Transmission fortnight: burying power lines next to rail & roads to make a national transmission grid

Happy Monday! Welcome back to Transmission Fortnight here at
Volts. Today’s a fun one.


In my previous post, I described the many difficulties facing new
high-voltage, long-distance transmission projects, from planning
to financing to permitting and siting. It’s a bureaucratic slog.


Today we’re going to look at a clever idea for bypassing many of
those problems, namely, stitching together a national power grid
by burying power lines along existing rail and road
infrastructure, where rights-of-way are already established, thus
eliminating the endless haggling with local governments and
landowners.


The idea has been gaining steam in the policy community for the
last few years. FERC issued a report in June on challenges to
transmission; siting along existing infrastructure was cited as a
promising solution. In his Build Back Better plan, Biden promised
to “take advantage of existing rights-of-way — along roads and
railways — and cut red-tape to promote faster and easier
[transmission] permitting.” This op-ed in The Hill sums up the
benefits quite nicely, both of a national grid and of building it
without siting battles.


The vision is taking hold. And at least one small piece of that
vision has gone beyond speculation into an actual permitting
process.


The SOO Green line will carry Iowa wind power to Chicago


A company called Direct Connect is currently in the development
and permitting phase of a privately financed, $2.5 billion
project called the SOO Green HVDC Link, a proposed 349-mile,
2.1-gigawatt (!), 525-kilovolt transmission line to run
underground along existing railroad from Mason City, Iowa, to the
Chicago, Illinois, area. It aims to go into operation in 2024.


Going underground will allow the line to minimize environmental
and visual impact. It will be much more resilient than an
overhead line against weather, temperature shifts, sabotage, or
squirrels.


Two side-by-side cables will run through tubes of Cross-Linked
Polyethylene (XLPE) and will be self-contained, lightweight, and
easy to handle. They won’t get hot, interfere with signaling
equipment (unlike AC lines), or affect rail operations. There are
fiber-optic sensors along the lines to monitor sound and heat for
any problems.


(Nemo Link, the world’s first 400 kilovolt line using XLPE, runs
undersea between the UK and Belgium; it began operation in
January 2019.)


Running alongside the railroad means SOO Green will have no need
to claim land via eminent domain. Almost all of that railroad is
owned by Canadian Pacific (one of seven large “class one”
railroads in the US), so there are a tractable number of parties
to deal with.


A deal like this offers railroads a new passive revenue stream;
royalty fees well exceed what they get from similarly buried
fiber-optic lines, of which there are more than 100,000 miles
along US railroads. And it’s also a chance for railroads to be
part of a positive sustainability story.


The project is privately funded, so there will be no need for any
complicated cost-allocation formulas. The financiers (including
Siemens, which very rarely puts direct capital in transmission
projects) will make their money back from those who use the line
— the suppliers that put power on it, the shippers that sell
power across it, and the buyers that consume the power — through
competitive bidding for capacity. SOO Green is holding an open
solicitation right now to allocate its 2,100 megawatts among
them.


The aim is to create a more robust energy market by, for the
first time, connecting the MISO and PJM territories. (MISO and
PJM are regional transmission organizations; see previous post
for details.) Wind power projects are backed up in MISO, waiting
to connect, stymied by grid congestion. Meanwhile, nextdoor
neighbor PJM is the largest liquid energy market in the world.


The idea is that SOO Green will unlock renewable energy
development in MISO; Direct Connect projects four to six new
gigawatts. That energy will be transported to population centers
in PJM, easing grid congestion, reducing the carbon intensity of
the East Coast energy mix, and lowering power prices.


The connection will also allow MISO and PJM to share reserves for
the first time, which could reduce the need for reserve capacity,
increase reliability, and save consumers money.


Because the MISO side will be drawing from such a geographically
broad region, it is likely to be in use almost continuously.
“When the wind isn't blowing in North Dakota, it likely is in
Minnesota,” Trey Ward, the CEO of Direct Connect, told me. “We
anticipate upwards of 90 percent line utilization.”


“It's as if we teleported a 2,100-megawatt wind turbine with a 90
percent capacity factor from Iowa into suburban Chicago,” he
says. In fact, the converter station in PJM has applied to be
treated as a capacity source in that market. (That will require
some updating of regulations, just as power market regulations
had to be updated to accommodate batteries.)


The converter stations at each end of the line are worth looking
at more closely. They will use the latest generation of Voltage
Source Converters (VSCs) to exchange power between the HVDC line
and the regional high-voltage alternating current (HVAC) systems
already in place.


VSC technology has been around since the late 1990s, but it has
only recently gotten efficient, compact, and cheap enough to
compete against the thyristors (solid-state valves) in common use
today on HVDC lines.


VSCs boast several important advantages. Thyristors need strong
AC systems on both sides of the line, they require power
filtering, and they have limited control over reactive power. (Do
not ask me, or anyone else, what “reactive power” is. That way
lies madness.)


VSCs, on the other hand, are “self-commutated converters,” which
means they can generate AC voltages (using IGBT capacitors)
without relying on an AC system. They can control power
independently, even with a weak AC system or no AC current at
all; they can “black start” a grid from a blackout automatically,
without any workers out throwing switches.


VSCs allow precise and instantaneous, bi-directional control of
both active and reactive power. They can provide services to the
grid other than just energy — things like voltage and frequency
regulation or “synthetic inertia” to support grid stability.


“You can go from zero to 2,100 megawatts in 1/100 of a second,
and back down again just as fast,” says Ward. “It will be the
fastest, most dynamic resource on the North American grid.”


Power electronics experts have been claiming for years that VSCs
would eventually replace thyristors in HVDC projects. (“We’re in
a race with Germany,” Ward says.) If built, SOO Green would be a
big step toward making it finally happen — the first deployment
of VSCs at this scale in the world.


The main thing these VSC stations will do is serve as regional
energy hubs, accepting gigawatts of energy from, or dispensing it
to, existing HVAC grids.


Energy users that require a large, reliable supply of
high-quality electricity, like data centers or technology parks
(perhaps ensconced in microgrids), can co-locate with the hubs to
take advantage of their high-quality power control, thus spurring
economic development.


Direct Connect estimates that the SOO Green project will create
2,000 temporary construction jobs, unlock more than 4,000 jobs in
renewable energy development, generate more than $2.7 billion in
economic development in the two states, and yield more than $3.75
billion in ratepayer savings over 20 years.


We shouldn’t exaggerate how easy things will be for SOO Green. It
won’t be completely free of siting hassles, and there are costs
outside its control. (The X factor is the cost of copper for the
lines themselves — if it spikes for some reason, SOO Green will
be in trouble.) But its costs will be much more predictable than
a typical overhead line’s. It knows its exact route from the
beginning and, because digging ditches is a pretty cheap and
well-established technology, 80 percent of its construction costs
will be for equipment.


Things might be trickier for the next rail-transmission project.
SOO Green is exploiting ideal conditions: a low-use railroad with
well-characterized geology, connecting an energy-producing region
with an energy-consuming one. Future projects could face more
physical and economic challenges. At some point, there will be
projects that don’t pencil out for private capital, but are
needed to link the lines together into a national grid; then
public money will have to step in.


But private capital can do a lot. Ward mentions two federal
policies that could help. One is a federal investment tax credit
(ITC) like the one renewable energy receives, to defray the cost
of investment, especially for early and pioneering projects.
(More details on that in the previous post.)


The other is some kind of manufacturing tax credit to spur more
US companies to manufacture the XLPE line that Direct Connect is
currently buying overseas.


Even without those policies, though, things are more or less on
track (har har) for SOO Green.


If things go well for the project — no sure thing, given
America’s history with transmission — it could serve as a
template for new HVDC backbones along other sections of the
elaborate US rail network. Ward estimates that as few as a
half-dozen such lines would completely transform the US
electricity system and spark billions of dollars of renewable
energy development. (Direct Connect is in talks with all the
class one railroads.)


An aside: as long as we’re talking about electricity and
railroads, you should check out Solutionary Rail, a plan to run
(overhead catenary) electricity lines along the nation’s rail
lines and electrify rail freight in the process.


Anyway, to date there are no HVDC lines being planned along roads
or highways, in part because state Departments of Transportation
are always thinking about adding lanes, in which case the lines
would have to be moved.


But it’s also because developers still have an inflated sense of
the cost of undergrounding lines. The news hasn’t widely spread
that modern lines require less conducting metal, horizontal
drilling has been perfected by natural gas frackers, and inverter
stations are as little as 25 percent the size they used to be.


Here’s what Dr. Christopher Clack, an energy modeler at Vibrant
Clean Energy (VCE), told me:


Data that I was provided from Tier 1 transmission vendors shows
that the cost of underground HVDC transmission has a similar
price point to the same overhead capacity of HVAC when the
transmission line is over approximately 250 miles. This includes
the cost to build inverter and rectifier stations at each end.


And of course the sticker price of building overhead lines does
not include the unpredictable expenses of regulatory hassles and
intransigent landowners. A line can not be cheap if it never gets
built.


In terms of long-distance transmission, underground HVDC is now
the smart choice.


But there’s one other step planners and developers can take to
bypass conventional transmission hassles.


A national grid made of two-state pieces


VCE is currently working on a detailed modeling exercise showing
how the US can decarbonize by 2050. (You can see a preview here.)


The modeling (like much other modeling before it) shows that a
national HVDC network is desperately needed for decarbonization.
But VCE is aware of the difficulty of siting lines that cross
multiple states. So it came up with a way to create a national
network that is comprised entirely of lines that only bridge two
states — each one originates in one state and terminates in a
neighboring state. And every one of the major HVDC trunk lines is
underground, running along rail or road infrastructure.


Here it is (a fancier map with more precise routes will be coming
with the final release):


The two-state pieces are like Legos from which a national grid
can be built. “You can get [energy] from Colorado to Chicago,”
Clack told me, “but you have to go through five rectifier
stations. It is the same as having one line.”


Building the system this way does come at some additional cost,
since the VSC stations at the terminus of each line are
expensive, and this would involve building more of them. And
since each conversion of energy loses a little bit, all the
additional conversions would add up to about 0.5 percent more
“line loss.”


But the advantage of this approach is that “each line is just a
contract between two states,” Clack says. “You would never have a
flyover state and you would never have a state that wouldn't get
access to the market.” Each participating state would have one or
more energy hubs and all the advantages — economic development,
less grid congestion, lower power prices — they bring. The end
result would be a functioning national energy grid. Clever!


(When VCE’s modeling is officially released I’ll take a closer
look at how the national grid operates and what it accomplishes.)


Let’s do this


A national energy grid composed of underground HVDC lines running
along existing rail and road infrastructure, with VSC stations in
every state, is an absolute home run of an idea. It ticks every
conceivable box: it’s economic development, jobs, clean energy,
lower prices, and most of all, an ambitious national project that
we can accomplish, red and blue states together, to regain some
of America’s lost mojo.


What’s more, transmission hasn’t yet fallen under the shadow of
partisanship, unlike … everything else. There is bipartisan
appetite for infrastructure spending and for unlocking the
domestic renewable energy that is often concentrated in red
states and needed in blue ones.


An underground national HVDC network would create thousands of
jobs and bring hundreds of millions or even billions of dollars
of new economic development to every single US state. It would
save every American money on their power bills. It would bring
national decarbonization within reach.


It would literally do what Biden promised: bring people together.
We should build it!


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