What kind of onshore transmission infrastructure would be necessary to accompany Humboldt offshore wind?

Offshore wind turbines produce a tremendous amount of electricity — far more than is needed locally here in Humboldt County. Because our existing transmission infrastructure is extremely limited and insufficient to transmit so much energy to other parts of California, successful implementation of offshore wind would necessitate the construction of new transmission lines to connect Humboldt with the rest of the State.

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The California Independent Systems Operator (CAISO) annually recommends the construction of new transmission infrastructure in a document known as the Transmission Plan. The Draft Transmission Plan for 2023-2024 (1) contains several recommendations for new transmission infrastructure specifically to serve offshore wind electricity generation, which are as follows:

• A new Humboldt 500-kilovolt AC substation

• A new 500/115-kilovolt transformer and approximately 6-mile line connecting offshore wind energy to the local Humboldt Bay grid

• A new 500-kilovolt AC line that would run approximately 140 miles east toward Redding

• A new 500-kilovolt HVDC line that would initially be operated as a 500-kilovolt AC line and run approximately 260 miles southeast toward the San Francisco Bay Area

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CAISO estimates that these improvements would cost approximately $4.2 billion and would be completed by 2035. The CAISO board approved this plan on May 23rd, 2024. For more info, watch this Schatz Energy Research Center video about Offshore Wind and Transmission Infrastructure in Northwestern California (2):