Myths about the use of solar energy abound. There’s the idea that solar panels are inefficient, unreliable or hard to maintain. Another myth states that solar panels are too expensive for widespread usage. (All untrue!) Perhaps one of the most persistent fallacies about solar is that PV panels can’t provide the energy you need when the sky is cloudy.
Good thing that’s not correct, either. Solar panels indeed can produce electricity under all sorts of weather conditions.
As evidenced by a sunburn collected on a cloudy day at the beach, ultraviolet light indeed reaches the earth’s surface on days that are foggy, rainy, cloudy or otherwise less than ideal. You might not see the sun on a cloudy day, but your solar panels are still illuminated by indirect sunlight.
Let’s look at the numbers. With the sun shining overhead on a clear day, about 1,000 W/m2 of irradiation reaches the earth’s surface. With light cloud cover, some sunlight will be absorbed by clouds and some will be scattered so that more of the light coming through is indirect — but you’ll still get roughly 800 W/m2 of irradiation. Medium cloud cover could reduce total irradiance down to 300 W/m2, while low-hanging clouds could bring the amount of sunlight reaching the ground down to, say, 230 W/m2.
The point is, overcast skies may limit the amount of irradiation that reaches the surface of a solar panel, however your solar panels will still receive enough sunlight to generate power. Even on the darkest, cloudiest day of the year, a solar system can capture roughly 15 to 20 percent of the energy that might be collected on bright, sunny days.
For proof, let’s take the example of Germany, which gets only about as much sunshine as the state of Alaska, yet boasts 25 GW of installed solar power. That’s roughly half the world’s supply. New Jersey is another example; despite snowy winters, rainy springs and less-than-sunny summers, the state ranks only behind sunny California among U.S. states in annual solar power generation.
You may be surprised to learn that darker days may help with solar panel efficiency, as cooler environments provide more optimal operating conditions. Why? As temperatures increase and panels heat up, the voltage output is reduced. As temperatures fall, the voltage increases — so output is greater. In fact, many studies have shown that solar panels lose efficiency at higher temperatures.
We know that solar panels can produce energy in virtually all types of conditions, but that doesn’t mean there isn’t room for improvement. For one, how do we meet electricity needs at night when the sun isn’t out? With better power storage options, photovoltaic panels can move closer toward becoming a major generating source of energy for the world.