Thursday, February 27, 2014

Can Solar Fill the Hydropower Gap During California’s Drought?

  • Although the scale of California's conventional hydropower remains much larger than that of solar power, solar's rapid growth provides a meaningful contribution to the grid.
  • Solar power can work nearly anywhere, but installing it where it's actually sunny much of the time pays big dividends.

After reading a San Jose Mercury article with the unwieldy title, “Drought threatens California’s hydroelectricity supply, but solar makes up the gap” I was intrigued enough to do a little fact-checking on state-level  electricity statistics. The article quoted the head of the California Energy Commission, who implied that solar power additions were sufficient to make up for any shortfall in hydro, historically one of the state’s biggest energy sources. My initial skepticism about that claim turned out to be largely unfounded.

Solar has been growing rapidly, especially in California, but even with nearly 3,000 MW of photovoltaic (PV) and solar thermal generation in place, it’s still well short of the scale of California’s 10,000 MW of hydropower dams, especially when you consider that the latter aren’t constrained to operate only in daylight hours. However, I also know better than to respond to a claim like this without checking the data on how much energy these installations actually deliver.

My first look at the Energy Information Administration’s annual generation data seemed to confirm my suspicions. In 2012 California’s hydropower facilities produced 26.8 million megawatt-hours (MWh), while grid-connected solar generated just 1.4 million MWh. However, when I looked at more recent monthly data, the mismatch was much smaller, due to solar’s strong growth in the Golden State. For example, in September 2013 California solar power generated 435 MWh, or nearly 24% of hydro’s 1.8 million MWh.

The potential drought benefits of solar stand out even more sharply when we compare the growth in solar generation to the change in output from hydro. Last year solar electricity in the state increased by 2.4 million MWh, compared to 2012, while hydropower fell by 2.3 million MWh. That added solar power won’t provide grid operators the same flexibility as the lost hydropower, because of its cyclical nature, but it is clearly now growing at a rate and scale that makes it a serious contributor.

I’d be remiss if I didn’t point out that solar in California is still nowhere near the scale of the state’s biggest electricity source, natural gas generation, which in 2013 produced over 100 million MWh, or 57% of the state’s non-imported electricity supply. Gas is also filling much of the roughly 18 million MWh shortfall left by the early retirement of Southern California Edison’s San Onofre Nuclear Generating Station last summer, and if the state’s drought worsens, gas will be the main backup for further declines in hydropower.

Yet solar’s growing contribution to the state’s energy mix provides a clear demonstration that while generous state and federal policies can make installing PV economically attractive nearly anywhere, it’s abundant sunshine like California’s that makes it a useful energy source, especially when drought conditions reduce the output of other, water-dependent energy supplies.

A different version of this posting was previously published on Energy Trends Insider.


Daniel said...

Wow! You mention solar without (as much of) the knee-jerk bashing of yesteryear...maybe in another few years you will have moved a neutral stance and a few years after that you may embrace solar--well one can dream!

Haven't checked your blog for nearly a year (you sorta asked me to stop commenting a couple-three years ago.)

Geoffrey Styles said...

Long time, no see. It's often hard for advocates to differentiate between objectivity and "bashing". If you review the past posts you perceived as anti-solar, I think you'll find they were critical of solar policies, which is not at all the same thing as criticizing the technology, which I have always thought had great potential. And as the gap closes with falling PV costs, the justification for policies that treat solar more generously than other energy sources also diminishes.

Unknown said...
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Geoffrey Styles said...

Angela Navejas,
If you'd like to advertise on this site, please contact me at the email provided.

Joseph Somsel said...

One point you missed is the dispatchability of California's hydro.

While some of the federal hydro projects have large storage resevroirs, power production is constrained by irrigation water deliveries. The privately owned hydro plants are largely run-of-river plants with little storage. Production in late summer or fall is close to nil.

Neither offer the flexibility to offset solar unreliability.

Just looking at annual energy sales gives you nowhere near the real story/ That's why environmentalists and crony capitalists tell you only part.

Geoffrey Styles said...

These are important concerns, particularly since energy storage is nowhere near the scale required to make intermittent sources like wind and solar dispatchable in the traditional sense. The state's new storage mandate seems aimed at integrating intermittent sources on an hourly basis, but the resulting storage capacity won't store enough energy to make up for long (days to months) gaps in hydro output. If the drought persists, CA will burn more gas as a result, even while solar reduces incremental gas demand from what it might have been otherwise.