As solar floods California grid, challenges loom
To fill the gaps when solar isn’t available, the state relies on plants that burn natural gas
The same clear, sunny weather that broiled much of California in near-triple-digit heat this past week also helped the state’s solar power plants set a record, briefly generating enough electricity for more than six million homes.
Just after 1 p.m. Tuesday, large solar plants scattered across California produced a record 8,030 megawatts of electricity, according to the California Independent System Operator, the organization that operates most of the state’s renewables grid. That’s nearly twice as much solar power as California could generate just two years ago.
But the push to add renewable power has other complications, given that the sun doesn’t shine at night and wind is intermittent, too.
The output from solar plants peaks at midday, stays close to that level for several hours and then tails off sharply in late afternoon. California’s wind farms produce most of their electricity from late afternoon into the night. Electricity demand, meanwhile, tends to hit its daily peak around 6 p.m. — just as solar power is fading and wind is still revving up.
To fill the gap, the state relies on power plants that burn natural gas, plants that can ramp their output up and down quickly. Utilities such as Pacific Gas & Electric Co. also offer customers incentives to use less power, through measures such as turning off lights, during the critical afternoon hours. On Friday, for example, PG&E asked some customers to power down between 2 and 7 p.m.
“We’re changing our paradigm from a grid that is largely traditional resources augmented by renewables to one that’s based on renewables augmented by traditional resources, mostly natural gas,” said Steve Berberich, CEO of the Independent System Operator. “Our goal is to make the gas element as small as possible.”
When electricity demand on Tuesday reached its peak almost 29 per cent of the electricity coursing over the grid came from renewable sources, according to the Independent System Operator.
For a brief time on May 16, renewables accounted for 56 per cent of the grid’s electricity, according to the operator.
These figures don’t count the electricity generated by the more than 537,000 rooftop solar arrays on houses and businesses. Together, those arrays can produce up to 4,211 megawatts of electricity.
PG&E, which is California’s largest utility, estimates that California’s increasing use of solar and wind energy pushes up electricity rates between one and two per cent each year. Renewable power prices, however, are dropping fast, as more solar and wind projects come online.
The growing availability and declining price of renewable power contributed to PG&E’s decision to close California’s last nuclear plant, Diablo Canyon, in 2025. PG&E has pledged to replace the plant with electricity sources that don’t pump greenhouse gases into the atmosphere, so that the utility would get 55 per cent of its electricity from renewable sources.
“Each time we go out for bids, renewable prices have been going down, particularly photovoltaic (solar), and we have no reason to believe that’s not going to continue,” Earley said.
One challenge, paradoxically, is that California has added so many solar plants that the grid doesn’t always have room for all of the electricity.
On Tuesday, for example, grid operators had to curtail 292 megawatt-hours of solar electricity, equal to 292 megawatts over the course of an hour.
To deal with occasional excess power, the Independent System Operator is exploring the possibility of launching a unified power market that would cover most western states, so that California’s solar plants and wind farms could sell their excess power to customers outside the state.
Our goal is to make the gas element as small as possible.” STEVE BERBERICH, INDEPENDENT SYSTEM OPERATOR