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Assume that we installed plenty of solar cells in all continents; mainly in Asia, Africa and America. Can we transfer the electrical power harvested from them around the World through wires? So that the continent(s) in daytime will feed the one(s) in nighttime.

Assume that we use a higher technology then we use today in practice. For example, we will use higher insulation technologies to transfer with higher voltages to decrease copper losses.

Do the practical limits make this scheme feasible?

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4 Answers 4

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No.

It is completely impractical. I would even go so far as to say that it will never be practical given that the cost of transmission system construction will never outpace that of local generation.

The copper capacity tables are here and I could do a bunch of math for you, but it is pointless.

Generating electricity is a relatively easy thing to do. There are so many different strategies: coal, wind, hydro, solar, nuclear, CNG, mixed-fuel, biofuel, et. c. ad. infin. At least one of them will be practical in any given locale -- at least more so than running greater than 20,000km of cable would be. I'm not even sure it's absolutely possible since the tremendous voltages you would need to overcome the staggering losses might make insulation requirements beyond the reach of today's materials.

Actual Power Lines

The longest power line on the planet is in China and only runs 2,059 km using a special extremely high voltage DC configuration (avoids the phase synchronization issue). It doesn't run through the ocean as that would dramatically increase the losses. It isn't cost effective (read: practical), which is why China is the only country with these types of lines in mandated use.

As a case study it cost 3.5 billion to put in and can transport 7.2e6 kw. For perspective, consider that 3.5 billion is the cost of building a local plant that can generate almost half that much power (and deliver it). In the Chinese case all they got for their money was the delivery -- they still have to finance the generation.

The longest conventional AC lines in the US are ~240 km. It just isn't practical to go planet-scale with transmission lines.

Even Space is More Practical

It is even much more efficient and practical to beam power from space using Wireless Power Transmission (WPT) technology (~160km), than to move it terrestrially half-way around the world (~20,000km). It is also more politically palatable since you don't cross any other foreign territory and "energy security" is a sensitive topic.

Google "Solar Power Satellites Wireless Power Transmission" and you will find a broad base of literature on this idea. Here are a few references to papers to get you started: 1 2 3

It appears to be gaining traction. Japan and others are seriously considering deploying such an energy architecture.

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Then, I'd like to know what is the practically (economically) useful maximum distance for transfer of energy using the current (wire) technology. Like 200 km, 1000 km, 10000 km? For example Germany is known to have lot of wind sources on its north and wants to transfer the energy to its south. Is that plan rational? –  Al Kepp Jan 14 '13 at 8:55
    
Whats CNG in your answer? –  Dean Jan 14 '13 at 9:33
    
@Dean -- Compressed Natural Gas (sometimes called LNG -- Liquified Natural Gas) –  DrFriedParts Jan 14 '13 at 11:39
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@Al -- Added some empirical references on practical limits –  DrFriedParts Jan 14 '13 at 12:21
    
The OP said to assume higher technology than available today. Your answer is based on current technology, for which it is correct, but you don't know what future advances might bring. Your catagorical answer of "No" is therefore somewhat irresponsible and closed-thinking. –  Olin Lathrop Jan 14 '13 at 14:40

No, it is not practical with today's technology or what we can reasonably forsee well today.

However, what you ask about is theoretically possible in that no laws of physics are being violated. Therefore it is impossible to say whether it could become practical in the future. Saying catagorically today that it will always be impractical is just wrong. Think of what would have seemed totally impractical not that long ago. Right after the Wright brother's first flight, how many would have thought something like a large commercial jetliner would ever be practical, let alone in just a few 10s of years? What about a man on the moon just a half century later? The list goes on.

To make this practical, long distance transmission would have to become much cheaper relative to power generation than it is today. I really can't see how this can happen with today's copper conductors, but the future may not be limited to that. Who is to say what advances will have been made in the next 100 years in superconductors, or carbon nanotube fibers, or something else we haven't even heard of yet? The cost of generation may also go up in the future relative to the average of the economy. That's quite likely even from today's viewpoint for any generation relying on fossil fuels.

So, definitely not today, almost certainly not for the next 10s of year, but in the range of 100 years or more, so much unforseeable technological advance is possible that it would be irresponsible to say it would be impractical then. Think about how relatively little back in time you need to go to where trans-ocean communications cables and communications satellites seemed completely impractical.

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It will only become practical when we have reasonably priced superconducting cables. That way losses would be eliminated. Ideally that would use room-temperature superconductors, which unfortunately are not available at the present time - and may not be possible in practice.

However, we already have materials that are superconducting at liquid hydrogen temperatures. One proposal is the Supergrid, which places the superconducting cable inside a liquid hydrogen pipeline. That would keep the cable cool, and at the same time allow us to use hydrogen as a fuel for vehicles.

Practicality of the system is a different matter though. For starters, it assumes that we will have an efficient and safe way to pump liquid hydrogen at ordinary petrol (gas) stations. Hydrogen is not a safe liquid! It also overlooks the energy needed to keep the hydrogen liquid. Over long distances that would become prohibitive. This site has a discussionof the system.

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Only possible with superconductors!? You know for sure for all time that there will never be any other technology to make long distance cables cost effective!? Also, there are already liquid nitrogen superconductors, which is a lot higher temperature than liquid hydrogen (at the usual pressures used for such things). Liquid nitrogen is much cheaper and easier to handle than liquid hydrogen. –  Olin Lathrop Jan 15 '13 at 14:07
    
@Olin The reason for using liquid hydrogen is that it is then useful as a fuel pipeline as well as a powerline. That will to some extent offset the cost of the cooling system. Liquid nitrogen is only a coolant, hence only an operating cost. –  hdhondt Jan 17 '13 at 0:10

Yes! it is possible to transfer electrical power around the world by wires. Over that, it all depends on the price paid by the consumer continent/country.

Cost+benefit analysis is to be done before establishing wires / transmission capabilities across continents / countries.

On a global scale it will be all about price, not about the efficiency in power transmission.

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-1 The question asks if it is practical. Could you give one scenario in which the numbers for your cost-benefit analysis suggest building such a transmission system is appropriate? There is no price currently being paid by any consumer world-wide where this is true. –  DrFriedParts Jan 14 '13 at 8:28
    
I discuss practicality in my answer, Yes it is possible. Practicality also means what one wants to pay for that KWH. –  Chetan Bhargava Jan 14 '13 at 8:33

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