Solar and nukes in a California summer

Things are changing rapidly on California’s electric grid, and they point the way to the future.

In early June 2013 SCE announced that it would permanently shutter 2.25 GW of operating capacity at the remaining two reactors at the San Onofre Nuclear Generating Station in San Diego. And late last week, PG&E shut down the 1.12 GW unit 1 at the Diablo Canyon nuclear power plant for repair work – directly preceding a heat wave in the Western US.

Which means that California is running on the 1.12 GW unit 2 at Diablo Canyon as its sole nuclear reactor.

This is an excellent test for the future. Diablo Canyon is built on a fault line, and both units should be shut down permanently. Especially after the Fukushima Disaster showed us exactly what can go wrong when you have a nuclear power plant operating on a fault line.

The nuclear industry would have you think that the sky will fall if we shut down our nuclear power plants, and that we are at risk of outages at times of intensified demand during heat waves. And while it is true that any drop in available capacity makes the grid more vulnerable, what the nuke industry and its small army of propagandists (including Breakthrough Institute) aren’t telling you is that nuclear power is not very well suited to meeting electricity demand during heat waves.

Nuclear generation is classified as “baseload” power. Nuclear power does not ramp well, and is run at near full capacity most all of the time. This is in part because turning nuclear plants up and down is costly, but also because, with many nuclear plant designs, reducing power puts excessive wear on components, which not only shortens plant lifetimes but becomes a safety issue over time.

Nuclear power is the least flexible “conventional” resource on the grid. These plants typically produce power 24/7 – including overnight, when it isn’t as valuable because we don’t need nearly as much of it.


Fortunately, we have a solution. We have solar power.

Solar is even less flexible than nuclear power. But the difference is that solar produces power during the day when it is sunny. Which is when we tend to need it the most, especially in places that are highly dependent upon air conditioning. Solar is the perfect solution to meet peak demand due to heat waves.

SCE has recognized that solar and other renewables are already helping to make up for the lost capacity at San Onofre, and stabilize the California grid. This is in large part because solar provides power when it is most needed.

California could get even greater “peak shaving” and environmental benefits if it installed more solar. SEIA puts California’s total solar electric capacity at 3.31 GW, and according to ISO data, the output of utility-scale solar photovoltaic (PV) and concentrating solar power (CSP) plants (not counting “behind the meter” residential and small commercial systems) hit a record output of just over 2 GW on a sunny day during the month of June.

By comparison, Germany had installed 32 GW of PV at the end of 2012, ten times as much as California. On a sunny day in June, Germany’s solar and wind power together peaked at 60% of demand with 29.6 GW, with solar providing 2/3 of that at 20.3 GW. What is particularly important is that Germany has shown that achieving this level of grid penetration is feasible, even without widespread electricity storage.

(Author’s note: This next paragraph was corrected following new data in August 2013)

To get to roughly to where Germany is at now, we would need to much more PV and CSP  to reach ~15.5 GW of PV & CSP. Which by my back-of-the-napkin math looks like enough to peak at roughly half of electricity demand during the day in the summer, which at times of peak output has been around 31 GW.

Of course, if we build CSP that incorporates thermal energy storage, it can be used to meet off-peak demand as well, and we can build much more.

California is on its way there. There are a number of very large PV and CSP plants which are due to be commissioned as early as this summer, including the 370 MW Ivanpah CSP project and the 250 MW California Valley Solar Ranch PV project.

Distributed solar will also play a large part, largely due to the success of third-party solar, which now represents ¾ of the state’s residential PV market. Of course, market success at both scales is driven by falling PV system prices.

If we can get there, heat waves will be a time to talk about electricity exports and low electricity prices, not possible outages.


One comment

  1. […] These new numbers, and more specifically more accurate numbers on peak demand and additional information on the role of other renewables have inspired a correction of a previous post: Solar and nukes in a California summer. […]

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