Getting More Offshore Wind Energy to Northern California & Southern Oregon

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We recently released a new report that evaluates potential scenarios for electric grid transmission development to support floating offshore wind along the northern coast of California and the southern coast of Oregon. The scenarios include onshore and offshore (undersea) transmission systems, with interconnections ranging from 7.2 to 25.8 gigawatts of generation capacity. The study encompasses multiple possible wind farm sites between Coos Bay, Oregon and Cape Mendocino, California, including the two currently awarded lease areas located 20 miles off California’s Humboldt Bay, and two Draft Wind Energy Areas near Brookings and Coos Bay, Oregon.

Because the existing transmission infrastructure in these rural, coastal areas is very limited, major investments will be required to support offshore wind development. This report estimates that transmission infrastructure costs could range from $7.5 billion for a 7.2 gigawatt wind farm to as much as $41.3 billion for a 25.8 gigawatt buildout. For the 7.2 gigawatt scenario, annual system-wide benefits are estimated to be roughly $1.2 billion, when compared to a base case without offshore wind generation. These savings include both production cost savings and greenhouse gas emissions savings; the latter is valued at $72 per metric ton of avoided emissions, based on the EPA’s projected social cost of carbon.

The report examines combinations of onshore and offshore transmission solutions, utilizing both high-voltage alternating current (HVAC) and high-voltage direct current (HVDC). Estimates also include the costs to deliver wind power to nearby coastal communities. The analysis indicates that coastal communities near wind farms could be connected to the new transmission infrastructure, thereby increasing the reliability and available capacity of electricity in those areas, for only 0.4% to 2.4% of the overall cost of the transmission upgrades.

This study also includes a preliminary assessment of anticipated permitting challenges related to environmental impacts, land use conflicts, and undersea cable routing. The findings indicate significant variations in permitting difficulty, ranging from low to very high among the various possible routes.

Because the Pacific offshore wind buildout will take decades to accomplish, the report emphasizes that infrastructure investment decisions made in the early phases must be informed by expected long-term strategies—both to minimize cost and impact, and so that developments do not become stranded. Proactive, regional transmission planning is critical. Likewise, technologies installed today must be designed to adapt to future solutions.

We recommend next steps including taking a more detailed look at near-term transmission needs for the first phase of offshore wind development; a detailed analysis of transmission routes, land ownership, and rights-of-way; and an assessment of the potential to couple battery energy storage with offshore wind.

This study was funded by the California Energy Commission and the Office of Local Defense Community Cooperation of the U.S. Department of Defense, and developed in close collaboration with the Oregon Department of Energy. Technical project partners included the National Renewable Energy Laboratory, Quanta Technology, H. T. Harvey & Associates, Mott MacDonald, and Conaway Geomatics.

News release from Schatz Energy Research Center.

Related Offshore Wind Energy Publications

Northern California and Southern Oregon Offshore Wind Transmission Study

• Volume 1: Executive Summary and Main Report (2023)
• Volume 2: Appendices (2023)

Transmission Alternatives for California North Coast Offshore Wind

• Volume 1: Executive Summary (2022)
• Volume 2: Description and Preliminary Analysis of Transmission Alternatives (2022)
• Volume 3: Transmission Analysis (2022)
• Volume 4: Cost-Benefit Analysis Report (2022)

Additional wind reports (2021-2023)

• Competitive Offshore Wind Leases on the U.S. Outer Continental Shelf: A Review of the Use of Multiple-Factor Auctions and Nonmonetary Credits (2023)
• California North Coast Offshore Wind Study: Wind Speed Resource and Power Generation Profile Augmentation Report (2022)
• Del Norte County Offshore Wind Preliminary Feasibility Assessment (2021)

California North Coast Offshore Wind Studies

• 1. Description of Study Assumptions (2020)
• 2. Wind Speed Resource and Power Generation Profile Report (2020)
• 3. Offshore Wind and Regional Load Compatibility Report (2020)
• 4. Interconnection Feasibility Study Report (2020)
• 5. Subsea Transmission Cable Conceptual Assessment (2020)
• 6. Electricity Market Options for Offshore Wind (2020)
• 7. Electricity Market Revenue Study (2020)
• 8. Interconnection Constraints and Pathways (2020)
• 9. Economic Viability of Offshore Wind in Northern California (2020)
• 10. Economic Development and Impacts (2020)
• 11. Coastal Infrastructure Co-Benefits Linked to Offshore Wind Development (2020)
• 12. Electricity transmission policy analysis (2021)
• 13. Existing Conditions and Potential Environmental Effects (2020)
• 14. Feasibility of Potential Subsea Cable Corridor Scenarios (2020)
• 15. Environmental permitting policy analysis (2021)
• 16. Overview of geological hazards (2020)
• 17. Anchoring technology risk assessment (2020)
• 18. Export cable landfall (2020)
• 19. Port infrastructure assessment report – and report appendixes (2020)

• 20. Social impacts to other communities that experienced offshore wind: a literature review (2020)
• 21. Stakeholder benefits and concerns (2020)
• 22. Subsea transmission cable stakeholder identification (2020)
• 23. Military mission compatibility (2020)
• 24. Summary report of the webinar series (2020)