CAISO and its sister state agencies released a final, more detailed analysis Wednesday of the mid-August blackouts and steps they are taking to prevent capacity shortfalls this summer and beyond.

“We recognize our shared responsibility for the power outages many Californians unnecessarily endured,” stated a cover letter to Gov. Gavin Newsom signed jointly by the heads of CAISO, the California Public Utilities Commission and the state’s Energy Commission. “The findings of the final analysis underscore this shared responsibility and give greater definition to actions that can be taken to avoid or minimize the impacts to those we serve.”

Requested by Newsom, the report incorporates data that was not yet available during the preparation of a preliminary root-cause analysis issued in October. (See CAISO Says Constrained Tx Contributed to Blackouts.)

The final report mainly confirms the preliminary conclusion that the rolling blackouts CAISO ordered Aug. 14-15 resulted from a combination of severe heat across the West, inadequate resource planning and market practices that undermined procurement. But it elaborates on those findings with more specific evidence and recommendations gleaned from months of investigation.

“This Final Root Cause Analysis provides important insights and lessons learned about the factors that contributed to the rotating power outages of last summer,” CAISO CEO Elliot Mainzer said in a statement. “As we prepare for summer 2021 and beyond, I look forward to working closely with the CPUC, CEC, policymakers and regional stakeholders to bring our planning, procurement and operational practices together into a modernized and well-integrated resource adequacy framework for California.”

CAISO previously said that import bids in the day-ahead market were 40 to 50% higher during the energy emergencies of August than typical resource adequacy requirements at that time of year, but transmission constraints limited the transfers into CAISO’s footprint. A major transmission line from the Pacific Northwest had been derated because of the weather, the preliminary analysis reported.

The final analysis newly reported that the line in question had experienced a forced outage because of a storm in May 2020 that damaged the line and derated the California-Oregon Intertie (COI) into August.

“The derate reduced the CAISO’s transfer capability by nearly 650 MW and caused congestion on usual import transmission paths across the COI and Nevada-Oregon Border,” the final report said. “In other words, more energy was available in the north than could be physically delivered, and the total import level was less than the amount the CAISO typically receives.”

One of CAISO’s current efforts — part of its Resource Adequacy Enhancements stakeholder initiative — is a controversial proposal to contract for the highest level of firm transmission into CAISO from the Northwest, guaranteeing delivery of essential hydropower resources. (See CAISO Seeks ‘Firm’ Tx for Resource Adequacy.)

Another RA effort involves more accurately accounting for the capacity of intermittent resources such as wind and solar, which can be unpredictable.

Updated figures in the final report showed combined RA values for solar and wind fell by 1,300 MW Aug. 14-15. Solar generation was reduced because of high cloud cover and smoke from wildfires raging at the time. Wind generation dropped without warning by 1,200 MW on Aug. 15 caused by tropical storm influences from the south.

When wind plummeted during the so-called net peak, as solar waned and demand remained high in the early evening, CAISO was unable to maintain its safety reserves to prevent larger grid failure.

The report recommends that the state update it estimations of wind and solar capacity.

“The CPUC has improved the methods for estimating the reliability megawatt value of solar and wind over the years, but the reliability value of intermittent resources is still over-estimated during the net peak hour,” it said. “Improvements to the RA program should account for time-dependent capabilities of intermittent resources.”

More RA, Batteries

The report noted other efforts underway to avoid future shortfalls. They include an emergency reliability rulemaking by the CPUC to procure additional resources to meet demand this summer.

“Through this proceeding, the CPUC has already directed the state’s three large investor-owned utilities to seek contracts for additional supply-side capacity and has requested proposals for additional demand-side resources that can be available during the net demand peak period (i.e., the hours past the gross peak when solar production is very low or zero) for summer 2021 and summer 2022,” the report said.

CAISO is performing an analysis to increase the CPUC’s RA procurement targets.

“Based on the analysis to date, CAISO recommends that the targets apply to both the gross peak and the critical hour of the net demand peak period during the months of June through October 2021,” it said.

The ISO is expediting a stakeholder process to consider market rule changes by June to “ensure the CAISO’s market mechanisms accurately reflect the actual balance of supply and demand during stressed operating conditions.” (See Summer Readiness Sought by CAISO, CPUC.)

CAISO is also working to integrate hundreds of megawatts of battery storage into its grid by summer to store excess solar and wind power for use during the evening net peak. The CPUC said it is trying to remove regulatory obstacles to battery and generation resources coming online by this summer.

“The acceleration of climate change demands we enhance our planning efforts and market practices at a faster pace and with broader anticipation for what is possible,” CPUC President Marybel Batjer said in a statement. “It is our top priority to ensure we have the demand- and supply-side resources needed to maintain reliability, and this [final root-cause] analysis demonstrates how we will do it and continue to decarbonize the grid.”