Total Eclipse of the Sun

Written By: Laurel Kruke, Sustainability Manager

How many of you took time on August 21, 2017 to check out the total eclipse? One of our Pierce Energy colleagues drove up to Idaho to view it in the path of totality. I was in the Chicago-area, and saw it at approximately 90% (with my safety glasses of course!). Even if you weren’t in a spot where you could see the full spectacle, it was still an exciting thing to witness – especially since it doesn’t happen very often – the next total eclipse won’t be visible in the continental U.S. until April 2024.

Even though the eclipse happened a few weeks ago, there are some interesting points to share. One relates to the eclipse’s impact on solar/photovoltaic (PV) arrays and production. In the path of totality, the sun was blocked for up to about three minutes; even outside of the path of totality, there was decreased sunlight in some areas of the country for up to three hours. This means that for a period of time on an otherwise sunny day in August (at least in some areas), solar panels were suddenly shaded and unable to produce power from their main source. In California, this was significant because large PV arrays produce approximately 40% of the country’s total solar capacity. To accommodate the power that would have come from solar and keep up with the typical electricity demand during the time of the eclipse, other sources, such as natural gas or hydroelectric, needed to ramp up to substitute power. According to (a website devoted to sharing news about new technologies that impact society), the electricity grids were well-prepared for the drop in solar production. Many locations in the path of totality saw mild conditions that day, which meant lower demand for air conditioning, and areas like California and North Carolina (which are home to large utility-scale PV arrays) could supply any excess needs with sufficient reserves from their hydroelectric sources.

Another outcome of the eclipse (and one that will continue to build during the years leading up to the next one) is the data collected by students and faculty at universities around the country. The total eclipse presented a prime opportunity to collect and study data about space, atmospheric conditions, and weather changes during events like this. For example, students and faculty at Maryville College, in Maryville, TN, gathered measurements about what was happening in the weather and atmosphere during the eclipse. In Maryville, TN, the total eclipse lasted for 97 seconds, and presented some interesting findings. The temperature in Maryville dropped by over 9°F, and wind speeds decreased by 1 meter per second. This presents questions about how wind power may also have been impacted during the eclipse. Wind power is not a significant contributor to the U.S.’s power grid (yet) so saw less eclipse questions and coverage (unlike solar power), but better understanding about how quick changes in wind speed could impact production of large-scale wind turbines could help understand the benefits of wind power in the future. This initial data collection will assist future studies of these questions, especially leading up to the 2024 total eclipse.

While the eclipse itself is over, there are still many related pieces of information students can discover. NASA and the Department of Energy provide some education and other resources to learn more about total eclipses. Hopefully these events, and the information and study surrounding them, will encourage heightened interest in science and engineering so we can uncover more of the secrets in the sky!