Comments
gerkletoss t1_ixd2pph wrote
Why underwater along coastlines though? Isn't that just harder to service?
EDIT: Perhaps my favorite thing about the r/futurology mods is the opaque childish behavior.
AcaiPalm t1_ixd5fg1 wrote
Cheaper to bury the cables to safe depth at sea compared to routing through overcrowded coastal area. Think of crossing roads, railways and rivers and dealing with topography and the cost of purchasing land for the cables. You can repair cables offshore but it is expensive and a bit risky as repair joints in marine cables are more likely to fail.
gerkletoss t1_ixd6jet wrote
But then why not just put it further inland and run branch lines off to the few places where this connects to local grids?
AcaiPalm t1_ixdee9d wrote
This game isn’t to improve grid connectivity at that resolution, you would need to convert the DC to AC in order to feed it into the main distribution (overhead lines etc). This would be costly and require more substations and infrastructure to meet a relatively small demand. It’s more a method of transmitting large amounts of electricity to the primary electrical hubs, usually locations where it is generated or consumed in large quantities (Power stations, industrial areas).
As you move into a more diversified energy mix which contains renewable sources you need to be able to rapidly and efficiently move the energy away from where it’s produced to where it’s not. This allows you to deal with the impact of varied meteorological controls on energy production, i.e. it only being windy or sunny in one state.
gerkletoss t1_ixdguka wrote
Yes. Those hubs are the few places it connects to local grids that I mentioned.
grinningbearit t1_ixd3pdu wrote
Just a shot in the dark, but maybe less maintenance and interruptions to service?
But I agree, I'm curious about the feasibility of that.
I'm also curious how shifting coastlines could potentially impact it.
gerkletoss t1_ixd5wvd wrote
It's certainly a thing that can be done. I just don't see the reason for it.
grinningbearit t1_ixd774g wrote
I agree. By feasibility, I more meant is it worth compared to the alternatives rather than is it possible. It might not have been the best word choice
chickenderp t1_ixd4lcj wrote
I'd be more worried about leaking insulating oil into the ocean, to be honest.
danielv123 t1_ixdx3z2 wrote
Long undersea cables isn't a new thing. New windmills are built at sea every day. There are a dozen undersea high power cables in northern Europe. There is a planned cable from Egypt to Greece and one from Algerie to the UK.
chickenderp t1_ixfwbmq wrote
don't get me wrong I'm not poo-pooing HVDC transmission, I just personally think I'd rather have it on top of transmission towers than underwater.
mweint18 t1_ixdx44c wrote
Modern Subsea DC cables are not insulated with oil anymore.
chickenderp t1_ixfw2x3 wrote
Someone needs to tell the utility I work for to get with the times then :p
Splenda t1_ixe9t46 wrote
Subsea lines avoid the politics of overland routing. When you're running a line 2,000 km on land, every local government enroute wants a piece of the revenue.
Hence, the 3,800 km Xlinks line that will soon power much of the UK from Morocco skirts the coasts of Portugal, Spain and France.
gerkletoss t1_ixea5iz wrote
That one has to go along the seabed though, and involving mote countries is a whole extra level of headache compared to this proposal if the coastal lines were moved inland.
I'm not saying it's wrong, but I'd really like to see the trade study.
planko13 t1_ixdcm23 wrote
No NIMBYs to whine about it
BoomZhakaLaka t1_ixex70k wrote
This is an inverter manufacturer's wet dream. Someone benefits tremendously by building a new bulk interconnected DC system. As someone in operations & planning with an understanding of the underlying technology (DC/DC converters) I understand the benefits but I'm still skeptical.
Even at 1000kvdc the losses for transmitting power from Nevada to new York would be pretty substantial, and I have doubts that the benefits outweigh the cost. Though I do understand the energy potential in the southwest, this must be weighed against the trade-off of keeping generation regional.
duckduckohno t1_ixdcgej wrote
2-7% improvement over line losses of HVAC.
The biggest advantage isnt reusing the same grid, it's building a NEW one and burying the transmission lines. Not only will the HVDC equipment be expensive, but so will the labor and new lines (these new lines need to be 600+ km to see a ROI and can't use the exact same existing infrastructure).
It'll be interesting to see if the cost of this project will exceed the cost of building more renewables and accepting the line losses.
danielv123 t1_ixdxc06 wrote
The problem is that the current grid doesn't have the capacity to move renewable energy far enough. This can be compensated for with storage, but that is very expensive.
Splenda t1_ixe8qae wrote
No, HVDC offers closer to 50% reduction in line loss versus AC.
UHVDC loses even less, and is now the standard for long-haul lines in China, the world leader in this. And few of these lines are buried.
frontiermanprotozoa t1_ixeif40 wrote
Yes, 6% and 3%. 3% benefit. when you make something thats 94% percent efficient 50% more efficient it doesnt become 141% efficent
Splenda t1_ixeqv5x wrote
>2-7% improvement over line losses of HVAC.
This statement is grammatically false. Yes, with imagination one can twist it into a correct interpretation, but I thought it so confusing that it deserved explanation.
WaitformeBumblebee t1_ixdycli wrote
Additional bonus over HVAC: underground HVDC is better shielded from EMP/sun flair.
TacTurtle t1_ixe6x4r wrote
Stepping up and down DC voltage is vastly more expensive than AC, which can use simple current transformers.
Only way HVDC makes real economic sense would be for a few key trunk lines, and even then it is pretty dubious vs standard AC since you would still need a substantial inverter at the end to make wall-outlet AC for most demand.
Admiral_Fancypants t1_ixcwgso wrote
I thought the whole reason we use alternating current is because direct current can't be transmitted over long distances.
manual_tranny OP t1_ixcx634 wrote
Admiral_Fancypants t1_ixcyqjv wrote
That's news to me. Glad to hear that our 100 year old grid can be improved upon.
VitaminPb t1_ixd9yq9 wrote
If you read it, they need buried lengths of 50-95 KM cable (big slop factor there, non trivial task to dig) to break even, and about 800+KM runs for non-buried cables. Those are very long cable runs.
danielv123 t1_ixdxq0o wrote
Yep. The reason we have AC instead of DC on the grid is because semiconductors wasn't a thing when the grid started, which meant there was no good replacement for transformers.
SentientHotdogWater t1_iy0nmlq wrote
Our grid isn't actually 100 years old. It's been getting continuously rebuilt and upgraded this entire time.
NH_Living_Free t1_ixdtwod wrote
The biggest thing standing in the way is politics. Texas, as one example, is on its own grid, which has failed several times over the past three years alone in both hot and cold weather. This map shows Texas connected to the same grid, which I don’t see as politically feasible. Remember, they still re-elected Greg Abbott.
jerzy4 t1_ixd0gtg wrote
Dc can be transmitted any distance but is only more efficient over ac in the very long distance range (with appropriate infrastructure = $$$). Our current grid uses ac as there are less losses to do so (arguably in certain areas) due to the smaller length of transmission.
Admiral_Fancypants t1_ixd0v2z wrote
I just remeber hearing about Edison's terrible DC lines that couldn't go more than a couple miles before losing strength and needing to have substations to keep it going.
glambx t1_ixd8xdx wrote
The issue was they didn't have semiconductors that could produce high voltage DC.
Transformers were easy to build, so achieving high voltage AC was a piece of cake.
At a given power level, line losses are inversely proportional to line voltage.
jerzy4 t1_ixd39dd wrote
I do too. If I remember correctly hearing that his experiment was trying to balance and send out 110v across the wires only a few miles.
But if he produced high voltage and ran his wires over 100 miles he might have shown how the losses are indeed less than ac in the same setup. Our cable technology is very different from back then too
putalotoftussinonit t1_ixd5cyy wrote
I have installed over 1,000,000km of fiber optic plant across the US and around the world and can confidently say that this company will never bury all of this plant. Never.
Why??? $150-300 a foot for rock boring that's why. He'll will freeze over before this venture becomes profitable.
danielv123 t1_ixdxhx5 wrote
150-300$/foot is peanuts compared to these cables. You gotta 10x that at least.
TacTurtle t1_ixe7g73 wrote
2200mcm high voltage cable is running closer to $11-15 per foot, uninstalled. You are talking triple or quadruple that for underground rated cable
Each phase would running multiple cables, so $11 x 5 x say 6 runs per phase x 3 phases = $990-1350 per for cable alone, uninstalled without external conduit.
Citation:
Trenching and laying pipe or cable subsurface is $800-1000 per foot in existing public right of way without additional permitting cost or fill.
Add in 360 degree thermographic inspection, that’s probably another $10-20 /foot.
Then for buried HV cable you need like a 200 foot corridor for safety, so that is like $1000-2000 per foot even at a modest $25,000 / acre
danielv123 t1_ixe7xu4 wrote
And thats thin for distribution. That is close to the minimum diameter of the cables we are planning to make for offshore windmills.
TacTurtle t1_ixe9unn wrote
Yeah at that point you end up running multiple cables per phase so the linemen can still actually physically bend and move the cable - at least on the distribution side.
Who even makes HV underground cable rated for DC? Okonite’s catalog only has underground rated to like 35kV, versus 69kV for above ground.
danielv123 t1_ixel5tr wrote
Prysmian group makes up to 1100kv AC underground apparently. Nexans has delivered 500kv underground systems in the past, don't know how high they go. For these projects the cables are always custom made though, so there isn't really a catalog to pick from.
[deleted] t1_ixed103 wrote
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FuturologyBot t1_ixczv8r wrote
The following submission statement was provided by /u/manual_tranny:
Vibrant Clean Energy (VCE) has proposed a ~210 line underground high-voltage DC transmission line network, with underwater lines along coastlines, which would improve the efficiency of electricity distribution across the US.
In the lowest cost scenario, solar capacity is expected to exceed 830 GW and wind capacity is expected to exceed 1130 GW, by 2050.
The colossal transmission system would cost only $400B if financed over 30 years at 3%, which would result in a cost of $7.5 per MWh, enabling extremely low electricity costs of $25/MWh. (That's $0.025/KWh)
Please reply to OP's comment here: https://old.reddit.com/r/Futurology/comments/z1uv5r/hvdc_macrogrid_would_reduce_climate_pollutants/ixcww54/
[deleted] t1_ixedsoz wrote
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9lukemartin t1_ixetmiz wrote
An underground/water grid has been proposed before* but it always fails to address some glaring issues.
First, the contiguous United States is not a single rock that never moves. There are several plates that are constantly shifting. Overtime this can break underground lines. On a small scale this doesn't really matter, it probably won't become a problem as long as regular maintenance is done, but when you move to a nationwide scale in the nation that can barely keep it's primary mode of transportation's infrastructure safe to use*, it's a problem and a big one.
Maintenance brings up the other point, this would be 1000s of miles of high transmission lines. Going underground largely mitigates the effects on local wildlife (at least in the long run*) but it also makes the whole system incredibly expensive and difficult to maintain.
Maybe VCE has more details on how they plan to deal with these issues, but this article sure doesn't address them at all.
*based on my prior knowledge need to find the reference
o-Valar-Morghulis-o t1_ixewfa5 wrote
We need to face the fact that the old grid delivery approach might move power a little more efficiently but it is limited in evolving to better tech and delivery and the only reason it hasn't evolved is because it favors the big oil and utilities control, keeps them wealthy. They'll never invest their own wealth if it opens the doors to others.
Jnorean t1_ixd3wg6 wrote
This works if there is no need to convert DC power into AC power at the receiving end of the transmission line meaning all homes run on DC power only. The DC to AC cost is expensive ( not included in the calculation of cost/KWh) and requires a large power plant and separate lines to do the job. May happen in the future but not until all homes only require DC and not AC power.
danielv123 t1_ixdz1w2 wrote
Well, no. You can't put 800kv in the outlets. Instead, you'll go 800kv HVDC -> 600kv AC > 70kv AC > DC > 50kv AC 50hz then feed it onto the existing grid for further stepping down. DC to AC and the other way around is expensive, but all your electronics already go both ways because it's the easiest way to transform voltage now.
Dwarfdeaths t1_ixdxnev wrote
If you make it go around the world you can significantly reduce the need for grid storage too.
riV3rwulf t1_ixd1fku wrote
By 2050 the coastlines will be 200 more miles inland so
curious_geoff t1_ixd3g97 wrote
How much emissions would it take to mine, smelt, transport and install all the metal for this grid you speak of?
glambx t1_ixd8c9f wrote
Eh, negligible, compared to the benefits.
The main problem with solar and wind are intermittency. One (partial) solution is a massive rollout of battery storage, which would have a thousand times that environmental impact.
If you can reduce the need by time and location shifting intermittents across the country? That's an absolute win.
If you're interested, though:
Lots of information and links to cost analysis there.
giltwist t1_ixdgv4x wrote
> One (partial) solution is a massive rollout of battery storage
Isn't that why we're experimenting with mechanical energy storage like pulling train cars full of rocks or pumping water uphill?
glambx t1_ixdhm7m wrote
Problem is that the amount of energy storage we need to convert 100% to renewables is enormous. Pumped hydro works just fine but takes a massive amount of area and the right topography. Compressed underground air storage also works, but is geology-specific.
The right answer is a blend of wind, solar, and nuclear fission, but there's still a ton of (mostly ignorant) folks against nuclear power.
urmomaisjabbathehutt t1_ixdakzx wrote
Since grids need to be maintained and upgraded for a variety of reasons including efficiency lowering overal running costs, maintenance advances such as increasing fault tolerance and reliability and benefits to customers brough by smart grids regardless of energy source used
the same emissions as if they were upgraded without being used with renewable energy in mind but since renewables will be part of the use and replacing polluting sources like coal and the grid more efficient the total annual emissions should be lower compared than currently
who knows, traditional energy suppliers may preffer to pocket the revenues that should had been used to maintain it and keep upgrading it till it roots instead and then claim it is not fit for purpose, at the end of the day those corporations are there to increase shareholders profit let the next CEO and/or tax payer deal with it
uasoil123 t1_ixd01k2 wrote
Wow but were would the companies make money? Your forgetting the most and only important part
gerkletoss t1_ixd2w36 wrote
Plenty of companies could profit from this, especially ones running renewable energy production and whoever gets to build the infrastructure.
uasoil123 t1_ixd5cmr wrote
Hmm I feel like we should get away from profit when it comes to energy use and instead just let the government deal with this.....the government already builds the infrustructure for everything.
gerkletoss t1_ixd69fo wrote
I believe the idea is that the government would build the cable network. The profit motive would be to get the bill passed.
uasoil123 t1_ixd8b91 wrote
I dont see why we need to give private companies any power in controlling our energy infrustructure....why give private companies the same power that oil companies have now...we are having all these issues on moving on because of these oil companies
danielv123 t1_ixdyadz wrote
How is it possible to not give private companies a big stake in energy prices? Federalize all companies that use or produce energy? And even then the government still has a profit motive.
gerkletoss t1_ixd9651 wrote
Well let me know when you come up with a solution for fixing the government. Until then, this is what we have.
[deleted] t1_ixdyafv wrote
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manual_tranny OP t1_ixcww54 wrote
Vibrant Clean Energy (VCE) has proposed a ~210 line underground high-voltage DC transmission line network, with underwater lines along coastlines, which would improve the efficiency of electricity distribution across the US.
In the lowest cost scenario, solar capacity is expected to exceed 830 GW and wind capacity is expected to exceed 1130 GW, by 2050.
The colossal transmission system would cost only $400B if financed over 30 years at 3%, which would result in a cost of $7.5 per MWh, enabling extremely low electricity costs of $25/MWh. (That's $0.025/KWh)