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Comment by pavanred | Hacker News Reader

May be a noob question, but if we can lay down cables for internet across the ocean floor connecting the entire world, why not lay down cables to connect all electricity grids. Half the earth always faces the sun. We shouldn't need batteries at all then, right? And we always have the traditional power stations (renewable and non-renewable) to augment the load. (At least in theory?)

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It's a very good question. I always thought that it's because of technical difficulties when transmitting electricity over long distances, but it turns out we already do it well (HVDC). When you think about it on a continent scale: why not move all PV panels from Germany to sunnier regions of Europe like Spain or Portugal where you can generate twice more power with them (in average 200 W/m² instead of 100 W/m²). The answer is simple: we'd need to have a common grid across EU member countries, but such a thing doesn't exist and it's unlikely to happen anytime soon. It turns out the biggest issue on this planet is always politics.

The amount of copper you would need to constantly convey electricity from the sunny side of the earth to the dark side would be absolutely massive. It is not an issue of common grids, as long distance high power transmission is done at many different voltages depending on the specific route, and has nothing to do with your mains voltage and frequency.

Current long distance power transmission is most often used as a way of 'balancing' production and demand between different types of plants; it is not intended or capable of transmitting the full power needs of the recieving area.

You can use aluminium instead of copper (see HVDC Gotland).

I didn't say it's just about "connecting countries with a common grid". Switching from fossil fuels to renewable sources is much more challenging than that. However, transmitting lots of power over long distances is doable and cheaper than many people think.

I know they run large (presumably) copper lines from Utah to California to pump out electricity. That can't have been cheap, how bad can it be to pump it trans atlantic? LOL

HVDC is High Voltage DC, therefore grids aren't really important. The bigger issues are losses and costs

The question was if it's possible to use someone's else electricity when the sun isn't shining in your place. While it's technically possible and in many cases economically reasonable, you probably won't see countries giving up their electricity production and importing power from overseas - the main reason is politics.

We need to get over this. Let's find better politicians.

you probably won't see countries giving up their electricity production and importing power from overseas - the main reason is politics.

Importing a whole country's power consumption is probably a bit much in terms of required infrastructure (except for the microstates which already do this), but smaller links are already present and make economic sense. I don't think the politics of energy security are an obstacle if the price is right.

In Spain we have ridiculous laws that make it unfeasible to a layman to have solar power installed in the houses. It would be quite ironic setting up solar panels for Germany with our current situation.

That's interesting. How does it work in Spain?

In threads like this I always like to promote Gridwatch: http://gridwatch.templar.co.uk/

While there isn't a complete grid, the UK has connections to Ireland, the Netherlands and France, enabling a bit more balancing. You can see the UK is currently running on 60% CCGT and 25% nuclear, although the 10GW solar capacity can't be shown because there's no central real-time metering for it. That's quite an impressive amount given the total (net of solar) demand is 30GW. Two and a half "Drax" worth of power, invisibly distributed around the country!

Because power losses will be absurd (unless you manage to find a room-temperature superconductor)

Pretty simple math, if you cable has 1 Ohm/km then the distance between the Northeastern most point in Canada to Ireland is around 3000 km (or 3x10E6m)

So suppose you have this very long extension cord, plug it on Canada (100V there to help the math) and plug a lamp on Ireland (an old incandescent 100W bulb, because it dims)

Your lamp is going to have 100 Ohms. Current is going to be 100V/(6100 ohms) = 16mA, making your lamp glow with 1.6W

Let me quote Ramez Naam here:

Transmission costs money, but less than many believe. The cost of high voltage DC (HVDC) transmission lines is roughly 1 cents per kwh for 500 miles, or 1.5 cents per kwh for 1,000 miles transmitted. Over 1,000 miles, an HVDC line may lose 5% or so of the electricity it transmits.

I don't consider 5% per 1000 miles an "absurd" amount.

Yes, losses are lower with a higher voltage (which for HVDC are around 100kV/1MV - in orders of magnitude)

However doing it on terrain is much easier than doing it under the ocean

Why easier. You just drop it on the floor. You don't need land right s or towers to build.

Isolating 100kV is not trivial

That's why we need big towers

When you can't use towers (on land) you have all kinds of special isolation techniques

And couldn't we up the voltage even higher for vey long distances?

You don't need a room temperature superconductor. High temperature superconductors can be economically refrigerated today. The problem overland is encapsulation - under the sea this goes away since the environment is much more stable (and colder).

Fixing a 3000 km long refrigerator at depth of 4 km will be an interesting challenge.

Cables are generally raised to the surface to repair.

Anyway, it's only 50 miles from Russia to Alasca making this a relatively simple connection. Hawaii would be hard to justify unless it's really cheap.

However grid storage is generally fairly cheap. Just going east to west across Eurasia also gives very good solar coverage.

Yes, but adding refrigeration to a cable will make it firstly about thousand times more likely to need a repair, and when repairing, rather a lot less bendable and more fragile, thus making it also more difficult to repair.

There are also -- of course -- a lot of political problems with the idea of a a global electric grid. Like, what happens to your electrical system in case of an international crisis. Russia has used its gas supplies for political pressure in Europe, and other nations may do the same with electricity.

Power transmission on large distances is a very difficult subject. To put it simply, wires have a non-zero resistance to current, increasing with its length.

For instance, Morocco plans to put solar panels in the Sahara. The solution that is considered in order to transmit power was that the solar station would charge batteries and the batteries would be carried by trucks.

Chemical energy storage looks interesting and it's not limited to batteries. Can be fuel as well. And it can be transferred via automated rail line (or even wire transport).

Battery sneakernet? EV trucks full of charged batteries going down the interstate across the country?

(Or pumped through pipes?)

There are technical and economic challenges.

To get started, read https://en.wikipedia.org/wiki/Submarine_power_cable

Slightly off-topic, but I stumbled across this fascinating documentary about the massive challenges of laying the first submarine transatlantic cable (1858) a few days ago:

https://www.youtube.com/watch?v=z_ErFUv8HYs

Great idea. Another factor an engineer told me about high voltage power lines is that they could send way more power through them but the limiting factor is heat. The lines start sagging.

But on the ocean floor the cold water could keep the lines cool.

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