The growing shift to more reliance on renewable resources for electric generation in California has put nearly 10,000 MW of natural gas-fired generation sources in a state of flux for grid planners in the state.

At a time when federal and state regulators are calling for closer coordination between power grid and gas transmission pipeline operators, the job is getting more complex as evidenced by the latest 378-page draft transmission plan released last Thursday by the California Independent System Operator (CAISO) that included six special reliability studies, one of which was the analysis of possible gas generating plant retirements.

As part of planning scenarios, CAISO identified 9,659 MW of gas-fired generation that are at risk of retiring at a time when the state has moved up its goal for renewable-based power supplies to 50% by 2030, keeping its current goal of 33% renewables by 2020. The state ban on the use of seawater to cool coastal plants is part of what is driving the push for more gas plants to retire.

“The significant amount of new renewable generation being added to the grid is also putting economic pressure on the existing gas-fired generation fleet, especially for those generators not obtaining resource adequacy contracts,” the CAISO report said.

CAISO’s report was in response to this economic uncertainty for gas-fired generators, and it attempted to look at the potential grid reliability issues that could arise from certain plant retirements when certain ancillary services for the grid might be “unduly compromised” by the unfolding changes in the power generation economic landscape.

The report’s focus was on what CAISO analysts’ called “the evolution of the grid to meet a 50% renewable portfolio standard (RPS) by 2030.”

CAISO documents the changing day-to-day operations of both the power and gas grids, and the corresponding need for more flexible capacity in the state’s generation mix. As a result, “capacity insufficiencies occur in early evening after sunset, which is the new peak load time,” the CAISO report said.

These capacity insufficiencies in the grid operations will begin to emerge when retirements for gas generation reach the 4,000 to 6,000 MW range, according to the report, which was prepared with the help of stakeholder meetings held last year and in the first two months of 2017.

As part of the stakeholder feedback, CAISO said there is strong interest in the specials studies, and the grid operator now has “numerous comments” on how it eventually responds to the issues raised in gas plant retirement analysis. Where additional work is needed has been identified.