Dive Brief:

• Staff of the California Energy Commission have completed an assessment of the state's transmission grid and its ability to bring online large amounts of additional renewable capacity, finding significant investment will be required to alleviate widespread constraints.
• The report finds several Transmission Assessment Focus Areas (TAFAs) where more than 40,000 MW of wind, solar and geothermal resources could be developed to help California meet its goal of 50% renewables by 2030.
• However, the report found the state's existing transmission system, including projects under development, has limited capability for new full capacity resource interconnections. More than $5 billion in investment could be required.

Dive Insight:

In order to source half its generation from renewables in the next 15 years, California is going to require significant investments in its transmission system. To that end, the state formed the Renewable Energy Transmission Initiative, which aims to identify necessary grid projects to help meet clean energy goals.

The Transmission Technical Input Group finalized its report last month, finding little room for growth for full capacity interconnections. For energy-only connections, the picture is better: the California ISO has estimated it could accommodate over 22,000 MW with the current system.

The cost to upgrade and build new transmission to bring on all of the identified renewables at full-capacity could be as much as $5.5 billion, the report found. The largest project, in the Sacramento River Valley and other nearby areas, could cost up to $4 billion and would access almost 5,500 MW of new renewable capacity.

"The area with the least potential to deliver new renewable energy is Northern California," the report concluded. " The bulk transmission system in the region is heavily utilized and would require substantial investment to allow for the delivery of new full capacity resources."

The high voltage transmission system in northern California includes three 500-kV lines called the California-Oregon Interties (COI), which extend from those states' border to the Tesla and Tracy Substations south of Sacramento. The lines are used to bring 4,200 MW of hydroelectricity into the state, but with an approved rating of 4,800 MW, there is little room left for additional solar and wind.

The upgrades, estimated at $2 billion to $4 billion, would likely include a new 500 kV line between California-Oregon border and Tracy/Tesla area.