Power from the North Slope by HVDC?

State-of-the-art high-voltage direct current, or HVDC, technology is changing the rule book for long-distance power transmission, thus perhaps making feasible the export of large-scale power supplies from the North Slope, Todd Glass, a partner with law firm Wilson Sonsini Goodrich & Rosati, told the Law Seminar International’s Energy in Alaska conference Dec. 8. An HVDC power transmission line hooked into a North Slope gas-fired power station might prove a viable alternative to a gas line for monetizing North Slope gas, he said.

“The estimated cost of bringing a 600- to 800-kilovolt HVDC system from the North Slope down at least to Valdez or thereabouts is about $1 billion to $1.2 billion,” Glass said. That cost compares very favorably with the cost of a gas line. Cheap power shipped from the North Slope could be connected into the Anchorage and Fairbanks areas as a power source for new industries. And it’s also possible to envisage extending a North Slope power transmission line down to the U.S. West Coast, Glass said.

A North Slope power transmission line might also support North Slope wind farms, or hydropower in the Brooks Range, he said.

“All of a sudden you’re going to have an electric power system that is robust and creates jobs, creates a whole lot of economic opportunity,” Glass said. “… This to me is exciting and this to me a real possibility.”

Long-distance HVDC transmission is a reality, and not a theoretical concept, with China for example having already established an HVDC transmission network, including a line connecting power generation near the Tibetan plateau into main electricity demand centers, Glass said.

“There are 800-kilovolt, 1,000-kilovolt lines that are being built from the generation systems to the load centers in China,” he said. “They are building them today.”

And in North America, there is a plan to lay a 500-kilovolt HVDC transmission cable between Vancouver Island offshore western Canada to the Olympic Peninsula of Washington state.

The traditional use of alternating current, as distinct from direct current, for transmitting electricity dates back to an 1880s feud between George Westinghouse and Thomas Edison over the appropriate technology for distributing electricity, with Westinghouse’s AC technology, devised by a Serbian called Nikola Tesla, winning out over Edison’s DC system.

But it has long been known that DC current moves power more efficiently than AC. And DC cabling, with few electromagnetic effects, can be buried underground or even run under water. A relatively thin DC line can carry a lot of power — rights of way for DC transmission lines are typically 70 percent smaller than those for AC lines, Glass said.

—Alan Bailey