good precision manufacturing couldn't create something amazing with. =Smidge=
Until you encounter a steep set of stairs, then simple wheels might not be sufficient. You'll either have to develop special wheels or tracks - which might not be that great at other non-stair-like terrain - or try a more universal mode of locomotion.
Ever see those photos of mountain goats climbing the nearly sheer face of a dam? I'd love to see a wheeled robot do that without grappling lines! =Smidge=
Slashdot Mirror
So called Brushless DC motors are actually permanent magnet rotor, synchronous AC motors?
They are virtually identical, yes. There might be some nuanced differences in their physical construction or drive (sinusoidal vs trapezoidal waveform, for example) but the operational principle is the same.
For fractional horsepower motors there's no cost-benefit to doing sophisticated controls in most cases. You just need it to turn on and off at one, sometimes two or three speeds and the load is more or less constant. I wouldn't expect that to change any time soon.
=Smidge=
...why would we replace the grid?
=Smidge=
Flywheels can be charged up lots faster than batteries.
That depends entirely on the design of the flywheel/battery. But you know what flywheels do better than batteries? Leak. An idle flywheel will lose energy much faster than an idle battery.
Supercapacitors are neat but have the worst volumetric energy efficiency of then all.
=Smidge=
But for the cost and weight, a battery is better than a flywheel in essentially every aspect. For however much you reduce the required size of a flywheel, you can reduce the battery size as well.
Battery systems are damn close to 100% efficient if you're not too close to fully charged or fully discharged, or not diving the current much higher than 1.0C.
There is no advantage to using a flywheel at all. None.
=Smidge=
In 2013, the average price for a new car was $32K. Many EVs available right now are below that even *before* any state or federal incentives, and many more hit that point after incentives.
Meanwhile, the average price for a used car was $16.8K. I don't know where you'd get a sub-$10K used vehicle from a reputable source (versus a cash transaction in someone's driveway...)
=Smidge=
Consider replacing the electric commuter-car battery with a flywheel. We have the tech to do this for ranges of 50 miles or so.
Why would you, though? Flywheels have atrocious energy densities.
We should be thinking about replacing batteries with "fuel cells", because, like hydrocarbon engines, only fuel (most agree hydrogen is best) needs to be carried around, and the waste (H2O) can be dumped.
Wrong. A fuel cell car also needs a sizable battery, because a fuel cell capable of providing sufficient output for acceptable performance would be massive and expensive. A battery needs to be included to provide the peak power and the fuel cell basically acts as an on board generator to keep it topped off.
And given that, it's a waste. For all the solar energy you collected to make and process the hydrogen, you could have put that directly into an EV's battery and come out way ahead.
=Smidge=
if you're going to have an internal module that "generates whatever voltages are needed" then you're just going through the conversions again, and you're saving nothing on efficiency (and losing a lot on costs).
The only way it'll work is if the DC input, eg solar panels, is matched to the unit's requirements. Anything other than that and you're just running in circles.
=Smidge=
Of course you can power everything with heat. Indeed, nearly everything *is* powered with heat; Most conventional power plants use thermal processes, converting heat energy into mechanical energy then into electrical energy.
A solar powered refrigerator (or any refrigeration cycle driven directly by heat) allows the use of fairly low quality heat sources to do useful work without losses converting it to electricity first. Very useful in some circumstances.
=Smidge=
And yet, in practice, HVDC is still more efficient than current AC lines in the end, even if still somewhat more expensive at the moment.
Yes and no.
AC power is far more efficient at higher voltage and short to medium distances, and you save a lot of material (and thus money) on conductor sizes. The voltage can be changed easily and it is safer and easier to switch on and off since there's 50 or 60 times per second where the voltage/current is zero - allowing for the circuit to be opened without arcing or inductive voltage spikes. AC arcs also tend to be self-extinguishing for this reason.
But AC systems also have inductance and capacitance to deal with. For very high power, very long distance runs, the capacitive losses start to add up. More current is required to charge/discharge this inherent capacitance, which means more power losses. This is where HVDC really shines.
=Smidge=
More and more commercial AC equipment is moving to variable frequency drive compressors for efficiency, so if you can provide sufficient DC current at the necessary voltage to can shave a few percent off of the conversion losses.
=Smidge=
having said that, WHY isnt there a breakdown, line item, for all costs that our government spends?
There is, but you're clearly too lazy to look for it and almost certainly too lazy to actually read through it.
http://www.si.edu/content/pdf/...
That took all of 5 seconds on Google. That's FY2013 but it's hard to imagine anything significant changed for FY2014.
Reports similar to this are available for just about every government agency. The budget omnibus that congress passes is a matter of public record as is the requests that each government agency submits (which the budget omnibus is based on).
Of course they aren't going to just mail these reports to you on a subscription basis - you actually have to get off your ass and find them or... god forbid... ask for them!
=Smidge=
The only expectation is that it works better than placebo. It doesn't even do that.
=Smidge=
https://www.youtube.com/watch?...
Fake acupuncture, where the skin isn't penetrated at all, was found to be much more effective than real penetrative acupuncture and acupuncture improperly applied (needles in the "wrong" locations).
And the tests were done on human volunteers. Citations in the video description.
=Smidge=
And it's not just replacing current electrical generation - there would probably have to be a two or three ORDER OF MAGNITUDE expansion of electrical generation capacity.
100 to 1000 times more electricity? Really?
2014: 136.78 billion gallons of gasoline consumed.
At 33 kWhr/gallon, that's 4,514 billion kWh if you completely ignore any differences in efficiency.
2014: 4,093 billion kWh of electricity produced.
So at the absolute WORST case, it's a little more than double. But when you figure that an electric vehicle uses that energy nearly three times more efficiently, it's under 50% more.
And that's if you go ahead and replace *everything* that burns gasoline with electric, which of course you wouldn't.
Then after all that, producing ~50% more kWh does not translate into needing ~50% more power plants. You would need to factor in some diversity factor as not all power plants are running all the time nor at full capacity.
=Smidge=
Written like someone who's old, bitter and crippled.
So what? The able-bodied people will fill those cars, because there will be fewer passengers in them at the start. And if it's really bad there is already priority seating for people with mobility problems, which is enforced by the train staff.
=Smidge=
It's not easy to add cars because you'd have to extend existing platforms to accommodate longer trains, which is usually expensive and time consuming.
It IS possible to move between cars once you're on the train, you know, and from my experience with taking the train to and from NYC, some people seem willing to walk the entire length of the train in search of a seat that doesn't have anyone sitting next to them.
There's even two stops on the line I take where the platform isn't long enough, and there's an announcement explaining that long in advance in addition to the warning being on the schedule itself. At one station the last two cars do not platform, at the other ONLY the last two cars platform.
Not to say there isn't an upper limit to the number of cars you can have, but you can easily have like six cars more than the platform can handle assuming there's another room otherwise. Walking three cars isn't terribly difficult and doesn't take a lot of time.
=Smidge=
Already done, decades ago:
https://www.youtube.com/watch?...
The tune was written to avoid said copyright, and the writer (Mike Jittlov) allows anyone to use it royalty-free. I don't think it's been properly licensed as such, though, since CC didn't exist at the time.
=Smidge=
I've simulated this exact scenario for hours, and I've gotten the same results from this study; moderate increase in usage but not enough to really address inner-city congestion.
They probably spent hundreds of thousands of dollars on their study, too - this only cost me $20 during the Steam Summer Sale. Stupid government!
=Smidge=
You evidently didn't read the last line in TFS. FOIAs aren't free to file.
Your UserID is low enough to know that TFS is often dead wrong.
FOIA law does not specify any fees, but it allows each agency to establish its own fee structure for filling requests.
Generally speaking, if filling the request takes minimal effort, there's no fee. This has always been true (in my limited experience) for electronic copies of electronic records; if all someone has to do is copy a file or whatever, no problem.
If you're going to start requesting printed copies of records, they're likely to start charging you at some point. A few pages probably isn't too bad, but the idea is to prevent some jerk from tying up the system asking for 50,000 prints from microfiche archives and not having to invest anything in such a request. Usually the fee is in line with expected costs (e.g. 10-15 cents per page or whatever, plus hourly rate for a worker to do it.)
If your local government whatever is charging a fee simply for filing a request, let alone providing the data, you might have a case for a lawsuit.
=Smidge=
But in the dirty air model, the dark veil over the plain soaked up much of the sun's warmth high in the atmosphere, while simultaneously cooling the streets and fields below. This altered thermal structure stabilized the daytime atmosphere and suppressed rainfall.
But as night fell, the moist air mass moved northward toward the Longmen Mountains, which tower some 2000 meters above the basin. The weather system that had been building energy over the plains for 12 hours was driven upward as it collided with the range's steep contours, triggering the postponed convection. A day's worth of rainfall from the plains was focused into a few hours over a handful of mountain valleys.
I know, I know... "Read the article" blah blah...
=Smidge=
The [lack of] precision in the bearings is much more significant than angular precision.
You solve that with better manufacturing techniques.
Harmonic drives are already used industrially and commercially. This is essentially a double harmonic drive driven with a planetary gearset. Nothing some good precision manufacturing couldn't create something amazing with.
=Smidge=
In fact, having wheels is a feature, not a bug.
Until you encounter a steep set of stairs, then simple wheels might not be sufficient. You'll either have to develop special wheels or tracks - which might not be that great at other non-stair-like terrain - or try a more universal mode of locomotion.
Ever see those photos of mountain goats climbing the nearly sheer face of a dam? I'd love to see a wheeled robot do that without grappling lines!
=Smidge=
Or maybe the real advantage lies not with torque multiplication, but reduction of movement.
Precise angular displacements of down to a billionth of a degree, at a scale you don't need an electron microscope to see.
=Smidge=
https://www.youtube.com/watch?...
Actual machinist doing some destruction testing on a 3D printed part. $2200 printer is not "10-20 times" the cost of a cheap mill either.
=Smidge=
Bad news - look under the hood of your car sometimes. Quite a few components have the ABS recycling number on them.
=Smidge=