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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?

JRE
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hkBattousai
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    In 2022 there are serious proposals to build a DC cable system from a massive new solar power station in northern Australia to Singapore. Practicality seems to have arrived. – ATCSVOL May 24 '22 at 22:23
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    There is another proposal to build one between Argentina and China. https://markets.businessinsider.com/news/stocks/building-a-2-billion-subsea-solar-power-cable-from-chile-to-china-1030989814 – user4574 May 25 '22 at 04:44

5 Answers5

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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.

Glorfindel
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DrFriedParts
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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 08:55
  • Whats CNG in your answer? – Dean Jan 14 '13 at 09:33
  • @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
  • @Olin -- Not at all. I explain why it will never be practical. Either (1) local generation will not be outpaced or (2) alternate futuristic architectures like space power, will always displace it. If you assume a future of unlimited possibilities then any answer is trivial and meaningless. Neither the technology, economics, or physics suggest that this will ever be a "practical" thing to do. – DrFriedParts Jan 14 '13 at 18:09
  • But that's the point. You can't "explain why it will never be practical". Even in today's terms, what if, for example, cables of the future could be made from carbon nanotube fibers with lower resistance, more current capacity, and much less cost than copper. Today carbon nanotubes are expensive, but the basic material is cheap and manufacturing technology of the future could make them abundant and cheap without stretching the imagination too much. I agree the OP's idea is infeasible now and for the medium future, but to say never is just irresponsible and something you can't know. – Olin Lathrop Jan 14 '13 at 18:53
  • "You can't explain why it will never be practical" -- I can and I did ;-) – DrFriedParts Jan 14 '13 at 21:11
  • It's interesting that you say it will never be practical since there are currently plans to build at least one 1500km undersea power cable between China and Argentina. https://oilprice.com/Energy/Energy-General/Building-A-2-Billion-Subsea-Solar-Power-Cable-From-Chile-To-China.html – user4574 May 25 '22 at 04:45
  • @user4574 -- 1. That "project" is an unfunded concept by Chile (not Argentina) from 2020 and has since gone nowhere, because... you guessed it, not practical. 2. A partially funded project by Australian billionaires to do the same thing (Australia to Singapore) also went no where: "Singaporean energy experts have poured cold water on plans backed by billionaires Andrew Forrest and Mike Cannon-Brookes to export solar power to the island nation, saying they are likely to be too expensive and impractical." – DrFriedParts May 26 '22 at 09:47
  • @DrFriedParts I did have the wrong country, thanks for catching that. I guess we will have to wait and see where this goes. From a physics standpoint, to do the proposed 600GW with 50% loss, they could use an aluminum wire with 25cm diameter running at about 5MV / 120KA. The aluminum itself would cost like $7B at todays prices. Obviously forming such a large stranded wire and insulating it to a 5MV rating in salt water + making 5MV DC-DC converter are going to be very hard, but not physically impossible. – user4574 May 26 '22 at 20:13
  • @user4574 -- Of course it's possible. The reason it will never be practical is that the physics require enormous amounts of material and maintenance, while the cost to moving energy enormous distances relative to the cost of harnessing local energy will never balance out... then add in the politics and national security issues of relying on such an exposed power source. – DrFriedParts May 27 '22 at 21:17
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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.

Olin Lathrop
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  • Aluminum wire is definitely going to be a lot cheaper than copper for this. A few billion dollars of aluminum + the cost of forming it into a wire can make just about any cable we might practically want. The real challenges are probably in constructing DC-DC converters operating in the range of a few megavolts and 10KA~100KA range. And also insulating something really long and high voltage that's submerged in salt water. – user4574 May 26 '22 at 20:20
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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.

Chetan Bhargava
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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 08:28
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    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 08:33
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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.

hdhondt
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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 00:10
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There are already some shorter undersea power cables that exist between England and mainland Europe. As well as between Itally and North Africa.

enter image description here

CREDIT: https://www.intertek.com/energy-water/subsea-power-cables-project-map/

Additionally there are plans to build larger cables. Most notably China is planning to build a 600GW solar farm in Chile, and then run a 15000KM cable back to China.

I was in an IEEE webinar just a few months ago with some experts in the power industry who were seriously considering the possibility of running long range undersea power cables.

Running long distance undersea power cables does have its challenges. But there are also some huge advantages to running cables around the Earth rather than using batteries. Using batteries to store solar power is expensive (both to initially build and also to replace batteries as they wear out). It's also not very environmentally friendly. Realistically there might not even be enough Lithium or other elements on the market to support building enough batteries.

user4574
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  • It’s obviously 15000km, not 1500 (and actually over 18000 km along the great circle route, so probably even longer to take into account geopolitical sensibilities), and it’s really just speculation at this point rather than any firm plan, they haven’t even made any feasibility studies yet. – jcaron May 25 '22 at 15:35
  • @jcaron Thanks for catching my typo. I changed it to 15000km. – user4574 May 26 '22 at 15:23