Track and Tilt

The Energy Department’s Energy Information Administration rocks! When EIA isn’t reporting accurate detailed data on our industry, it’s publishing insightful analyses of the data.

Last week EIA published an analysis of solar systems that track the sun through the day.

Solar-tracking is very important: “Because photovoltaic panels operate more efficiently when oriented directly at the sun, some systems use solar-tracking technology to increase electricity generation by rotating the panels along one or two axes.”

Utilities and independent power producers with solar-tracking make more electricity per dollar than those without solar-tracking (and much more than home and other buildings with solar roofs that generally don’t have solar-tracking). And, so, solar with tracking prevents more carbon emissions per dollar.

The solar of the grid’s utilities and independent producers (now fifty-three percent tracking), is superior from both a dollar and environmental perspective.

In 2016, the solar of utilities and independent power producers had a twenty-seven percent capacity factor. Not bad. The capacity factor of home solar roofs averages sixteen percent.

EIA points out that solar-tracking is highly regional: “… tracking technologies have no benefit when capturing diffuse radiation because diffuse radiation is not concentrated in a certain trackable direction. The eastern United States has more average yearly cloud coverage than the western United States.”

Almost all the solar with dual-axis tracking is in California, Texas and Arizona. Almost all the solar with single-axis tracking is in California, Arizona, Nevada, New Mexico and Colorado. North Carolina and Georgia to a lesser extent are the sole eastern states with significant solar-tracking.

Makes sense. The best southwest areas for solar are deserts with little cloud cover. Solar is great there, even better with solar-tracking.

The best southeast areas for solar have far more cloud cover. Solar is not as good there, and solar-tracking doesn’t help much.

As for the northwest, Midwest and northeast, meh. New Jersey and Massachusetts are in the top ten states in solar capacity. Although their solar is almost exclusively fixed tilt (not solar-tracking).

The solar maps of the Energy Department’s National Renewable Energy Laboratory tell the story best.

The nation’s most productive solar will be in the desert areas of southern California to west Texas, including Arizona, New Mexico and southern Nevada. A solar panel put there will be much more cost-effective, and much more effective at slowing climate change, than if it’s put anywhere else in the continental U.S.

Last chance for you to weigh in on where solar and everything else in our industry is going in the coming years. Take our survey on electricity’s future. Just fifteen questions. Like wind power, it's a breeze. (Available through May 5, 2017)

Steve Mitnick, Editor-in-Chief, Public Utilities Fortnightly
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