By - Jim Vess

A third of gas-fired plants on the California grid could be closed without a reliability impact, study says

Energize Weekly, August 15, 2018

Nearly a third of the natural gas-fired power plants on the California grid could be retired without impairing reliability, according to an analysis by the Union of Concerned Scientists (UCS).

There are 89 natural gas plants on the California Independent System Operator’s (CAISO) grid. Modeling by the UCS, a non-profit environmental group, found that 28 of them could be retired, with a blend of renewable generation and batteries taking up the load.

California has mandated a reduction in greenhouse gas emissions to 40 percent below 1990 levels by 2030 and 80 percent cut by 2050. The state also has a requirement of 50 percent renewable energy generation by 2030.

In 2017, renewables comprised 29 percent of the state’s electricity mix, and utilities are on a pace to meet the 2030 target. But meeting the pollution standards and future renewable energy goals will require limiting and focusing the use of natural gas, the UCS said.

Natural gas generation still made up 33 percent of California’s energy mix in 2017, with almost all units either “peaker” plants or combined cycle natural gas turbine plants (CCGT). Peakers are more flexible, but less efficient than CCGTs.

Natural gas-fired plants, both peakers and CCGT, can be ramped up in a relatively short period of time so that demand can be met even with the swing in solar and wind generation. “Natural gas generation will be needed through at least 2030 as cleaner energy sources and other grid reliability technologies come online,” the UCS analysis said.

The analysis said that California does not need to build any additional gas generation capacity in the CAISO territory to meet 2030 energy or reliability needs.

UCS said it used an investment-optimization model to see how much gas-fired capacity on the CAISO system could economically be retired between 2018 and 2030 to meet the state’s emission-reduction target and still assure reliability. CAISO manages a grid that covers about 80 percent of California.

The model showed that 23 percent of the CCGT capacity and 24 percent of the peaker capacity, 28 out of the 89 plants, could be retired starting in 2018 without jeopardizing reliability.

Many of the targeted plants are in the Central Valley, an area affected by year-round air pollution, the study said.

As more renewable generating capacity comes online between 2018 and 2030, natural gas generation’s production will drop by 8 percent or 4.2 million gigawatt-hours, the modeling projects.

The aggregate numbers, however, don’t tell the entire story. For while there may be less overall generation, natural gas-fired plants may be called on to ramp up and down more frequently—which could lead to more emissions of nitrogen oxides, precursors to ozone pollution, even as carbon emissions decline.

CCGTs would be used more often because they are more efficient, and the peaker plants that haven’t been retired by 2030 would be rarely used. Still, in 2018, there were zero cases of CCGT plants going from stopping to starting. By 2030, 16 of the CCGT plants still on the CAISO grid could see stop-starts 200 times a year.

“Unless investments are made in clean energy resources to reduce and satisfy evening ramp electricity needs, California’s gas fleet will cycle on and off much more frequently than it does today,” the analysis said.

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