A total solar eclipse will cut a narrow path across the breadth of the United States on August 21, 2017, bringing the first total eclipse to the contiguous states for nearly 40 years. But that narrow path of totality brings with it a much broader swath of partial blockage of the sun that will affect all of the country except Hawaii.
When the shadow of the last total solar eclipse swept across the Pacific Northwest back in 1979, the lack of interconnected solar power meant that it had a minimal impact on the grid. But because that situation has changed dramatically, NREL researchers will be keeping close tabs on the August eclipse to see how the grid reacts.
The NREL project includes a pre-event analysis on how the eclipse will affect the output of solar photovoltaic (PV) systems across the Western Electricity Coordinating Council (WECC) territory—that is, the western half of the US power grid. Supported by the US Department of Energy’s (DOE's) SunShot Initiative, NREL will receive data from Peak Reliability, which manages grid reliability for all or parts of 14 Western states; British Columbia, Canada; and the northern portion of Baja California, Mexico.
NREL will focus on understanding the spatial and temporal profile of the eclipse and how the PV output across the WECC will be affected. While the size and location of utility-scale PV sites are known and their outputs are monitored, rooftop PV systems pose a greater challenge for grid operations because their size and location are often unknown. NREL will use databases of distributed PV sites developed through previous efforts to determine how much distributed PV is present at the substation level and then estimate the impact of the eclipse on their output.
NREL researchers will apply the predictions of reduced PV output to expected baseline grid conditions on the day of the eclipse to determine if new generation schedules and power dispatches are needed. WECC system models will then determine the critical operating times for the grid, Peak Reliability will use those models to perform contingency analyses, and Peak Reliability and NREL will develop any needed mitigation measures.
During the eclipse, NREL will use two large PV arrays at the National Wind Technology Center to monitor performance and verify simulations. Denver will experience a 92% solar eclipse, so the impact should be significant. Meanwhile, Peak Reliability will provide NREL with a wide assortment of grid data collected during the event, to validate the pre-event analysis. The results will be used by utilities and Peak Reliability to gain some insight into how much distributed PV is present on their systems at the substation level. It will also result in a validated framework for studying the impact of wide-area disturbances, such as large storms, through their geospatial profile on grid operations.
Written by Kevin Eber, Kevin Eber, NREL’s Communications & Public Affairs Office