High Voltage DC and Ultra High Voltage DC are mature technologies that excel at integrating variable power sources like solar and wind into local grids. This is especially important for large scale offshore wind projects, or large scale solar power production. HVDC has numerous advantages over traditional HVAC transmission beginning with less transmission losses that accrue to significant levels:
A basic rule of thumb: for every 1,000 kilometres the DC line losses are less than 3% (e.g. for 5,000 MW at a voltage of 800 kV). Typically, DC line losses are 30–40% less than with AC lines, at the same voltage levels, and for long-distance cable transmission DC is the only solution, technically and economically.
Siemens website.
Above ground transmission: HVDC uses a right of way footprint about one third that of HVAC. HVDC is two conductor, HVAC is three conductor plus the neutral, resulting in lower installed cost per mile.
Graphic courtesy of
HVDC is better than HVAC in offshore underwater applications:
For underwater transmission systems, the line losses due to capacitance are much greater, which makes HVDC economically advantageous at a much shorter distance than on land.
Wiki
Siemens installs Ultra High Voltage DC transmission systems with a capacity of 7 gigawatts at 800Kv, with distances exceeding 2000 miles. 7 gigawatts is about the equivalent output of 7 nuclear power plants.
HVDC systems allow Utilities to move power from far flung locations to where its needed and to integrate solar and wind power generation as levels change geographically day to day and hour to hour.
HVdc has emerged as an economically viable solution for long distance large power applications.
-- HVdc cables keep energy losses to 3% per 1,000 km
-- Long underwater AC cables are impractical due to losses
-- HVdc cables generate virtually no electromagnetic fields
-- HVdc systems offer excellent (4 quadrant) control over power flows
-- Underwater routes minimize environmental impact
-- HVdc transmission has a high rate of availability and reliability
-- Underwater HVdc systems have extremely high reliability of service and are almost invulnerable to weather outage events.
H/t to jamess for the above bullet points.
But jamess, I would add one more significant point, yes HVDC is better, its also cheaper to build than AC for long distance transmission.
Several HVDC projects have been built, or will be built, on the east coast of the US:
Long Island NY to NJ
NJ to NYC
Atlantic Wind Connection, a 350 mile long HVDC trunkline from roughly Sayreville NJ to Virginia Beach Virginia to support 6,000 to 7,000 Mw of Wind power.
Thematic representation of the Eastern European Supergrid
North Sea HVDC supergrid
Maine Express will be able to move power from Maine to the city of Boston:
The DOE estimates that the goal of 20% of electricity from wind in 20 years can easily create long term jobs, this does not include HVDC smartgrid work.
Next time someone tells you "what happens when the wind doesn't blow?", you can answer that the wind is always blowing someplace, we just have to move the power to where its needed. And HVDC can do that. Green Bay to LA, Detroit to NY.
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The companion diary to this one, a look at the Atlantic Wind Connection
http://www.dailykos.com/...