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Comment by tomkinstinch | Hacker News Reader

We can build power plants in the middle of the desert and ship power out. The technology exists; we just haven't done it yet. Transmission losses are not a concern for superconducting cables (though maintaining the cryostat jacket is). Such cables are currently being proven before being used in larger grid connections.

http://spectrum.ieee.org/energy/the-smarter-grid/superconduc...

http://www.htstriax.com/columbus.html

http://www.ornl.gov/sci/htsc/documents/pdf/fy2003/HTS_Cable_...

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Forget supercondictivity, what about HVDC [1]?

HVDC can be as efficient as 97%, compared with the US average of 93%. That 4% "inefficiency tax" would likely pay for long-haul HVDC connectors (as outlined in one of Obama's 2008 energy proposals) within years.

[1] http://en.wikipedia.org/wiki/High-voltage_direct_current#Adv...

New Zealand has had a 600V HVDC link from the South Island to the North Island for quite some years - most of the power is generated by the hydro lakes in the south, then delivered via a 610km link to a substation in the north, where it is fed into the normal high-voltage transmission grid.

http://en.wikipedia.org/wiki/HVDC_Inter-Island

So it is a proven technology to have this as a long distance link (been in operation since 1965) and it is capable of bi-directional power transfer as well.

I'm curious where you get the "600V" number from -- is that 600 volts? According to the Wikipedia page you linked the system uses "+270kV and −350kV", which is in the range I would expect. Maybe you meant 620kV, the difference between +270kV and -350kV?

My apologies, that must've been some confusion in my mind... it was a 600MW HVDC link... although it is higher now, and works are underway to bring it up to somewhere near 1.4GW.

HVDC definitely makes sense for connecting islands together. The cable goes underwater, and in water, the capacitance of the cable is much increased by the greater dielectric constant of the water, which makes AC transmission less efficient.

You know I've never heard of HVDC until I read this. So was Edison right all along?

No. AC is still far more useful in many key scenarios [1]. However, for long-distance power transmission, lots of money could be saved (and jobs created in doing so) by switching from AC to HVDC.

[1] http://en.wikipedia.org/wiki/High-voltage_direct_current#Dis... (note: some of these are due to AC parts having economies of scale and decades of efficiencies and process that HVDC may not be able to tap into without widescale implementation)

Not really. The AC transformer was the most efficient way to adapt voltages until very recently. The IGBT and GTO thyristors are the technology that makes something like HVDC affordable today, and they are very modern developments.

Mercury-arc rectifiers (the technology replaced with IGBTs and GTOs) were very large and expensive, and also less efficient (even more so before the 1930s or so) so HVDC only made sense for submarine cables (which have huge capacitive losses). With IGBTs and GTO thyristors it start to become feasible to e.g. do an HVDC line across a continent.

As an example the HVDC inter-island was built using mercury-arc valves (it included a submarine leg), but they have since benn replaced with solid-state devices.

HVDC is also a good to tie two separate grids together; since they will be on different time-bases you can't just directly AC couple them.

The real problem is that a nuclear power plant needs a staff of several hundred people. They can't travel 500 miles every day to work to the middle of a desert. Even if they wanted to relocate there, they would have to build a little town to serve these people and their families, and now we are back to the original problem.

I think he meant a solar plant in the middle of the desert, not a nuclear plant. Solar plants don't need staffs that large.

Other problems with building nuclear plants (or any other type of plant that requires large steam turbines) in the desert include:

* Difficulty cooling. If you build next to an ocean or river, you can just use some of that water to provide the cold end of the temperature differential that you're using to generate power. Deserts are trickier, and more expensive.

* Transportation. If you build next to navigable waterways, you can ship really big components on barges. In deserts, you can ship some things by rail.

But hey, at least it's politically convenient to stick scary power plants in deserts.

Some of the GenIV designs don't require water cooling.

They all require some kind of cooling. Fundamentally, a nuclear reactor sets up one end of a temperature differential that you can use to do work:

http://en.wikipedia.org/wiki/Thermodynamic_cycle

Water just happens to be a particularly convenient coolant.

I'm aware of that, but water isn't the only convenient coolant. Molten salt, sodium, molten lead, and helium are other options.

Water has some disadvantages. It's a good neutron moderator, but with its low boiling point you have to keep it under a lot of pressure (160 atmospheres for most light-water reactors). That means you need very strong, thick steel, and a huge oversize containment dome, since if a pipe breaks, the steam will flash into 1000 times as much volume. Then some of it will split, and you'll be at risk of a hydrogen explosion, which is what we all saw at Fukushima.

Molten salt, on the other hand, works at atmospheric pressure, and if something leaks it just drips out and cools into rock.

Sodium has a disadvantage in being reactive with oxygen and water, but it also works at atmospheric pressure. The integral fast reactor design uses a big pool of sodium, which provides so much thermal inertia that Argonne was able to switch off the cooling system entirely, and the reactor just quietly shut down.

Either design works at higher temperatures than LWRs, giving better thermodynamic efficiency.

The technology exists; we just haven't done it yet.

Actually, we have, albeit with varying degrees of success: http://en.wikipedia.org/wiki/Solar_power_plants_in_the_Mojav... http://articles.latimes.com/print/2012/mar/04/local/la-me-so...

Wow, those are pretty cool. Hate to be around when they lost cooling (dropping out of superconductivity would be a pretty energetic event :-). But its good news on that front.

If you've ever seen the insulator jacket in an underground HVDC cable it is huge.

Most of these systems both carry power and sit in a pool of coolant so they rarely experience such an 'energetic event'. AKA, if they lose power they don't need to keep things cool AND it usually takes a few hours for things to warm up anyway.

Not a superconducting cable, but this is a great read:

http://www.jwz.org/blog/2002/11/engineering-pornography/

Thank you for the link - this was a great read =)

No superconductors needed, DC power conversion is the key. There is a large project on the way in Europe/Northern Afria called Desertec.

https://en.wikipedia.org/wiki/Desertec

Forget about superconductivity.

How about flywheels?

Flywheels are for energy storage, not transmission.

just let them roll to their destination!

Heh. Never underestimate the power of a station wagon full of flywheels hurtling down the highway?

Steering a car full of gyroscopes in fast moving traffic? Sign me up!

http://en.wikipedia.org/wiki/Gyrobus

That's really cool, I'd never heard of these. I imagine the flywheels are horizontal so that the bus can turn without trying to change their angular momentum, but I wonder if there's any effect on banked curves or going up hills.

I think he means install them for each house, store the non-peak surplus energy, and then use it during peak times.

Most of the power loss is related to using AC instead of DC.

Citation needed?

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