Today at 1:20 pm in Gates County, NC the skies will begin to darken as the moon passes in between the Sun and the Earth, obscuring approximately 88% of the sun in this rural North Carolina location. This will mark the first eclipse to cross the entire US, from Oregon to South Carolina, in the last 99 years. The eclipse will peak at 2:46 pm EST, and last for up to three hours, but the total time that the sun is completely shaded will only be about 2 minutes and 40 seconds (1).

Figure 1: Utility Scale Solar Farms in the Eclipse Path (EIA)

So what is the significance of this Gates County community, with a population of less than 2,000 people, in relation to this celestial phenomenon? It is home to the Gates Solar farm, a 5 Megawatt solar power plant that generates enough power to meet the needs of almost 1,000 average US homes every year. The Gates Solar Farm is owned and operated by O2 emc, an independent power producer based out of Cornelius, NC.

Figure 2: Gates Solar Farm in Eure, NC

The solar farm generates about 11,000 MWh of clean energy a year that is delivered into the Dominion Energy electric grid. The local electric grid powers the farms, homes, schools and business in Gates County.

Figure 3: NEXTracker TrueCapture System

The Gates Solar Farm uses a single axis tracking system that shifts the panels according to the sun’s position in the sky throughout the day to maximize solar energy capture. This system should allow the solar array to accurately measure the effect of decreased radiation during the 3 hour solar eclipse window, since it maximizes the angle of the solar panels towards the sun throughout the day. In addition, O2 emc has partnered with NEXTracker, the manufacturer of the state of the art tracking system, to allow Gates Solar to serve as a field trial site for the new NEXTracker TrueCapture™ self-adjusting tracker control system. The TrueCapture system uses advanced sensors, weather forecasting, and machine learning technologies to maximize energy yield by enabling each tracker row to compensate for geographic features, terrain, and weather in real time (2). Watch this video animation to learn more.

O2 emc’s solar farm in Gates County is one of 1,900 utility-scale solar power plants in the US that lie in the path of the eclipse today (3). With such a large number of solar power plants being affected by this phenomenon, scientists, utilities, news stations, and the public have been asking, “How will the sudden drop of in solar energy production affect the stability of the grid for these 3 hours?”

Figure 4: Solar Generation Capacity Obscured by the Eclipse (EIA)

This question is especially significant to states with larger amounts of installed solar capacity, namely California and North Carolina. Most of North Carolina will experience a 90% obscuration of the sun during the peak of the eclipse. This means that nearly 2,000 MW, or 61%, of the state’s solar generating capacity will be lost for a few hours today (4). Although solar power plants generate less than 3% on average of the electricity to meet demand in North Carolina, solar can generate more than 10% in some areas of North Carolina. The gradual ramp down of solar generating capacity during the eclipse will be well within the 20% reserve margin that utilities are required to maintain, so no problems are anticipated. However, the Gates Solar Farm provides an excellent case study for the future as reliance on distributed solar energy generation grows.

Brad Micallef, Director of Operations and Maintenance for O2 emc said, “This eclipse offers a first-of-its-kind opportunity to directly observe the impact on distributed solar generation at a national scale. Furthermore, there has never been a time when such a high density of instrument grade irradiance sensors are installed on solar farms across North Carolina that will directly measuring the eclipse as it happens. It’s truly unprecedented!”

“This remarkable event is the perfect demonstration of our TrueCapture control instrumentation,” stated NEXTracker CEO Dan Shugar. “With the Gates solar farm directly in the path of the eclipse, these complex irradiance sensors will provide detailed information regarding the amount of direct and diffuse light as the eclipse evolves. Thanks to partner O2 emc for embracing this scientific moment to educate the public about how varying light conditions affect solar power production.”

Since today marks the momentous occasion of the total solar eclipse, O2 emc and NEXTracker are releasing the solar irradiance data recorded during today’s eclipse, as well as several reference days, free for everyone. The data is available at the following links:

EXCEL FILE
ZIP FILE WITH CSV

These two companies hope that this rare dataset will aid in the research of solar energy and power system planning.

For more information about O2 emc, visit www.o2emc.com

For more information about NEXTracker, visit www.nextracker.com

Sources:

1. https://www.vox.com/science-and-health/2017/7/25/16019892/solar-eclipse-2017-interactive-map

2. https://www.nextracker.com/product-services/truecapture/

3. https://www.greentechmedia.com/articles/read/solar-eclipse-shadow-us-solar-fleet

4. https://www.wwaytv3.com/2017/08/11/how-will-the-eclipse-affect-solar-energy-production-in-north-carolina/