Can Solar Fill the Hydropower Gap During California’s Drought?
Solar Is Growing, But Hydro Remains Much Bigger
A tweet this morning sent me on a fact-checking expedition into state-level electricity statistics. The subject was a San Jose Mercury article with the unwieldy title, “Drought threatens California’s hydroelectricity supply, but solar makes up the gap.” The article’s quote from the head of the California Energy Commission 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 gut reaction was to be skeptical: 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.
The Comparison Has Shifted In the Last Year
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 October 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. On a January-November basis — December 2013 data isn’t yet available — solar electricity in the state increased by 1.5 million MWh, compared to the same period in 2012, while hydropower fell by nearly 1.8 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.
The Benefits of Installing Solar Where It’s Sunny
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 that same 11-month period produced over 93 million MWh, or 56% of the state’s non-imported electricity supply. It’s mainly gas that is filling 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.
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