Why Is DC Power Transmission 10X More Efficient Than AC?

A googlie netcop! ROFLMAOPIMP!!!!

Cheers! Rich

"Inverters" convert DC to AC.

Not directly. Voltage dividers/multipliers are notoriously inefficient ("lossy"), but via the sequence "inverter -> transformer -

Tom Davidson Richmond, VA

At the source end of DC transmission lines, polyphase transformer-rectifier circuits convert the AC to high-voltage DC.

At the load end, the DC must be converted back to AC, using "inverters".

It's easy to google stuff like this, instead of relying on old memories.

John

In sci.physics, Phil Allison

wrote on Wed, 23 Apr 2008 07:32:37 +1000 :

Presumably, 99.2%. The loss for 92% efficiency is 8%; reducing that loss by a factor of 10 generates 0.8%.

I do wonder. We were born about a century too late; Tesla and Edison produced various papers and/or actions (including electrocutions!) based on AC (Tesla) and DC (Edison).

Tesla won, as it turns out.

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The 8% figure is an average and an arbitrary one at that.

The only reason the 92% efficiency figure appeared is because electric power just isn't shipped thousands of miles when it is cheaper to build plants in every town and ship the fuel instead.

The situation changes if a power plant needs to be in a very remote location like the Sahara. To ship the solar thermal back to N. Europe would waste 1/2 the energy using HVAC.

This is no thread for bean counters. If it isn't a significant improvement then you can be sure I'm not interested in it.

Even HVDC transmission requires AC at the terminals.

Supposedly Edison, not the greatest theortical physicist, thought that AC wouldn't work or work as well with his incandescent light bulbs.

Supposedly Edison once asked the Serb if he ever ate human flesh but that might have been a joke.

They hated each other.

Bret Cahill

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| > "Dope Bowey" | >

| > "JeffM" | >

| >>> Bret Cahill wrote: | >>> :10X More Efficient | >>>

| >>> Cite your sources for 920% efficiency. | >>

| >> Cite where you think he said that. It's not in this thread. | >

| >

| > ** What is 10 times more efficient than 92 % ?? | >

| > 920% ? | | Presumably, 99.2%. The loss for 92% efficiency | is 8%; reducing that loss by a factor of 10 | generates 0.8%. | | >

| > The OP's question is an absurd troll. | >

| > Like you. | | I do wonder. We were born about a century too late; | Tesla and Edison produced various papers and/or actions | (including electrocutions!) based on AC (Tesla) and DC | (Edison). | | Tesla won, as it turns out.

If you have a high voltage then you can use less current and you only need a small conductor ... but then you need to step it down again for safety in domestic applications. The transformer and AC makes it all possible. Edison's DC was not a option, there are no DC transformers (or AC batteries) - besides which a DC generator needs an expensive commutator.

Solar thermal isn't electricity, it's heat. I assume you mean PV solar.

Why do you think that ? Is there any scientific rationale for it ?

Graham

I think it's a solar trough vapor cycle. Anyway a turbine drives an alternator in the desert. The voltage is stepped up, rectified, probably filtered and transmitted to Finland by HVDC where it is inverted back to ac.

Do the math. If 8% is lost every 200 km using HVAC, then 0.92^8 is lost going 1600 km.

Bret Cahill

It's not. Since what your talking about circulating current losses, not power losses. Which is why the people who understand the problem invented digital computers, artifical intelligence, fiber optics, lasers, laser disks and robots to solve the problem, rather than more jerks like science light bulb crtics.

"The Ghost In The Machine TROLL "

** ???????????????

Absurd gobbledgook.

........ Phil

I'm sure Edison, or one of his employees, tested incandescent lamps on AC. Edison's real problem with AC was a monumental case of "Not Invented Here!"

Note that high-voltage DC transmission had to wait for the development of efficient gas-tube and then solid-state inverters. It just wasn't practical on a large scale when the only way to make AC from DC was a motor-generator set.

DC generators with commutators are 19th century technology. Solid state converters and inverters are essentially DC transformers, but would have been only wet dreams to Edison and Tesla. It may be that Tesla was the winner (although not financially and emotionally), but Edison may prove to be the winner by a few percentage points as solid state technology becomes cheaper and more efficient.

High voltage is more efficient and practical because insulation is much cheaper and lighter weight than copper, silver, aluminum, or other good conductors. And superconductors are not practical for really long transmission. AC at high voltage will have some losses due to radiation, inductance, capacitance, and phase shift, as well as resistance, corona and insulator leakage, which affect both AC and DC. A balanced three phase, 3 wire system transfers 50% more power than a two wire DC system with the same size wires, and the same voltage to ground, but the AC system will have inductive and capacitive losses, requires 40% better insulation to handle peaks, and may have shorter insulator life due to capacitive current. Also, the AC system is often not well balanced, which puts extra load on one of the conductors and consequently higher losses.

A DC system can also use the earth (possibly with a smaller buried conductor) for a return path, which shifts efficiency in its favor as compared to AC.

But maybe Tesla will prove to be the ultimate winner if his methods of transmitting power by means of atmospheric and earth resonance ever prove to be practical and safe.

Paul

d

Well, in he already is in that sense. Since earth resonance is just self-fullfilling prophecy, and the only reason it's even still persued, is because power scientists are nothing historic asswipes. Which is mostly why GPS and Cruise Missiles were invented to solve their idiot Telsa ve Edison problem.

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| > "The Ghost In The Machine" wrote in | > message | > news: snipped-for-privacy@sirius.tg0suus7038.net... | > | | > | I do wonder. We were born about a century too late; | > | Tesla and Edison produced various papers and/or actions | > | (including electrocutions!) based on AC (Tesla) and DC | > | (Edison). | > | | > | Tesla won, as it turns out. | >

| >

| > If you have a high voltage then you can use less current and | > you only need a small conductor ... but then you need to | > step it down again for safety in domestic applications. | > The transformer and AC makes it all possible. Edison's DC | > was not a option, there are no DC transformers (or AC | > batteries) - besides which a DC generator needs an expensive | > commutator. | | DC generators with commutators are 19th century technology.

My goodness... you are right, how could I have missed that? And Edison lived when?

| Solid state | converters and inverters are essentially DC transformers, but would have | been only wet dreams to Edison and Tesla. It may be that Tesla was the | winner (although not financially and emotionally), but Edison may prove to | be the winner by a few percentage points as solid state technology becomes | cheaper and more efficient.

Take down the wires between the pylons and beam the energy across country using masers, huh? And for the next wet dream we'll have big mirrors in space focussing sunlight on Antarctica to terra-form it, melt that damned ice and show those tree huggers some new trees to cuddle up to while we get on with a bit of rape and plunder of the mineral wealth there. All the crap about global warming and we've a whole continent to explore. Too much water? Syphon some off and leave it on the Moon. All it takes is energy and the Sun has more than enough.

| | High voltage is more efficient and practical because insulation is much | cheaper and lighter weight than copper, silver, aluminum, or other good | conductors.

Oh, I didn't know HV power lines were insulated...

| And superconductors are not practical for really long | transmission.

Superconductors are only a wet dream to Edison and Tesla.

| AC at high voltage will have some losses due to radiation, | inductance, capacitance, and phase shift, as well as resistance, corona and | insulator leakage, which affect both AC and DC.

Losses due to phase shift, huh? Power factor correction wasn't an Edison and Tesla wet dream, was it?

| A balanced three phase, 3 | wire system transfers 50% more power than a two wire DC system with the | same size wires, and the same voltage to ground, but the AC system will | have inductive and capacitive losses, requires 40% better insulation to | handle peaks, and may have shorter insulator life due to capacitive | current.

Capacitive losses? They get hot, those nasty capacitors...

| Also, the AC system is often not well balanced, which puts extra | load on one of the conductors and consequently higher losses. | A DC system can also use the earth (possibly with a smaller buried | conductor) for a return path, which shifts efficiency in its favor as | compared to AC.

That sounds like an Edison wet dream to me. Just connect to the steel frame of the building and the copper pipes from the bathtub. Very useful for fluorescent lights, I'm sure.

| But maybe Tesla will prove to be the ultimate winner if his methods of | transmitting power by means of atmospheric and earth resonance ever prove | to be practical and safe. | Got any more wet dreams for us? There is no "ultimate", we go with what we have... NOW. And the process will continue to evolve until it blows up in all our faces.

Man, as a species, has survived without technology for 2-3 million years. What science and technology have done is caused massive overpopulation. That CANNOT continue. We live in the Golden Age preceding the mighty crash that will be as dark an age as the demise of the dinosaur, and we are doing it to ourselves.

The lines themselves are not insulated, but they are suspended on insulting bushings, and of course air itself is an insulator.

Insulators have their own capacitance, and power factor correction capacitors have some losses from ESR. Also, their cost of procurement and maintenance need to be factored into the overall efficiency.

It's already being done for some transmission lines. But I would not advocate earth ground return path for distribution.

Now that is something with which I can at least partially agree. We, the "enlightened" people of the industrial and technological age, are exerting unprecedented stresses on our fragile biosphere, and a privileged and greedy few are reaping temporary financial benefits from human activities that simply cannot continue on a sustainable basis. The world population continues to rise, and much of that increase is composed of individuals who are genetically and behaviorally challenged so that they reperesent more of a burden than an asset in the grand scheme of things. Dogmatic religions oppose any sort of limitations or social engineering, yet will not take direct responsibility for the continued supervision, care, and protective containment of those who make negative contributions to the advancement of civilization. And business models and economic metrics require ever increasing growth as a requirement for success, which encourages conspicuous consumption, planned obsolescence, depletion of resources, and waste of energy.

The long-bearded old weirdo in robes has been professing that "The end is near", and perhaps that is becoming more of a reality that we could see in our lifetimes.

Paul

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| > "Paul E. Schoen" wrote in message | > news:4813cc89$0$19806$ snipped-for-privacy@news.coretel.net... | > | | > | High voltage is more efficient and practical because insulation is much | > | cheaper and lighter weight than copper, silver, aluminum, or other good | > | conductors. | >

| >

| > Oh, I didn't know HV power lines were insulated... | | The lines themselves are not insulated, but they are suspended on insulting | bushings,

Which are cheaper and lighter weight than aluminium or other good conductors?

| and of course air itself is an insulator.

Now that raises an interesting question. In a CRT the electron beam passes through vacuum ( a conductor, of course), so let air in and it's a DC insulator (of course). But is it an AC insulator?

| | >

| > | AC at high voltage will have some losses due to radiation, | > | inductance, capacitance, and phase shift, as well as resistance, corona | > | and insulator leakage, which affect both AC and DC. | >

| > Losses due to phase shift, huh? Power factor correction wasn't | > an Edison and Tesla wet dream, was it? | >

| > | A balanced three phase, 3 | > | wire system transfers 50% more power than a two wire DC system with the | > | same size wires, and the same voltage to ground, but the AC system will | > | have inductive and capacitive losses, requires 40% better insulation to | > | handle peaks, and may have shorter insulator life due to capacitive | > | current. | >

| > Capacitive losses? They get hot, those nasty capacitors... | | Insulators have their own capacitance, and power factor correction | capacitors have some losses from ESR. Also, their cost of procurement and | maintenance need to be factored into the overall efficiency.

So a Lamborghini is less efficient than a Ford due to its procurement and maintenance cost? I learn something new every day.

| > | Also, the AC system is often not well balanced, which puts extra | > | load on one of the conductors and consequently higher losses. | > | A DC system can also use the earth (possibly with a smaller buried | > | conductor) for a return path, which shifts efficiency in its favor as | > | compared to AC. | >

| > That sounds like an Edison wet dream to me. Just connect to the steel | > frame of the building and the copper pipes from the bathtub. Very useful | > for fluorescent lights, I'm sure. | | It's already being done for some transmission lines. But I would not | advocate earth ground return path for distribution.

Funny that the return path carries no current in a balanced three phase 3 wire system... that would make earth an ideal return path with nothing to return, wouldn't it? You can't do that with DC.

| >

| > | But maybe Tesla will prove to be the ultimate winner if his methods of | > | transmitting power by means of atmospheric and earth resonance ever | > prove | > | to be practical and safe. | > | | > Got any more wet dreams for us? | > There is no "ultimate", we go with what we have... NOW. And the process | > will continue to evolve until it blows up in all our faces. | >

| > Man, as a species, has survived without technology for 2-3 million years. | > What science and technology have done is caused massive overpopulation. | > That CANNOT continue. We live in the Golden Age preceding the mighty | > crash that will be as dark an age as the demise of the dinosaur, and we | > are | > doing it to ourselves. | | Now that is something with which I can at least partially agree. We, the | "enlightened" people of the industrial and technological age, are exerting | unprecedented stresses on our fragile biosphere, and a privileged and | greedy few are reaping temporary financial benefits from human activities | that simply cannot continue on a sustainable basis. The world population | continues to rise, and much of that increase is composed of individuals who | are genetically and behaviorally challenged so that they reperesent more of | a burden than an asset in the grand scheme of things. Dogmatic religions | oppose any sort of limitations or social engineering, yet will not take | direct responsibility for the continued supervision, care, and protective | containment of those who make negative contributions to the advancement of | civilization. And business models and economic metrics require ever | increasing growth as a requirement for success, which encourages | conspicuous consumption, planned obsolescence, depletion of resources, and | waste of energy. | | The long-bearded old weirdo in robes has been professing that "The end is | near", and perhaps that is becoming more of a reality that we could see in | our lifetimes. | | Paul Yep... that's evolution in action and there isn't a damn thing anyone can do about it. Mr. and Mrs. Microbe live in a petri dish for 2 minutes and die, but first they reproduce and double the population in 1 minute.

The process begins at 11:00 pm and continues until midnight when the dish is full, all the agar nutrient is eaten and all microbes die, but first they slaughter each other for the last remaining nutrient. What time was it when the dish was half full? Is getting another dish a solution?

I was wondering if anyone would catch that... You win!!!

Actually if an insulator broke off and fell on my head, it would be quite insulting :)

Paul

Now that you've 'fessed up you need to go to

and get on their 7 step program, just like those rehab clinics in Arizona that treat sex offenders.

Insulator cost vs conductor cost doesn't change anything but explicitly stating it is still an interesting [more general] way to present the problem.

After all, if aluminum was $0.0001/lb you could just lay 3 foot diameter bar on the ground and run high current/low voltage. I'm guessing someone has already tried that somewhere.

You could eliminate all those unsightly dangerous crop duster snagging overheat wires.

WHOOooops! I just made a typo. Now I have to go back on the program.

Or maybe sue for malpractice . . .

Bret Cahill