Matthew Wald in his New York Times blog, has more information about the construction of the Electric Superhighway up and down Delaware’s coast.

Onshore, we use an AC grid, or one based on alternating current. But the link in the Atlantic would have to be buried, and alternating current does not work well in long cables that are enclosed because the interaction between the current and the cable casing drives up voltage to unwanted levels. So the system has to be direct-current.

Nearly all the submarine cables use direct current, a form of transmission favored by Thomas Edison but mostly rejected in the late 1800s in favor of alternating current, the kind of electricity now used to run most appliances. But alternating-current lines are hard to bury, because an interaction between the current and the cable casing drives up voltage to unwanted levels.

The cost of putting a cable under water can be lower than burying cables on land, because workers can lay the cables from giant reels, allowing stretches of more than a mile with no splices. But underwater lines are still more expensive than lines on transmission towers. Much of the cost in each case is to transform the electricity to direct current, a form that is easier to use in buried cables.

New technology offered by two European companies, Siemens and ABB, has lowered the cost for some direct current projects, and shrunk the size of the terminals where alternating current is converted to direct current and back, a crucial consideration in urban projects.

One of those companies Siemens, has a plant here in Glasgow, Delaware. Recently, European transmission experts were in town to deliberate.

So the new proposal for an Atlantic Wind Connection is actually about a series of links terminating at substations built on platforms that would sit in the ocean like oil drilling platforms, except, of course, these are clean-energy installations harnessing wind power. They would have to be hurricane-proof and include a spot where a service vessel could moor. Wind farms would tie into the system here.

The cable itself, weighing about 30 pounds a foot, would be lowered into a shallow trench that would be blasted by a device called a jet plow that squirts ocean water into the soil. The cable goes into the trench and is gradually covered over with sediment.

The cable itself is copper, with 1.75 to 2 inches of insulation and multiple shielding layers. It may have a steel outer guard. The outer diameter would be about six inches.

But beyond three miles from shore, no matter where it goes, the cable has a major advantage over cables on land: it faces only one landlord at the outset, the Department of Interior. And the department is sympathetic to wind.

This is a wake up call for Delaware. Governor Markell, Congressman-elect John Carney, Senator-elect Chris Coons, and Senators Ted Kaufman and Tom Carper, all need to get moving on this opportunity now, if only to head off those other states who will be trying to muscle in… These next 24 hours are critical.

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