Several miles south of Rawlins, Wyoming,
on a cattle ranch east of the Continental
Divide, construction crews have begun
laying down roads and pads that could
eventually underpin up to 1,000 wind turbines. Once complete, the Chokecherry
and Sierra Madre project could generate
around 12 million megawatt-hours of electricity annually, making it the nation’s largest wind farm.
But how do you get that much wind
power to where it’s actually needed?
The Denver-based company behind
the project hopes to erect a series of steel
transmission towers that would stretch a
high-voltage direct-current transmission
(HVDC) line 730 miles across the Ameri-
can West. It could carry as much as 3,000
megawatts of Wyoming wind power to the
electricity markets of California, Nevada,
The $3 billion Trans West Express
Transmission Project is among a hand-
ful of proposed direct-current transmis-
sion lines in the United States, and one of
the furthest along in the planning process.
It underscores the huge promise of these
high-capacity lines to unlock the full poten-
tial of renewable energy.
Transmission isn’t sexy. It’s basic infra-
structure: long wires and tall towers. But
a growing body of studies conclude that
building out a nationwide network of
DC transmission lines could help enable
renewable sources to supplant the majority
of US energy generation, o;ering perhaps
the fastest, cheapest, and most e;cient
way of slashing greenhouse-gas emissions.
Developing these transmission lines,
however, is incredibly time-consuming and
expensive. The Trans West project was first
proposed in 2005, but the developers will
be lucky to secure their final permits and
begin moving dirt at the end of next year.
There’s no single agency in charge of
overseeing or ushering along such projects,
leaving companies to navigate a thicket of
overlapping federal, state, county, and city
jurisdictions—every one of which must
sign o; for a project to begin. As a result,
few such transmission lines ever get built.
Direct current, in which electric charges
constantly flow in a single direction, is an
old technology. DC and AC—alternating
current—were the subject of one of the
world’s first technology standards battles,
pitting Thomas Edison against his former
protégé Nikola Tesla in the “War of the Currents” starting in the 1880s.
AC won this early war, mainly because,
thanks to the development of transformers,
its voltage could be cranked up for long-distance transmission and stepped down
for homes and businesses.
But a series of technological improvements have substantially increased the
functionality of DC, opening up new ways
of designing and interconnecting the electricity grid.
For the past two years, James McCalley,
an engineering professor at Iowa State University, has been studying the best way to tie
together those massive grid systems as part
of the US Department of Energy’s $220
million Grid Modernization Initiative.
One way to solve the problem is to
expand existing “back-to-back” conversion stations to provide more east-to-west
transmission capacity. These systems allow
transmission between two grids, by converting the power to DC and then back to
AC again at the point where they “cross
How to get Wyoming wind
High-voltage direct-current transmission lines hold the key to slashing greenhouse gases.