The uncertainties around solar power are well understood — when the sun doesn’t shine as much as expected, power grids that rely heavily on that generation must turn elsewhere to meet consumer demand. And while a shortfall in solar generation can be challenging to navigate, the difference between actual and forecast levels is typically only a few percentage points and power grids are usually ready and able to make up any difference. But what happens when the sun is largely obscured by the moon for several hours across a wide swath of the country? In today’s RBN blog, we’ll discuss the impact of the October 14 partial eclipse, preview the path of the April 8 total eclipse, and outline the steps being taken to ensure that power grids are ready for it.
Figure 1. Types of Solar Eclipses. Source: American Astronomical Society
Before we get too far into any discussions about the April eclipse’s impact on solar generation and the power grid, let’s review some basic definitions. A solar eclipse occurs when the moon passes between the sun and the Earth, casting a shadow on the Earth that either fully or partially blocks the sun’s light in some areas. During an annular solar eclipse (far right in Figure 1 above), like the one last October (see Total Eclipse of the Heart), the moon is not big enough to cover the entire sun. This happens when the moon is farthest away from the Earth. The sun’s outer edge remains visible and forms a “ring of fire” in the sky, although most sunlight will be blocked in the eclipse’s path. During a total solar eclipse (far left), like the one happening April 8, the moon completely covers the sun. This takes place when the moon’s orbit is closest to the Earth. A total solar eclipse is only visible if you are in the path where the moon casts its darkest shadow. (If you are outside the eclipse’s path on April 8, the sun will only be partially obscured.) A partial solar eclipse (middle) occurs when the moon obscures a portion of the sun. (There is also a hybrid solar eclipse, which occurs when the same eclipse changes from annular to total — or the reverse — along its path. It’s the rarest type of eclipse.)
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