On what basis do you make this statement?
That was the point of trying to apply it to the real world, to show that costs alone make it impractical.
Transmission losses are at best roughly 3 or 4 percent or so for every 1,000 km. With the circumference of the earth being 40,000 km, going half that distance is still 20,000 km, which makes the transmission losses pretty high. A system that large would lose roughly half of its energy to transmission losses, at least on the parts that ran over land. Underwater losses are higher.
I can’t even imagine the cost of trying to run a high voltage DC line across the Atlantic.
It would help a lot if we started using power when it’s available rather than to try to make power available when people happen to feel like using it. With that, how much power use could we shift to prime solar / wind hours? 50%? 80%? And then storage becomes much easier.
Building new coal and/or nuclear plants is stupid because for about the same money you can install solar and then have clean, free energy for decades rather than pollute for decades/centuries. Also, you can install solar on your roof. Nuclear, not so much.
The only way building new nuclear/coal plants makes sense is to replace the really bad old plants with less bad modern ones.
Right now (and probably for the foreseeable future), it’s much more feasible to have solar power feed into the grid for local use, and supplement that with quick-start generating plants.
The constraints are mainly economic. We have (or could have) the technology to do so, but why would we bother? It would cost more and be less efficient.
Just electrical induction makes such a cable “significantly different”.
I suppose it’s implied there, but I read the OP through a reasonableness filter that said no one would be foolish enough to build an undersea power line across a major ocean. Silly me.
Someone up above said the longest HVDC transmission line is 2000 km. Where is that? I didn’t think there were any much longer than the Pacific Intertie.
China.
[QUOTE=Wikipedia]
The longest HVDC link in the world is currently the Xiangjiaba–Shanghai 2,071 km (1,287 mi), ±800 kV, 6400 MW link connecting the Xiangjiaba Dam to Shanghai, in the People’s Republic of China.
[/QUOTE]
From here:
This document (long PDF) goes into ta lot of the questions about the economies of renewables on a continental scale. Including undersea. This document provides some useful costing estimates.
If you use a DC interconnect an undersea interconnect isn’t as brutal as an AC one - you don’t have the AC losses. Looking at the cost of the UK to France interconnect that only cost about three times the cost per unit length of a similar one overland. But the Channel is a very easy target. Proper deep sea stuff will be significantly more.
Pushing the voltage up drops resistive losses, and moving to DC removes reactive and dielectric losses. But both add cost.
The existing interconnects seem to top out at about 3GW. Most seem to be 2GW, or multiple 2GW links. Your worst case global interconnect is half way around the planet - so 20,000km. So your losses would be approaching 60%. You might reasonably be able to interconnect the planet and not need to move power more than 1/3rd the way around, so your loss drops to 40%.
But the costs are going to be insane. The rectifier/inverter stations seem to cost about $20M each, one at each end of a 2GW interconnect. So about $10M per GW per station Undersea lines cost about $1.6M per km for a 2GM link. However those prices were across the English Channel - which is not exactly challenging. Estimate $0.25 per km for overland per GW.
The world generates about 2,200 GW of power. The users of the power are roughly evenly distributed around the longitudes, so assume that we need to shift about 2/3rd of the power needed on average about 1/3rd of the way around the world. So that is about 1,500GW * 1.4 (to make up for the loss) so 2100 GW of power being moved.
So call it about 1000 2GW equivalent links. And you need to span the globe (although at any one time not all the links will be in use, you still need them in place.) So 1000 * 3 * $10M = $30 Billion in rectifier/inverters. (3 because rectifier/inverters can be made to work either way, and you spread them around the planet - averaging 3 needed for each link.) Undersea is ruinous - $1.6 billion per km, so we try to avoid it. Covering the globe isn’t too hard if we jump over the near points of the continents. We’ll make it just overland. 40,000 * 1000 * $0.25M = 10 trillion dollars.
Plus or minus a factor of two probably. But $10[sup]13[/sup] as a start.
Read this:
There are already methods of energy storage which are 50-70 percent efficient. Your 20,000 km hvdc link will be around 30 percent efficient unless it’s suoer conducting.
Very good analysis - thank you.
If you add to this the fossil fuels that have to be burnt to produce the copper / aluminum / steel / silicon / concrete needed for this project - you’ll get another surprising answers . Also add to it the fossil fuels that need to be used to transport / drill .
Now consider the water resources that will be needed /polluted to produce all of the above.
Now add to it all the forests that may need to be destroy to produce all of the above.
Yeah, thanks for the participation all.
HVDC is being considered as a replacement for the backbone of existing national grids which are under a lot of strain at the moment from highly variable renewable generators. This article discusses the HVDC developments in Germany where this problem is acute. It also solves some of the problems of interconnects between countries.
Interesingly, the big challenge is not so much to do with supporting long distances as with switching DC during fault conditions.
Existing national grids mostly aren’t under strain because of renewables; they’re mostly under strain because consumption is high and a lot of the infrastructure is old.
That’s overstating the case. There is a genuine distribution-scale superconducting power cable in operation today. Yes, it’s only a kilometer and 40 megawatts, and it will be a number of years before that can be scaled up to thousands of kilometers and gigawatts. But it’s hardly science fiction.
That’s a field test for a research study. There’s no telling IF it will be scaled up to thousands of kilometers and gigawatts.
That’s just economics, and in the same vein as your original question. The technology is there–it’s just a question of whether it’s cost-effective. That’s not what’s usually called “science fiction” (contrast with, say, fusion, where breakeven still hasn’t been achieved).
One thing that I don’t really see come up that often in discussion: some materials have a great deal of embedded energy in their production. Aluminum is the prototypical example of this (though there are others)–refining bauxite into elemental aluminum requires a tremendous amount of energy, to the point where aluminum smelters are often located near hydroelectric plants.
It might make a lot of sense to relocate industries like these to places with a high density of solar energy. Aluminum smelting would require some plant redesign to account for the nightly loss of power, but I’m sure this could be accounted for (more thermal insulation, larger pots to take advantage of cube-square scaling, etc.).
Data centers are another example that comes to mind. The industrial output of a data center fits in a fiber optic line of much lower diameter than the power cables feeding into it.
OK, accepted.
This is just a straight function of the cost of energy. If solar energy does become cheaper than other sources, solar-abundant places will have a comparative advantage in energy intensive tasks. Right now, solar is not there, though it might get there at some point. But intermittency will add to (indirect) solar costs in a number of ways.
Good thing then that solar panels conveniently produce DC. Although I guess now you need DC/DC voltage converters…
Yeah, otherwise if you want that 500kV, you are going to have to series up a heck of a lot of solar cells.
This is the big problem with the DC interconnects. The voltages needed to justify them are mind numbing. As alluded to above, building breakers for them is really hard too. The arcs don’t quench, and once drawn, they won’t go away.
In essence an inverter station is one half of a DC-DC converter anyway. Two stations back to back can be viewed as a full DC-DC converter. Indeed, this underlines an advantage of the systems - you can decouple the grids - both power delivery and frequency with a pair of stations.
Yeah, definitely. But the trend seems fairly inevitable. I guess my point is that if we accept your implicit premise that we can get cheap solar somewhere on Earth, and that the problem is distribution, then shipping ore to that locale and getting pure aluminum back is a lot like shipping an uncharged battery and getting a charged one back. Except that in this case, the equivalent energy density is way higher than any battery.
In the long run, there’s no reason we can’t do the same with fossil fuels. Electrolyze the hydrogen out of water, extract carbon from the atmosphere, and process to form natural gas or whatever. Then ship that to whoever needs it. Expensive, yes… but mainly the energy cost. Drive that down and it might make sense.
A typical 2 m[sup]2[/sup], 300-ish watt panel is about 30 volts. So, 17,000 panels for 500 kV. That’s only 5 MW worth; small even by solar standards. Of course, that’s just one string, which is problematic since a single shadowed or broken panel will disrupt the whole string. So you’d want a fair amount of parallelism as well. Doable if you’re building a 100+ MW plant.
Still, doing it that way is insane. You would have to hang the panels way up to keep them isolated. And you’ll need some crazy maintenance workers (I guess drawn from the same pool as high-tension powerline workers…).