It Looks Like California Passed the Solar Gigawatt Mark Today

That little yellow line climbs higher today than it ever has before | Graph courtesy California Independent System Operator

According to live data provided by the California Independent System Operator (CaISO), the agency that manages the state's power distribution grid, the state of California reached a long-anticipated milestone this afternoon (as I predicted last month). More than 1,000 megawatts of electrical power is coming into the state's transmission grid from solar sources, making solar the largest renewable energy contributor to the state's power consumption -- at least for a few hours. Statewide demand this afternoon is running at about 41,600 megawatts, so this solar milestone accounts for about 2.4% of total grid energy being used in California.

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According to the admittedly preliminary graph, which should be confirmed or adjusted when CaISO updates its Daily Renewables Output database, the grid started receiving more than 1,000 megawatts of solar electricity around 11:30 this morning.

The 1,000-megawatt (1-gigawatt) figure reflects only those solar facilities with power coming into the transmission grid: it doesn't include distributed generation such as net-metered rooftop solar panels, off-the-grid generation, or solar power generating capacity that happens to be offline -- in other words, the CaISO total is significantly less than the amount of solar power Californians are actually using this afternoon.

Until CaISo releases confirmation or clarification of this possible solar milestone details are going to be murky, but it's a safe bet that the majority of the solar power entering the grid today is coming from smaller-scale generating plants, and it's near certain that at least two thirds of the power is being generated by photovoltaic installations, given the technology's percentage of California's installed solar capacity. A report issued late last year by the National Renewable Energy Laboratory (NREL) said that of California's grid-tied solar generating capacity, which was 1385 megawatts in 2010, PV accounted for just under 1022 megawatts, with concentrating solar thermal making up the other 364 megawatts. Since then, the market bias in favor of PV has only deepened.

Solar power production is intermittent, and peaks during late morning and early afternoon. In terms of overall contribution to the state's energy demand, solar remains in third place after wind and geothermal. Wind's contribution to the grid generally peaks at between 2,600 and 3,000 megawatts each day, though it dies down to almost nothing during the hours when solar peaks. Geothermal provides a bit more than 900 megawatts of non-intermittent base load power pretty much 24/7.

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