California Solar Beats Wind For Several Days This Autumn

A turbine at Altamont Pass in Northern California | Photo: KQEDQuest/Flickr/Creative Commons License

As California heads into the slightly less windy days of autumn with more solar power generating capacity than it's ever had, something interesting is starting to happen -- there are days when solar provides more power to California's grid than wind does.
For at least three days this fall, the state's solar power generators pumped more total power into the grid than all the state's wind turbines, which usually provide more power than any other form of renewable energy. And it looks like we're on track for the same thing to happen today.

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On September 27, according to figures from the California Independent System Operator (CaISO), which operates most of the state's grid, solar power facilities pumped a total of 8,257 megawatt-hours into CaISO's grid. That's enough power to keep a 100W incandescent lightbulb burning for 9,419 years and seven months. On that day, wind turbines -- which usually feed somewhere between 25,000 and 50,000 megawatt-hours into the grid each day -- provided only 6,914 megawatt-hours to CaISO.

ReWire contacted CaISO's Steven Greenlee the next day for an explanation, and he might just as well have told us to open a window:

The weather pattern we had yesterday was very similar to a hot summer day where there is ridging over California and low pressure off the coast, which keeps the pressure gradient from building up along the coast. This pressure gradient along with a thermal gradient is the main source for wind production during summer conditions. (The pressure gradient is stronger from west to east and you have temperatures hotter from east to west, which causes air to move from the coast to inland.) Thus, we had low amounts of wind and nice sunny weather.

The same thing happened on October 1, when solar output 7,333 megawatt hours to wind's 5,424, and on October 14, with solar and wind providing 7,364 and 5,712 megawatt-hours, respectively.

That's not to say that solar outpaced all other forms of renewable energy on those days. Even on October 1, when solar beat wind by 1909 megawatt-hours, the state's geothermal power plants -- which run 24/7 unless they're being repaired or upgraded -- put a reliable 20,869 megawatt-hours into the grid.

And for perspective's sake, the three days mentioned here -- and possibly October 15, from the looks of CaISO's preliminary figures -- are unusual even for autumn. On October 5 wind produced nearly ten times the power solar did in California, at 52,340 and 5,509 megawatt-hours, respectively.

But still, this is an indication that the state's solar capacity -- most of it PV -- is growing by leaps and bounds. And it's a reminder that -- despite what your in-laws in Ohio tell you -- California actually does have seasons.

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