California ISO (CAISO) Draft 2021-2022 Transmission Plan

February 3, 2022
John Dalton

California ISO (CAISO) just released its Draft 2021-2022 Transmission Plan, which included an offshore wind (OSW) sensitivity that included the following resources: Humboldt Bay (1,607 MW), Diablo Canyon (4,419 MW) and Morro Bay (2,324 MW). Humboldt Bay and Morro Bay are two wind energy areas that have been identified by BOEM, which is expected to conduct an auction for them in the Fall. In addition, the Draft Transmission Plan identifies what is characterized as the remaining OSW resource potential in California, all in Northern California (Del Norte @ 6,605 MW and Cape Mendocino @ 6,216 MW).   The Morro Bay OSW is assumed to connect to the Morro Bay 230 kV substation.  A high level evaluation indicated that the 230 kV substation does not have the required capacity and a new 500 kV substation would be required, at a cost of about $110 million. The Draft Transmission Plan indicated that with the 4.4 GW from Diablo Canyon a new 500 kV line from Diablo to Gates would be required. With the Diablo Canyon WEA conflicted, the development of just Morro Bay would avoid that 500 kV line. Not surprisingly, given the sparseness of transmission infrastructure in coastal Northern California, landing OSW from Humboldt Bay is considerably more difficult. There are no existing substations with sufficient capacity close to the Humboldt Bay WEA. In addition, the Transmission Plan notes “the CPUC guidance in selecting transmission solutions for 1,607 MW at Humboldt Bay, is to be “least regret” if ultimate potential of 14,428 MW in outlook is developed... Therefore a conceptual interconnection option for the 14,428 MW was needed to ensure the interconnection option for the 1,607 MW Humboldt Bay is part of a bigger plan”. This bigger plan involves an assessment of a range of EHV AC and DC alternatives, with costs that suggest any such “least regret” transmission development strategy will need to be accompanied by a CAISO Tehachapi-style coordinated transmission solution. Furthermore, this analysis suggests that absent a commitment to coordinated transmission development with requisite cost sharing it’s unclear how a Humboldt Bay lease area would attract much attention from other than the most patient capital.