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Earth from Orbit: Satellites and Solar Energy

July 23, 2021

Sometimes when looking at satellite imagery, you can see areas of light that gleam or sparkle with an unusual brightness. This effect is known as sunglint, and occurs when sunlight is reflected off the surface of Earth at the same angle that the sensor views it. Sunglint in satellite imagery is often seen over water, but it is also seen reflected from solar panels. While an interesting phenomenon to see, there’s actually an important connection between satellite observations and solar energy production. Detailed data about clouds from NOAA satellites can aid solar energy forecasts. 

Solar radiation, or the electromagnetic energy emitted by the sun, can be captured and converted into useful forms of energy such as heat and electricity. Clouds play a key role in the transfer of energy through the atmosphere. Therefore, clouds affect the output of ground-based solar power generation systems. The amount of power these systems can produce is dependent on the level of light they receive, both directly from the sun and via light reflected from all parts of the sky in the hemisphere above.

So how can the solar industry determine how much sunlight their systems will get, monitor efficiency, and maintain a balance between power generation and consumption? The view from 22,300 miles above can help. Geostationary Operational Environmental Satellites (GOES) are particularly useful in the short-term prediction of solar radiation for renewable energy production. 

Because NOAA’s GOES-16 (GOES East) and GOES-17 (GOES West) constantly watch over the same area of Earth and provide frequent, high-resolution data, they can communicate what types of clouds are present, how they are distributed in the sky, how much shadow they are creating over solar farms, and where they will move next. This provides valuable information about the variations that can occur in power production over the next few minutes to hours. Optimizing solar energy production requires advanced knowledge of both the general likelihood and specific timing of both cloud cover and direct sunlight.

GOES cloud information can also be used to improve the starting point of numerical forecast models as well, through a process called data assimilation. Techniques for relating the observed clouds to characteristics of the environment such as temperature, moisture, vertical motion, and horizontal winds can help better inform models, leading to better cloud forecasts at multi-hour time scales, when the details of the currently-observed cloud field will have changed significantly.

Certain cloudy conditions can actually increase the amount of light reaching solar power generation systems. Frozen water molecules inside of high-altitude clouds can refract the sun’s light, which can in turn cause brighter-than-normal conditions on the ground compared to the darker blue skies of a clear day. This phenomenon, which is called “cloud lensing,” is unusual, but can last for hours. More commonly, side illumination from broken cloud fields can also enhance solar power compared to clear days.

The data provided by GOES satellites is also key to balancing the energy load on electrical grids. Grid managers need to accurately calculate how much electricity the grid needs to carry at any given time. They must maintain the critical balance between generation and consumption. Too much or too little power can damage the millions of electrical devices connected to the grid or even trigger a power outage.

According to the Department of Energy, the amount of solar power installed in the U.S. increased more than 23 times from 2008 to 2015. As demand grows, the need for timely, detailed information about solar radiation and cloud cover is essential. GOES-16 and GOES-17 provide critical data for harnessing solar energy and efficiently delivering it to consumers.